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Palmer, Shiree. "The ecological role of a common seastar (Patiriella spp.) within intertidal cobble fields : a thesis submitted to the Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Marine Biology /." ResearchArchive@Victoria e-Thesis, 2010. http://hdl.handle.net/10063/1240.
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Palmer, Penny L., and n/a. "The biology of Dendrogaster (Crustacea, Ascothoracida), parasitic in sea stars from Otago, New Zealand." University of Otago. Department of Marine Science, 2009. http://adt.otago.ac.nz./public/adt-NZDU20090731.161951.
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Little is known of the biology of the parasite Dendrogaster (Crustacea: Ascothoracida), an obligate endoparasite of sea stars. There are some 25 species of Dendrogaster reported worldwide. The highly modified females live within the coelomic cavity of the host, and heterochronous males are parasitic within the mantle cavity of the female. Two sea star species from the Otago Coast were found to be infected with two species of Dendrogaster. These parasite populations were studied from July 1993 to December 1994 to investigate specific aspects of their biology and the interactions between these parasites and their hosts.
The parasite found in Allostichaster insignis (Asteridae) was identified as Dendrogaster argentinensis Grygier and Salvat 1984, and Asterodon miliaris (Odontasteridae) was found to contain a previously unknown species, herein described and named Dendrogaster otagoensis n. sp. The structure and function of the mantle of female Dendrogaster sp were determined using light, scanning and transmission electron microscopy. The ultrastructure of the mantle is modified, sharing characteristics found in Rhizocephala (Crustacea: Cirripedia), copepods, and Ulophysema oeresundense (Ascothoracida: Dendrogasteridae), which enable these crustaceans to absorb nutrients. Such modifications include a very thin, crenulated epicuticle, a soft, unscleratinised procuticle, and infoldings of the apical plasma membrane. In Dendrogaster the gut is likely to retain the capacity to absorb nutrients.
In general, aspects of infestation of Dendrogaster argentinensis and D. otagoensis are the same. Prevalence of Dendrogaster sp. in Otago sea stars is high and parasitism occurs throughout the year. Seventy-seven point five percent of Asterodon miliaris are infected with D. otagoensis and 97.4% of Allostichaster insignis are infected with D. argentinensis. Up to 144 females are found in a single host, and as many as 34 males in a single female. Mean number of parasites per host changes little over time, but began to decrease in D. argentinensis towards the end of the sample period. The female population is dominated by small individuals, with maximum size likely to depend on space available within the host. Males achieve a large size quickly, but their growth is also restricted by the size of the female they are within. The size and number of females per host are not related to size of the host. Females acquire new males and males grow larger with an increase in female size. Males occur in females of all reproductive stages, but occur with the greatest frequency in brooding females. Reproduction is spread evenly through females in less heavily infected hosts, and there is a reduction in mean size of females as the number of females per host increases, indicative of the crowding effect. Three indices of aggregation show that both sexes of Dendrogaster are highly aggregated in their hosts, with few hosts harbouring most of the parasites.
Dendrogaster is a parasitic castrator. Infected hosts have parasite loads ranging from 0.1% - 112% total sea star wet weight. Infected sea stars have smaller pyloric caecae and gonads, however, no gonads were present in uninfected Allostichaster insignis. Effect on the gonads and pyloric caecae increases as parasite load increases. Rather than directly affecting the germinal tissue of the host, Dendrogaster castrates its host indirectly through crowding and/or competitive castration. This castration is variable among hosts in Asterodon miliaris, but is important in Allostichaster insignis. The presence of D. argentinensis in A. insignis is associated with an increase in the incidence of asexual reproduction among larger (R>25mm) individuals. Specific growth rates of intact and regenerating arms in fed and starved A. insignis are lower in infected individuals.
Larvae are brooded in the mantle cavity of the female until reaching the infective, swimming ascothoracid II stage. The larval development of Dendrogaster argentinensis and D. otagoensis is abbreviated. Larvae moult directly from the egg into the metanauplius. Metanauplii moult into ascothoracid I stage, which moult into the ascothoracid II stage immediately upon release from the female. Ultrastructure confirms the putative sensory function of the lattice organs. Other larval cuticular structures are also sensory.
Histological examination revealed that Dendrogaster has unique system of ovulation among Crustacea. The ovarian membrane contains primary oocytes, early vitellogenic and vitellogenic oocytes, but not maturing oocytes, which are found outside the ovarian membrane. The ovarian membrane forms follicles from which vitellogenic oocytes burst into the surrounding mesodermal tissue. These oocytes mature within the mantle wall tissue until entering the mantle cavity, where they are fertilised. Ovaries are absent in most brooding females. Spermatogenesis takes place within the males posterior protrusions and is continuous. Dendrogaster are likely to be labile hermaphrodites, as sperm are found in 20% of ovaries. Female Dendrogaster display asynchronous reproduction, with females of all sizes at different stages throughout the year. Females within one host are also at different stages. Spermatogenesis is present in males of all sizes. The presence of spent males in some females is indicative of a females outliving the males.
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Martel, André. "Cycle et comportement de reproduction du néogastéropode Buccinum undatum L. dans le golfe Saint-Laurent /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1985. http://theses.uqac.ca.
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Boivin, Yves. "Le cycle de reproduction d'une étoile de mer couveuse subarctique Leptastérias polaris /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1985. http://theses.uqac.ca.
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Peters, Kevin J. "The chemical ecology of Antarctic sponges." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009p/peters.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2009.Additional advisors: Bill J. Baker, James B. McClintock, Donald D. Muccio, Robert W. Thacker. Description based on contents viewed June 3, 2009; title from PDF t.p. Includes bibliographical references.
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Cambell, Stephen Sean. "Morphology and histochemistry of the extracellular matrix of embryos following freeze substitution of the starfish Pisaster ochraceus." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28938.
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All developing embryos contain an extracellular matrix (ECM) consisting of proteins, glycoproteins, and proteoglycans. These components are important for morphogenetic processes such as cell migration, cell differentiation and cell death. The ECM of the starfish, Pisaster ochraceus, consists of three major components: A hyaline layer which coats the external surface of the embryo; a basal lamina which lines the basal surfaces of the epithelia; and a blastocoelic component which fills the embryonic cavity or blastocoel.
Observations of chemically fixed asteroid embryos have revealed the hyaline layer to contain five sub-layers of fibrous strands encrusted with amorphous material. Strands of a similar nature form a meshwork within the fluid-filled blastocoel. Recent studies of the living embryo, however, have suggested that the ECM within the blastocoel of echinoderms, including the asteroid, is a gel-like substance and not a fluid with extracellular fibres. Since artefacts imposed by chemicals such as aldehydes and osmium are well documented, a method of preservation, which does not involve the use of these chemicals, may resolve the apparent conflict over the nature of the ECM of the asteroid embryo.
Freeze substitution, an expensive cryofixation technique which has proven successful in fixing vertebrate tissue, does not require the use of aldehydes and osmium. The initial objective of this study was to devise an inexpensive, easily employable freeze substitution technique which would allow good preservation of cellular and extracellular elements of the embryonic starfish, Pisaster ochraceus. A plunge freezing apparatus was constructed which consisted of a Dewer flask filled with liquid nitrogen, a small cup was filled with cryogen and inserted into the nitrogen, and a motor which constantly stirred the cryogen. Embryos were isolated on copper
freeze-fracture grids and plunged into the cryogen. After considering four different cryogens and four separate cryoprotectants, cryoprotecting asteroid embryos with propylene glycol and plunging them into supercooled propane was found to provide optimal preservation. Frozen embryos were freeze substituted in anhydrous ethanol at -90 °C, osmicated, and embedded for ultrastructural and histochemical analysis.
Following freeze substitution, the blastocoel appears to contain a gel-like substance, rich in sulfated GAG's, with extracellular fibres and not a fluid with fibres. In addition, the hyaline layer was found to consist of at least six sub-layers of greater thickness than was seen in chemically fixed embryos. Histochemical studies demonstrated that both sulfated and unsulfated GAG's were present in these layers. The morphological differences among the sub-layers suggest that some sub-layers may have unique functions while others may have functions shared by other sub-layers. Freeze substitution also revealed the presence of microvillus associated bodies, structures which may represent major attachment points of the hyaline layer to the epithelium.
Although the fixation of asteroid embryos by freeze substitution is a lengthy process, taking four to five days, the resulting preservation, particular!ly of the ECM components, justifies its use over chemical fixations. Material preserved by freeze substitution can be used for histochemical studies and, since aldehydes and heavy metals are not necessary for successful preservation, may also prove useful for immunocytochemical studies.Medicine, Faculty of
Graduate
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Poorbagher, Hadi, and n/a. "Life-history ecology of two New Zealand echinoderms with planktotrophic larvae." University of Otago. Department of Marine Science, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081029.160011.
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The importance of parental nutritional status on planktotrophic larvae was investigated in both laboratory-conditioned and field (populations) parents of two New Zealand echinoderms: the sea urchin Pseudechinus huttoni and the starfish Sclerasterias mollis.
Three questions were addressed: (i) Does parental nutritional status affect the reproductive features (gonad index, gametogenesis, fecundity and biochemical composition) both in the laboratory and under natural conditions? (ii) Does parental nutritional status affect egg characteristics (diameter, number, dry weight, fertilization rate and biochemical composition)? (iii) Are the characteristics of larvae (growth, development, morphology, mortality rate and body composition) influenced by parental or larval nutrition (or both)?
To answer the first question, adult P. huttoni and S. mollis were maintained in the laboratory with a low or high diet (in terms of quantity and quality for P. huttoni, and in terms of quantity for S. mollis) for one year. The effect of low and high diets on reproductive features was studied and the same parameters were studied in two parental populations with dissimilar food availability (for P. huttoni: Otago Shelf and Doubtful Sound populations; for S. mollis: Otago inshore and offshore populations). To address the second question, egg characteristics of the laboratory-held and field parents were measured. The third question was answered by rearing larvae of the laboratory and field parents with both low and high concentration planktonic diets.
P. huttoni reared in the laboratory with a higher food ration had greater gonad indices and lipid concentration and larger oocyte area. Sea urchins from the Doubtful Sound population had higher food availability, greater gonad lipid concentration and larger oocytes.
Parental nutrition had some effect on the characteristics of the egg in P. huttoni. The laboratory-held urchins fed a high diet produced larger eggs: P. huttoni from Doubtful Sound produced larger eggs with a greater carbohydrate concentration.
P. huttoni larvae from low-fed laboratory and Otago Shelf parents had faster development The effect of larval nutrition was more important than parental food availability on larval growth and development. Feeding parents in the laboratory had no effect on larval morphology but larvae from Doubtful Sound, which had better food availability, had longer arms relative to body width. A higher cell concentration in the planktonic diet led to shorter larval arm relative to body width.
In S. mollis reared in the laboratory, a higher food ration led to larger gonad and pyloric caeca indices. The starfish from an Otago inshore population mainly had a higher gonad index than those from an Otago offshore population.
In the laboratory-held parents S. mollis, nutrition had no effect on the egg characteristics. In the field, starfish with higher food availability produced smaller eggs with lower carbohydrate concentration.
There was no significant difference between development rates of S. mollis larvae from low and high fed laboratory parents. However, those from the Otago inshore parents, with better food availability, had faster development than the larvae from Otago offshore parents.
In S. mollis larvae, the origin of the parents (either from the laboratory or the field) had no effect on larval shape. A higher concentration planktonic diet led to longer larvae relative to body width in larvae from high-fed laboratory parents.
In both P. huttoni and S. mollis, parental and larval diet had no effect on rate of instantaneous larval mortality.
In both P. huttoni and S. mollis larvae, biochemical composition of the larvae and the egg were different to each other. Egg reserves appear not to be a factor which affects larval characteristics in these species.
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BOYER, EDWARD HENRI. "THE NATURAL DISAPPEARANCE OF A TOP CARNIVORE AND ITS IMPACT ON AN INTERTIDAL INVERTEBRATE COMMUNITY: THE INTERPLAY OF TEMPERATURE AND PREDATION ON COMMUNITY STRUCTURE (GULF OF CALIFORNIA)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184109.
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The predatory sea star, Heliaster kubiniji, has been hypothesized to be a "keystone species" that is instrumental in maintaining diversity in the intertidal zones of the northern Gulf of California (Paine 1966). Four hundred and one Heliaster stomach samples collected in 1974-1976 from Station Beach, Puerto Penasco, Sonora, Mexico indicated that Heliaster consumed a variety of prey but preferred barnacles, Chthamalus anisopoma (93% of all prey items). The catastrophic decline of Heliaster in the Gulf of California in 1978 resulted in mortalities approaching 100% (Dungan et al 1982). Pre-die-off community data from the intertidal reef at Station Beach (Mackie and Boyer 1977) were compared with post-die-off (1981-1984) data to determine effects of the Heliaster disappearance. Community structure data included abundance and intertidal distributions of 20 species of macro-invertebrates including 11 Heliaster prey and 9 non-prey species and consisted of 6 carnivores, 7 herbivores, 5 detritivores and 2 filter feeders. Comparisons were made in two distinct habitats: a basalt boulder habitat (Heliaster's preferred habitat) and a reef flat habitat. In the reef flat zone three prey species increased density while seven were unchanged; two non-prey species decreased while seven were unchanged. In the boulder zone six prey species increased, three decreased and two were unchanged; one non-prey increased, three decreased and five were unchanged. An examination of prey vs. non-prey guild structure indicated an increase in prey guild density in the boulder zone from 1976 to 1981 and a reshuffling of rank order of prey density. Analysis of trophic guild structure revealed an increase in carnivore guild density (but no change in ranks) in the boulder zone only and an increase in herbivore guild boulder density (with change in ranks) between 1976 and 1981. No significant changes in species diversity were observed during the study. Heliaster did not act as a keystone species in this community, but it influenced the abundance and structure of prey species and trophic guilds. A continuum is proposed for the potential effects of predation on community structure.
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Şahin, Özge Turna İsmail İbrahim. "Antalya Körfezi Doğu Kıyıları' nda (Antalya - Gazipaşa) echinodermata faunasının belirlenmesi /." Isparta : SDÜ Fen Bilimleri Enstitüsü, 2008. http://tez.sdu.edu.tr/Tezler/TF01185.pdf.
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Miller, Bruce Allen 1953. "Larval abundance and early juvenile recruitment of echinoids, asteroids, and holothuroids on the Oregon coast." Thesis, Thesis (M.S.)--University of Oregon, 1995, 1995. http://hdl.handle.net/1794/10056.
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Harvey, Christian. "Analyse chimique des astérosaponines chez Leptastérias polaris et leur rôle dans la réponse défensive de Buccinum undatum /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1985. http://theses.uqac.ca.
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García, Cisneros Álex. "Estructura, distribución e historia evolutiva de las poblaciones de estrellas de mar Echinaster sepositus y Coscinasterias tenuispina." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/398123.
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El conocimiento de la filogeografía, la estructura y la diversidad genética de las poblaciones es importante para entender y evaluar la situación de las diferentes especies, detectar su posible vulnerabilidad y desarrollar estrategias para su gestión. En el Mediterráneo hay un total de 154 especies de equinodermos y, de las cuales 33 son asteroideos. A pesar de tratarse de un grupo muy conocido, hay pocos estudios de filogeografía o genética de poblaciones de estrellas de mar realizados en el Mediterráneo. En esta tesis doctoral se estudian dos especies de asteroideos atlanto-mediterráneos, Echinaster sepositus y Coscinasterias tenuispina, dos estrellas muy comunes en el litoral rocoso mediterráneo Ambas especies tienen estrategias vitales diferentes, pero distribuciones geográficas parecidas, y hasta ahora se desconocía su historia evolutiva y algunas de sus características biológicas.
Echinaster sepositus es una estrella roja, vistosa y que puede llegar a ser muy común en algunas áreas. Se encuentra en el Mediterráneo y áreas templadas del Atlántico. E. sepositus se reproduce únicamente de forma sexual; el resultado de la fecundación es una larva lecitotrófica, que no se alimenta durante su vida planctónica, que en la mayoría de los casos, no supera una semana. Coscinasterias tenuispina es una estrella espinosa de talla mediana y coloración variable. Puede reproducirse sexual (larvas planctotróficas) y asexualmente (fisiparidad). Se caracteriza por presentar un número de brazos normalmente superior a cinco y está ampliamente distribuida en el Mediterráneo y a ambos lados del Atlántico.
Para estudiar ambas estrellas de mar se han utilizado marcadores moleculares, como el gen de la citocromo oxidasa subunidad I (COI), diferentes loci microsatélite del genoma nuclear (diseñados a partir de bibliotecas de pirosecuenciación 454), y la longitud de los telómeros en individuos clonales. Además, se ha realizado el seguimiento de poblaciones de Coscinasterias tenuispina para conocer su dinámica poblacional y su ciclo biológico a lo largo del año.
Los resultados de este estudio muestran que ambas especies presentan una baja diversidad genética comparada con otros equinodermos de igual distribución, aunque los motivos de esta baja diversidad son diferentes para cada una. Por un lado, la baja diversidad de Echinaster sepositus se explica por un proceso de expansión demográfica muy reciente, a partir de un número reducido de individuos con pocos alelos. En el caso de Coscinasterias tenuispina, la baja diversidad está más relacionada con su elevada clonalidad, ya que existen poblaciones exclusivamente monoclonales y también se encuentran clones en el resto de poblaciones. Estos valores de diversidad podrían dar lugar, en ambas especies, a un bajo potencial de adaptación y, por tanto, hacerlas más sensibles a cambios ambientales. De hecho, dos poblaciones de Echinaster sepositus cercanas a zonas contaminadas han mostrado una estructura genética diferente al resto de poblaciones.
Se ha observado que las barreras marinas originadas por el frente Almería-Orán y por el estrecho Sículo-Tunecino actúan restringiendo el flujo genético entre las poblaciones de ambas especies, aunque permiten un cierto grado de permeabilidad e intercambio genético entre las mismas.
Los procesos de asexualidad en Coscinasterias tenuispina le permiten mantener poblaciones monoclonales densas a lo largo del tiempo, así como aumentar su área de distribución. La fisiparidad parece modularse en función de la inestabilidad ambiental, tanto térmica como física. En cualquier caso, el potencial sexual de los individuos (desarrollo de gónadas, masculinas en todos los casos) se mantiene siempre y cuando la condición alimentaria sea favorable. Se ha observado también que esta estrella de mar dispone de recursos para evitar algunos de los efectos deletéreos que podrían aparecer tras sucesivas o ilimitadas generaciones generadas por fisión, como es el caso del mecanismo de alargamiento de telómeros.Understanding the phylogeography and genetic structure of populations, and the processes associated with their patterns, is important for assessing vulnerability of marine species and developing strategies for their management. Along the Mediterranean Sea, there are 154 echinoderm species, of which 33 are asteroids. However, there are few studies that describe their phylogeographic patterns or genetic structure. We studied two common atlanto-mediterranean species that share part of their distribution along the rocky shores, Echinaster sepositus and Coscinasterias tenuispina. E. sepositus reproduces sexualy and generates lecithotrophic larvae, and C. tenuispina is able to reproduce both sexually (with planctotrophic larvae) and asexually by fission. Here, we analysed the genetic structure and phylogeography of both species by using mitochondrial cytochrome c oxidase subunit I gene (COI) and nuclear microsatellite loci, previously described using 454 pyrosequencing genome libraries. Furthermore, we studied the reproductive cycle and population dynamics of a monoclonal population of C. tenuispina. Finally, we studied the telomere length, as a molecular marker of senescence, in different populations of C. tenuispina and different tissues from different parts of the same individuals. Our results reveal a low genetic diversity in both species, lower than other echinoderms with the same distribution range. However, the reasons differ depending on the species. Low diversity in E. sepositus can be explained by a recent demographic expansion from few individuals with few alleles, while in C. tenuispina by the presence of asexual reproduction processes along all its distribution range, even with totally monoclonal populations. Marine barriers, like Almeria-Oran front or Siculo-Tunisian strait, limit the gene flow through populations, although allow certain permeability in both starfish. In areas located near the distribution edges of C. tenuispina, increases the asexuality rates, and fission processes are maintained over time. Events of fissiparity also increase with environmental instability, by both thermal and physical factors. However, well-fed individuals do not lose their potential for sexual reproduction (development of gonads, only males), even the absence of sexuality in many generations. Finally, C. tenuispina presents at least one mechanism to avoid or postpone senescence and ensure persistence of clonal populations: telomere elongation.
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Potton, Derrick John. "Neurohormonal control of feeding in the starfish." Thesis, Royal Holloway, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267555.
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Dean, Juliette. "Evolutionary diversification of asteroids and ophiuroids [Echinodermata]." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/251696.
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Baeta, Alacio Marc. "Ecology of some keystone invertebrates inhabiting shallow soft bottom communities of the Maresme coast (NW Mediterranean Sea)." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/295965.
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Bivalves living in large aggregations of individuals (reefs or beds), such as mussels, clams, cockles and some high trophic predators such as sea stars, play an essential ecological role in the structure, integrity, stability, and diversity of the biological communities; being usually considered as keystone species. Their disappearance or decline could lead to disproportionate effects in their communities, even affecting the survival of other species. Although keystone species are crucial for maintaining the Earth biodiversity, often their study has not taken enough attention. The main aim of this Doctoral Thesis was to study the ecology of some keystone invertebrates inhabiting shallow soft bottom communities of the Maresme coast (Northwestern Mediterranean Sea). The results enhance the knowledge of the smooth clam (Callista chione) and also of its potential predators, several species of sea stars (Astropecten spp.) co-occurring in the area. But at the same time, our findings help to understand their trophic interactions, the status of their populations and propose guidelines for their conservation. Maresme coast is close to Barcelona and it has concentrated historically a high anthropogenic pressure that has altered and modified its environment. Our results have showed the critical status of the smooth clam bed as a consequence of the combination of different human coastal uses: sand dredging and clam fisheries. These anthropogenic pressures have also led to significant changes in Astropecten populations. A. aranciacus has been shown to be the most vulnerable, and consequently the most affected, to the extent that its population suffers an important and worrying decline. Moreover, A. aranciacus reproductive cycle, growth and depth segregation between size classes along the continental shelf have been described for the first time. Our results have documented Astropecten species niche segregation, which allow them to co-occur within a biological community scale, without compete for the same available recourses. Sea stars showed a partitioning of the prey (species) and microhabitats in the Maresme coast. This Doctoral Thesis aims to provide a valuable background to improve the conservation of these keystone invertebrates, as well as to promote the sustainable exploitation of shellfish.Els bivalves que viuen en grans agregacions d'individus, com ara algunes espècies de musclos, cloïsses i escopinyes; i alguns predadors que ocupen elevats nivells tròfics com ara les estrelles de mar juguen un paper fonamental en l'estructura, integritat, estabilitat i diversitat de les comunitats biològiques, sent habitualment considerats com espècies clau. La seva desaparició o declivi pot conduir a efectes desproporcionats sobre el conjunt de les comunitats on habiten, fins i tot afectant la supervivència d'altres espècies. Tot i que les espècies clau són essencials per mantenir la biodiversitat al planeta Terra, sovint no s'ha prestat prou atenció al seu estudi. El principal objectiu d'aquesta Tesi Doctoral ha estat l'estudi de l'ecologia d’algunes d’aquestes espècies clau que habiten els fons tous poc profunds de la costa del Maresme (nord-oest del Mar Mediterrani). Els resultats obtinguts milloren de manera significativa el coneixement de la població de petxinot de sang (Callista chione) i dels seus potencials depredadors, diferents espècies d'estrelles de mar (Astropecten spp.) que cohabiten a la zona. Al mateix temps ajuden a entendre les seves relacions tròfiques, l'estat de les seves poblacions i es proposen pautes per a la seva conservació. La costa del Maresme és molt propera a la ciutat Barcelona, i per això ha concentrat històricament una elevada pressió antropogènica que ha modificat i alterat el seu medi ambient. Els resultats d'aquesta Tesi Doctoral mostren com l'estat crític de la població de petxinot de sang (C. chione) és conseqüència de la combinació de diferents pressions antropogèniques: dragatges de sorres i la pesca de bivalves amb dragues. També s'ha observat que aquestes mateixes pressions han produït canvis significatius en les poblacions d'estrelles de mar Astropecten. A. aranciacus ha resultat ser l'estrella més vulnerable a aquestes pressions i en conseqüència ha estat la més afectada, veient-se la seva població disminuir a un ritme preocupant. A més, s'ha descrit per primera vegada la reproducció, el creixement i la segregació batimètrica per mida de A aranciacus. Els resultats obtinguts també mostren que les diferents espècies de Astropecten poden cohabitar per la segregació dels seus nínxols ecològics permeten-los no competir pels recursos disponibles (preses i hàbitat). Aquesta Tesi Doctoral pretén proporcionar un rerefons valuós per a millorar la conservació d'aquestes espècies clau, així com promoure l'explotació sostenible dels mol·luscs bivalves.
Los bivalvos que viven en grandes agregaciones de individuos, como por ejemplo algunas especies de mejillones, almejas y berberechos; y algunos predadores que ocupan elevados niveles tróficos como por ejemplo las estrellas de mar juegan un papel crucial en la estructura, integridad, estabilidad y diversidad de la comunidades biológicas, siendo habitualmente considerados como especies clave. Su desaparición o declive puede conducir a efectos desproporcionados sobre el conjunto de sus comunidades, incluso afectando la supervivencia de otras especies. Aunque las especies clave son esenciales para mantener la biodiversidad en el planeta Tierra, a menudo no se ha prestado suficiente atención a su estudio. El principal objetivo de esta Tesis Doctoral fue el estudio de la ecología de algunas especies clave que habitan los fondos blandos y someros de la costa del Maresme (noroeste del Mar Mediterráneo). Los resultados obtenidos mejoran de forma significativa el conocimiento sobre la concha fina (Callista chione) y sus depredadores potenciales, distintas species de estrellas de mar del género Astropecten que cohabitan en la zona. Al mismo tiempo ayudan a entender sus relaciones tróficas, el estado de sus poblaciones y se proponen pautas para mejorar su conservación. La costa del Maresme se halla cerca de la ciudad Barcelona, y por ello ha concentrado históricamente una elevada presión antropogénica que ha modificado y alterado su medio ambiente. Los resultados de esta Tesis Doctoral muestran como el estado crítico de la población de concha fina (C. chione) es consecuencia de la combinación de distintas presiones antrópogenicas: dragados de arenas y pesquerías de moluscos bivalvos. También se ha observado que estas mismas presiones han producido cambios significativos en las poblaciones de estrellas de mar Astropecten. A. aranciacus ha resultado ser la estrella más vulnerable a dichas presiones y en consecuencia ha sido la más afectada, viéndose su población disminuir a un rito preocupante. Además, se ha descrito por primera vez la reproducción, el crecimiento y la segregación batimétrica por tallas de A. aranciacus. Los resultados documentados también muestran que las distintas especies de Astropecten pueden cohabitar por la segregación de sus nichos ecológicos permitíendoles no competir por los recursos disponibles (presas y hábitat). Esta Tesis Doctoral pretende proporcionar un trasfondo valioso para mejorar la conservación de estas especies clave, así como promover la explotación sostenible de los moluscos bivalvos.
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Tsow, Alexander W. "Starfish a table-centric tool for design derivation /." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3277963.
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Thesis (Ph.D.)--Indiana University, Dept. of Computer Science, 2007.Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6092. Adviser: Steven D. Johnson. Title from dissertation home page (viewed May 8, 2008).
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Vogler, Catherine. "Phylogeography and evolution of the crown-of-thorns starfish Acanthaster planci." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-133642.
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Yun, Sang Seon. "Biochemical, molecular and pharmacological characterisation of SALMFamide neuropeptides from the starfish Marthasterias glacialis." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313518.
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Deaker, Dione. "Resilience of juvenile crown of thorns starfish and the implications for population outbreaks." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/28204.
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Population outbreaks of the corallivorous crown of thorns starfish (COTS, Acanthaster sp.) are one of the leading causes of coral loss throughout the Indo-Pacific. Decades of research and significant investment have been directed towards understanding and managing the potential causes of outbreaks with a focus on the larval and adult stages. However, the role of the juvenile stage in population dynamics of COTS is poorly understood. This thesis provides new insights on the biology and ecology of juvenile COTS addressing critical knowledge gaps in their growth, diet, behaviour and physiology.
Juvenile COTS are initially obligate herbivores with a known diet of crustose coralline algae (CCA) before they transition to a coral diet. I found that juveniles are also capable of eating a geniculate coralline algae, Amphiroa sp., and can survive on biofilm with diet-dependent growth rates. An important finding is that the juveniles exhibited extreme growth plasticity and paused their growth for more than six years on an algal diet in the absence of coral and continue growing when offered coral. During the transition to coral, juveniles were injured and killed by coral and, if they survived, they regenerated the damaged tissue. Juveniles also exhibited defensive behaviours that were affected by the presence of their natural enemy, coral guard crabs. I also determined the metabolic rate of both herbivorous and corallivorous juveniles.
To reduce the loss of critical coral reef habitat and manage COTS outbreaks, it is crucial to understand and address the inherent biology of COTS that underlie their success. The growth plasticity and diet flexibility of juvenile COTS is a novel finding of this thesis that is likely to drive their resilience in unfavourable conditions, their success when conditions benefit their development, and contribute to the boom-and-bust dynamics of COTS populations.
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Cha, Mei-wah. "The ecology of tapes philippinarum (Bivalvia: Veneridae) in Starfish Bay, Hong Kong, and its potential as a biological indicator of coastal pollution /." [Hong Kong : University of Hong Kong], 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13762370.
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Puppo, Studer Agostina Margarita. ""Modulation of calcium signalling by F-actin during maturation and fertilization of starfish oocytes"." Thesis, Open University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520773.
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The Calcium ion (Ca2+) is a universal intracellular messenger that is implicated in the regulation of a great variety of intracellular processes. Among them, there is the meiotic maturation of oocytes from several species and their fertilization. The cell model system chosen for the work of this thesis has been the starfish oocytes. They constitute an exceptional model to study the properties of the dynamic release of Ca2+. First, the cells are large and nearly transparent, making them suitable for imaging experiments after microinjection of fluorescent markers. Immature oocytes extracted from the gonad are arrested at the prophase stage of the first meiotic division. Overcoming the meiotic arrest (maturation), is induced by the application of the maturing hormone I-Methyladenine (l-MA), whose action involves intracellular Ca2+ transients. During the maturation process, the oocytes develop their ability to be successfully activated by a fertilizing spermatozoon by liberating higher levels of calcium. I-MA also induces dramatic actin cytoskeleton rearrangements. In the present work, the relevance of the actin cytoskeleton in the modulation of the Ca2 + signals generated by hormonal stimulation and by the sperm has been studied. For this purpose, actin-specific disrupting agents and a specific antibody targeting the actin binding protein depactin have been delivered into living cells by needle microinjection, to study their effects using confocal laser fluorescent microscopy. Thus, the Ca2 + increases induced either by I-MA, by the fertilizing sperm or by the injection of exogenous InsP3. which is the canonical Ca2+ mobilizer second messenger, have been monitored with video fluorescent microscopy. The results described indicate that actin filaments play direct and indirect roles in modulating the intracellular Ca2 + mobilization induced by the maturation process triggered by I-MA as well as in the Ca2+ responses induced by the sperm.
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Burdyniuk, Mariia [Verfasser], and Alexander [Akademischer Betreuer] Aulehla. "Actin synchronizes chromosome capture by microtubules in starfish oocyte meiosis / Mariia Burdyniuk ; Betreuer: Alexander Aulehla." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177251493/34.
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Vogler, Catherine [Verfasser], and Gert [Akademischer Betreuer] Wörheide. "Phylogeography and evolution of the crown-of-thorns starfish Acanthaster planci / Catherine Vogler. Betreuer: Gert Wörheide." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2010. http://d-nb.info/1015170579/34.
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Bischof, Johanna [Verfasser], and Alexander [Akademischer Betreuer] Aulehla. "The molecular mechanism of surface contraction waves in the starfish oocyte / Johanna Bischof ; Betreuer: Alexander Aulehla." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180616111/34.
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Hannah, Lucie C. "Maturation promoting factor (MPF) in relation to the fertilization and early development of lugworm and starfish oocytes." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423995.
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Lim, Dmitri. "Ca²⺠signals induced by InsP₃ and NAADP during maturation and fertilization of starfish oocytes." Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397915.
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Lin, Ming. "Identification and functional characterization of relaxin-type and pedal peptide/orcokinin-type neuropeptides in the starfish Asterias rubens." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/30715.
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Neuropeptides are neuronal signaling molecules that regulate many physiological and behavioural processes in vertebrates and invertebrates. Investigation of neuropeptide signaling in echinoderms (e.g. starfish) can provide insights into the evolution of neuropeptide systems because as deuterostomian invertebrates they occupy an "intermediate" phylogenetic position between vertebrates and protostomian invertebrates. Recent analysis of neural transcriptome data from the starfish Asterias rubens has identified 40 transcripts encoding neuropeptide precursors. Here the expression and function of neuropeptides derived from four of these precursors was investigated: relaxin-like gonad-stimulating peptide precursor (AruRGPP), relaxin-like peptide precursor 2 (AruRLPP2), pedal peptide-like neuropeptide precursors 1 and 2 (ArPPLNP1 and ArPPLNP2). AruRGP induces spawning of ovarian fragments from A. rubens. Analysis of the expression of AruRGPP in A. rubens using mRNA in situ hybridization revealed expression by cells in the radial nerve cords, circumoral nerve ring and tube feet. Furthermore, a band of AruRGPP-expressing cells was also identified in the body wall epithelium lining the cavity that surrounds the sensory terminal tentacle and optic cushion at the tips of the arms. Discovery of these cells is important because they are candidate physiological mediators for hormonal control of starfish spawning in response to environmental cues. Interestingly, AruRLPP2 is also expressed in the same region of the arm tip as AruRGPP but the physiological role(s) of AruRLP2 is not yet known. Analysis of the expression of ArPPLNP1 and ArPPLNP2 using mRNA in situ hybridization revealed a widespread pattern of expression in A. rubens. Furthermore, immunohistochemical localization of peptides derived from these precursors revealed immunostaining in neuronal processes innervating muscles. Consistent with this pattern of expression, peptides derived from ArPPLNP1 and ArPPLNP2 act as muscle relaxants in starfish. Interestingly, this contrasts with previous findings from protostomian invertebrates, where pedal peptide/orcokinin-type neuropeptides act as muscle contractants.
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Cha, Mei-wah, and 車美華. "The ecology of tapes philippinarum (Bivalvia: Veneridae) in Starfish Bay, Hong Kong, and its potential as a biological indicator of coastalpollution." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31233442.
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Carver, Leland Joseph. "A Clockwork Orange: Student Advising and Technology." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou159621692037443.
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Rahman, Ridzwan Abdul. "Recovery processes of coral communities following the crown-of-thorns starfish, Acanthaster planci, infestations on the east coast islands of peninsular Malaysia." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283767.
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Reimer, Corinne L. "The distribution of glycoconjugates in the basal lamina and ECM during esophageal muscle formation in embryos of the starfish Pisaster ochraceus as revealed by lectin hsitochemistry." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27626.
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Morphogenetic events consist of complex interactions of cells and extracellular materials resulting in the movement and rearrangement of groups of cells and their subsequent differentiation to form organs or organ systems. Although we can predict these movements for any given event, we have little understanding of how morphogenesis is controlled. In the starfish Pisaster ochraceus. assembly of mesenchyme cells on one particular region of the larval gut, the oesophagus, and their subsequent differentiation into muscle is an example of a simple morphogenetic event which is readily accessible for study. In their migration to the gut, the mesenchyme cells travel through a rich substrate of ECM. Upon their arrival at the presumptive esophagus, they come to settle on the BL underlying the endodermal epithelium. It is quite possible that interactions between the mesenchymal cells and 'the ECM/basal lamina are important in directing and regulating their differention into muscle.
The basal laminae and ECM of vertebrates and invertebrates is rich in glycoconjugates, including glycoproteins, proteoglycans and glycosaminoglycans. Ultrastructural studies of embryos of the asteroid Pisaster ochraceus have demonstrated that at the late gastrula stage, the endodermal basal lamina is thinner and less alcianophilic in the esophageal region. FITC and colloidal gold labelled lectins, which act as specific probes for carbohydrate moities, usually those at the terminal end of oligosaccharide chains, have been used to localize these sugars at the light and electron microscope levels. These studies show that a heterogeneity exists with respect to terminal sugars in the basal lamina, i.e. lectin binding of the basal lamina is not uniform in all regions of the embyro. Specifically, a statistical analysis of lectin binding determined that labelling with the two lectins, Au₂₅-Con A and Au₂₅-LFA was significantly reduced in the esophageal region as compared with the other regions of the embyro, while labelling of the BL with AU₂₅-DBA showed a similar intensity in all areas of the embryo. These results confirmed the alcian blue results described above and suggest that there are some sugar containing molecules, perhaps specific glycoproteins, GAGs and/or proteoglycans, which are present in reduced quantities in this region. In addition, these studies show a distinct labelling pattern of the ECM through which the mesenchymal cells migrate on route to the esophagus. Different lectins label different regions of the ECM, however it can not yet been said whether there is a regionally distinct pattern in the area of the migratory path of mesenchymal cells to the esophagus.
Proteoglycans and GAGs are involved in cell movement in vertebrates and sulfated glycoconjugates have been shown to be necessary for mesenchyme cell movement in echinoids. A decrease in proteoglycans and GAGs in the esophageal BL could therefore help to direct movement of the presumptive muscle cells to the esophagus by providing a "stop" signal.Medicine, Faculty of
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Lafontaine, Tania. "Ecocriticism and Science Fiction Theory: the Role of Environments and Representations of Post-Nature in Starfish, Maelstrom and Behemoth by Peter Watts and The Road by Cormac McCarthy." Mémoire, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/77.
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(Résumé) Ce mémoire propose une analyse des représentations de la nature et de l’environnement dans deux œuvres de science-fiction: la trilogie des Rifters—de l’auteur canadien Peter Watts—, qui comprend trois romans en quatre tomes: Starfish (1999), Maelstrom (2001), Behemoth B-Max (2004) et Behemoth Seppuku (2005); et le roman The Road (2006) de l’auteur américain Cormac McCarthy. Cette étude vise à théoriser les implications critiques et littéraires de ces représentations. Pour ce faire, un survol de quelques-unes des principales théories de la science-fiction précède l’analyse des romans. L’intégration de ces théories et des concepts qu’elles mettent de l’avant à l’analyse des romans me permet d’articuler le fait que, dans les récits choisis, les novums science-fictionnels entraînent la défamiliarisation de la nature et de l’environnement, ce qui produit un effet d’étrangeté.
En effet, dans ces récits la nature est soit hybride— transformée par l’intervention des humains et de la technologie—, soit malade, mourante, détruite, ou absente et pleurée par les personnages, qui se la remémorent en rêve. Dans les deux cas, la nature est ré-imaginée, l’environnement est recontextualisé et des mondes post-naturels sont présentés d’une façon qui implique des stratégies littéraires semblables, mais une différence critique importante: la trilogie de Watts met en évidence les conséquences tragiques possibles de notre échec à surmonter les enjeux environnementaux de notre époque. Le roman de McCarthy dresse le portrait de la destruction de la société et de la planète tels que nous les connaissons, mais en tait les causes. // (Abstract) This thesis analyzes the representations of nature and environments in two works of science fiction: the Rifters Trilogy, by the Canadian author Peter Watts, comprised of three novels in four volumes: Starfish (1999), Maelstrom (2001), Behemoth B-Max (2004), and Behemoth Seppuku (2005); and the novel The Road (2006), by the American author Cormac McCarthy, in order to theorize their critical and literary implications. To do so, some significant theories in the field of science fiction theory are explored and appropriated in order to develop analyses of the novels. The integration of these theories and their concepts in the analyses allows me to articulate how nature and environments are defamiliarized and generate an estrangement effect within the selected narratives because of their respective sf novums and the consequences they entail. Nature is presented in the primary texts as hybrid — transformed by human intervention and technology — but also as sick, dying, destroyed, and as something lost, absent, mourned and virtually only remembered in dreams. Both works re-imagine nature, re- contextualize environments, and ultimately present post-natural worlds in ways that evidence similar literary strategies. However, they offer a major critical difference: for the Rifters trilogy points out the possible tragic consequences of the failure to overcome environmental issues in our time, while The Road portrays the destruction of society and the planet as we know them but silences the causes.
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Nance, David. "Settlement of the scallops Pecten maximus (L.) and Aequipecten opercularis (L.) and their predators : the starfish Asterias rubens L. and the crabs Necora puber (L.) and the Cancer pagurus L. on the west coast of Scotland." Thesis, University of Aberdeen, 2000. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=124328.
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Zhuang, Zhenpeng. "Comparative Physiology of Calcium Transport in Crustacean (Homarus Americanus) and Echinoderm (Helianthoides Pycnopodia) Gastrointestinal Epithelia." Thesis, 1996. http://hdl.handle.net/10125/10564.
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Navarrete, Sergio A. "Effects of interactions between predators, variable predation regimes, and species body size on rocky intertidal communities : comparative and experimental approaches /." 1994. http://hdl.handle.net/1957/14234.
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Oliveira, Bárbara Xavier Louro de. "Dynamics of circulating coelomocytes during starfish regeneration." Master's thesis, 2016. http://hdl.handle.net/10451/25862.
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Tese de mestrado, Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2016A regeneração é um fenómeno regulado com implicações biológicas variadas. No Reino Animal, há diversos exemplos deste processo que envolvem a reparação de tecidos, órgãos e membros. No entanto, a regeneração nos vertebrados é limitada na medida em que não se observa a regeneração completa de todos os órgãos. Nos invertebrados, existe uma maior flexibilidade em termos de reparação e até mesmo de substituição de tecidos e/ou órgãos. Após predação ou autotomia, alguns animais são capazes de substituir o órgão ou a porção perdida e muitas vezes esta pode levar uma vida autónoma podendo ela própria regenerar e até formar um individuo completo, dependendo sempre da perda, mas também da capacidade de regeneração do organismo. Este fenómeno acaba por se sobrepor nos invertebrados com a reprodução assexuada. Muitos equinodermes têm uma capacidade regenerativa elevada que se mantém ao longo de toda a sua vida, incluindo na fase adulta. A primeira resposta na regeneração é o fecho das feridas pelas contrações musculares e a formação de agregados de celómocitos, as células circulantes do fluído celómico que banha toda a cavidade interna dos equinodermes. Estas células têm um papel reconhecido na primeira linha de defesa do sistema imunitário que inclui várias funções, como coagulação e defesa contra organismos patogénicos por fagocitose. Os equinodermes têm uma grande proximidade filogenética com os cordados. Contudo o estudo destes organismos ao nível molecular não é muito frequente. Devido à pouca informação relativamente ao seu genoma, transcriptoma, proteoma ou metaboloma e por haver outros organismos com mais informação reportada, estes facilitam as comparações extrapoladas com cordados. Embora o ouriço do mar Strongylcentrotus purpuratus seja o único equinoderme a ter o genoma sequenciado e anotado, e consequentemente vários estudos moleculares tenham sido possíveis, estes organismos têm a menor capacidade de regeneração observada entre as diferentes classes de equinodermes, tendo sido muito reduzida a sua contribuição para o estudo da regeneração. Para uma maior compreensão dos coelomócitos, este trabalho apresenta a caracterização das populações celulares e a sua variância percentual durante o processo de regeneração. Embora a classe Asteroidea não tenha sido utilizada extensamente, os organismos desta são uma excelente escolha para o estudo do processo da regeneração. Marthasterias glacialis L. é uma estrela do mar espinhosa, betónica que pode ser encontrada ao longo de toda a costa oeste portuguesa capaz de viver a vários níveis de profundidade (0–200m), podendo atingir até 70 centímetros de diâmetro e com capacidade de regenerar todas as partes do corpo (internas e externas), incluindo o sistema nervoso central. Devido ao facto de haver pouca informação relativa aos equinodermes e mais especificamente às estrelas do mar, é por vezes difícil encontrar correlações na literatura com o estudo aqui apresentado. Efetuar analogias com outras classes de equinodermes é também desafiante, devido às diferenças inter-espécie, na metodologia escolhida para o estudo das células (diferentes tipos de microscopia) ou até no manuseamento dos celomócitos (células vivas ou fixadas, ex vivo ou em cultura). Desta forma, a primeira fase deste estudo foi dedicada à caracterização das populações celulares do fluído celómico através da citometria de fluxo e por microscopia de fluorescência. De forma a prosseguir com a caracterização do fluído celómico, algumas etapas de otimização tiveram de ser efetuadas para que o manuseamento das células ex vivo se fizesse sem comprometer o estudo ou os seus objetivos. Estas otimizações foram feitas ao nível das condições que reduzissem a agregação dos celomócitos após recolha do fluído celómico com o uso de diferentes tampões anticoagulantes, de diferentes condições de centrifugação, de diversas concentrações de corantes para que a análise de diferentes estudos (viabilidade celular e ciclo celular) fosse possível. Iii O desafio da optimização do ensaio de viabilidade celular centrou-se na escolha de dois corantes compatíveis, ou seja, que apresentassem comprimentos de onda de emissão e locais de ligação ao DNA distintos para que a análise fosse mais fiável. Duas populações celulares no fluído celómico (aqui designadas como P3 e P5) foram distinguidas através da citometria de fluxo e analisadas individualmente em termos de abundância no fluído celómico, morfologia, viabilidade celular e ciclo celular. A células da população P3 são as menos abundantes no fluído celómico, têm uma forma arredondada com um diâmetro nunca superior a 4 μm. Quanto à sua caracterização ao nível da viabilidade celular estas incorporam os diferentes corantes de exclusão de viabilidade celular após a recolha do fluído celómico, indicando uma baixa ou até nenhuma viabilidade celular. A população celular P5, que é regularmente 4 vezes mais numerosa que a população P3, apresenta várias morfologias, dependendo da concentração salina do meio ou do substrato que contactam, assim o seu tamanho varia entre 7 μm a 23 μm. Estas têm uma alta viabilidade celular no momento em que abandonam o organismo, observada pela não incorporação dos corantes de exclusão. A sua viabilidade vai diminuindo ao longo do dia da experiência mesmo em condições de escuridão e baixa temperatura (4ºC). As diferentes fases do ciclo celular variam na quantidade de DNA em cada célula (a fase G2M tem o dobro do conteúdo de DNA da fase G0G1). Para o estudo do ciclo celular, a concentração do corante (iodeto de propídeo) tem de ser saturante para que se possa inferir em que fase do ciclo as células se encontram. Para as células P3 não foi possível detectar eventos para todas as fases do ciclo celular, podendo ser devido à falta de viabilidade que apresentam, tendo uma atividade metabólica ou mitótica reduzida. As células P5 apresentam um ciclo celular bem definido, no qual a maioria das células se encontra na primeira fase do mesmo. Devido ao aparecimento de gâmetas masculinos, em algumas amostras de fluído celómico, a sua caracterização morfológica e análise citométrica foi também possível. Os estudos feitos até ao momento envolvendo celomócitos da espécie M. glacialis centraram-se na caracterização do seu proteoma total, sem separação das diferentes populações, e na proteómica diferencial nas diferentes fases da regeneração. Para isso a caracterização do proteoma de cada população, isolada por citometria de fluxo seria o próximo passo. Contudo houve algumas dificuldades na recuperação das células após a sua separação por citometria de fluxo. Sendo este processo provavelmente violento física e osmoticamente para as células. A reprodutibilidade da técnica para estes tipos celulares foi muito baixa, devido à disparidade dos resultados nos diferentes ensaios. O estudo da proteómica diferencial foi feito para pontos temporais que cobrissem as diferentes fases da regeneração (48 horas, 13 dias e 10 semanas). A maioria dos estudos feitos em celomócitos durante a regeneração sugere que o seu papel é mais determinante na primeira fase do processo regenerativo – cicatrização. Assim optou-se pelo estudo dos celomócitos durante o primeiro dia de regeneração. Algumas diferenças estatisticamente significativas foram observadas nas percentagens de células P5 nas primeiras horas (2, 8 e 24 horas) após amputação comparando com os valores relativos a um grupo controlo. Antes da indução da regeneração (t=0), a população P5 no grupo de animais posteriormente amputados apresenta uma média de valores percentuais superior à do grupo controlo. Após indução da regeneração, as proporções da população P5 diminuem significativamente. Os principais fatores a contribuírem para esta perda de células será a perda de fluido celómico através das feridas e o seu recrutamento para o processo de coagulação. A variação da proporção da população P3 ao longo do tempo mostrou ser independente do processo de regeneração. Os gâmetas masculinos apareceram durante o estudo dos celomócitos na regeneração apenas nos indivíduos que foram amputados. A caracterização das populações de celomócitos apresentada nesta dissertação constitui um contributo para o conhecimento das funções fisiológicas dos celomócitos circulantes desta espécie de equinoderme.
Regeneration is a phenomenon that occurs throughout the Animal Kingdom and it has wide biological implications. Echinoderms have an outstanding regeneration ability that allows the replacement and regrowth of lost organs or body parts due to injury caused by autotomy or predation. The first response in the regeneration process is to close all the wounds with muscle contraction and coelomocytes clots. Coelomocytes are free circulating cells in coelomic fluid, which fills the internal cavity of echinoderms. These cells are known to have a role in the first defence by the immune system, with different functions as clotting, and defence against pathogens such as phagocytosis. Starfishes are excellent organisms to explore organ and tissue regeneration. Marthasterias glacialis L. belongs to Asteroidea class and it has whole body regeneration ability, including the central nervous system. Due to a lack of knowledge, it is difficult to find information about coelomocytes characteristics or to compare it with other classes of echinoderms, due to interspecies variability and to the diverse methodical approaches used in the several published studies. Thus the first part of this study was to characterize different coelomocytes population through flow cytometry and fluorescence microscopy. In order to perform coelomic fluid cells characterization, several optimization steps had to be done so as to know how to handle these cells ex vivo. Two different populations (here named P3 and P5) were found among coelomocytes and they were studied individually in terms of abundance, morphology, cell viability and cell cycle. P5 showed to have morphological similarities with phagocytes population whereas P3 cell populations seemed to have low metabolic or mitotic activity. Due to male gametes appearance in coelomic fluid samples, its characterization through flow cytometry was possible. Coelomocytes dynamics during regeneration was also assessed during the first day after amputation. There were a few statistically significant differences only in P5 cell population percentage in the first hours (2h, 8h and 24h) after amputation when compared with values for non-amputated animals. The work presented in this dissertation will hopefully contribute to an increase on the available cellular and molecular knowledge about circulating coelomocytes in M. glacialis.
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Pinto, Joana Borrego. "The Mechanism of Centriole Inactivation in Starfish Oocytes." Doctoral thesis, 2015. http://hdl.handle.net/10362/17416.
Full textAbstract:
The centrosome is the major organizing center in a cell, composed by two
centrioles, one mother and one daughter, and surrounded by a pericentriolar
material, which nucleates microtubules. Centriole duplication and segregation is
tightly coupled to cell cycle, which guarantees that centriole number is maintained
over generations. During the somatic cell cycle, a pair of centrioles duplicates,
after which each daughter cell receives a pair, forming a closed cycle. However,
during fertilization, if both cells were to contribute with their pair of centrioles,
gamete fusion would result in the double of the normal centriole number.(...)
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Zeng, Jyun-Ze, and 曾鈞澤. "Study of Starfish Instruction Set Usage for H.264." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/10469655682258980566.
Full textAbstract:
碩士國立清華大學
資訊工程學系
96
As the multimedia technology development, there are more and more video/audio standards. In order to encode or decode different video/audio standards in one system, DSP (Digital Signal Processor) is a good choice to do video/audio process. The speed of DSP is influenced much by the hardware architecture and the efficiency of compiling instructions, and both of them are decided when defining instruction set. In this paper, we profile the instruction usage with different compilers to analyze why some instructions are nearly used in H.264. We use the instruction set and compilers of Starfish DSP, which is developed by TsingHua University and ChiaoTung University to do our experiment.
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CHU, SHIH-CHIEN, and 朱詩倩. "A Creative Discourse on the Documentary Film Starfish Girl." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7nc35m.
Full textAbstract:
碩士國立臺灣藝術大學
電影學系
106
‘I can’t be with you all your life. But I love you with all my life.’ She said. It is hoped that through Starfish Girl, we would get to see the beautiful experiences and the value of life of a unique individual. One should never be labelled, as the labels tend to blur one’s true nature. Gradually stripping off the labels attached to the protagonist, Starfish Girl shows the audience the process of understanding a person from a fresh point of view. Every creation is a result of a journey of awakening in mind and body. The story of a family is often incomprehensible to the others. Starfish Girl also reflects the author’s mind, and by exchanging the inner characters with the protagonist, the author reveals more secrets hidden deep in their hearts. The director has no intention to conceal her intimate interaction with the protagonist as they both appear in this realist film as participants as well as observers. It reveals the life of a highly sensitive person and how a girl, who was forced to be socialised, try to not only understand but also live in harmony with herself. Moreover, by comparing it with two more widely known documentaries, I Love 080 by Yang Li-chou and Small Talk by Huang Hui-chen, we get to see the intricate and complicate relationships disclosed in the films. Furthermore, the author looks into the cases, in which the filmmakers’ self-awareness is influenced and changed by the reality as well as the protagonists’ frankness revealed in the films during her years’ experience in documentary production. Starfish Girl is a 20-minute participatory documentary shot in full HD. It was premiered at the 2017 Taipei Golden Horse Film Festival and was selected as the opening film of the 2017 Formosa Festival of International Filmmaker Awards. Furthermore, it will be screened at various international film festivals and social welfare organisations.
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Rivera, Posada Jairo A. "Pathogenesis of crown-of-thorns starfish (Acanthaster planci L)." Thesis, 2012. https://researchonline.jcu.edu.au/23660/1/01front.pdf.
Full textAbstract:
Outbreaks of the crown-of-thorns starfish, Acanthaster planci (L.), represent one of the most significant biological disturbances on coral reefs, contributing greatly to widespread habitat degradation across the Indo-Pacific. While the cause(s) of outbreaks are still being debated, an equally important question is what causes population declines at the end of outbreaks. Like all echinoderms, A. planci appear to be susceptible to disease, which may explain sudden declines in abundance that have been observed in the wild, as well as providing a unique opportunity to potentially control starfish populations. The purpose of this thesis was to document potentially pathogenic organisms that are normally associated with A. planci, as well as describing the pathological progression of artifially-induced disease, following injection of Thiosulfate-citratebile-sucrose (TCBS).
Thiosulfate-citrate-bile-sucrose (TCBS) agar is a selective media culture that inhibits gram-positive organisms, suppresses coliforms, and allows selective growth of Vibrio bacteria. These bacteria constitute an important part of the bacterial microflora of numerous marine animals, and are also recognized as important pathogens of echinoderms and other estuarine animals. This study showed that injection of TCBS broth into A. planci organs induced disease characterized by skin lesions, loss of body turgor, matting of spines, and accumulation of mucus on spine tips. All starfish then died within 24 hours. TCBS broth promoted population growth of naturally occurring Vibrio spp., leading to an imbalance in natural symbiont communities. Moreover, diseased starfish often infected seemingly healthy A. planci that were either in direct contact or in very close proximity.
To identify potential causative agents of observed disease, and specifically identify all naturally occurring bacteria associated with A. planci, starfish were collected from two distinct locations in the western Pacific; Lizard Island (Great Barrier Reef, Australia) and Guam (USA, Western Pacific Ocean). A polyphasic approach, involving histology, scanning electron microscopy (SEM), biochemical profiling using the bacterial API identification system, PCR amplification and sequencing of 16S rRNA, topA (topoisomerase I) and mreB (rod shaping protein MreB) genes, was used to identify all bacterial isolated. The most significant bacteria isolated from A. planci were V. rotiferianus, V. harveyi, V. owensii, Photobacterium eurosenbergii, V. fortis, V. natriegens with sequences identities of 99%-100% for 16S rRNA, topA, and mreB. Specific bacteria isolated from infected tissues were V. rotiferianus, V. owensii and V. harveyi, which are considered as the most likely causative agents of observed disease.
Histological changes in tissues of A. planci following TCBS injection were assessed using conventional and scanning electron microscopy (SEM). Digestive glands were processed and stained with hematoxylin and eosin (H&E) to describe the histological architecture of the intestinal epithelium. Subsequent comparison of healthy versus infected tissues and Gram stains were carried out to confirm bacterial occurrence on infected tissues, characterize the structural changes induced by bacterial communities in COTS tissues and to determine if the histopathological changes of intestinal tissues were consistent with Vibrio infection. TCBS injections induced marked epithelial desquamation, hypertrophy and hypersecretion of glandular cells, epithelial cell destruction, pyknosis, reduction of thickness and disorganization of connective tissue and associated nerve plexus, presence of bacterial colonies, irregular eosinophilic foci in glandular cells, brush border disruption, atrophy and detachment of intestinal microvilli and cell debris in the lumen. All these changes were attributed to a fulminating systemic dysbiosis and were consistent with Vibrio infections.
Standard histological procedures used to test for the presence of bacteria are often ineffective for marine organisms. As such, this study developed modified techniques to assess the presence of Vibrio bacteria and the preservation of A. planci delicate tissues. Detection of Vibrio bacteria was improved by the (1) use of short washes before fixation (2) the implementation of short cycles in the processing step; (3) embedding samples in agar prior to automated processing. The use of short cycles also decreased the amount of epithelial desquamation of COTS digestive glands. The study contributes to the standardization of histological techniques and biochemical test (API strips) for partial identification of marine bacteria, ensuring more accurate results, improving performance, enhancing reproducibility and increasing efficiency compared to standard operating procedures.
In order to reverse sustained and ongoing degradation of reef habitat, increasing attention is being given to management and control of A. planci outbreaks. Previous control methods, such as hand collecting individual starfish, are extremely labour intensive and often ineffective in either eradicating the coral-feeding starfish or preventing extensive coral loss. As a first step towards assessing whether injections of thiosulfate-citrate-bile-sucrose agar (TCBS) culture medium could be used to eradicate A. planci, especially during population outbreaks, we exposed a range of echinoderms to diseased starfish within a closed environment, and also compared naturally occurring bacteria across these echiinoderms. Vibrio rotiferianus, which was reported as a likely pathogen isolated from experimentally infected A. planci, was recovered from Linckia guildingi. Moreover, several L. guildingi exhibited skin lesions after several days of direct contact with sick Acanthasther planci. However, unlike infected A. planci, which all died within 48 hrs, all L. guildingi starfish fully recovered after 53 days. Further studies need to be carried out to test for cross-infection of Vibrio bacteria isolated from sick A. planci to corals, fishes and other echinoderms.
To better understand the specific effects of thiosulfate-citrate-bile-sucrose agar (TCBS) on A. planci, we tested responses of A. planci to individual components of TCBS culture medium. Four out of nine TCBS chemical ingredients tested induced allergic reactions and death in A. planci. Peptone 10 g l⁻ ¹ and oxgall 8 g l⁻ ¹ induced 100% mortality, while yeast extract and agar induced death in 40% and 20% of starfish, respectively, 48h after injection. Peptone was evaluated at three different concentrations (10g, 5g, and 1g l⁻ ¹). Peptone 10 g l⁻ ¹ induced 100% mortality, peptone 5 g l⁻ ¹ killed 60% of injected starfish, and peptone 1 g l⁻ ¹ induced death in only 20% of starfish, indicating that toxicity of peptone is concentration dependent. Sodium citrate induced moderate mucus production, but disease did not progress and all starfish completely recovered after 52 h. The remaining chemicals tested, sodium thiosulfate, ferric citrate, mix of sodium thiosulfate + ferric citrate, sucrose and sodium chloride did not produce any kind of clinical signs of disease. This study reported four new components that induced disease and death in A. planci. Peptone, oxgall, and yeast are potentially useful in controlling outbreaks because these simple protein extracts can be safer to use compared to previously used noxious chemicals. In addition, lowered concentrations are required to kill A. planci, potentially increasing efficiency and effectiveness of established control programs.
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Wen-Li, Tang. "A Fast, and Flexible Simulation Framework for Starfish DSP Architecture." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709292475.
Full text
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Marques, Vera Cristina J. "Impact of seawater acidification in starfish regeneration: a proteomic approach." Master's thesis, 2015. http://hdl.handle.net/10451/22554.
Full textAbstract:
Tese de mestrado, Biologia Molecular e Genética, Universidade de Lisboa, Faculdade de Ciências, 2015Since the start of the industrial revolution (XVIII century), atmospheric levels of carbon dioxide (CO2) have been rising at a far greater rate than previously experienced, increasing CO2 dissolved in seawater. This process is recognized as ocean acidification and can severely damage calcifying organisms. Since echinoderms have an endoskeleton composed of magnesium calcite, they are predicted to be a sensitive taxa affected by this acidic environment. Taking into account that some species of this filo have a faster regeneration capacity under low pH, analysis of the proteome represents a powerful tool to examine these physiological trait at a molecular level. Trying to strengthen this work on ocean acidification effects, we studied Asterias rubens’ behaviour by observing their preference in choosing a leading arm when submitted to different regeneration time-points (non-regeneration and regeneration after 1, 4, 9 and 14 days) and at two pH environments (control (CpH) – 8.1 and low (LpH) – 7.7). It was concluded that they do not have a preference leading arm before ablation in both pH environments. Although, one day after ablation they drastically decrease the use of the wounded arms, as expected, while the non-amputated arms did not suffer any changes. Furthermore, after nine days subjected to these conditions, it seems that sea stars recovered completely the movement of the amputated arms. Asterosaponins search was also a vital part of this work, since they are known for having important functions in sea stars. We observed that two of the nine asterosaponins detected in the control pH were also detected in low pH samples, and that their concentration decreased, suggesting that acidic pH may alter their biosynthesis. Proteins from both cell-free coelomic fluid (CFF) and radial nerve cord (RNC) were extracted, digested and further analyzed by nano LC-MS/MS. We were able to identify 298 proteins, being 81% of all proteins identified differentially expressed. A surprising finding was the almost absence of stress proteins in an acidic pH environment. In this work, we propose a correlation between an acidic environment and asterosaponins’ biological effects. The decline in diversity and amount of these biomolecules can be caused by already known decreases in respiratory rate and cholesterol absorption. Although, asterosaponins might have positive effects in predation and reproduction. The detected increase in vitellogenin expression seems to be associated with the amplified spawning event induced by the low levels of asterosaponins at acidic pH, thereby also enhancing reproduction.
Desde o início da revolução industrial (século 18) que os níveis atmosféricos de dióxido de carbono (CO2) têm aumentado a um ritmo nunca antes registado (de 280ppm para 380ppm, e espera-se que duplique no final do século), essencialmente devido à emissão de gases com efeito de estufa resultantes de atividades humanas. Como consequência, a concentração de CO2 dissolvido nos oceanos também aumenta, e por sua vez, também a concentração de iões hidrogénio e iões bicarbonato, conduzindo a uma diminuição de pH e de iões carbonato. Este conjunto de reações é designado por acidificação dos oceanos, e pode danificar seriamente o funcionamento de organismos marinhos que de alguma forma utilizam o processo de biocalcificação na sua estrutura corporal. Os equinodermes possuem um endosqueleto composto por calcite de magnésio, têm uma extraordinária capacidade de regeneração, mas também são osmoconformadores. Isto significa que o fluido celómico (CF) que preenche a cavidade corporal é muito semelhante, a nível de composição iónica, ao ambiente externo a que está submetido. Embora também muito idêntico, o pH do fluido celómico é geralmente 0.11-0.58 unidades mais baixo que o pH do exterior, devido a taxas de difusão de CO2 mais ou menos lentas, que podem aumentar ou reduzir a concentração de dióxido de carbono no CF, respetivamente. Por estas razões prevê-se que os equinodermes sejam um taxa sensível a ambientes ácidos. Apesar de se esperar que todas as espécies sejam afetadas de forma negativa, é do conhecimento científico que algumas espécies deste filo crescem e desenvolvem-se mais depressa quando expostas a pH ácido, enquanto outras apresentam diminuição de metabolismo ou redução da expressão proteica global. Considerando a diversidade incongruente de resultados publicados, e tendo a estrela-do-mar comum A. rubens como espécie-alvo, realizámos análises de expressão proteica para estudar estas observações fisiológicas de uma perspetiva molecular. Por forma a ter um estudo mais completo sobre o efeito da acidificação nesta espécie, observámos estrelas-do-mar sob diferentes tempos de regeneração (não-amputação e amputação após 1 dia, 4, 9 e 14) submetidas a dois pHs (controlo (CpH) – 8.1 e ácido (LpH) – 7.7), com o propósito de determinar com que braço preferencialmente elas iniciavam a deslocação. Os braços escolhidos para amputação foram os mais próximos à madreporita. As estrelas-do-mar não apresentaram preferência no braço ‘líder’ antes de amputadas e sob CpH, o que não é consistente com resultados já publicados. No entanto, como esperado, os braços amputados apresentaram uma diminuição do número de movimentos um dia após a regeneração ser imposta, enquanto o número de movimentos dos braços não-amputados permaneceu igual. Após nove dias os movimentos dos braços amputados foram restabelecidos para os valores iniciais (sem amputação), e por isso considerámos que as estrelas recuperaram o movimento normal dos braços. É vantajoso para a estrela-do-mar que este movimento seja restabelecido o mais rapidamente possível, para que possa, entre outros, alimentar-se e/ou fugir de possíveis predadores. Para estudar os fatores moleculares que possam estar envolvidos em resposta a uma futura diminuição do pH dos oceanos, foram recolhidos dois tipos de amostra: fluido celómico (dois pHs e 15 dias pós-amputação), e nervo radial (RNC; dois pHs e não-amputação; dois pHs e 15 dias pós-amputação). O CF foi centrifugado para que fossem retirados os coelomócitos, designando-se desta forma fluido celómico livre de células (CFF). Este fluido foi submetido a centrifugação e ultrafiltração para separar a fração de alta massa molecular (proteínas) da fração de baixa massa molecular. Esta última contém asterosaponinas, moléculas que são conhecidas por terem funções importantes a nível de sinalização química mas também a nível digestivo e reprodutivo, e que por isso considerámos essenciais neste estudo. Esta fração foi então sujeita a extração de fase sólida (SPE) com diferentes eluições de acetonitrilo e ácido fórmico para isolamento das asterosaponinas, e posteriormente analisadas por ESI-MS. Os dados foram adquiridos por um espectrofotómetro linear ion trap mass Thermo Finnigan LTQ, controlado pelo software Xcalibur v 2.0, também usado na análise dos espectros resultantes da leitura das amostras. Todas as asterosaponinas investigadas estavam presentes no pH controlo, mas apenas duas delas foram detetadas em estrelas-do-mar submetidas a pH ácido. Para além disto, as suas concentrações diminuíram em pH ácido. Tendo em conta que a A. rubens apresenta um baixa taxa de respiração após 27 dias exposta a pH 7.7 do que quando submetida a pH 8.1, podemos assumir que este decréscimo irá alterar a disponibilidade de ATP, e consequentemente comprometer a biossíntese de asterosaponinas. Por sua vez, a diminuição destas biomoléculas poderá ter efeitos negativos a nível digestivo, através da redução da absorção de colesterol, mas poderá também ter efeitos positivos ao nível da predação. As proteínas do CFF foram extraídas e precipitadas com recurso a ácido tricloroacético e beta-mercaptoetanol, enquanto as proteínas do RNC foram extraídas e precipitadas recorrendo a azoto líquido e a um buffer suplementado com SDS, Tris-HCl, DTT, um cocktail anti-protease e PMSF. A quantificação das proteínas do CFF e RNC foi feita com recurso ao QuantiPro BCA Assay KIT 0.5-30μg/mL protein, e a digestão, embora diferente, teve como base o uso de redutores de pontes persulfureto (DTT e TCEP), iodoacetamida para alquilação das cisteínas e tripsina para quebrar a proteína em péptidos. As amostras digeridas de ambos os tecidos foram analisadas por nano LC-MS/MS. Foram identificadas 213 proteínas no RNC, mas apenas uma estava presente em todas as condições estudadas. Por esta razão, podemos concluir que o procedimento experimental deve ser otimizado. A análise do CFF permitiu identificar 298 proteínas, das quais 19% eram comuns às duas condições de pH. De acordo com estes resultados, 81% de todas as proteínas identificadas estavam diferencialmente expressas. Comuns a ambas as condições de pH, e como esperado, foram detetadas actinas, tubulinas e ubiquitinas. A quantificação realizada permitiu observar um aumento de expressão significativo apenas em 2 proteínas no pH ácido: alfa-tubulina e vitellogenina 1. A primeira está envolvida na formação do citoesqueleto, e por isso, será importante numa fase de rápida proliferação celular. A segunda proteína é responsável pelo transporte de lípidos para os oócitos, e o seu aumento de expressão parece aumentar o número de eventos de desova em estrelas-do-mar. Os baixos níveis de asterosaponinas presentes em pH ácido também parecem favorecer este acontecimento, aumentando desta forma, o sucesso reprodutivo. Com base em estudos recentes realizados em corais e em zooplâncton, previa-se um aumento na expressão de proteínas de stress em condições de pH ácido. No entanto, no presente estudo, as estrelas-do-mar submetidas a esta condição de pH, exibiram apenas uma proteína de stress. Para melhor compreensão dos efeitos da acidificação dos oceanos em cada uma das proteínas aqui identificas, será necessário realizar estudos mais detalhados para avaliar o impacto biológico da expressão proteica diferencial que observámos.
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Keesing, John Kenneth. "Feeding biology of the crown-of-thorns starfish, Acanthaster planci (Linnaeus)." Thesis, 1990. https://researchonline.jcu.edu.au/24112/1/01front.pdf.
Full textAbstract:
Field and laboratory studies were undertaken to examine aspects of the feeding biology of Acanthaster planci (Linnaeus) in the central region of the Great Barrier Reef. Day and night surveys were carried out to examine feeding periodicity, and measurements of feeding and movement rates were made by monitoring tagged animals. Diet and feeding preferences were assessed in the field and laboratory studies were undertaken to assess the importance of nutritional quality of food in governing feeding preferences.
Small starfish feed nocturnally and remain cryptic during the day. Large starfish are primarily diurnal feeders and are rarely cryptic. Starfish are most mobile around dawn and dusk. It is proposed that the observed behaviour patterns have evolved as a predator avoidance strategy with large starfish achieving a refuge in size. These size dependent behavioural patterns, together with changes in population size structure, have important implications for assessing the numbers of starfish remaining undetected in A. planci survey and control programs.
Rates of movement in A. planci are dependent on food availability. These are about 1 m.day¯¹ in areas of high coral cover and about 4 m.day¯¹ in patches of low coral cover. Starfish in extensive areas of depleted coral cover move at rates of about 10 m.day¯¹.
Feeding rates in A. planci are dependent on starfish size and season, being greatest prior to the summer spawning season. Starfish at Davies Reef in summer averaged 1.5 feeds per day, killing about 300 cm² of coral cover or 15 g DW (dry weight) of soft coral tissues per day. Biomass utilization is about 4 g DW or 90 kJ per day. Feeding rates in winter are about half those of summer. Feeding rate measurements were applied to ecological and physiological considerations in A. planci. The magnitude of changes to coral communities in terms of area and biomass of coral killed during A. planci outbreaks is substantial. Outbreaking populations (ca. 100000 starfish per reef) will kill thousands of square metres of coral; equivalent to hundreds of kilograms dry weight of soft tissues per day. Feeding rate measurements were used to predict a threshold population level of about 1000 starfish per km² which would cause minimal damage to coral communities on the Great Barrier Reef. It is evident that large scale fluctuations in A. planci populations can occur without causing extensive coral mortality. Comparison of physiological requirements with feeding rates confirms that, despite increased feeding rates in large adults, growth is determinant and senility of large A. planci can be expected. As suggested in previous studies, this occurs because as the starfish grows its capacity to feed cannot meet the demands of metabolising tissue.
The diet of A. planci is almost exclusively scleractinian corals (90 - 95 %). Non-coral prey are taken in increasing abundance in areas of low coral availability. A. planci exhibits strong feeding preferences in both the field and the laboratory. The scleractinian families Acroporidae and Pocilloporidae are most favoured. Non-preferred prey are taken in increasing abundance in areas depleted of favoured species. The nutritional value of different species of coral prey was assessed and related to the observed feeding preferences. Several attributes may affect a coral species suitability as food; these are surface area complexity, biomass, nutritional value and abundance. Prey preference was more closely related to a general assessment of food suitability than to the absolute predictions of optimal diet theory. It is proposed that the ability to feed more efficiently on certain prey types is the most important factor giving rise to observed and published patterns of prey selection.
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Lin, Shin-Jung, and 林欣榮. "Studies on Toxins and Their Sources of Torafugu, Ggoby and Starfish in Taiwan." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/15853684082864384826.
Full textAbstract:
博士國立海洋大學
食品科學系
87
ABSTRACT In the recent decade, food poisoning incidents due to marine toxins such as tetrodotoxin (TTX) and paralytic shellfish poison (PSP) were sporadically occurred in Taiwan. The causative fish and shellfish of these food poisoning incidents were mainly puffer fish, followed by purple clam, gastropod Nassariidae and goby fish. In order to have a clearly understanding of the toxicity, toxin and toxin source of those toxic fish and shellfish, the toxicological studies of cultured puffer Takifugu rubripes, goby fish and starfish Astropecten scoparius, the possible prey of toxic gastropods, have been undertaken. To monitor toxicity of cultured puffer, T. rubripes specimens were monthly collected from two aquacultural farms in Ilan County and one farm in Taipei County from November 1996 to October 1997. These specimens were dissected into various parts, and their toxicity was determined by the standard tetrodotoxin bioassay. All specimens collected from Ilan County were non-toxic (<10 MU/g), while the specimens collected from Taipei County during the period from January to March 1997 showed certain toxicity in the ovary and liver. The toxicity was as follows: 105 ± 9 (mean ± S.E.) MU/g ovary and 13 ± 3 MU/g liver in January, 88 ± 12 MU/g ovary in February, and 253 ± 55 MU/g ovary and 17 ± 6 MU/g liver in March. The highest toxicity in ovary and liver was 624 MU/g and 119 MU/g, respectively. Further, among ten specimens of the flatworm Stylochus orientalis collected from the Taipei''s farm in February 1997, four worms showed a low toxicity (1-3 MU/specimen). Flatworms contained TTX-related substances as analyzed by HPLC and GC-MS. In the same period of time, the microflora of the digestive gland in the puffer, aquacultural water and sediment were examined. The results showed that the predominant genus was Vibrio and comprised 37-65% and 40-65% of the microflora incubated aerobically and facultative anaerobically, respectively. Furthermore, HPLC and GC-MS analyses demonstrated that some of the bacteria isolated, such as Aeromonas sp., Pseudomonas vesicularis, V. alginolyticus, V. parahaemolyticus and Vibrio sp. produced TTX and/or its related substances. On the other hand, two paralytic food poisoning incidents due to ingestion of two kinds of fishes included goby Yongeichthys nebulosus and Sillago japonica occurred in Kaohsiung Prefecture in February 1997 and Kaohsiung City in March 1998. After TTX bioassay, the causative fish was identified as Y. nebulosus. The toxicity of retained goby specimens ranged from 2,860-7,650 and 276-950 mouse units (MU), respectively. The toxins were partially purified from the methanolic extracts of toxic fishes by ultrafiltration and Bio-Gel P-2 column chromatography. Cellulose acetate membrane electrophoresis and high performance liquid chromatography analyses demonstrated that the compositions of toxins were tetrodotoxin and anhydrotetrodotoxin. These results indicated that goby fishes inhabited in the estuaries and the downstream portions of rivers and the coast area in Taiwan might contain toxins and cause food poisoning. At the same time, the intensive investigation of toxic goby was also performed from August 1996 to July 1998. More than 300 specimens of twelve species of goby were collected from fifteen locations and examined for toxicity. The specimens of three goby Y. nebulosus, Prachaeturichtys palynema and Radigobius caninus collected from Pingtung, Penghu, Kaohsiung, Miaoli, and Hsinchu were found to contain toxins. The most toxic goby was Y. nebulosus, and its frequency of being found toxic was 93%. Specimens collected from Pingtung Prefecture were most toxic, the toxicity was over 1,000 MU/specimen. The seasonal variation of toxicity in Y. nebulosus was found that the highest toxicity was in winter with the value of 4,998 MU/specimen. The toxin was partially purified from methanolic extract of each toxic goby species by Diaflo YM-1 membrane ultrafiltration and Bio-Gel P-2 column chromatography. HPLC and electrophoresis analyses indicated that each toxin was composed of tetrodotoxin and anhydrotetrodotoxin. In order to elucidate relationship between the toxicity and microflora of the intestine in the goby and environmental materials, the goby Y. nebulosus specimens, seawater and sediment were collected from Penghu Prefecture in September 1998 to assay the aerobic microflora in intestines and environmental materials. The results showed that the predominant genus of goby intestines was Vibrio comprising 46% of the microflora, with V. alginolyticus as the major isolate. The predominant genus in seawater was Pasteurella that comprised 47% of the microflora. Moreover, the predominant genera of sediment were Flavobacterium and other unidentified bacteria that comprised 51% of the microflora. Furthermore, HPLC, UV and GC-MS analyses demonstrated that some isolated bacteria, such as Aeromonas sp., Pseudomonas sp. and V. alginolyticus, could produce TTX and/or its related substances. As known, same gastropods inhabiting in the coastal waters in Pingtung Prefecture were found to contain TTX and paralytic shellfish poison (PSP). To elucidate the food chain of TTX and PSP in these toxic gastropods, the toxicity of marine animals inhabiting in the coastal waters of southern Taiwan was examined. It was first found that a starfish Astropecten scoparius showed lethal potency. Hence, paralytic toxicity was seasonally detected in every 10 specimens of the starfish A. scoparius from Pingtung in Taiwan from January 1996 to December 1997. The highest toxicity of specimen collected in 1996, expressed as TTX, was 5,938 MU. The average toxicity of these specimens was 1,679 MU. But, the pattern of starfish toxicity in 1997 was somewhat different from that collected in 1996. The average highest specimen toxicity was 16,821MU found in November 1997. The toxin obtained from specimens collected in February, April, July and November 1997 was partially purified by YM-2 membrane ultrafiltration and Bio-Gel P-2 column chromatography. Electrophoresis, HPLC and GC-MS analyses showed that the toxins of starfish obtained from April 1997 were composed of 88% TTX and 12% PSP. The toxin of starfish collected in the other three months was found to be TTX only. Furthermore, in order to elucidate the intoxification mechanism of TTX in starfish A. scoparius, the compositions in the digestive gland of starfish were examined. It was found that the compositions in the digestive gland of less toxic starfish were mainly bivalves with Veremolpa scabra as the major species. As to the compositions in the digestive gland of more toxic specimens, collected in October and November 1997, were mainly species of gastropods, Umborium suturale and Natica pseustes. The toxicities of U. suturale, V. scabra and N. pseustes found in digestive gland of starfish were 65 MU/g, 33 MU/g and 28 MU/g, respectively. The toxins in these three mollusks were TTX and anh-TTX. The other specimens of U. suturale and N. pseustes, re-collected from the coastal waters of Pingtung Prefecture, were also found to be toxic with average toxicity value of 20±3 MU/g and 77±7 MU/g, respectively. However, V. scabra specimens were found to be nontoxic. It indicated that the starfish A. scoparius might accumulate the toxin from V. scabra and N. pseustes. Furthermore, to elucidate relationship between the toxicity and microflora in starfish viscera, the starfish A scoparius inhabiting in the coastal waters of Pingtung Prefecture was collected in November 1997 for determination of aerobic and facultative anaerobic microflora in the viscera. The results showed that the predominant bacterial genus in the viscera and other parts was Vibrio that comprised 38% and 47% of the aerobic microflora, respectively. The major isolates were V. alginolyticus and V. parahaemolyticus. On the other hand, the predominant genus of viscera was also Vibrio that comprised 51% of facultative anaerobic microflora. Moreover, HPLC, UV and GC-MS analyses demonstrated that bacteria isolated from aerobic microflora, such as Aeromonas sp., V. alginolyticus A011, A018 and A035, and V. parahaemolyticus A026 and A047 could produce TTX and/ or its related substances. TTX-producing bacteria were also found in the facultative anaerobic microflora, such as Aeromonas sp., Alcaligenes sp., Pasteurella multocida, V. alginolyticus and V. parahaemolyticus. In order to compare the TTX-producing ability of bacteria incubated aerobically and facultative anaerobically, two strains of TTX-producing bacteria V. alginolyticus AF089 and V. parahaemolyticus AF067 were enriched in BHI broth aerobically and facultative anaerobically, and then the amount of toxin was analyzed. The results showed that both strains grew better and produced more toxin in facultative anaerobic incubation than aerobic condition. Moreover, the TTX-producing ability of V. alginolyticus AF089 was much better than that of V. parahaemolyticus AF067 incubated either in aerobic or in facultative anaerobic conditions. In conclusion, Taiwanese cultured puffer T. rubripes, goby Y. nebulosus, and starfish A. scoparius all showed an ability to accumulate high toxicity of TTX or PSP. Moreover, the toxin sources of these three aquatic animals might be closely related to food chain and the intrinsic TTX-producing bacteria.
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Burgoyne, David L. "Chemical studies of metabolites from Pacific Ocean marine sponges and the starfish Dermasterias imbricata." Thesis, 1992. http://hdl.handle.net/2429/2251.
Full textAbstract:
A study of biologically active extracts of several Pacific Ocean marine sponges has led to the isolation of eight new and nine previously known natural products. The structures of the compounds were determined by a combination of spectroscopic data analysis and chemical interconversions. In addition, the partial synthesis of imbricatine (3), a cytotoxic metabolite of the starfish Dermasterias imbricata, was accomplished. Crude extracts from the sponge Petrosia contignata collected in Papua New Guinea showed potent cytotoxicity against the murine leukemia L1210 cell line. These extracts yielded contignasterol (24), a new highly oxygenated steroid that inhibited histamine release from rat peritoneal mast cells with an IC50 of 0.8 gM, and petrolactone (37), a new sesquiterpene with the drimane carbon skeleton. The structure of contignasterol, which contains the "unnatural" 1413 proton configuration and a cyclichemiacetal functionality in its side chain, was elucidated via spectroscopic studies of its tetraacetate and its reduction product penta acetate. A known polybrominated diphenylether 41 accounted for the cytotoxicity of the crude extracts. The sponge Acanthella sp. yielded ten sesquiterpenes, four of which were new. Compounds 80-87, 89 and 90 contained isonitrile, isothiocyanate, formamide, carbamate and chloride functional groups. In addition, violacene (88), a halogenated monoterpene previously isolated from the red algae Plocamium violaceum, was isolated from the sponge extracts. The Northeastern Pacific sponge Neoesperiopsis digitata yielded neoesperlactone (96), an eighteen carbon fatty acid derived y-lactone. In addition, the major aromatic component was found to be identical by tic and 1H NMR comparison to commercially obtained p-hydroxybenzaldehyde. The study of the Papua New Guinea sponge Pseudaxinella massa led to the identification of a novel cyclic heptapeptide pseudaxinellin (103) which contained standard protein amino acid residues with the L configuration. The study of two species of marine sponges, Ptilocaulis trachys and Amphimedon sp. , collected at Enewetak lagoon, led to the isolation and identification of the depsipeptide majusculamide C (104)which had previously been found in the blue green alga Lyngbya majuscula collected at Enewetak. The synthetic confirmation of the tetrahydroisoquinoline substructure of the starfish metabolite imbricatine (3) was accomplished using a Pictet-Spengler reaction to couple the starting materials 3-(3,5-dihydroxyphenyl) alanine methyl ester (143) and sodium 3-(4-benzyloxyphenyl) glycidate (141). A series of deprotections and protections on the resulting racemic benzyltetrahydroisoquinoline led to a product 140 that was identical by 1H NMR and mass spectroscopic analysis to the protected Raney nickel reduction product of imbricatine (3).
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Maghsoodi, Bita. "The role of two extracellular matrix glycoproteins in the development of the starfish Pisaster ochraceus." Thesis, 2005. http://hdl.handle.net/2429/17198.
Full textAbstract:
Cell-extracellular matrix (ECM) interactions are crucial for the development of
the embryos. ECM provides an environment through which cells can migrate, and a
substratum for their adhesion and guidance. In this study, cell-ECM interactions were
investigated in early morphogenesis of the starfish Pisaster ochraceus. Two monoclonal
antibodies (HL-1 and PM-2) generated against ECM components of the hyaline layer and
the blastocoel, respectively, were used to identify, localize and characterize these
components.
Immunocytochemical studies using HL-1 antibody shows that HL-1 epitope is
synthesized by the ectodermal cells from the early blastula stage to the bipinnaria stage,
and is secreted into the hyaline layer. The epitope was first observed around the Golgi
apparatus and deglycosylation of the epitope resulted in the loss of its antigenicity,
implicating HL-1 as a glycoprotein. When embryos were incubated in seawater
containing an antibody to block the function of the HL-1 antigen, show that the hyaline
layer was exfoliated. The results indicated that this E CM component may play a role in
development and maintenance of the structural integrity of the hyaline layer.
Furthermore, embryos exposed to seawater containing the HL-1 antibody were unable to
swim and failed to develop a proper GI tract. This indicated that the HL-1 epitope is
necessary for ciliary activity and GI tract development. PM-2 epitope also showed the characteristics of a glycoprotein and it too
appeared to be important in the development of starfish embryos. Immunofluorescence
and immunogold studies showed that the PM-2 epitope was present in the cortical
granules and it was synthesized by the early blastomeres through to the bipinnaria stage.
These studies also showed that the PM-2 epitope was concentrated in the blastocoel, in
the hyaline layer and in the lumen of the Gl tract. Functional blocking experiments using
anti-PM-2 antibody revealed that the PM-2-perturbed embryos contained very few
migratory mesenchyme cells and failed to develop a proper Gl tract. This indicated that
the PM-2 epitope may play a role in mesenchyme cell migration, development of the Gl
tract and overall growth ofthe embryo.Medicine, Faculty of
Graduate
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Cowan, Zara-Louise. "Predation on the early life stages of the crown-of-thorns starfish (Acanthaster cf. solaris)." Thesis, 2017. https://researchonline.jcu.edu.au/51582/1/51582-cowan-2017-thesis.pdf.
Full textAbstract:
Population outbreaks of crown-of-thorns starfish (CoTS, Acanthaster spp.) represent one of the most significant biological disturbances on tropical reefs, contributing to widespread and significant coral depletion throughout the Indo-Pacific. On the Great Barrier Reef, for example, CoTS outbreaks account for 42% of recorded coral loss from 1985-2012. Despite their importance, the demography and biology of CoTS is poorly understood, especially in terms of understanding the potential causes(s) of population outbreaks. For effective management of outbreaks, it is critical to understand the factors that both promote sudden population explosions, and that normally regulate CoTS populations at very low densities.
Predatory release has long been considered a potential contributor to population outbreaks of CoTS, initiating extensive searches for potential predators that may consume large numbers of these starfish at high rates, but are also vulnerable to over-fishing. As such, most research into predation on CoTS has focused on large reef fishes and invertebrates capable of capturing and consuming adult starfish. By contrast, consideration of smaller-bodied and potentially cryptic predators that could consume gametes, larvae or newly settled juveniles has received little attention. Thus, the overarching objective of this research was to explore predation on the early life stages of CoTS by two suites of predators: planktivorous damselfishes, and benthic invertebrates. Specifically, this research compares the predatory responses of a range of damselfishes, testing for interspecific variation in their potential importance as predators of CoTS eggs and larvae, and tests the influence of benthic predators on microhabitat preferences and settlement success of CoTS.
Although CoTS are equipped with anti-predator chemicals at every stage of their life cycle, the effectiveness of these chemicals in deterring predators is increasingly being questioned. In particular, planktivorous damselfishes, which are highly efficient zooplankton predators, may be capable of consuming the early life stages of CoTS in vast quantities, potentially reducing the reproductive and settlement success of this starfish. Nine planktivorous damselfishes are shown to readily consume food pellets that contain concentrations of up to 80% CoTS eggs, however all fishes exhibit increasing rejection of food pellets that contain higher proportions of eggs. This suggests that chemicals within the eggs are unpalatable, however palatability thresholds varied greatly among the damselfishes, indicating species that are likely to be more important as predators of CoTS eggs (or larvae). Notably, Amblyglyphidodon curacao consumed food pellets comprising 100% starfish eggs 1.5 times more than any other fish species, and appeared largely insensitive to increases in the concentration of starfish eggs. However, after standardising for size, smaller species, such as Pomacentrus moluccensis and Chrysiptera rollandi, consume a disproportionate amount of pellets comprising high proportions of starfish eggs and could be particularly important in regulating larval abundance and settlement success of CoTS.
To further explore the role of damselfish predation in potentially structuring CoTS populations, the feeding behaviour and functional responses of eleven damselfishes were examined by offering individual damselfish with increasing concentrations of larvae of either CoTS or Linckia laevigata (a co-occurring species with morphologically similar larvae). Consumption rates of CoTS larvae by damselfishes were independent of predator size, however when pooling across all predator species there was a significant negative relationship between predator size and consumption rate of L. laevigata. Most predatory species (all except A. curacao and Pomacentrus amboinensis) exhibited a Type II functional response, whereby the increasing feeding rate decelerated with increasing prey density. In addition, Acanthochromis polyacanthus and A. curacao, consumed larval CoTS at a greater rate than for L. laevigata, and consumption capacity of CoTS by Dascyllus aruanus was extremely high (158 larvae h⁻¹). These data reveal that a wide range of planktivorous fishes will prey upon CoTS larvae (at least when offered as the only available prey), and suggest that planktivorous damselfishes may have the capacity to buffer against population fluctuations of CoTS.
Predation rates on specific prey species can vary depending on availability of alternative prey. In the extreme, predators may exhibit prey switching, whereby they preferentially feed on the most abundant, or most readily accessible, prey species. Defining predatory responses to changes in prey availability is critical to evaluating the ability of predators to regulate prey populations. To extend the single-prey experiments, exploring prey preference and testing for prey switching, nine damselfishes were simultaneously offered varying relative densities of CoTS and L. laevigata larvae. Again, feeding responses varied among the damselfishes. While no evidence of prey switching was detected, five damselfishes (A. polyacanthus, A. curacao, Dascyllus reticulatus, P. amboinensis and P. moluccensis) exhibited increased consumption of CoTS larvae with increasing prey density, despite the availability of alternative prey. Moreover, Abudefduf sexfasciatus and P. amboinensis exhibited preference for CoTS larvae over L. laevigata larvae. These findings suggest that planktivorous damselfishes will consume CoTS larvae even in the presence of alternative, and presumably more palatable, prey. Further, most of the damselfishes responded to increasing larval CoTS densities by increasing theirprey intake, suggesting that they could be important in regulating successful settlement and recruitment, especially at low (non-outbreak) densities.
CoTS are also expected to suffer high levels of predator-induced mortality during settlement, as they transition to living in the benthic habitat and are exposed to an entirely new suite of predators. Accordingly, these larvae might be expected to exhibit behavioural adaptations, which serve to reduce predation at this critical stage in their life history. Pairwise choice experiments revealed that late stage brachiolaria larvae are able to detect predators in the substrate and where possible, will preferentially settle in microhabitats without predators. Settlement assays (without choices) revealed that larvae do not necessarily delay settlement in the presence of predators, but high levels of predation on settling larvae by benthic predators significantly reduce the number of larvae that settle successfully. Taken together, these results show that CoTS are highly vulnerable to benthic predators during settlement, and that variation in the abundance of benthic predators may significantly influence patterns of settlement and recruitment.
This research shows that eggs, larvae and newly settled CoTS are readily consumed by a wide range of coral reef organisms, such that predation during and soon after settlement may represent a significant bottleneck in their life history. Unfortunately, many of the predators that consume these early life stages are vulnerable to reef degradation and coral loss. Thus it is possible that anthropogenic degradation of reef ecosystems is contributing to the incidence and/or severity of CoTS outbreaks by mediating the abundance of these potentially key predators. Although it seems unlikely that predatory release in and of itself could account for initial onset of CoTS outbreaks, reducing anthropogenic stressors that reduce the abundance and/or diversity of potential predatory species represents a "no regrets" management strategy, but will need to be used in conjunction with other management strategies to prevent, or reduce the occurrence, of CoTS outbreaks.
48
Okaji, Ken. "Feeding ecology in the early life stages of the crown-of-thorns starfish, Acanthaster planci (L.)." Thesis, 1996. https://researchonline.jcu.edu.au/27235/1/27235_Okaji_1996_thesis.pdf.
Full textAbstract:
Evaluating factors affecting survivorship during early life stages of the crown-of-thorns starfish, Acanthaster planci (L.), is essential to understand mechanisms of the population outbreaks. The objective of this study was to determine whether food availability is a crucial factor controlling the growth, development and survival of the larvae and the juveniles of A. planci. This was done through field and laboratory studies on their feeding ecology.
Larvae were reared in an in situ rearing apparatus to assess the relative importance of different natural foods. This apparatus was designed to create different food environments inside its chambers by progressive filtration: 100 µm mesh filtered seawater (100 µm FSW), 1 and 0.2 µm filtered seawater (1 µm FSW and 0.2 µm FSW), and activated charcoal filtered seawater (ACF). In a preliminary rearing experiment, larvae successfully developed through to metamorphosis in 100 µm FSW, 1µm FSW and 0.2 µm FSW, but not in ACF. These results suggested that adequate amount of particulate and dissolved foods was available in ambient seawater to support larval development. However, subsequent deployment of the apparatus revealed that chlorophyll a concentrations inside the rearing chambers, except for ACF, were significantly higher than in ambient seawater. The initial objective was not achieved, because this apparatus created enriched food environments. The importance of food limitation needed to be assessed by means other than in situ larval rearing.
To test food limitation, larvae were reared in freshly collected and coarse filtered seawater, and the same seawater treated by further filtration or food enrichment. Larvae were also reared in nutrient enriched seawater (NES), where the concentration of natural phytoplankton was elevated by adding nutrient solution and incubating for a few days. Larvae reared in 2 µm filtered seawater consistently failed to develop. Larval development and survival were nil or significantly slower in the coarse filtered seawater than in the same seawater enriched with cultured microalgae, dissolved free amino acids (DFAA), or in NES. When larvae were reared in NES having different fixed phytoplankton (chlorophyll a) concentrations, a change from modest larval survival to optimal survival through rapid development occurred between 0.5 and 0.8 µg ^(L-1). This range is slightly higher than typical chlorophyll a levels found in the Great Barrier Reef (GBR) waters.
These results altogether suggest that, if total chlorophyll a concentration is used as the sole index of food availability, larvae are usually food limited. However, there are also the factors of particle size that the larvae can filter and ingest, and the contribution of dissolved organic matter (DOM) to the larval nutrition.
The feeding rates of larvae on naturally-occurring particles, plastic beads of different sizes or cultured microalgae were measured to determine the dependence of larval feeding on particle size. The clearance rate of larvae feeding on eukaryotes (3.6-4.6 µm mean equivalent spherical diameter) was 118-358µL larva^(-1 h-1), while the rate when feeding on cyanobacteria (1-2 µm) was 0.035-0.349 µL larva^(-1 h-1). This was despite ambient conditions where cyanobacteria were magnitudes more abundant, showing that larvae selectively feed on nanoplankton (> 2 µm). Clearance rates of cultured microalgae were significantly higher than those of 6 and 20 µm beads, suggesting that feeding is also dependent on chemical properties of food particles.
The net uptake rates of three DFAA, alanine, glutamic acid and arginine, by larvae were measured to estimate their potential contribution on the larval nutrition. Larvae selectively took up alanine (neutral amino acid) over glutamic acid (acidic) and arginine (basic). The net uptake rates of alanine from the initial concentrations of 148, 150 and 465 nM were 8.9, 15.4 and 36.9 pmol larva(-1 h-1), respectively. The alanine uptake at these substrate concentrations could account for 13.1, 23.1 and 55.3 % of the basic metabolic demand of a larva. Neutral DFAA are a potentially important food source, however, their ambient concentrations (trace - ca. 200 nM) generally seem too low to make a significant contribution to the larval nutrition.
Post-metamorphic juveniles were reared in the laboratory and deployed in the field to test the effect of different coralline algae on growth rates. Juveniles feeding in the laboratory on the coralline alga, Lithophyllum insipidium, grew significantly faster than those feeding on the algae, Neogoniolithon clavacymosum and Lithothamnium pseudosorum. The estimated growth rate of juveniles in the field was relatively high, compared to rates in the laboratory, and was similar to the previous growth data obtained with animals feeding on multi-specific natural food. Because a wide range of algae is accessible to juveniles, food quality may not influence growth rate and hence survivorship in relatively shallow reef environments.
Phytoplankton and DFAA were identified as potential food sources for larvae. Comparison between potential contributions of these food sources to the larval nutrition, in terms of ambient concentrations and the ability of larvae to utilise these food sources, indicates that nanoplankton are the major food. Because the availability of phytoplankton (chlorophyll a concentration) in the GBR waters is lower or marginal to the critical range, larvae are usually food limited. Food limitation is likely to have a significant impact not only on larval survival by extending the vulnerable planktonic period, but also on juvenile survival by reducing juvenile size at metamorphosis. This study confirms that food is a crucial environment factor controlling the growth, development and survival of A. planci larvae in the GBR waters.
49
Caballes, Ciemon Frank. "Environmental influences on the reproductive biology and early life history of the crown-of-thorns starfish." Thesis, 2017. https://researchonline.jcu.edu.au/51628/1/51628-caballes-2017-thesis.pdf.
Full textAbstract:
Population outbreaks of the coral-eating crown-of-thorns starfish, Acanthaster spp., often result in extensive coral mortality with highly extended recovery times, thereby contributing significantly to sustained and ongoing declines in coral cover across the Indo-Pacific. Long-term or permanent solutions depend on filling crucial gaps in our knowledge of the biology of crown-of-thorns starfish, particularly its reproductive biology and early life history, to understand the initiation and spread of outbreaks. Populations of crown-of-thorns starfish are typically predisposed to major fluctuations due to inherent properties of their life history such as high fecundity, high fertilization rates, and short generation times. However, densities vary enormously in space and time, pointing to major fluctuations in reproductive success. The overarching question therefore is: what limits recruitment success in crown-of-thorns starfish and which stages or processes in its life cycle are most vulnerable to these constraints? Small environmental perturbations that trigger life-stage-specific responses can have pronounced effects on recruitment success and hence, on the dynamics of adult populations. My research explored the role of environmental factors on (1) gametogenesis and reproductive timing; (2) spawning induction and synchronicity; (3) fertilization and embryonic development; and on (4) larval vitality, in relation to maternal provisioning and larval nutrition.
To assess gametogenic activity and reproductive timing in crown-of-thorns starfish, intensive and extensive sampling of crown-of-thorns starfish from Australia's Great Barrier Reef (GBR) was conducted. This study revealed marked inter-annual variation in reproductive timing and output, possibly depending on local environmental conditions. In the first sampling season (September 2013 to March 2014), there was only minor and repeated spawning that occurred over a highly protracted spawning period, while in the second sampling season (September 2014 to March 2015), there was evidence of comprehensive and synchronous spawning by crown-of-thorns starfish.
I then examined the role of environmental and biological cues for spawning in crown-of-thorns starfish. For gonochoric and broadcast spawning species such as crown-of-thorns starfish, spawning synchrony is fundamental for achieving high rates of fertilization. Highly synchronized gamete release within and among distinct populations is typically the result of the entrainment of neurohormonal endogenous rhythms by cues from the environment. In this study, I conducted multiple spawning assays to test the effects of temperature change, reduced salinity and nutrient enrichment of seawater, phytoplankton, gametes (sperm and eggs), and the combined effect of sperm and phytoplankton on the likelihood of spawning in male and female crown-of-thorns starfish. I also investigated sex-specific responses to each of these potential spawning cues. I found that (1) abrupt temperature change (an increase of 4°C) induced spawning in males, but less so in females; (2) males often spawned in response to the presence of phytoplankton, but none of the females spawned in response to these cues; (3) the presence of sperm in the water column induced males and females to spawn, although additive and synergistic effects of sperm and phytoplankton were not significant; and (4) males were more sensitive to the spawning cues tested and most likely spawn prior to females. These results suggest that environmental cues act as spawning 'inducers' by causing the release of hormones (gonad stimulating substance) in sensitive males, while biological cues (pheromones) from released sperm, in turn, act as spawning 'synchronizers' by triggering a hormonal cascade resulting in gamete shedding by conspecifics. Given the immediate temporal linkage between the timing of spawning and fertilization events, variability in the extent and synchronicity of gamete release will significantly influence reproductive success and may account for fluctuations in the abundance of crown-of-thorns starfish.
Following spawning, larval stages develop in the water column for at least 14-16 days, where environmental factors could constrain survivorship and effective development. The persistence and success of marine invertebrate populations is fundamentally dependent upon larval survival and settlement; hence the variable sensitivity of planktonic stages and processes (i.e. gametes, fertilization, embryonic development) to environmental stressors (e.g. temperature, salinity, pH) may be a potential population bottleneck. Here, I compared sperm swimming speeds and proportion of motile sperm and rates of fertilization and early development under a range of environmental variables (temperature: 20-36°C, salinity: 20-34 psu, and pH: 7.4-8.2) to identify environmental tipping points and thresholds for reproductive success. I also tested the effects of water-soluble compounds derived from eggs on sperm activity. This study demonstrated that gametes, fertilization, and embryonic development are robust to a wide range of temperature, salinity, and pH levels that are outside the range found at the geographical limits of adult distribution and can tolerate environmental conditions that exceed expected anomalies as a result of climate change. Water-soluble compounds associated with eggs also enhanced sperm activity, particularly in environmental conditions where sperm motility was initially limited. These findings suggest that fertilization and embryonic development of crown-of-thorns starfish are tolerant to a wide range of environmental conditions, though environmental constraints on recruitment success may occur at later ontogenic stages.
Previous studies on crown-of-thorns starfish have primarily focused on the effects of water quality and nutrient availability on larval growth and survival, while the role of maternal nutrition on reproduction and larval development has been overlooked. To examine the effects of maternal nutrition on oocyte size and early larval development, I pre-conditioned females for 60 days on diets of preferred coral (Acropora abrotanoides) versus non-preferred coral prey (Porites rus) and compared resulting gametes and progeny to those produced by females that were starved over the same period. Females fed ad libitum with Acropora increased in weight, produced heavier gonads and produced larger oocytes compared to Porites-fed and starved females. Fed starfish (regardless of whether it was Acropora or Porites) produced bigger larvae with larger stomachs and had a higher frequency of normal larvae that reached the late bipinnaria / early brachiolaria stage compared to starved starfish. Females on Acropora diet also produced a higher proportion of larvae that progressed to more advanced stages faster compared to Porites-fed starfish, which progressed faster than starved starfish. These results suggest that maternal provisioning can have important consequences for the quality and quantity of progeny.
Based on these findings, I proceeded to test whether maternal provisions from the egg were able to offset limitations imposed by limited access to exogenous sources of nutrients during the formative stages of larval development. This study examined the individual, additive, and interactive effects of endogenous (maternal diet: Acropora, Porites, mixed, and starved) and exogenous (larval diet: high concentration at 10⁴ cells·mL⁻¹, low concentration at 10³ algal cells·mL⁻¹, and starved) nutrition on the survival, growth, morphology, and development of larvae of the crown-of-thorns starfish. Female starfish on Acropora and mixed diet produced bigger oocytes compared to Porites-fed and starved treatments. Using oocyte size as a proxy for maternal provisioning, endogenous reserves in the oocyte had a strong influence on initial larval survival and development. This suggests that maternal reserves can delay the onset of obligate exogenous food acquisition and allow larvae to endure prolonged periods of poor environmental nutritive conditions or starvation. The influence of exogenous nutrition became more prominent in later stages, whereby none of the starved larvae reached the mid-to-late brachiolaria stage 16 days after the onset of the ability to feed. There was no significant difference in the survival, development, and competency of larvae between high and low food treatments. Under low algal food conditions, larvae compensate by increasing the length of ciliated feeding bands in relation to the maximum length and width of the larval body, which improve food capture and feeding efficiency. However, the effects of endogenous nutrition persisted in the later developmental stages, as larvae from starved females were unable to develop larger feeding structures in response to food-limiting conditions. Phenotypic plasticity influenced by endogenous provisions and in response to exogenous food availability may be an important strategy in boosting the reproductive success of crown-of-thorns starfish, leading to population outbreaks.
The tolerance of early life history stages and processes to a suite of environmental stressors and the plasticity in reproductive behavior and larval morphology add to a growing list of traits that predispose crown-of-thorns starfish to pronounced fluctuations in abundance. Taken together, these results demonstrate that variable sensitivity of early life history stages and processes to environmental factors can have flow-on effects that disproportionately impact recruitment success and population replenishment in crown-of- thorns starfish. The cumulative effects of environmental variables on the success of different stages and processes in the life cycle of crown-of-thorns starfish ultimately dictate the available number of larvae that settle and recruit on reefs, and consequently, the patterns of abundance of adult crown-of thorns starfish.
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Lee, Chi-Chiu, and 李志昭. "Studies on Bioactive Effects of Spine Venom and Asterosaponin Extract from Crown-of-Thorns Starfish (Acanthaster planci) in Taiwan." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/39281713512224043013.
Full textAbstract:
博士國立臺灣海洋大學
食品科學系
103
The crown-of-thorns starfish (Acanthaster planci) is the venomous starfish as well as a destroyer of coral reefs. The crown-of-thorns starfish A. planci destroys coral reefs and has been involved in significant events, such as the crown-of-thorns starfish abnormal outbreaks. The back of A. planci is covered with many sharp spines. Previous studies showed that the crude toxin extracted from the spines exhibits the following diverse biological activities: mouse lethality, hemolytic activity, capillary permeability increasing activity, edema-forming activity, phospholipase A2 (PLA2) activity and histamine releasing activity from mast cells. In this study, the active substance extracts were done with PBS buffer. To assay the cytotoxic, hemolytic, and antioxidant properties of the water soluble extract from spine, body wall, pyloric cecum, and gonad of A. planci. Relative to other parts extract, the spine extract possessed the most biological activity, especially in cytotoxic activity. A. planci spine venom (ASV) caused hemolysis and cytotoxicity at a dose-dependent significantly. The highest activity of ASV was measured at pH 7.0-7.4; ASV-dependent hemolysis was sharply reduced when the pH was lower than 3.0 or greater than 8.0. There was almost no hemolytic activity when the concentration of Cu2+ was increased to 10 mM. Furthermore, incubation at 100 °C for 60 min sharply decreased the hemolytic activity of ASV. The cytotoxicity of ASV to human melanoma cell A375.S2 was relatively well retained at temperature less than 40°C, and sharply lost at temperature more than 80°C. The cytotoxicity of ASV also sharply lost at extreme pH environments (pH was lower than 2.0 and higher than 12.0). The cytotoxicity of ASV was attenuated when treated with Cu2+ and anti-oxidant N-acetylcysteine. In order to understand the antitumor activity of toxin from A. planci in Penghu, Taiwan, the cytotoxic toxin of A. planci venom (CAV) was purified by fast protein liquid chromatography (FPLC) and identified as plancitoxin I. The results indicated that cells after incubating with A. planci spine venom (ASV) and purified toxin (CAV) significantly decreased cell viability and lactate dehydrogenase (LDH) level in a concentration-dependent manner was increased. The assays indicated that purified toxin promoted reactive oxygen species (ROS) productions, loss of mitochondrial membrane potential (ΔΨm), and inter-nucleosomal DNA fragmentation in A375.S2 cells. Following, the study was investigated the molecular mechanism underlying the cytotoxicity function of palncitoxin I by focusing on the oxidative stress, mitochondrial dysfunction and endoplasmic reticulum (ER) stress pathway in human melanoma A375.S2 cells. The CAV was found to reduce the cellular antioxidant enzymes such as SOD and CAT, and there was significantly decreased in total thiols level and mtDNA integrity, and enhanced the lipid peroxidation. In addition, CAV increased cytosolic Ca2+ concentration, and enhanced the expression of the ER molecular chaperones GRP78 and CHOP in a dose-dependent manner. CAV significantly elevated the activity of caspase-3, -8 and -9, and reduced the ratio of Bcl-2/Bax. The results demonstrated that plancitoxin I inhibits the proliferation of A375.S2 cells through induction of oxidative stress, mitochondrial dysfunction and ER stress associated apoptosis. Many studies currently researching marine invertebrates to determine the therapeutic potential of their bioactive materials have been showing very promising results. Starfish possesses many useful pharmacological and biological characteristics. In this study, A. planci was extracted with 70% ethanol and lyophilized to obtain an ethanol fraction. The ethanol fraction was dissolved with water and defatted with petroleum ether to obtain a non-polar fraction. The residual solution was successively partitioned with ethylacetate and butanol to obtain an ethylacetate fraction and butanol fraction, respectively. Four fractions were used to examine the antioxidant and anticancer properties. The ethanol fraction of A. planci contained the highest antioxidant effects such as ABTS, DPPH, Fe2+ chelating activity and reducing power when compared with four fractions. Among the four fractions, the butanol fraction was especially shown to inhibit human malignant melanoma A375.S2 cells’ proliferation, which is involved in the apoptotic progression. This fraction could induce apoptosis and even necrosis in A375.S2 cells as evidenced by double staining with an annexin V-FITC and PI assay and DNA fragmentation analysis. These results indicated that the starfish A. planci is a good resource for obtaining the biologically active substances for antioxidant and anticancer effects. However, there was little toxicological information of asterosaponins. The study evaluated potential toxicity of the asterosaponins and analyzed the oxidative stress harm in mice. The present work evaluated the toxicity of the butanol fraction (BF) of crown-of-thorns starfish (Acanthaster planci) in ICR mice, and the BF was used as the asterosaponins extract sample. In acute toxicity assay, the LD50 of the BF is about 520.34 mg/kg body weight. In sub-acute toxicity test for 28 days, the BF significantly increases in hematological parameters, including red blood cell, hemoglobin, hematocrit and mean corpuscular hemoglobin concentration, it also causes hemolytic activities. The BF induces the hepatotoxic injury through induction of oxidative stress by elevating the lipid peroxidation and decreasing the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and total thiols. Based on microscopic observations, the BF showed harmful effect on the histomorphology change of liver. Thus, the bioactive secondary metabolites in the BF of A. planci induce a harmful effect in ICR mice.