Journal articles on the topic 'Ascidians'
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1
Morton, Brian, and Grete E. Dinesen. "The biology and functional morphology of Modiolarca subpicta (Bivalvia: Mytilidae: Musculinae), epizoically symbiotic with Ascidiella aspersa (Urochordata: Ascidiacea), from the Kattegat, northern Jutland, Denmark." Journal of the Marine Biological Association of the United Kingdom 91, no. 8 (December 15, 2010): 1637–49. http://dx.doi.org/10.1017/s0025315410001980.
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This study of the little known north-eastern Atlantic mytilid Modiolarca subpicta suggests a more intimate relationship with ascidians and, especially, Ascidiella aspersa, than has hitherto been appreciated. Both live for ~18 months and the reproductive cycle of both is approximately co-ordinated so that juvenile ascidians become available as hosts to the settling spat of the symbiotically epizoic M. subpicta each summer. Settling spat of M. subpicta are thought to be attracted to the exhalant flow from the ascidian's anal siphon. After the ascidian's death, the liberated mussels may adopt a wandering, free-living, lifestyle they have occasionally been reported to pursue. Anatomically, M. subpicta is of the typical mytilid plan, albeit simplified commensurate upon its normal lifestyle of protective envelopment within the host's tunic. The foot, however, is highly mobile and in addition to being used for locomotion, especially in juveniles, is responsible for the planting of byssal threads, typically dorsally above the shell, so that each individual stimulates the ascidian to produce an epidermal pocket into which it manœuvres itself and reposes, securely attached, but dorsal side down Modiolarca subpicta, epizoic in the tests of ascidians, could have evolved from a more isomyarian, equivalve, ancestor via a nestling, epibyssate, Trichomusculus-like shaped intermediary with ventral flattening and, hence, stability characteristic of the more familiar heteromyarian mytilids of rocky shores and lotic freshwaters being achieved through living dorsal side down.
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Tatian, M., R. J. Sahade, M. E. Doucet, and G. B. Esnal. "Ascidians (Tunicata, Ascidiacea) of Potter Cove, South Shetland Islands, Antarctica." Antarctic Science 10, no. 2 (June 1998): 147–52. http://dx.doi.org/10.1017/s0954102098000194.
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Certain physical factors, substrate type and ice action appear to be important determinants for ascidian distribution. Three different substrate types were sampled at depths between 0–30 m by SCUBA diving: soft bottoms, hard bottoms and moraine deposits. The species found were Aplidium radiatum, Synoicum adareanum, Distaplia cylindrica, Sycozoa gaimardi, Sycozoa sigillinoides, Tylobranchion speciosum, Corella eumyota, Ascidia challengeri, Cnemidocarpa verrucosa, Styela wandeli, Dicarpa insinuosa, Pyura bouvetensis, Pyura discoveryi, Pyura obesa, Pyura setosa, Molgula enodis and Molgula pedunculata. Highest diversity and patchy distribution was found in less stringent environments, where epibiosis is a commmon phenomenon on stolidobranch ascidians. Differences in stalk development were found in the most abundant species Molgula pedunculata and Cnemidocarpa verrucosa. Ice action may be the main factor that determines the absence of ascidians above 15 m in all the stations sampled.
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KNEER, DOMINIK, FRANCOISE MONNIOT, THOMAS STACH, and MARJOLIJN J. A. CHRISTIANEN. "Ascidia subterranea sp. nov. (Phlebobranchia: Ascidiidae), a new tunicate belonging to the A. sydneiensis Stimpson, 1855 group, found as burrow associate of Axiopsis serratifrons A. Milne-Edwards, 1873 (Decapoda: Axiidae) on Derawan Island, Indonesia." Zootaxa 3616, no. 5 (February 22, 2013): 485–94. http://dx.doi.org/10.11646/zootaxa.3616.5.5.
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A new tunicate, Ascidia subterranea sp. nov., was found in burrows of the axiid crustacean Axiopsis serratifrons on De-rawan Island, Indonesia. It differs from other ascidians in its habitat as well as numerous morphological peculiarities which are described in detail. The shrimp Rostronia stylirostris Holthuis, 1952 was found inside A. subterranea sp. nov., and 4 species of bivalves, 3 species of polychaetes, 1 gastropod, 1 polyplacophoran and 1 sponge species were found as burrow associates besides the ascidian.
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Malintoi, Adrianus, Inneke F. M. Rumengan, Kakaskasen A. Roeroe, Veibe Warouw, Ari B. Rondonuwu, and Medy Ompi. "KOMUNITAS ASCIDIA DI PESISIR MALALAYANG DUA, TELUK MANADO, SULAWESI UTARA." JURNAL PESISIR DAN LAUT TROPIS 8, no. 1 (January 15, 2020): 39. http://dx.doi.org/10.35800/jplt.8.1.2020.27403.
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Field survey on ascidian community was conducted along the coastal area of Malalayang Dua in order to find out species of ascidia, species abundance, and ascidian substrates. A survey method and quadrant transects were applied. Pictures were taken, while species and their substrates were sampled. Species identification was based on morphological characteristics, while substrate type identification was based on ascidian species attachment. The results shows that 21 ascidian species were found in the the coastal of Malalayang Dua. Didemnum molle was the highest abundant species in the area, followed by Polycarpa aurata, Polycarpa sp.4. and Polycarpa sp.2.. Dead coral algaes (DCA) were found to be the most preferred substrates by ascidians in the area. Keywords : ascidia, species, substrate, distribution, and abundance Survei lapangan terhadap komunitas ascidia dilakukan di pesisir Malalayang Dua untuk mendapatkan data jenis, kelimpahan, dan substrat ascidia. Metode yang digunakan yaitu metode survei jelajah dan transek kuadran. Identifikasi jenis ascidia dilakukan berdasarkan karakteristik morfologi. Hasil penelitian ditemukan ada 21 jenis ascidia. Substrat jenis death coral algae (DCA) merupakan substrat yang paling banyak ditempati ascidia. Kelimpahan ascidia tertinggi adalah Didemnum molle di pesisir Malalayang Dua, diikuti oleh Polycarpa aurata, Polycarpa sp.4. dan Polycarpa sp.2. Death coral alga (DCA) ditemukan sebagai substrat yang paling disukai oleh ascidia di daerah itu. Kata Kunci : ascidia, spesies, substrat, distribusi, dan kelimpahan
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Sargent, P. S., J. F. Hamel, and A. Mercier. "The life history and feeding ecology of velvet shell, Velutina velutina (Gastropoda: Velutinidae), a specialist predator of ascidians." Canadian Journal of Zoology 97, no. 12 (December 2019): 1164–76. http://dx.doi.org/10.1139/cjz-2018-0327.
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Velvet shell, Velutina velutina (Müller, 1776), is a specialist predator of ascidians, like other members of the gastropod family Velutinidae. Globally, invasive ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, with a preference for the latter. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January–May), growth occurred as water temperature increased to the annual maximum (June and July), transitioning to mating during the warmest period (July–August), and egg capsule deposition dominated as water temperature declined (November–January). Larvae hatched between January and July after 2–4 months of development. Velutina velutina preyed on all ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred.
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Rocha, Rosana Moreira, Edlin Guerra-Castro, Carlos Lira, Sheila Marquez Pauls, Ivan Hernández, Adriana Pérez, Adriana Sardi, et al. "Inventory of ascidians (Tunicata, Ascidiacea) from the National Park La Restinga, Isla Margarita, Venezuela." Biota Neotropica 10, no. 1 (March 2010): 209–18. http://dx.doi.org/10.1590/s1676-06032010000100021.
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Although ascidians form a conspicuous part of sessile assemblages in the Caribbean, no specialized inventories have been developed in Venezuela, except for a list of 15 species reported from Margarita Island (1984). Here we present the results of a taxonomic workshop held in the Universidad de Oriente, Boca del Rio, Margarita Island during April 20-25 of 2009, sponsored by the NaGISA-Caribbean Sea program. La Restinga National park was surveyed and we found 29 species belonging to 19 genera and 10 families. The most abundant colonial species were Clavelina oblonga, Aplidium accarense, Polyclinum constellatum, Distaplia bermudensis, Symplegma rubra, S. brakenhielmi, Botrylloides nigrum and Ecteinascidia turbinata. Among the solitary ascidians Phallusia nigra, Ascidia curvata, Microcosmus exasperatus, Styela canopus, Styela sp.1 and Styela sp. 2 were the most abundant. The ascidian diversity in this lagoon is one of the highest for similar habitats in the Caribbean and seven species are new registers for Venezuela (Ascidia curvata, Ecteinascidia styeloides, Aplidium accarense, Distaplia stylifera, Trididemnum orbiculatum, Symplegma rubra, and S. brakenhielmi). One point of concern for the conservation of la Restinga National Park is the presence of possible introduced species, and some management procedures are suggested.
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Dou, Xiaoju, and Bo Dong. "Origins and Bioactivities of Natural Compounds Derived from Marine Ascidians and Their Symbionts." Marine Drugs 17, no. 12 (November 28, 2019): 670. http://dx.doi.org/10.3390/md17120670.
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Marine ascidians are becoming important drug sources that provide abundant secondary metabolites with novel structures and high bioactivities. As one of the most chemically prolific marine animals, more than 1200 inspirational natural products, such as alkaloids, peptides, and polyketides, with intricate and novel chemical structures have been identified from ascidians. Some of them have been successfully developed as lead compounds or highly efficient drugs. Although numerous compounds that exist in ascidians have been structurally and functionally identified, their origins are not clear. Interestingly, growing evidence has shown that these natural products not only come from ascidians, but they also originate from symbiotic microbes. This review classifies the identified natural products from ascidians and the associated symbionts. Then, we discuss the diversity of ascidian symbiotic microbe communities, which synthesize diverse natural products that are beneficial for the hosts. Identification of the complex interactions between the symbiont and the host is a useful approach to discovering ways that direct the biosynthesis of novel bioactive compounds with pharmaceutical potentials.
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Macpal, Yuliana, Veibe Warouw, Deiske A. Sumilat, James J. H. Paulus, Natalie D. C. Rumampuk, and Reni L. Kreckhoff. "AKTIVITAS ANTIBAKTERI DAN ANTI-UV BEBERAPA ASCIDIAN DARI PERAIRAN PANGALISANG BUNAKEN." JURNAL PESISIR DAN LAUT TROPIS 7, no. 3 (July 23, 2019): 271. http://dx.doi.org/10.35800/jplt.7.3.2019.26019.
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Ascidians are sesile marine invertebrates that have bioactive compounds such as antibacterial and anti-UV. The purpose of this study is to determine the antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria and to test the anti-UV activity of the ascidian water fraction. Antibacterial activity test was carried out using the diffusion method (disc diffusion Kirby & Bauer) and the water fraction of ascidian that showing antibacterial activity tested in a UV spectrophotometer to see the anti-UV activity. Results of the study were obtained 4 types of ascidians extracted from partitioned into water fraction, n-hexane fraction, methanol fraction. All three fractions were tested for antibacterial activity and the result showed that there were antibacterial activities of ascidian extract Clavelina sp. against both test bacteria with inhibition of S. aureus and E. coli with strong categories. Ascidian Phlebobranch sp. showed the presence of antibacterial activity with inhibition of S. aureus and E. coli with very strong categories (16,6 mm). extract Eudistoma sp. showed the presence of antibacterial activity with inhibition S. aureus and E. coli in the medium category (9 mm). The water fraction found active in antibacterial testing is then tested using a UV spectrophotometer for anti UV testing, the result show that water fraction of the four ascidians can absorb UV-B (290-320nm) and UV-A ( 320-400nm).Keywords : Ascidian, Antibacterial, Partition, Anti- UV.
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Casertano, Marcello, Marialuisa Menna, and Concetta Imperatore. "The Ascidian-Derived Metabolites with Antimicrobial Properties." Antibiotics 9, no. 8 (August 13, 2020): 510. http://dx.doi.org/10.3390/antibiotics9080510.
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Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.
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White, Kristine, Louis Ambrosio, and Christa Edwards. "Anthropogenic Sound in the Sea: Are Ascidians Affected?" Gulf and Caribbean Research 32 (2021): 1–7. http://dx.doi.org/10.18785/gcr.3201.02.
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Sound pollution in the marine environment has been increasing largely due to anthropogenic sources such as vessel traffic, coastal development, fossil fuel extraction, and military exercises. Studies determining the effects of anthropogenic sound on marine organisms have mostly focused on vertebrates, namely fish and marine mammals; however, less research has been done to study the effects of sound on marine invertebrates. The goal of this research is to examine the effect of anthropogenic sound on the ascidian Styela plicata (Lesueur, 1823) in Tampa Bay, FL. A total of 48 ascidians were collected from 2 sites with differing amounts of boat traffic and thus different anthropogenic soundscapes. Ascidians were individually exposed to 3 separate stimuli: a recording of a boat motor, a song recording, and a water current to simulate turbulence. Ascidian reactions were recorded as the frequency of siphon closing events and the length of time the siphons remained closed after disturbance. Ascidians from both sites increased the frequency and longevity of siphon closure events in response to anthropogenic stimuli but showed only a minor difference in response between sample sites. Research into the effect of anthropogenic sound on invertebrates such as ascidians and their symbionts may provide a better understanding of larger scale ecological impacts from such disturbances.
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Dias, G. M., R. M. Rocha, T. M. C. Lotufo, and L. P. Kremer. "Fifty years of ascidian biodiversity research in São Sebastião, Brazil." Journal of the Marine Biological Association of the United Kingdom 93, no. 1 (June 7, 2012): 273–82. http://dx.doi.org/10.1017/s002531541200063x.
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The city of São Sebastião (SS), in south-eastern Brazil, is one of the hotspots for marine research since the establishment of the Centre of Marine Biology of the University of São Paulo in the 1960s. The SS region experienced intense transformation during the past 50 years, including increasing urbanization and construction of maritime facilities. Ascidian surveys during the past 50 years have found 62 species, eight of which were described as new and 12 are introduced. Didemnidae and Styelidae are the most speciose families in São Sebastião Channel, with 20 and 15 species respectively. Phallusia nigra, Didemnum psammatodes, Trididemnum orbiculatum, Botrylloides nigrum and Symplegma rubra are the most common ascidians. Most of the species are of tropical origin and São Paulo is their southern geographical limit. Comparisons of reports of the ascidians from different time periods allowed detection of species introductions and shifts in assemblage structure in terms of both species composition and abundance. Additionally, we discuss the main taxonomic issues regarding ascidians from south-eastern Brazil and identify profitable areas for future research. We believe that the temporal data compiled here will serve as a baseline for monitoring and management of ascidians in SS. Additionally, this study provides one of the most detailed datasets of ascidian diversity from the south-western Atlantic Ocean.
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Ma, Kevin C. K., Don Deibel, Kenneth K. M. Law, Mai Aoki, Cynthia H. McKenzie, and Maria L. D. Palomares. "Richness and zoogeography of ascidians (Tunicata: Ascidiacea) in eastern Canada." Canadian Journal of Zoology 95, no. 1 (January 2017): 51–59. http://dx.doi.org/10.1139/cjz-2016-0087.
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Managers and policymakers in eastern Canada embrace science-based management of nonindigenous species and may benefit from having comprehensive regional species checklists at subnational jurisdictional levels. In this paper, regional checklists provide an account of the richness of ascidians in eastern Canada. Records of 58 ascidians resulted from reviewing 108 published sources, accessing data from two online databases, and collecting some common indigenous ascidian specimens. Analysis comparing the similarity of species among nine regions indicates that there is greater similarity in species composition between contiguous regions than between noncontiguous regions and suggests that there are four zoogeographic clusters in eastern Canada. Our checklists can inform managers and policymakers of the diversity of the ascidian taxa and can minimize taxonomic uncertainties of established nonindigenous and prospective invading species, for example, by identifying indigenous species that are congeners of nonindigenous species. The maintenance of checklists can be a valuable tool for the management of nonindigenous species as baselines to estimate changes in richness and to document the invasion status of nonindigenous species over time. For example, more importance can be placed on the spread of nonindigenous ascidians from one zoogeographic cluster to another than spread within the same cluster.
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Bates, William R. "Environmental factors affecting reproduction and development in ascidians and other protochordates." Canadian Journal of Zoology 83, no. 1 (January 1, 2005): 51–61. http://dx.doi.org/10.1139/z04-164.
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Protochordate reproduction and development are influenced by many kinds of environmental factors. For example, spawning, sexual and asexual reproduction, larval behaviour, and life-cycle transitions (metamorphosis) are key processes known to be affected by environmental factors. This review must be restricted primarily to only one group of protochordates, the ascidians or "sea squirts", because information on the reproductive ecology of hemichordates and cephalochordates is limited to only a few studies. Topics discussed in the present review include (i) environmental factors that regulate larval settlement, (ii) how pelagic embryos avoid damage to DNA caused by UV radiation, (iii) the effect of water temperature and food availability on sexual reproduction in colonial ascidians, (iv) environmental regulation of asexual budding, (v) environmental regulation of metamorphosis, and (vi) the possible role of the environment in the evolution of direct-developing ascidians. A novel role for HSP90 and nitric oxide signaling in the integration of environmental factors with cell signaling pathways in ascidians is discussed near the end of this review. Throughout this review, the multiple roles of environmental stress on ascidian reproduction and development are emphasized.
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Kawada, Tsuyoshi, Michio Ogasawara, Toshio Sekiguchi, Masato Aoyama, Kohji Hotta, Kotaro Oka, and Honoo Satake. "Peptidomic Analysis of the Central Nervous System of the Protochordate, Ciona intestinalis: Homologs and Prototypes of Vertebrate Peptides and Novel Peptides." Endocrinology 152, no. 6 (April 5, 2011): 2416–27. http://dx.doi.org/10.1210/en.2010-1348.
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The phylogenetic position of ascidians as the chordate invertebrates closest to vertebrates suggests that they might possess homologs and/or prototypes of vertebrate peptide hormones and neuropeptides as well as ascidian-specific peptides. However, only a small number of peptides have so far been identified in ascidians. In the present study, we have identified various peptides in the ascidian, Ciona intestinalis. Mass spectrometry-based peptidomic analysis detected 33 peptides, including 26 novel peptides, from C. intestinalis. The ascidian peptides are largely classified into three categories: 1) prototypes and homologs of vertebrate peptides, such as galanin/galanin-like peptide, which have never been identified in any invertebrates; 2) peptides partially homologous with vertebrate peptides, including novel neurotesin-like peptides; 3) novel peptides. These results not only provide evidence that C. intestinalis possesses various homologs and prototypes of vertebrate neuropeptides and peptide hormones but also suggest that several of these peptides might have diverged in the ascidian-specific evolutionary lineage. All Ciona peptide genes were expressed in the neural complex, whereas several peptide gene transcripts were also distributed in peripheral tissues, including the ovary. Furthermore, a Ciona neurotensin-like peptide, C. intestinalis neurotensin-like peptide 6, was shown to down-regulate growth of Ciona vitellogenic oocytes. These results suggest that the Ciona peptides act not only as neuropeptides in the neural tissue but also as hormones in nonneuronal tissues and that ascidians, unlike other invertebrates, such as nematodes, insects, and sea urchins, established an evolutionary origin of the peptidergic neuroendocrine, endocrine, and nervous systems of vertebrates with certain specific molecular diversity.
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Chen, Lei, Xue-Ning Wang, Chang-Ming Fu, and Guang-Yu Wang. "Phylogenetic Analysis and Screening of Antimicrobial and Antiproliferative Activities of Culturable Bacteria Associated with the Ascidian Styela clava from the Yellow Sea, China." BioMed Research International 2019 (August 28, 2019): 1–14. http://dx.doi.org/10.1155/2019/7851251.
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Over 1,000 compounds, including ecteinascidin-743 and didemnin B, have been isolated from ascidians, with most having bioactive properties such as antimicrobial, antitumor, and enzyme-inhibiting activities. In recent years, direct and indirect evidence has shown that some bioactive compounds isolated from ascidians are not produced by ascidians themselves but by their symbiotic microorganisms. Isolated culturable bacteria associated with ascidians and investigating their potential bioactivity are an important approach for discovering novel compounds. In this study, a total of 269 bacteria were isolated from the ascidian Styela clava collected from the coast of Weihai in the north of the Yellow Sea, China. Phylogenetic relationships among 183 isolates were determined using their 16S rRNA gene sequences. Isolates were tested for antimicrobial activity against seven indicator strains, and an antiproliferative activity assay was performed to test for inhibition of human hepatocellular carcinoma Bel 7402 and human cervical carcinoma HeLa cell proliferation. Our results showed that the isolates belonged to 26 genera from 18 families in four phyla (Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes). Bacillus and Streptomyces were the most dominant genera; 146 strains had potent antimicrobial activities and inhibited at least one of the indicator strains. Crude extracts from 29 strains showed antiproliferative activity against Bel 7402 cells with IC50 values below 500 μg·mL−1, and 53 strains showed antiproliferative activity against HeLa cells, with IC50 values less than 500 μg·mL−1. Our results suggest that culturable bacteria associated with the ascidian Styela clava may be a promising source of novel bioactive compounds.
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Koike, I., M. Yamamuro, and PC Pollard. "Carbon and nitrogen budgets of two Ascidians and their symbiont, Prochloron, in a tropical seagrass meadow." Marine and Freshwater Research 44, no. 1 (1993): 173. http://dx.doi.org/10.1071/mf9930173.
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Two species of ascidian, Didemnum molle Herdman and Lissoclinum voeltzkowi Michaelsen, were collected from a Fijian seagrass meadow. The primary production of their symbiont (Prochloron), the inorganic nitrogen metabolism and the filtration rate were measured to assess the nutritional coupling between the symbiont and the host animal. The loss of organic carbon due to the respiration of D. molle (1.1 �g at. C (mg dry wt)-1 day-1) was greater than that supplied through photosynthesis of the Prochloron (0.69 �g at. C (mg dry wt)-1 day,-1). The carbon supplied through filter-feeding appeared to supplement the ascidian's carbon budget. In contrast, organic carbon from the Prochloron of L. voeltzkowi appeared to meet the colony's respiration needs. The nitrogen budgets of both ascidian colonies were estimated from their respiration rates, the nitrogen requirement of the Prochloron, and the uptake of inorganic nitrogen and particulate organic nitrogen uptake from the water column. The nitrogen incorporated from the surrounding environment could contribute to the net nitrogen gain of the colony. However, our estimate of the nitrogen needed by the Prochloron was much greater than that which could be supplied externally. The amount of nitrogen released by the ascidians was also greater than that which could be supplied externally. This suggests that nitrogen is efficiently recycled within the symbiotic Prochloron-ascidian relationship.
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Nakatani, Y., R. Moody, and W. C. Smith. "Mutations affecting tail and notochord development in the ascidian Ciona savignyi." Development 126, no. 15 (August 1, 1999): 3293–301. http://dx.doi.org/10.1242/dev.126.15.3293.
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Ascidians are among the most distant chordate relatives of the vertebrates. However, ascidians share many features with vertebrates including a notochord and hollow dorsal nerve cord. A screen for N-ethyl-N-nitrosourea (ENU)-induced mutations affecting early development in the ascidian Ciona savignyi resulted in the isolation of a number of mutants including the complementing notochord mutants chongmague and chobi. In chongmague embryos the notochord fails to develop, and the notochord cells instead adopt a mesenchyme-like fate. The failure of notochord development in chongmague embryos results in a severe truncation of tail, although development of the tail muscles and caudal nerve tracts appears largely normal. Chobi embryos also have a truncation of the tail stemming from a disruption of the notochord. However, in chobi embryos the early development of the notochord appears normal and defects occur later as the notochord attempts to extend and direct elongation of the tail. We find in chobi tailbud embryos that the notochord is often bent, with cells clumped together, rather than extended as a column. These results provide new information on the function and development of the ascidian notochord. In addition, the results demonstrate how the unique features of ascidians can be used in genetic analysis of morphogenesis.
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Dalby, JE. "Consequences of aggregated living in the ascidian Pyura stolonifera: Evidence for non-contact intraspecific competition." Marine and Freshwater Research 46, no. 8 (1995): 1195. http://dx.doi.org/10.1071/mf9951195.
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Non-contact intraspecific competition was examined as a possible consequence of the aggregated distribution of the ascidian Pyura stolonifera near Melbourne, Australia. In a field experiment designed so that experimental individuals did not touch surrounding conspecific individuals, ascidians inside aggregations grew significantly more slowly than those outside aggregations: at the end of the 24-month experiment, the former animals had shorter body lengths, lighter bodies, lighter tunics, and lighter gonads. This is one of few conclusive demonstrations of the existence of this type of intraspecific competition in sessile marine invertebrates occupying hard substrata, and the only demonstration for ascidians.
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Palomino-Alvarez, Lilian A., Rosana Moreira Rocha, and Nuno Simões. "Checklist of ascidians (Chordata, Tunicata) from the southern Gulf of Mexico." ZooKeys 832 (March 19, 2019): 1–33. http://dx.doi.org/10.3897/zookeys.832.31712.
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This study is the first inventory of ascidians from shallow waters (0–25 m) of coastal and reef habitats in the southern Gulf of Mexico where ascidian diversity is poorly known. Sampled environments in 14 locations (38 sites) with 134 samples collected from 2015 to 2017 included coral reefs, coastal lagoons, mangroves, seagrass, ports, and artificial platforms. The 31 identified species comprise 19 genera and 13 families. Ten species are newly reported in the Gulf of Mexico:AscidiapanamensisBonnet & Rocha, 2011;Ecteinascidiastyeloides(Traustedt, 1882);CystodytesroseolusHartmeyer, 1912; Eudistomaaff.amanitum Paiva & Rocha, 2018;EudistomarecifenseMillar, 1977;EuherdmaniafasciculataMonniot, 1983; Euherdmaniaaff.vitrea Millar, 1961;Polycarpacartilaginea(Sluiter, 1885);Botrylloidesmagnicoecum(Hartmeyer, 1912) andDidemnumgranulatumTokioka, 1954. Two new species will be described separately (Clavelinasp. andPyurasp.). This study provides the first records for 26 species ascidians for the region as well as describes increased distributions of ten Atlantic species. Thus, our data provide a starting point for future ecological, experimental and taxonomic studies of ascidians of the Gulf of Mexico.
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Hirose, Euichi, Ryuma Adachi, and Koji Kuze. "Sexual reproduction of the Prochloron-bearing ascidians, Trididemnum cyclops and Lissoclinum bistratum, in subtropical waters: seasonality and vertical transmission of photosymbionts." Journal of the Marine Biological Association of the United Kingdom 86, no. 1 (January 12, 2006): 175–79. http://dx.doi.org/10.1017/s0025315406013002.
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The seasonality of sexual reproduction was studied in two Prochloron-bearing ascidians, Trididemnum cyclops and Lissoclinum bistratum, on a subtropical coral reef off Okinawajima Island, Japan. These colonial ascidians had testes and/or eggs/embryos from spring to summer. Embryos with tails occurred in summer. Whereas many photosymbiotic didemnids are thought to be sexually mature throughout the year in the tropics, sexual reproduction of the same species in subtropical waters may be limited to spring and summer. The subtropical winter may be too cold for gonad formation. A histological study of sexually mature colonies showed no Prochloron cells attached to ascidian larvae in the pre-hatch stage.
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Rocha, Rosana M. da, and Laura P. Kremer. "Introduced ascidians in Paranaguá Bay, Paraná, southern Brazil." Revista Brasileira de Zoologia 22, no. 4 (December 2005): 1170–84. http://dx.doi.org/10.1590/s0101-81752005000400052.
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Exotic (introduced) species are a growing problem in ports worldwide and comprise the most important impacts in marine ecosystems. Periodic monitoring to detect introduced species is extremely important for effective population control. Here we sampled ascidian species near the port of Paranaguá for a taxonomic study of this fauna to attempt to detect introduced species. Larval stages in ascidians are short-lived, and dispersal is restricted to small distances, and so ascidians are very good bioindicators for exotic introductions due to ship transport. Four locations were sampled within Paranaguá Bay (Ilha das Cobras, Pier Tenenge, Ilha do Mel and Ilha da Galheta) and one location outside of the bay (Parque dos Meros). Information for the nearby fauna and for geographic distributions of the species involved was obtained from the literature. Eighteen species were found: Perophora multiclathrata (Sluiter, 1904), Ascidia curvata (Traustedt,1882), A. sydneiensis Stimpson, 1855, Clavelina oblonga Herdman, 1880, Cystodytes dellechiajei (Della Valle, 1877), Eudistoma carolinense van Name, 1945, Distaplia bermudensis van Name, 1902, Didemnum granulatum Tokioka, 1954, Diplosoma listerianum (Milne-Edwards, 1841), Lissoclinum fragile (van Name, 1902), Botryllus planus (van Name, 1902), B. tuberatus Ritter & Forsyth 1917, Botrylloides nigrum Herdman, 1886, Symplegma rubra Monniot, 1972, Styela canopus (Savigny, 1816), S. plicata (Lesueur, 1823), Microcosmus exasperatus Heller, 1878 and Molgula phytophila Monniot, 1970. The known geographic distributions based on the literature and collections suggest that three species are native, one is a inter-regional introduction, two are introduced from the Pacific and the remaining 12 are cryptogenic.
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Wilding, Martin, Marcella Marino, and Daniela Dale. "Nicotinamide alters the calcium release pattern and the degradation of MPF activity after fertilisation in ascidian oocytes." Zygote 7, no. 3 (August 1999): 255–60. http://dx.doi.org/10.1017/s0967199499000647.
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Fertilisation in ascidian oocytes triggers a plasma membrane current, the release of intracellular calcium and the degradation of Maturation Promoting Factor (MPF) activity leading to the completion of meiosis and the initiation of embryo development. We have previously shown that the fertilisation current in ascidians is produced through the metabolism of nicotinamide nucleotide (NN) metabolites to ADP ribose. In this study we have used nicotinamide to test whether NN metabolism plays additional roles in fertilisation in ascidians. Nicotinamide treatment blocked calcium-induced calcium release (CICR) and arrested the cell cycle prior to the completion of meiosis I. Nicotinamide further prevented the abolition of MPF activity after fertilisation. Interestingly, nicotinamide treatment caused ascidian oocytes to form interphase-like pronuclei after fertilisation, despite the high MPF activity. The data demonstrate that NN metabolism is involved in calcium signalling through CICR and further suggest that a NN metabolite acts as a messenger connecting MPF activity to the formation of the meiotic apparatus.
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Cone, Angela C., and Robert W. Zeller. "Using ascidian embryos to study the evolution of developmental gene regulatory networks." Canadian Journal of Zoology 83, no. 1 (January 1, 2005): 75–89. http://dx.doi.org/10.1139/z04-165.
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Ascidians are ideally positioned taxonomically at the base of the chordate tree to provide a point of comparison for developmental regulatory mechanisms that operate among protostomes, non-chordate deuterostomes, invertebrate chordates, and vertebrates. In this review, we propose a model for the gene regulatory network that gives rise to the ascidian notochord. The purpose of this model is not to clarify all of the interactions between molecules of this network, but to provide a working schematic of the regulatory architecture that leads to the specification of endoderm and the patterning of mesoderm in ascidian embryos. We describe a series of approaches, both computational and biological, that are currently being used, or are in development, for the study of ascidian embryo gene regulatory networks. It is our belief that the tools now available to ascidian biologists, in combination with a streamlined mode of development and small genome size, will allow for more rapid dissection of developmental gene regulatory networks than in more complex organisms such as vertebrates. It is our hope that the analysis of gene regulatory networks in ascidians can provide a basic template which will allow developmental biologists to superimpose the modifications and novelties that have arisen during deuterostome evolution.
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Katsuyama, Y., S. Wada, S. Yasugi, and H. Saiga. "Expression of the labial group Hox gene HrHox-1 and its alteration induced by retinoic acid in development of the ascidian Halocynthia roretzi." Development 121, no. 10 (October 1, 1995): 3197–205. http://dx.doi.org/10.1242/dev.121.10.3197.
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Ascidian embryogenesis shares several developmental features with vertebrates. Thus, it is presumed that some molecular mechanisms that are critical for vertebrate development may also act in the early development of ascidians. Here, we investigated expression of the ascidian labial group Hox gene HrHox-1 in the development of Halocynthia roretzi. HrHox-1 showed a spatially restricted expression pattern along the anterior-posterior axis, which is remarkably similar to that of the vertebrate gene, Hoxb-1. The expression of HrHox-1, however, was exclusively in tissues of ectoderm origin unlike its vertebrate counterpart. Exposure of the embryos to 10(−6) M all-trans retinoic acid induced a larval phenotype with elimination of the anteriormost structures, the papillae. In this phenotype, the level of HrHox-1 expression was enhanced and ectopic expression was observed at the anterior terminal epidermis where the papillae are otherwise formed. These observations suggest that there are some conserved mechanisms in the spatial regulation of expression of labial group genes in embryogenesis of ascidians and vertebrates.
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Murugan, Rajaram, and Gnanakkan Ananthan. "Ascidian diversity (Chordata: Tunicata) from Andaman and Nicobar Islands, India." Oceanological and Hydrobiological Studies 47, no. 2 (June 26, 2018): 107–17. http://dx.doi.org/10.1515/ohs-2018-0012.
Full textAbstract:
Abstract Ascidians are filter-feeding sac-like marine urochordates of great evolutionary, ecological and economic importance. Andaman and Nicobar Islands are one of the most important hot spots of biodiversity in India, while the ascidian diversity of this region is very scanty. Ascidians belonging to 29 species were identified at the Andaman and Nicobar Islands during the field research carried out from March 2014 to April 2015. Eight species (Didemnum granulatum, Didemnum molle, Didemnum psammatodes, Diplosoma listerianum, Lissoclinum fragile, Lissoclinum levitum, Lissoclinum patella, Trididemnum Cyclops) from the Didemnidae family were found and identified. Various diversity indices, such as the Shannon -Wiener index (H’), Margalef’s index (D), Pielou’s index (J’), K-dominance curves, Cluster Analysis and Multidimensional Scaling, were used to analyze the diversity, richness and evenness of species, and to compare the diversity between samples and their resemblance in terms of species composition. The maximum species richness was observed in Campbell Bay (2.424) and the minimum in Haddo Wharf (0.910). This finding shows the rich species diversity of ascidian fauna at Andaman and Nicobar Islands.
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Hirose, Euichi, Kaori Ohtsuka, Masaharu Ishikura, and Tadashi Maruyama. "Ultraviolet absorption in ascidian tunic and ascidian-Prochloron symbiosis." Journal of the Marine Biological Association of the United Kingdom 84, no. 4 (August 2004): 789–94. http://dx.doi.org/10.1017/s0025315404009956h.
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To characterize the ultraviolet (UV) light-absorbing function of the ascidian tunic, the light absorption spectrum was compared in 22 ascidian species collected from tropical and temperate waters. Non-photosymbiotic ascidians (17 species) had transparent tunics transmitting both visible and UV light, or pigmented or opaque tunics equally absorb both UV and visible light. However, a prominent absorption peak around 320 nm was exclusively found in the colonial ascidians hosting the algal symbiont Prochloron sp., and this absorption peak corresponded to absorption of UV-A (320–400 nm) and UV-B (280–320 nm). The UV-absorbing substances were extracted with methanol. They were mycosporine-like amino acids (MAAs): mycosporine-glycine, palythine, shinorine, and porphyra-334. The MAAs are thought to be synthesized by the shikimic acid pathway that does not occur in animals. Since the isolated Prochloron cells contain MAAs, the symbionts are the most possible candidates as the source of the MAAs in the tunic. In Diplosoma virens, the composition of MAAs was different between isolated Prochloron cells and colony residue from which Prochloron cells were extracted.
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Pichon, Julien, Nicholas M. Luscombe, and Charles Plessy. "Widespread use of the “ascidian” mitochondrial genetic code in tunicates." F1000Research 8 (December 10, 2019): 2072. http://dx.doi.org/10.12688/f1000research.21551.1.
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Background: Ascidians, a tunicate class, use a mitochondrial genetic code that is distinct from vertebrates and other invertebrates. Though it has been used to translate the coding sequences from other tunicate species on a case-by-case basis, it is has not been investigated whether this can be done systematically. This is an important because a) some tunicate mitochondrial sequences are currently translated with the invertebrate code by repositories such as NCBI GenBank, and b) uncertainties about the genetic code to use can complicate or introduce errors in phylogenetic studies based on translated mitochondrial protein sequences. Methods: We collected publicly available nucleotide sequences for non-ascidian tunicates including appendicularians such as Oikopleura dioica, translated them using the ascidian mitochondrial code, and built multiple sequence alignments covering all tunicate classes. Results: All tunicates studied here appear to translate AGR codons to glycine instead of serine (invertebrates) or as a stop codon (vertebrates), as initially described in ascidians. Among Oikopleuridae, we suggest further possible changes in the use of the ATA (Ile → Met) and TGA (Trp → Arg) codons. Conclusions: We recommend using the ascidian mitochondrial code in automatic translation pipelines of mitochondrial sequences for all tunicates. Further investigation is required for additional species-specific differences.
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Pichon, Julien, Nicholas M. Luscombe, and Charles Plessy. "Widespread use of the “ascidian” mitochondrial genetic code in tunicates." F1000Research 8 (April 14, 2020): 2072. http://dx.doi.org/10.12688/f1000research.21551.2.
Full textAbstract:
Background: Ascidians, a tunicate class, use a mitochondrial genetic code that is distinct from vertebrates and other invertebrates. Though it has been used to translate the coding sequences from other tunicate species on a case-by-case basis, it is has not been investigated whether this can be done systematically. This is an important because a) some tunicate mitochondrial sequences are currently translated with the invertebrate code by repositories such as NCBI GenBank, and b) uncertainties about the genetic code to use can complicate or introduce errors in phylogenetic studies based on translated mitochondrial protein sequences. Methods: We collected publicly available nucleotide sequences for non-ascidian tunicates including appendicularians such as Oikopleura dioica, translated them using the ascidian mitochondrial code, and built multiple sequence alignments covering all tunicate classes. Results: All tunicates studied here appear to translate AGR codons to glycine instead of serine (invertebrates) or as a stop codon (vertebrates), as initially described in ascidians. Among Oikopleuridae, we suggest further possible changes in the use of the ATA (Ile → Met) and TGA (Trp → Arg) codons. Conclusions: We recommend using the ascidian mitochondrial code in automatic translation pipelines of mitochondrial sequences for all tunicates. Further investigation is required for additional species-specific differences.
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Lambert, Gretchen, and Karen Sanamyan. "Distaplia alaskensis sp.nov. (Ascidiacea, Aplousobranchia) and other new ascidian records from south-central Alaska, with a redescription of Ascidia columbiana (Huntsman, 1912)." Canadian Journal of Zoology 79, no. 10 (October 1, 2001): 1766–81. http://dx.doi.org/10.1139/z01-141.
Full textAbstract:
Alaskan ascidians are incompletely known and rarely sampled. The Smithsonian Environmental Research Center recently conducted an extensive survey of harbors and marinas for nonindigenous species at major marine traffic sites on the Kenai Peninsula and Prince William Sound in Alaska. Collections made during summer 1998 and 1999 included 12 species of ascidians, one of which is a new species of Distaplia, D. alaskensis. We consider it indigenous, though it could be cryptogenic because it was collected only from marina floats and no neighboring natural subtidal areas have ever been sampled. All the other species are natives except Botrylloides violaceus. This aggressive invader from Japan has recently spread rapidly along both coasts of the U.S.A. and Canada as well as in many other parts of the world, and is here reported from Alaska for the first time. Ascidia columbiana (Huntsman, 1912), synonymized in 1924 by Hartmeyer under Ascidia callosa, has now been shown to be a valid species, based on differences in morphology and reproductive mode; a redescription of A. columbiana is included here. Several species collected in 2000 at the Sitka Sea Farm mariculture facility near Sitka are also included. Because all these collections are from areas never before sampled for ascidians, all are new records for these species.
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Van Volkom, Kaitlin S., Larry G. Harris, and Jennifer A. Dijkstra. "The influence of invasive ascidian diets on the growth of the sea star Henricia sanguinolenta." Journal of the Marine Biological Association of the United Kingdom 101, no. 1 (February 2021): 151–57. http://dx.doi.org/10.1017/s0025315420001228.
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AbstractInvasive species can disrupt food webs by altering the abundance of prey species or integrating into the food web themselves. In the Gulf of Maine, there have been a suite of invasions that have altered the composition of the benthic ecosystem. These novel prey species can potentially benefit native predators depending on their nutritional value and relative abundance. We measured feeding instances of the native blood star, Henricia sanguinolenta, and changes in the seasonal abundances of invasive ascidian prey species. Results indicate that H. sanguinolenta forages optimally, as the blood star will prey on invasive ascidians when in high abundance, but feed on other species during periods of scarcity. Further, our study shows that blood stars prey on a wider variety of species than was previously known, such as small bivalves and barnacles. Additionally, we compared growth and reproduction of sea stars fed different combinations of invasive ascidians (Diplosoma listerianum or Botrylloides violaceus) or a native sponge (Haliclona oculata). Sea stars grew more on the native diet when compared with the invasive ascidian species, and D. listerianum appeared to be a superior quality food source when compared with B. violaceus. By comparing our data with historical data, we determined that there was a dramatic increase in sea star populations between 1980 and 2011, but then populations decreased by almost half from 2011 to 2016–2017. These data suggest that while invasive ascidians may have helped sea star populations at one point, sea stars are declining without their native food source.
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Mastrototaro, F., G. D'Onghia, and A. Tursi. "Spatial and seasonal distribution of ascidians in a semi-enclosed basin of the Mediterranean Sea." Journal of the Marine Biological Association of the United Kingdom 88, no. 5 (July 25, 2008): 1053–61. http://dx.doi.org/10.1017/s0025315408001392.
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A total of 25 species of ascidians were collected in the Mar Piccolo of Taranto, a semi-enclosed Mediterranean basin. Three are non-indigenous for the Mediterranean Sea: Microcosmus squamiger, Polyandrocarpa zorritensis and Distaplia bermudensis. The substrate features, season and depth affect the distribution of ascidians in the study area. Some species, such as Pyura dura and Pyura microcosmus, were found only on artificial substrates, while Ascidiella aspersa was almost exclusively recovered on natural bottoms. Seasonal variation in the ascidian distribution and abundance seems to be due mainly to their biological cycles, larval recruitment and adaptation. During the autumn and winter the most abundant species were Clavelina phlegraea and Ciona intestinalis, while A.aspersa was particularly abundant during spring. Depth and more directly light intensity play an important role in ascidian distribution. In the upper few metres the shallow-water species Polyandrocarpa zorritensis was abundant due to its photopositive larvae. Even though the distribution and abundance changed significantly between substrates, seasons and depths, the most abundant species in the Mar Piccolo of Taranto were Clavelina phlegraea, Ciona intestinalis and Styela plicata all of which are able to tolerate the variations in environmental conditions, low rate of water renewal and continuous silting of this semi-enclosed sea. Assuming the role that the above mentioned species have as marine pollution indicators and the abundance recorded for some of them, a high degree of environmental stress can be confirmed for the Mar Piccolo of Taranto. A comparative list of the ascidians recorded in this and previous studies is also reported.
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Łukowiak, Magdalena. "First record of late Eocene ascidians (Ascidiacea, Tunicata) from southeastern Australia." Journal of Paleontology 86, no. 3 (May 2012): 521–26. http://dx.doi.org/10.1666/11-112.1.
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Ascidian spicules are reported for the first time from the upper Eocene (Paleogene) biosiliceous marls and mudstones of the Blanche Point Formation in the St. Vincent Basin, southeastern Australia. The spicules that belong to the family Polycitoridae are identified as a Recent species Cystodytes cf. dellechiajei, and Cystodytes sp. and spicules of the family Didemnidae are indentified as representing genera Lissoclinum, Didemnum, and Polysyncraton. Five other different morphological spicule types which can be classified only at the family level also belong to the Didemnidae. This study demonstrates that ascidians had a very wide distribution by the late Eocene and that ascidian fauna was already of a modern character.
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Leleran, Andreas J. P. L., Silvester B. Pratasik, Meiske S. Salaki, Lawrence J. L. Lumingas, Alex D. Kambey, and Suzanne L. Undap. "Distribution and Diversity of Ascidian in Manado Bay, North Sulawesi." Jurnal Ilmiah PLATAX 10, no. 1 (April 14, 2022): 124. http://dx.doi.org/10.35800/jip.v10i1.38842.
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The purpose of this study was to determine the distribution and the diversity of ascidians in Manado Bay including species composition, density, diversity, and dominance. This study used the quadrat transect method. This study found differences in the number of ascidian species with water depth, 11 species of 5 families at 15 M depth, and 8 species of 3 families at 7 M depth. The diversity index ranged from 0.868 to 1.844 at 15 M depth and 0.965 to 1.864 at 7 M depth, the evenness index was 0.533 – 0.839 at 15 M depth and 0.600 – 0.897 at 7 M depth, the dominance index was 0.254 – 0.745 at 15 M depth and 0.254 – 0.708 at 7 M depth. Ascidian in Manado Bay had two distribution patterns, a uniform distribution pattern and a clustered distribution pattern. Environmental parameters had a water temperature of 27 oC – 31 oC, the salinity of 30 0/00 – 32 0/00, the brightness of 12 m – 14 m, and pH of 8 – 10.*Keywords: Ascidian; diversity; ecological index; distribution patternAbstrakTujuan dari penelitian ini adalah untuk mengetahui distribusi dan keanekaragaman jenis ascidia di perairan Teluk Manado meliputi: komposisi jenis, kepadatan individu, keanekaragaman, dan dominansi. Serta mengetahui pola distribusi ascidia. Penelitian ini menggunakan metode transek kuadran. Pada penelitian ini ditemukan perbedaan jumlah spesies ascidia menurut kedalaman, 11 spesies dari 5 family pada 15 M dan 8 spesies dari 3 famili pada kedalaman 7 m. Nilai indeks keanekaragaman ascidia di kedalaman 15 m = 0.868 – 1.844 dan 7 m = 0.965 - 1.864, indeks keseragaman 15 m = 0.533 – 0.839 dan 7 m = 0.600 – 0.897, indeks Dominasi15 m = 0.254 – 0.745 dan 7 m = 0.254 – 0.708. Ascdia di perairan Teluk Manado memiliki dua pola distribusi yaitu pola distribusi seragam dan pola distribusi mengelopok. Parameter lingkungan memiliki suhu air 27 oC – 31 oC, salinitas 30 0/00 – 32 0/00, kecerahan 12 m – 14 m, dan pH 8 – 10.*Kata kunci : Ascidia; keanekaragaman; indeks ekologi; pola distribusi
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MONNIOT, FRANÇOISE. "Some new data on tropical western Pacific Ascidians." Zootaxa 2561, no. 1 (August 9, 2010): 1. http://dx.doi.org/10.11646/zootaxa.2561.1.1.
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Numerous collections of ascidians have been made in the Pacific and Indian Oceans but the inventory is far from complete. Each sampling provides new species. Two new didemnids are described here from Palau and Vanuatu. New records are given for 22 additional species with complementary descriptions and underwater photographs. The tropical ascidian fauna is highly diverse and successive new collections show that many of the species are not only widely distributed from the central to western Pacific but also common to the Indian Ocean.
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Wada, H., H. Saiga, N. Satoh, and P. W. Holland. "Tripartite organization of the ancestral chordate brain and the antiquity of placodes: insights from ascidian Pax-2/5/8, Hox and Otx genes." Development 125, no. 6 (March 15, 1998): 1113–22. http://dx.doi.org/10.1242/dev.125.6.1113.
Full textAbstract:
Ascidians and vertebrates belong to the Phylum Chordata and both have dorsal tubular central nervous systems. The structure of the ascidian neural tube is extremely simple, containing less than 400 cells, among which less than 100 cells are neurons. Recent studies suggest that, despite its simple organization, the mechanisms patterning the ascidian neural tube are similar to those of the more complex vertebrate brain. Identification of homologous regions between vertebrate and ascidian nervous systems, however, remains to be resolved. Here we report the expression of HrPax-258 gene: an ascidian homologue of vertebrate Pax-2, Pax-5 and Pax-8 genes. Molecular phylogenetic analyses indicate that HrPax-258 is descendant from a single precursor gene that gave rise to the three vertebrate genes. The expression pattern of HrPax-258 suggests that this subfamily of Pax genes has conserved roles in regional specification of the brain. Comparison with expression of ascidian Otx (Hroth) and a Hox gene (HrHox1) by double-staining in situ hybridizations indicate that the ascidian brain region can be subdivided into three regions; the anterior region marked by Hroth probably homologous to the vertebrate forebrain and midbrain, the middle region marked by HrPax-258 probably homologous to the vertebrate anterior hindbrain (and maybe also midbrain) and the posterior region marked by Hox genes which is homologous to the vertebrate hindbrain and spinal cord. Later expression of HrPax-258 in atrial primordia implies that basal chordates such as ascidians have already acquired a sensory organ that develops from epidermal thickenings (placodes) and expresses HrPax-258; we suggest it is homologous to the vertebrate ear. Therefore, placodes are not likely to be a newly acquired feature in vertebrates, but may have already been possessed by the earliest chordates.
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Demers, Marie-Claire A., Nathan A. Knott, and Andrew R. Davis. "Under the radar: Sessile epifaunal invertebrates in the seagrassPosidonia australis." Journal of the Marine Biological Association of the United Kingdom 96, no. 2 (August 13, 2015): 363–77. http://dx.doi.org/10.1017/s0025315415000612.
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Despite the current global decline in seagrass, sessile epifaunal invertebrates inhabiting seagrass ecosystems, particularly sponges and ascidians, have been poorly studied due to their taxonomic complexity. Understanding patterns of distribution of sessile epifaunal communities in seagrass meadows is an important precursor to determining the processes driving their distribution and species interactions. This study (1) identified the sponge and ascidian assemblage associated withPosidonia australismeadows and (2) determined distributional patterns of these invertebrates at a hierarchy of spatial scales in Jervis Bay, Australia. We used a fully nested design with transects distributed in the seagrass (10s m apart), two sites (100s m apart), and six locations (km apart). Within these transects, we recorded the abundance, volume, diversity and substratum used for attachment by sponges and ascidians. We encountered 20 sponge species and eight ascidian species; they were sporadically distributed in the seagrass meadows with high variability among the transects, sites and locations. A few sponge and ascidian species dominated the assemblage and were widespread across the largest spatial scale sampled. The remaining species were mostly rare and sparsely distributed. Sponges attached to a variety of substrata but most notably shells,P. australisand polychaete tubes. No obligate seagrass species were recorded although three species predominantly usedP. australisas a substratum. These sponge species relying heavily on seagrass for their attachment are likely prone to disturbances impacting their host habitat. Examining the response of sessile epifauna to the degradation of their seagrass habitat remains a key challenge for the future.
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Manni, Lucia, Federico Caicci, Chiara Anselmi, Virginia Vanni, Silvia Mercurio, and Roberta Pennati. "Morphological Study and 3D Reconstruction of the Larva of the Ascidian Halocynthia roretzi." Journal of Marine Science and Engineering 10, no. 1 (December 24, 2021): 11. http://dx.doi.org/10.3390/jmse10010011.
Full textAbstract:
The swimming larva represents the dispersal phase of ascidians, marine invertebrates belonging to tunicates. Due to its adhesive papillae, the larva searches the substrate, adheres to it, and undergoes metamorphosis, thereby becoming a sessile filter feeding animal. The larva anatomy has been described in detail in a few species, revealing a different degree of adult structure differentiation, called adultation. In the solitary ascidian Halocynthia roretzi, a species reared for commercial purposes, embryogenesis has been described in detail, but information on the larval anatomy is still lacking. Here, we describe it using a comparative approach, utilizing 3D reconstruction, as well as histological/TEM observations, with attention to its papillae. The larva is comparable to those of other solitary ascidians, such as Ciona intestinalis. However, it displays a higher level of adultation for the presence of the atrium, opened outside by means of the atrial siphon, and the peribranchial chambers. It does not reach the level of complexity of the larva of Botryllus schlosseri, a phylogenetically close colonial ascidian. Our study reveals that the papillae of H. roretzi, previously described as simple and conform, exhibit dynamic changes during settlement. This opens up new considerations on papillae morphology and evolution and deserves to be further investigated.
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Mackie, G. O., and P. Burighel. "The nervous system in adult tunicates: current research directions." Canadian Journal of Zoology 83, no. 1 (January 1, 2005): 151–83. http://dx.doi.org/10.1139/z04-177.
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This review covers 25 years of progress on structural, functional, and developmental neurobiology of adult tunicates. The focus is on ascidians rather than pelagic species. The ascidian brain and peripheral nervous system are considered from the point of view of ultrastructure, neurotransmitters, regulatory peptides, and electrical activity. Sensory reception and effector control are stressed. Discussion of the dorsal strand plexus centres on its relationship with photoreceptors, the presence in it of gonadotropin-releasing hormone and its role in reproductive control. In addition to hydrodynamic sense organs based on primary sensory neurons (cupular organs), ascidians are now known to have coronal sense organs based on axonless hair cells resembling those of the vertebrate acustico-lateralis system. The peripheral nervous system is remarkable in that the motor neuron terminals are apparently interconnected synaptically, providing the equivalent of a nerve net. Development of the neural complex in ascidians is reviewed, highlighting recent embryological and molecular evidence for stomodeal, neurohypophyseal, and atrial placodes. The nervous system forms similarly during embryogenesis in the oozooid and blastogenesis in colonial forms. The regeneration of the brain in Ciona intestinalis (L., 1767) is discussed in relation to normal neurogenesis. Finally, the viviparous development of salps is considered, where recent work traces the early development of the brain, outgrowth of nerve roots, and the targetting of motor nerves to the appropriate muscles.
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Jeffery, W. R., W. R. Bates, R. L. Beach, and C. R. Tomlinson. "Is maternal mRNA a determinant of tissue-specific proteins in ascidian embryos?" Development 97, Supplement (October 1, 1986): 1–14. http://dx.doi.org/10.1242/dev.97.supplement.1.
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The generation of different cell types during embryonic development is thought to be mediated by the combined activity of cytoplasmic factors (determinants), which are localized in the egg, and inductive interactions, which occur between different embryonic cells and tissues. Ascidians, animals that exhibit rapid and exceptionally autonomous development (reviewed by Jeffery, 1985), appear to employ cytoplasmic determinants to generate embryonic cell diversity. Although determinants have not been identified in ascidians or other animals, it is hypothesized that they function in at least two different ways. First, as initially pointed out by Morgan (1934), determinants may be regulatory factors which promote differential gene expression in specific cell lineages. Consistent with this possibility, inhibitors of transcription, added prior to gastrulation, block the appearance of some ascidian tissue-specific enzymes and morphological markers whose expression is regulated by the activity of cytoplasmic determinants (Whittaker, 1973; Crowther & Whittaker, 1984). Second, determinants may be localized factors which promote cell diversification independent of zygotic gene expression.
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SANAMYAN, KAREN, DANIEL F. GLEASON, and NADEZHDA SANAMYAN. "A new species of Polyzoa (Ascidiacea: Styelidae) from the Atlantic coast of N America, U.S.A." Zootaxa 2088, no. 1 (May 1, 2009): 65–68. http://dx.doi.org/10.11646/zootaxa.2088.1.7.
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A new species of colonial Styelid ascidian of the genus Polyzoa was found attached to the test of solitary ascidians collected by divers off the coast of Georgia, U.S.A. The colony of this new species, consisting of small sandy zooids, is cryptic and difficult to detect. The species is characterized by three longitudinal branchial vessels on each side of the body and is the second species of the genus reported for the Atlantic.
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Fodor, Alexander C. A., Megan M. Powers, Kristin Andrykovich, Jiatai Liu, Elijah K. Lowe, C. Titus Brown, Anna Di Gregorio, Alberto Stolfi, and Billie J. Swalla. "The Degenerate Tale of Ascidian Tails." Integrative and Comparative Biology 61, no. 2 (June 28, 2021): 358–69. http://dx.doi.org/10.1093/icb/icab022.
Full textAbstract:
Abstract Ascidians are invertebrate chordates, with swimming chordate tadpole larvae that have distinct heads and tails. The head contains the small brain, sensory organs, including the ocellus (light) and otolith (gravity) and the presumptive endoderm, while the tail has a notochord surrounded by muscle cells and a dorsal nerve cord. One of the chordate features is a post-anal tail. Ascidian tadpoles are nonfeeding, and their tails are critical for larval locomotion. After hatching the larvae swim up toward light and are carried by the tide and ocean currents. When competent to settle, ascidian tadpole larvae swim down, away from light, to settle and metamorphose into a sessile adult. Tunicates are classified as chordates because of their chordate tadpole larvae; in contrast, the sessile adult has a U-shaped gut and very derived body plan, looking nothing like a chordate. There is one group of ascidians, the Molgulidae, where many species are known to have tailless larvae. The Swalla Lab has been studying the evolution of tailless ascidian larvae in this clade for over 30 years and has shown that tailless larvae have evolved independently several times in this clade. Comparison of the genomes of two closely related species, the tailed Molgula oculata and tailless Molgula occulta reveals much synteny, but there have been multiple insertions and deletions that have disrupted larval genes in the tailless species. Genomics and transcriptomics have previously shown that there are pseudogenes expressed in the tailless embryos, suggesting that the partial rescue of tailed features in their hybrid larvae is due to the expression of intact genes from the tailed parent. Yet surprisingly, we find that the notochord gene regulatory network is mostly intact in the tailless M. occulta, although the notochord does not converge and extend and remains as an aggregate of cells we call the “notoball.” We expect that eventually many of the larval gene networks will become evolutionarily lost in tailless ascidians and the larval body plan abandoned, with eggs developing directly into an adult. Here we review the current evolutionary and developmental evidence on how the molgulids lost their tails.
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MONNIOT, FRANÇOISE. "Additional records of bathyal ascidians (Tunicata) from the New Caledonia region." Zootaxa 5195, no. 3 (October 12, 2022): 201–23. http://dx.doi.org/10.11646/zootaxa.5195.3.1.
Full textAbstract:
Two expeditions EXBODI (2011) and SPANBIOS (2021) sampled the invertebrate fauna of deep bottoms on each side of New Caledonia. Many ascidians were collected and the most part are already known species. Among the 13 species described and figured, two are new to science. All have typical characters of a deep habitat. Variability of the internal anatomy is described for abundant specimens of the same species from the same location. There is no concordance with the littoral ascidian fauna.
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Swalla, B. J., M. R. Badgett, and W. R. Jeffery. "Identification of a cytoskeletal protein localized in the myoplasm of ascidian eggs: localization is modified during anural development." Development 111, no. 2 (February 1, 1991): 425–36. http://dx.doi.org/10.1242/dev.111.2.425.
Full textAbstract:
The myoplasm of ascidian eggs is a localized cytoskeletal domain that is segregated to presumptive larval tail muscle cells during embryonic development. We have identified a cytoskeletal protein recognized by a vertebrate neurofilament monoclonal antibody (NN18) which is concentrated in the myoplasm in eggs and embryos of a variety of ascidian species. The NN18 antigen is localized in the periphery of unfertilized eggs, segregates with the myoplasm after fertilization, and enters the larval tail muscle cells during embryonic development. Western blots of one-dimensional and two-dimensional gels showed that the major component recognized by NN18 antibody is a 58 × 10(3) Mr protein (p58), which exists in at least three different isoforms. The enrichment of p58 in the Triton X-100-insoluble fraction of eggs and its reticular staining pattern in eggs and embryos suggests that it is a cytoskeletal protein. In subsequent experiments, p58 was used as a marker to determine whether changes in the myoplasm occur in eggs of anural ascidian species, i.e. those exhibiting a life cycle lacking tadpole larvae with differentiated muscle cells. Although p58 was localized in the myoplasm in eggs of four urodele ascidian species that develop into swimming tadpole larvae, this protein was distributed uniformly in eggs of three anural ascidian species. The eggs of two of these anural species contained the actin lamina, another component of the myoplasm, whereas the third anural species lacked the actin lamina. There was no detectible localization of p58 after fertilization or segregation into muscle lineage cells during cleavage of anural eggs. NN18 antigen was uniformly distributed in pre-vitellogenic oocytes and then localized in the perinuclear zone during vitellogenesis of urodele and anural ascidians. Subsequently, NN18 antigen was concentrated in the peripheral cytoplasm of post-vitellogenic oocytes and mature eggs of urodele, but not anural, ascidians. It is concluded that the myoplasm of ascidian eggs contains an intermediate filament-like cytoskeletal network which is missing in anural species that have modified or eliminated the tadpole larva.
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Berná, Luisa, Fernando Alvarez-Valin, and Giuseppe D'Onofrio. "How Fast Is the Sessile Ciona?" Comparative and Functional Genomics 2009 (2009): 1–6. http://dx.doi.org/10.1155/2009/875901.
Full textAbstract:
Genomewide analyses of distances between orthologous gene pairs from the ascidian speciesCiona intestinalisandCiona savignyiwere compared with those of vertebrates. Combining this data with a detailed and careful use of vertebrate fossil records, we estimated the time of divergence between the two ascidians nearly 180 My. This estimation was obtained after correcting for the different substitution rates found comparing several groups of chordates; indeed we determine here that on average Ciona species evolve 50% faster than vertebrates.
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Matos, Ana, Dany Domínguez-Pérez, Daniela Almeida, Guillermin Agüero-Chapin, Alexandre Campos, Hugo Osório, Vitor Vasconcelos, and Agostinho Antunes. "Shotgun Proteomics of Ascidians Tunic Gives New Insights on Host–Microbe Interactions by Revealing Diverse Antimicrobial Peptides." Marine Drugs 18, no. 7 (July 13, 2020): 362. http://dx.doi.org/10.3390/md18070362.
Full textAbstract:
Ascidians are marine invertebrates associated with diverse microbial communities, embedded in their tunic, conferring special ecological and biotechnological relevance to these model organisms used in evolutionary and developmental studies. Next-generation sequencing tools have increased the knowledge of ascidians’ associated organisms and their products, but proteomic studies are still scarce. Hence, we explored the tunic of three ascidian species using a shotgun proteomics approach. Proteins extracted from the tunic of Ciona sp., Molgula sp., and Microcosmus sp. were processed using a nano LC-MS/MS system (Ultimate 3000 liquid chromatography system coupled to a Q-Exactive Hybrid Quadrupole-Orbitrap mass spectrometer). Raw data was searched against UniProtKB – the Universal Protein Resource Knowledgebase (Bacteria and Metazoa section) using Proteome Discoverer software. The resulting proteins were merged with a non-redundant Antimicrobial Peptides (AMPs) database and analysed with MaxQuant freeware. Overall, 337 metazoan and 106 bacterial proteins were identified being mainly involved in basal metabolism, cytoskeletal and catalytic functions. 37 AMPs were identified, most of them attributed to eukaryotic origin apart from bacteriocins. These results and the presence of “Biosynthesis of antibiotics” as one of the most highlighted pathways revealed the tunic as a very active tissue in terms of bioactive compounds production, giving insights on the interactions between host and associated organisms. Although the present work constitutes an exploratory study, the approach employed revealed high potential for high-throughput characterization and biodiscovery of the ascidians’ tunic and its microbiome.
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MONDAL, JHIMLI, C. RAGHUNATHAN, and KAILASH CHANDRA. "A new species of Ascidiacea (Herdmania andamanensis sp. nov.) from Andaman and Nicobar Islands, India." Zootaxa 4286, no. 3 (July 3, 2017): 445. http://dx.doi.org/10.11646/zootaxa.4286.3.13.
Full textAbstract:
Ascidians are the least explored fauna in Andaman and Nicobar Islands of India; only 85 species have been recorded from this area. The present paper describes a new species of ascidian, Herdmania andamanensis sp. nov. from Andaman and Nicobar Islands collected from two localities at the depth of 8–10 m. The species closely resembles Herdmania coutieri C. Monniot, 2002 and Herdmania mauritiana (Drasche, 1884), however differs in several anatomical characters which distinguishes it as a new species of the genus Herdmania.
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McDougall, A., M. Levasseur, A. J. O'Sullivan, and K. T. Jones. "Cell cycle-dependent repetitive Ca(2+)waves induced by a cytosolic sperm extract in mature ascidian eggs mimic those observed at fertilization." Journal of Cell Science 113, no. 19 (October 1, 2000): 3453–62. http://dx.doi.org/10.1242/jcs.113.19.3453.
Full textAbstract:
Sperm-triggered Ca(2+) oscillations occur throughout the animal kingdom. The mechanism sperm use to trigger Ca(2+) oscillations at fertilization has not been resolved in any egg. The temporal, spatial and regulatory characteristics of the Ca(2+) oscillations during fertilization in ascidians offer a unique advantage over other systems for determining the mechanism of fertilization. For example, sperm trigger two phases of Ca(2+) oscillations that are all waves in ascidians. The first of these Ca(2+) waves begins at the point of sperm-egg fusion while a second phase of Ca(2+) waves originates at a vegetal protrusion termed the contraction pole. In addition, cyclin B1-dependent kinase activity provides a form of positive feedback, maintaining the second phase of Ca(2+) waves during meiosis and thereby ensuring meiotic exit. We therefore prepared cytosolic ascidian sperm extracts or MonoQ-fractionated ascidian sperm extracts from this urochordate to investigate if a Ca(2+)-releasing sperm-borne factor was responsible for egg activation. Spatially, ascidian sperm extract induced repetitive Ca(2+) waves that mimicked the spatial pattern displayed during fertilization: all the second-phase Ca(2+) waves originated at a vegetal protrusion termed the contraction pole (thus mimicking fertilisation). We also demonstrated that ascidian sperm extract-induced Ca(2+) oscillations were maintained when CDK activity was elevated and MAP kinase activity was low, as found previously for sperm-triggered Ca(2+) oscillations. As would be predicted, large doses of ascidian sperm extract injected into prophase-stage oocytes, lacking CDK activity, failed to induce any Ca(2+) release even though they responded to microinjection of the Ca(2+)-releasing second messenger inositol 1,4,5-trisphosphate. Finally, since the Ca(2+)-releasing activity from Mono-Q fractionated ascidian sperm extract eluted predominantly as one fraction, this may imply that one factor is responsible for the Ca(2+)-releasing activity. These data support a model of egg activation whereby the sperm introduces a Ca(2+)-releasing cytosolic factor into the egg. We demonstrated that ascidian sperm contain a protein factor(s) that is regulated by the egg CDK activity and can trigger all the Ca(2+)waves observed at fertilization with a spatial pattern that mimics those initiated by sperm.
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Sordino, Paolo, Lisa Belluzzi, Rosaria De Santis, and William C. Smith. "Developmental genetics in primitive chordates." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 356, no. 1414 (October 29, 2001): 1573–82. http://dx.doi.org/10.1098/rstb.2001.0919.
Full textAbstract:
Recent advances in the study of the genetics and genomics of urochordates testify to a renewed interest in this chordate subphylum, believed to be the most primitive extant chordate relatives of the vertebrates. In addition to their primitive nature, many features of their reproduction and early development make the urochordates ideal model chordates for developmental genetics. Many urochordates spawn large numbers of transparent and externally developing embryos on a daily basis. Additionally, the embryos have a defined and well–characterized cell lineage until the end of gastrulation. Furthermore, the genomes of the urochordates have been estimated to be only 5–10% of the size of the vertebrates and to have fewer genes and less genetic redundancy than vertebrates. Genetic screens, which are powerful tools for investigating developmental mechanisms, have recently become feasible due to new culturing techniques in ascidians. Because hermaphrodite ascidians are able to self–fertilize, recessive mutations can be detected in a single generation. Several recent studies have demonstrated the feasibility of applying modern genetic techniques to the study of ascidian biology.
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Mohsin A. Al-Sofyani, Abdul, and Sathianeson Satheesh. "Recruitment patterns of the solitary ascidian Phallusia nigra Savigny, 1816 on artificial substrates submerged in the central Red Sea, Saudi Arabia." Oceanological and Hydrobiological Studies 48, no. 3 (September 25, 2019): 262–69. http://dx.doi.org/10.2478/ohs-2019-0023.
Full textAbstract:
Abstract The solitary ascidian Phallusia nigra is commonly found on hard substrates along the Jeddah coastal waters of the central Red Sea. In this study, the recruitment pattern of P. nigra on artificial substrates was assessed in relation to their type, surface color and orientation. The results showed a higher recruitment rate of the ascidian species on concrete and dark panels. The abundance of the ascidian on test panels varied between the four seasons. The orientation (vertical or horizontal) of the panels did not show any major difference in the recruitment. Significant effects of light intensityon the recruitment of P. nigra were observed on test panels, with higher abundance on panels submerged in the shade. In conclusion, this study clearly indicates the importance of the type and color of substrates in the recruitment of ascidians on artificial materials.
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TATIÁN, MARCOS, RICARDO SAHADE, and GRACIELA B. ESNAL. "Diet components in the food of Antarctic ascidians living at low levels of primary production." Antarctic Science 16, no. 2 (June 2004): 123–28. http://dx.doi.org/10.1017/s0954102004001890.
Full textAbstract:
Coupling between pelagic and benthic systems has been described in numerous shallow water communities. In Potter Cove, where pelagic primary production is low (not only during the Antarctic winter but also during the summer), the rich benthic community present there must depend on other food sources than phytoplankton. Over a year-round period we determined the abundance of the different seston particles which constituted the stomach contents of the Antarctic ascidian Cnemidocarpa verrucosa (Lesson, 1830) at Potter Cove. Stomach repletion was highest in November and lowest in June. Ascidians took in a wide range of particles from large detritus (macroalgal debris and faecal pellets) to minute particles < 5 μm. Large detritus and minute particles together represent the main percentage of contents throughout the year (mean 91%). Diatoms were a low percentage (mean 4.5%). Unidentified flagellates, dinoflagellates and coccolithophorids were scarce, with mean values lower than 4%. Among diatoms benthic species were more abundant in summer and pelagic ones prevailed from March to November. Resuspension of benthic material due to wind mixing and the input of allochthonous particles by currents are important mechanisms that ensure food for ascidians and the community of suspension feeders in Potter Cove.