Pour voir les autres types de publications sur ce sujet consultez le lien suivant : 18st century.
Articles de revues sur le sujet « 18st century »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 19 meilleurs articles de revues pour votre recherche sur le sujet « 18st century ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Leray, Matthieu, et Nancy Knowlton. « Censusing marine eukaryotic diversity in the twenty-first century ». Philosophical Transactions of the Royal Society B : Biological Sciences 371, no 1702 (5 septembre 2016) : 20150331. http://dx.doi.org/10.1098/rstb.2015.0331.
Texte intégralRésumé :
The ocean constitutes one of the vastest and richest biomes on our planet. Most recent estimations, all based on indirect approaches, suggest that there are millions of marine eukaryotic species. Moreover, a large majority of these are small (less than 1 mm), cryptic and still unknown to science. However, this knowledge gap, caused by the lack of diagnostic morphological features in small organisms and the limited sampling of the global ocean, is currently being filled, thanks to new DNA-based approaches. The molecular technique of PCR amplification of homologous gene regions combined with high-throughput sequencing, routinely used to census unculturable prokaryotes, is now also being used to characterize whole communities of marine eukaryotes. Here, we review how this methodological advancement has helped to better quantify the magnitude and patterns of marine eukaryotic diversity, with an emphasis on taxonomic groups previously largely overlooked. We then discuss obstacles remaining to achieve a global understanding of marine eukaryotic diversity. In particular, we argue that 18S variable regions do not provide sufficient taxonomic resolution to census marine life, and suggest combining broad eukaryotic surveys targeting the 18S rRNA region with more taxon-focused analyses of hypervariable regions to improve our understanding of the diversity of species, the functional units of marine ecosystems. This article is part of the themed issue ‘From DNA barcodes to biomes’.
2
KOLBASOVA, G., et T. NERETINA. « A new species of Pelagobia (Lopadorrhynchidae, Annelida), with some notes on literature records of Pelagobia longicirrata Greeff, 1879 ». Zootaxa 5023, no 1 (17 août 2021) : 77–92. http://dx.doi.org/10.11646/zootaxa.5023.1.4.
Texte intégralRésumé :
Since the second half of the XX century, almost all Pelagobia samples from the Arctic, Antarctic, Atlantic and Pacific oceans had been identified as cosmopolitan P. longicirrata. The indistinct nuchal organs in P. longicirrata samples from the South China Sea (Spratly Islands and Taiwan) were considered a morphological feature of the Pacific population. Our morphological and genetic investigation of Pelagobia specimens from the Nhatrang Bay, Vietnam reveals a new species in this region. Pelagobia rubromaculata sp. nov. differs from P. longicirrata by its triangle head, with nuchal organs closely adjacent to the lateral sides of prostomium, by short tentacular cirri reaching only the posterior edge of the third segment, and by a specific colouration pattern with red spots. Using nuclear 18S and 28S rDNA markers reveals that P. rubromaculata sp. nov. forms a well-supported clade, confirming the validity of the new species. Phylogenetic analysis of all available P. longicirrata sequences using both single 18S and concatenated 18S and 28S genes shows at least three distinct clades: Central Atlantic, Arctic and South Atlantic. Antarctic specimens do not form any distinct clade and fall between other clades with low support.
3
Gyulai, G., M. Humphreys, R. Lagler, Z. Szabo, Z. Toth, A. Bittsanszky, F. Gyulai et L. Heszky. « Seed remains of common millet from the 4th (Mongolia) and 15th (Hungary) centuries : AFLP, SSR and mtDNA sequence recoveries ». Seed Science Research 16, no 3 (septembre 2006) : 179–91. http://dx.doi.org/10.1079/ssr2006251.
Texte intégralRésumé :
Seed remains of common millet (Panicum miliaceumL.) were excavated from sites of ad 4th-century Darhan (Mongolia), and ad 15th-century Budapest (Hungary). Because the 15th-century medieval grains looked so intact, a germination test was carried out under aseptic conditions, which resulted in swelling of the grains but no cell proliferation or germination. Ancient DNA (aDNA) was extracted from the aseptic grains; analysed for amplified fragment length polymorphisms (AFLP), simple sequence repeats (SSR) and mitochondrial DNA (mtDNA); and compared with the modern millet cultivar ‘Topaz’. AFLP analysis revealed that extensive DNA degradation had occurred in the 4th-century ancient millet, resulting in only 2 (1.2%) AFLP fragments (98.8% degradation) amplified byMseCAA–EcoAGT, compared to the 15th-century medieval millet, with 158 (40%) fragments (60% degradation), and modern millet cultivar ‘Topaz’ with 264 fragments (100%).EcoAGT–MseCAA was found to be the most effective selective-primer combination for the analysis of medieval and modern millet. Eight AFLP fragments were sequenced after re-amplification and cloning. Microsatellite (SSR) analysis at the nucleargln4,sh1,rps28 andrps15 loci revealed one SNP (single nucleotide polymorphism) at the 29th position (A→G) ofrps28 locus, compared to modern millet. An mtDNA fragment (MboI), amplified at the 18S–5S ribosomal DNA (rDNA) locus in the medieval millet, showed no molecular changes compared to modern millet. The results underline the significance of aDNA extraction and analysis of excavated seeds for comparative analysis and molecular reconstruction of ancient and extinct plant genotypes.
4
Zakiyah, Zakiyah. « KITAB AL-SANĪ AL-MAṬĀLIB : INTERKONEKSI NAHWU DAN TASAWUF ». Walisongo : Jurnal Penelitian Sosial Keagamaan 20, no 2 (15 décembre 2012) : 371. http://dx.doi.org/10.21580/ws.2012.20.2.204.
Texte intégralRésumé :
<p class="IIABSBARU">This paper reviews a book entitled al-Sanī al-Maṭālib written by Kiai Nur Iman Mlangi Yogyakarta. This book is written in Arabic containing an interconnection between Arabic grammar and mysticism. This book is very interesting due to the fact that those two knowledges have its own rules. In addition, there is only small number of authors who had written with the same model, to name one of them is Shaikh Abdul Qadir bin Ahmad al-Kuhany with his work entitled Manniyat al-Fāqir al-Munjarid wa Sayrat al-Murīd al-Mutafarrid”. The book al-Sanī al-Maṭālib was predicted written in the late 18s Century or the beginning of 19s century, it is based on the period of Kiai Nur Iman’s life in which around the mid of 18s century. The grammatical rule of Arabic in this book was explained theosophically, it is started with the explanation of tauhid (oneness) as the basic learning for Muslim, followed by the meaning of each Arabic rule in mystical aspect.</p><p class="IKa-ABSTRAK">***</p><p class="IIABSBARU">Tulisan ini mereview buku yang berjudul <em>al-Sanī al-Maṭālib</em> yang ditulis oleh Kiai Nur Iman Mlangi Yogyakarta. Buku ini ditulis dalam bahasa Arab yang mengandung interkoneksi antara ilmu Nahwu (tata bahasa Arab) dengan mistisisme. Buku ini sangat menarik karena kenyataan bahwa kedua pengetahuan tersebut memiliki aturan sendiri-sendiri. Selain itu, sangat sedikit penulis yang menulis dengan gaya seperti itu. Salah satunya adalah Syaikh Abdul Qadir bin Ahmad al-Kuhany dengan karyanya yang berjudul <em>Manniyat al-Fāqir al-Munjarid wa Sayrat al-Murīd al-Mutafarrid</em>. Buku al-Saniy al-Muthalib diduga telah ditulis pada akhir abad ke-18 atau awal abad ke-19, menurut periode kehidupan Kiai Nur Iman yaitu sekitar pertengahan abad ke-18. Aturan Nahwu dalam buku ini dijelaskan secara teosofi yang dimulai dengan penjelasan mengenai tauhid (keesaan Tuhan) sebagai kajian dasar bagi orang Islam, yang diikuti dengan makna dari masing-masing aturan bahasa Arab dalam aspek mistiknya.</p>
5
Escamilla Pérez, Rocío G., Javier Reyes Trujeque, Tezozomoc Pérez López, Víctor Monteón Padilla et Ruth López Alcántara. « Identification of Microorganisms Associated to the Biodegradation of Historic Masonry Structure in San Francisco de Campeche City, México ». MRS Proceedings 1374 (2012) : 187–94. http://dx.doi.org/10.1557/opl.2012.1388.
Texte intégralRésumé :
ABSTRACTTropical climate create ideal conditions for the development of microbial communities associated with biodegradation of historic buildings made with stony materials. This is the case of Fort San Carlos, a historic colonial building representative of military tendencies during the XVII century in San Francisco de Campeche City. In this study the Polymerase Chain Reaction (PCR), was used to identify microorganisms related with the biodegradation of its masonry structure. Specific primers for amplification of 16S and 18S ribosomal RNA genes were used for organisms identification by PCR. Amplification products were sequenced and after that compared with GENBANK nucleotide database using-BLASTn. Results indicated that microbial communities associated to biodegradation of the Fort San Carlos are bacteria from the Phyla Cyanobacteria, Proteobacteria and Actinobacteria.
6
Edgecombe, Gregory D., et Gonzalo Giribet. « A century later - a total evidence re-evaluation of the phylogeny of scutigeromorph centipedes (Myriapoda:Chilopoda) ». Invertebrate Systematics 20, no 5 (2006) : 503. http://dx.doi.org/10.1071/is05044.
Texte intégralRésumé :
Scutigeromorpha (‘house centipedes’) play a pivotal role in myriapod systematics in being the sister group to all other chilopods, but their internal phylogeny has not been comprehensively appraised since K. W. Verhoeff’s morphological investigations a century ago. Relationships between the three families of Scutigeromorpha are inferred based on a combined analysis of approximately 5.5 Kb of sequence data from five molecular markers (complete 18S rRNA, a 2.2-Kb fragment of 28S rRNA, 16S rRNA, cytochrome c oxidase subunit I, histone H3) and 33 ingroup morphological characters. Molecular data are available for 19 ingroup terminals representing 14 morphospecies that include the genera Scutigerina, Madagassophora (family Scutigerinidae), Sphendononema (family Pselliodidae), Scutigera, Thereuopoda, Thereuopodina, Thereuonema, Allothereua and Parascutigera (family Scutigeridae). Morphology resolves the southern African–Malagasy Scutigerinidae as sister to all other Scutigeromorpha, whereas rival sister-group relationships between the Neotropical–Afrotropical Pselliodidae and Scutigerinidae + Scutigeridae or Pselliodidae + Scutigerinidae and Scutigeridae are resolved by the molecular and combined analyses. Monophyly of Scutigeridae and Thereuoneminae are stable across a broad range of analytical parameters. Thereuoneminae is composed of two stable clades: an Allothereua + Parascutigera group, and a grouping of Thereuopoda, Thereuonema and Thereuopodina. Molecular and combined analyses resolve the genus Scutigerina and the morphospecies Scutigerina weberi as paraphyletic, in both cases with a Malagasy clade excluding populations from southern Africa.
7
Lágler, Richárd, Gábor Gyulai, Zoltán Szabó, Zoltán Tóth et László Heszky. « Sequence stability at SSR, ISSR and mtDNA loci of common millet (Panicum miliaceum) from the middle ages ». Acta Agraria Debreceniensis, no 27 (15 novembre 2007) : 10–19. http://dx.doi.org/10.34101/actaagrar/27/3093.
Texte intégralRésumé :
Seed remains of medieval millet, recovered from a 15th century layer (King’s Palace, Budapest, Hungary), showed reddish yellow grain color after rehydrating on tissue culture medium that was close to grain color of modern cultivar Omszkoje. aDNA of medieval c. millet was extracted successfully, analyzed and compared to modern common millets by ISSR, SSR, CAPS and mtDNA. Analyses of fragments and sequences revealedpolymorphism at seven ISSR loci (22 alleles) and at the 5S-18S rDNA locus of mtDNA. CAPS analysis of the 5S-18S rDNA fragment revealed no SNPs in the restriction sites of six endonucleases TaqI, BsuRI, HinfI, MboI, AluI and RsaI. Sequence alignments of the restriction fragments RsaI also revealedconsensus sequence in the medieval sample compared to a modern variety. Morphological characterization of twenty common millet (Panicum miliaceum L., 2n=4×=36) cultivars and landraces revealed four distinct clusters which were apparently consistent with the grain colors of black, black and brown, red, yellow, and white. In the comparative AFLP, SSR and mtDNA analysis modern millet cv. ‘Topáz’ was used. AFLP analysis revealed that extensive DNA degradation had occurred in the 4th CENT. ancient millet resulting in only 2 (1.2%) AFLP fragments (98.8% degradation),compared to the 15th CENT. medieval millet with 158 (40%) fragments (60% degradation) and modern millet cv. ‘Topáz’ with 264 fragments (100%). Eight AFLP fragments were sequenced after reamplification and cloning. Microsatellite (SSR) analysis at the nuclear gln4, sh1, rps28 and rps15 loci of the medieval DNA revealed one SNP (single nucleotide polymorphism) at the 29th position (A to G) of rps28 locus compared to modern millet.Mitochondrial (mtDNA) fragment (MboI) amplified at the 5S-18S-rDNA locus in the medieval millet showed no molecular changes compared to modern millet. The results underline the significance of survived aDNA extraction and analysis of excavated seeds for comparative analysis and molecular reconstruction of ancient and extinct plant genotypes. An attempted phenotype reconstruction indicated that medieval common millet showed the closest morphological similarity to modern millet cultivar Omszkoje.
8
Oliveira, Vanessa C. S., Marie Altmanová, Patrik F. Viana, Tariq Ezaz, Luiz A. C. Bertollo, Petr Ráb, Thomas Liehr et al. « Revisiting the Karyotypes of Alligators and Caimans (Crocodylia, Alligatoridae) after a Half-Century Delay : Bridging the Gap in the Chromosomal Evolution of Reptiles ». Cells 10, no 6 (5 juin 2021) : 1397. http://dx.doi.org/10.3390/cells10061397.
Texte intégralRésumé :
Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a probe, whole chromosome painting (WCP), and comparative genome hybridization. All Caimaninae species have a diploid chromosome number (2n) 42 and karyotypes dominated by acrocentric chromosomes, in contrast to both species of Alligatorinae, which have 2n = 32 and karyotypes that are predominantly metacentric, suggesting fusion/fission rearrangements. Our WCP results supported this scenario by revealing the homeology of the largest metacentric pair present in both Alligator spp. with two smaller pairs of acrocentrics in Caimaninae species. The clusters of 18S rDNA were found on one chromosome pair in all species, except for Paleosuchus spp., which possessed three chromosome pairs bearing these sites. Similarly, comparative genomic hybridization demonstrated an advanced stage of sequence divergence among the caiman genomes, with Paleosuchus standing out as the most divergent. Thus, although Alligatoridae exhibited rather low species diversity and some level of karyotype stasis, their genomic content indicates that they are not as conserved as previously thought. These new data deepen the discussion of cytotaxonomy in this family.
9
Manuel, M. « Phylogeny and evolution of calcareous sponges ». Canadian Journal of Zoology 84, no 2 (1 février 2006) : 225–41. http://dx.doi.org/10.1139/z06-005.
Texte intégralRésumé :
The most recent advances concerning the phylogeny and evolution of calcareous sponges (Calcarea or Calcispongia) are reviewed here, in the light of the history of taxonomy of the group and conceptions about its evolution, starting from Haeckel's works at the end of the 19th century. Calcisponge phylogeny has recently started to be addressed using modern tools of phylogenetic reconstruction: cladistic analysis of morphological characters and molecular phylogeny (so far using 18S and 28S rDNA sequences). The monophyly of calcareous sponges is strongly supported in these works, as is their subdivision into two clades, Calcinea (whose proposed synapomorphy is the basal position of nuclei in choanocytes, with no relation to the flagella) and Calcaronea (whose possible synapomorphy is the formation of the amphiblastula larva through the original process of eversion of the stomoblastula). While the molecular phylogeny of Calcinea is still in its infancy because of insufficient taxonomic sampling, several lines are emerging for the phylogeny of Calcaronea, and these are in strong disagreement with the classification issued from the "traditional" morphological approach. Phylogenetic hypotheses also permit the reconstruction of morphological character evolution, which appears complex and subject to a high level of homoplasy.
10
Galindo, Luis Javier, Guifré Torruella, David Moreira, Yana Eglit, Alastair G. B. Simpson, Eckhard Völcker, Steffen Clauß et Purificación López-García. « Combined cultivation and single-cell approaches to the phylogenomics of nucleariid amoebae, close relatives of fungi ». Philosophical Transactions of the Royal Society B : Biological Sciences 374, no 1786 (7 octobre 2019) : 20190094. http://dx.doi.org/10.1098/rstb.2019.0094.
Texte intégralRésumé :
Nucleariid amoebae (Opisthokonta) have been known since the nineteenth century but their diversity and evolutionary history remain poorly understood. To overcome this limitation, we have obtained genomic and transcriptomic data from three Nuclearia , two Pompholyxophrys and one Lithocolla species using traditional culturing and single-cell genome (SCG) and single-cell transcriptome amplification methods. The phylogeny of the complete 18S rRNA sequences of Pompholyxophrys and Lithocolla confirmed their suggested evolutionary relatedness to nucleariid amoebae, although with moderate support for internal splits. SCG amplification techniques also led to the identification of probable bacterial endosymbionts belonging to Chlamydiales and Rickettsiales in Pompholyxophrys . To improve the phylogenetic framework of nucleariids, we carried out phylogenomic analyses based on two datasets of, respectively, 264 conserved proteins and 74 single-copy protein domains. We obtained full support for the monophyly of the nucleariid amoebae, which comprise two major clades: (i) Parvularia–Fonticula and (ii) Nuclearia with the scaled genera Pompholyxophrys and Lithocolla . Based on these findings, the evolution of some traits of the earliest-diverging lineage of Holomycota can be inferred. Our results suggest that the last common ancestor of nucleariids was a freshwater, bacterivorous, non-flagellated filose and mucilaginous amoeba. From the ancestor, two groups evolved to reach smaller ( Parvularia–Fonticula ) and larger ( Nuclearia and related scaled genera) cell sizes, leading to different ecological specialization. The Lithocolla + Pompholyxophrys clade developed exogenous or endogenous cell coverings from a Nuclearia -like ancestor. This article is part of a discussion meeting issue ‘Single cell ecology’.
11
Hammersley, Richard, Marie Reid et John Minkes. « Treatment for substance use problems among young offenders : Difficulties and dilemmas for implementation and evaluation in the UK ». Educational and Child Psychology 23, no 2 (2006) : 40–51. http://dx.doi.org/10.53841/bpsecp.2006.23.2.40.
Texte intégralRésumé :
Youth offending is assumed in part to be caused by substance use problems, consequently policy and practice in youth justice emphasise their treatment. We review four types of difficulty for substance use treatment of the under-18s and of youth offending team clients, then consider what might work. (1) Working with children raises systemic and ethical issues that complicate intervention and evaluation. (2) Assessing or diagnosing substance use problems in this age group is inherently problematic and often neglects the systemic aspects of pathways to treatment. Ineffective treatment may seem effective because change has occurred naturally with time. (3) Defining realistic and acceptable long-term outcomes for substance use in this age group is problematic. In the early 21st century it is developmentally normative for substance use to increase between ages 10 and 20, so interventions should strictly aim for a reduced rate of increase, rather than decrease or abstinence. Separating drugs from alcohol and tobacco in policy, over-problematising youthful drug use and assuming that drugs simply cause crime have hindered the setting of realistic objectives. (4) Operating, auditing and evaluating a substance problems service for children requires flexibility and sensitivity of practice that can work against evaluation; firm recommendations about the effectiveness of specific treatment packages are as yet inappropriate. Systemic and cognitive-behavioural therapies have most evidence of efficacy, while humanistic advocacy counselling is widely used, but interventions developed for adults cannot be applied unmodified to younger clients.
12
Wang, Yong, Tie Gang Li, Meng Ying Wang, Qi Liang Lai, Jiang Tao Li, Zhao Ming Gao, Zong Ze Shao et Pei-Yuan Qian. « Archive of bacterial community in anhydrite crystals from a deep-sea basin provides evidence of past oil-spilling in a benthic environment in the Red Sea ». Biogeosciences 13, no 23 (30 novembre 2016) : 6405–17. http://dx.doi.org/10.5194/bg-13-6405-2016.
Texte intégralRésumé :
Abstract. In deep-sea sediment, the microbes present in anhydrite crystals are potential markers of the past environment. In the Atlantis II Deep, anhydrite veins were produced by mild mixture of calcium-rich hydrothermal solutions and sulfate in the bottom water, which had probably preserved microbial inhabitants in the past seafloor of the Red Sea. In this study, this hypothesis was tested by analyzing the metagenome of an anhydrite crystal sample from the Atlantis II Deep. The estimated age of the anhydrite layer was between 750 and 770 years, which might span the event of hydrothermal eruption into the benthic floor. The 16S/18S rRNA genes in the metagenome were assigned to bacteria, archaea, fungi and even invertebrate species. The dominant species in the crystals was an oil-degrading Alcanivorax borkumensis bacterium, which was not detected in the adjacent sediment layer. Fluorescence microscopy using 16S rRNA and marker gene probes revealed intact cells of the Alcanivorax bacterium in the crystals. A draft genome of A. borkumensis was binned from the metagenome. It contained all functional genes for alkane utilization and the reduction of nitrogen oxides. Moreover, the metagenomes of the anhydrites and control sediment contained aromatic degradation pathways, which were mostly derived from Ochrobactrum sp. Altogether, these results indicate an oxic, oil-spilling benthic environment in the Atlantis II basin of the Red Sea in approximately the 14th century. The original microbial inhabitants probably underwent a dramatic selection process via drastic environmental changes following the formation of an overlying anoxic brine pool in the basin due to hydrothermal activities.
13
Huston, Daniel C., Scott C. Cutmore et Thomas H. Cribb. « Trigonocephalotrema (Digenea : Haplosplanchnidae), a new genus for trematodes parasitising fishes of two Indo-West Pacific acanthurid genera ». Invertebrate Systematics 32, no 4 (2018) : 759. http://dx.doi.org/10.1071/is17075.
Texte intégralRésumé :
The Great Barrier Reef is the largest coral reef ecosystem on the planet and supports a diverse community of marine fishes, as well as the organisms that parasitise them. Although the digenetic trematodes that parasitise fishes of the Great Barrier Reef have been studied for over a century, the species richness and diversity of many trematode lineages is yet to be explored. Trigonocephalotrema, gen. nov. is proposed to accommodate three new species, Trigonocephalotrema euclidi, sp. nov., T. hipparchi, sp. nov. and T. sohcahtoa, sp. nov., parasitic in fishes of Naso Lacepède and Zebrasoma Swainson (Acanthuridae) in the tropical Pacific. Species of Trigonocephalotrema are characterised with morphological and molecular data (18S rRNA, ITS2 and 28S rRNA). Species of Trigonocephalotrema are morphologically distinguished from all other haplosplanchnid lineages by having terminal, triangular, plate-like oral suckers. With the inclusion of the new molecular data, Bayesian inference and maximum likelihood analyses of the Haplosplanchnidae Poche, 1926 recovered identical tree topologies and demonstrated Trigonocephalotrema as a well-supported monophyletic group. Although species of Trigonocephalotrema are differentiated from all other haplosplanchnid lineages on the basis of morphology, species within the genus are morphologically cryptic; thus, accurate species identification will require inclusion of host and molecular data. Species of Trigonocephalotrema cannot be assigned to a recognised subfamily within the Haplosplanchnidae using either morphological or molecular data and would require the erection of a new subfamily to accommodate them. However, we find little value in the use of subfamilies within the Haplosplanchnidae, given that there are so few taxa in the family, and herein propose that their use be avoided.
14
GĄSIOREK, PIOTR, DANIEL STEC, WITOLD MOREK et ŁUKASZ MICHALCZYK. « An integrative redescription of Hypsibius dujardini (Doyère, 1840), the nominal taxon for Hypsibioidea (Tardigrada : Eutardigrada) ». Zootaxa 4415, no 1 (27 avril 2018) : 45. http://dx.doi.org/10.11646/zootaxa.4415.1.2.
Texte intégralRésumé :
A laboratory strain identified as “Hypsibius dujardini” is one of the best studied tardigrade strains: it is widely used as a model organism in a variety of research projects, ranging from developmental and evolutionary biology through physiology and anatomy to astrobiology. Hypsibius dujardini, originally described from the Île-de-France by Doyère in the first half of the 19th century, is now the nominal species for the superfamily Hypsibioidea. The species was traditionally considered cosmopolitan despite the fact that insufficient, old and sometimes contradictory descriptions and records prevented adequate delineations of similar Hypsibius species. As a consequence, H. dujardini appeared to occur globally, from Norway to Samoa. In this paper, we provide the first integrated taxonomic redescription of H. dujardini. In addition to classic imaging by light microscopy and a comprehensive morphometric dataset, we present scanning electron photomicrographs, and DNA sequences for three nuclear markers (18S rRNA, 28S rRNA, ITS-2) and one mitochondrial marker (COI) that are characterised by various mutation rates. The results of our study reveal that a commercially available strain that is maintained in many laboratories throughout the world, and assumed to represent H. dujardini sensu stricto, represents, in fact, a new species: H. exemplaris sp. nov. Redescribing the nominal taxon for Hypsibiidae, we also redefine the family and amend the definitions of the subfamily Hypsibiinae and the genus Hypsibius. Moreover, we transfer H. arcticus (Murray, 1907) and Hypsibius conifer Mihelčič, 1938 to the genus Ramazzottius since the species exhibit claws and eggs of the Ramazzottius type. Finally, we designate H. fuhrmanni as subjectively invalid because the extremely poor description precludes identifying neotype material.
15
Wittmann, Karl J., et Pierre Chevaldonné. « First report of the order Mysida (Crustacea) in Antarctic marine ice caves, with description of a new species of Pseudomma and investigations on the taxonomy, morphology and life habits of Mysidetes species ». ZooKeys 1079 (31 décembre 2021) : 145–227. http://dx.doi.org/10.3897/zookeys.1079.76412.
Texte intégralRésumé :
SCUBA diving explorations of three islands off Dumont d’Urville Station at the coast of Adélie Land, East Antarctica, enabled the observation of marine ice caves. Sampling in this unusual habitat yielded a total of three species of Mysidae, altogether previously poorly known or unknown to science. Pseudomma kryotroglodytumsp. nov. is described, based on the structure of the antennal scale, telson and on cornea-like lateral portions set off against the main body of eyeplates. Mysidetes illigi is re-established at species level after almost a century in synonymy. Re-descriptions are provided for M. illigi and M. hanseni, based on types and ice cave materials. Keys to the Southern Ocean species of Pseudomma and to the world-wide species of Mysidetes are given. Phylogenetic trees are provided for the genera Pseudomma and Mysidetes. 18S rDNA sequences of P. kryotroglodytum differ from GenBank sequences of other Pseudomma species. First sequence data are given for species of the genus Mysidetes: 18S differs between the two examined species and COI is quite diverse between and within species. We found previously unknown, probably sensorial structures in these ice cave species: in P. kryotroglodytum, the basal segment of the antennula shows a pit-like depression with striated pad on the bottom and a median cyst, connected with the bottom of the eyeplate cleft. M. illigi shows a female homologue of the appendix masculina bearing a field of modified setae. Subsequent investigations demonstrated these structures also in species from other habitats. The feeding apparatus and stomach contents of the three ice cave species point to brushing of small particles (detritus, microalgae) from available surfaces, such as sediment, rock and the ice surface. Differences in the feeding apparatus are very subtle between the two Mysidetes species. The high content of fat bodies in M. hanseni could help it to survive periods of starvation. The large storage volume of the foregut in P. kryotroglodytum points to the collection of food with low nutritional quality and could help to balance strongly fluctuating food availability. Summer specimens of M. hanseni showed a bimodal frequency of developmental stages in the marsupium and bimodal size-frequency distribution of free-living stages. The females with younger brood (embryos) were, on average, larger and carried more marsupial young than those with older brood (nauplioid larvae). All examined incubating and spent females showed (almost) empty foreguts and empty ovarian tubes, suggesting possible semelparity and death following the release of young. The absence of juveniles and immature females from summer samples suggests that growth and accumulation of fat and yolk occur outside ice caves, while such caves could be used by fattened adults as shelter for brooding. A provisional interpretation proposes a biannual life cycle for M. hanseni, superimposed with shifted breeding schedules, the latter characterised by early breeding and late breeding females, probably in response to harsh physical and trophic conditions along the continental coast of Antarctica.
16
Champion, Tony. « The United Kingdom’s ‘going away to university’ migration and its changing impact on local populations in the twenty-first century ». Local Economy : The Journal of the Local Economy Policy Unit, 18 juillet 2022, 026909422211146. http://dx.doi.org/10.1177/02690942221114625.
Texte intégralRésumé :
Against the background of strong growth in tertiary education globally, this paper documents the continued expansion of the United Kingdom’s higher education sector in the twenty-first century and examines the impact which the British tradition of ‘going away to university’ has been having on both the receiving and sending ends of this process. For each of the UK’s 379 local and unitary authorities, it compares the numbers of modal undergraduate age (19–21 year olds) with the number that would have been living there if the late school-age population (16–18 year olds) had merely aged in place. This approach is applied initially to 2019, with the findings then being compared with those for 2001, revealing that this migration funnels school leavers into a relatively small number of university cities and towns containing up to four times as many 19–21s as 16–18s, while siphoning off over 30% of school leavers from some of the main recruiting grounds–a pattern that has intensified since 2001. This raises questions about the future scale and nature of this process and its implications for local economies, given the current questioning of role of higher education in the UK and developments such as Brexit and the COVID-19 pandemic.
17
Novotny, Andreas, Kinlan Mehdi Goulwen Jan, Jan Dierking et Monika Winder. « Niche partitioning between planktivorous fish in the pelagic Baltic Sea assessed by DNA metabarcoding, qPCR and microscopy ». Scientific Reports 12, no 1 (29 juin 2022). http://dx.doi.org/10.1038/s41598-022-15116-7.
Texte intégralRésumé :
AbstractMarine communities undergo rapid changes related to human-induced ecosystem pressures. The Baltic Sea pelagic food web has experienced several regime shifts during the past century, resulting in a system where competition between the dominant planktivorous mesopredatory clupeid fish species herring (Clupea harengus) and sprat (Sprattus sprattus) and the rapidly increasing stickleback (Gasterosteus aculeatus) population is assumed to be high. Here, we investigate diet overlap between these three planktivorous fishes in the Baltic Sea, utilizing DNA metabarcoding on the 18S rRNA gene and the COI gene, targeted qPCR, and microscopy. Our results show niche differentiation between clupeids and stickleback, and highlight that rotifers play an important role in this pattern, as a resource that is not being used by the clupeids nor by other zooplankton in spring. We further show that all the diet assessment methods used in this study are consistent, but also that DNA metabarcoding describes the plankton-fish link at the highest taxonomic resolution. This study suggests that rotifers and other understudied soft-bodied prey may have an important function in the pelagic food web and that the growing population of pelagic stickleback may be supported by the open feeding niche offered by the rotifers.
18
Itoïz, Sarah, Sebastian Metz, Evelyne Derelle, Albert Reñé, Esther Garcés, David Bass, Philippe Soudant et Aurélie Chambouvet. « Emerging Parasitic Protists : The Case of Perkinsea ». Frontiers in Microbiology 12 (13 janvier 2022). http://dx.doi.org/10.3389/fmicb.2021.735815.
Texte intégralRésumé :
The last century has witnessed an increasing rate of new disease emergence across the world leading to permanent loss of biodiversity. Perkinsea is a microeukaryotic parasitic phylum composed of four main lineages of parasitic protists with broad host ranges. Some of them represent major ecological and economical threats because of their geographically invasive ability and pathogenicity (leading to mortality events). In marine environments, three lineages are currently described, the Parviluciferaceae, the Perkinsidae, and the Xcellidae, infecting, respectively, dinoflagellates, mollusks, and fish. In contrast, only one lineage is officially described in freshwater environments: the severe Perkinsea infectious agent infecting frog tadpoles. The advent of high-throughput sequencing methods, mainly based on 18S rRNA assays, showed that Perkinsea is far more diverse than the previously four described lineages especially in freshwater environments. Indeed, some lineages could be parasites of green microalgae, but a formal nature of the interaction needs to be explored. Hence, to date, most of the newly described aquatic clusters are only defined by their environmental sequences and are still not (yet) associated with any host. The unveiling of this microbial black box presents a multitude of research challenges to understand their ecological roles and ultimately to prevent their most negative impacts. This review summarizes the biological and ecological traits of Perkinsea—their diversity, life cycle, host preferences, pathogenicity, and highlights their diversity and ubiquity in association with a wide range of hosts.
19
Giribet, Gonzalo, Kate Sheridan, Caitlin M. Baker, Christina J. Painting, Gregory I. Holwell, Phil J. Sirvid et Gustavo Hormiga. « A molecular phylogeny of the circum-Antarctic Opiliones family Neopilionidae ». Invertebrate Systematics, 2021. http://dx.doi.org/10.1071/is21012.
Texte intégralRésumé :
The Opiliones family Neopilionidae is restricted to the terranes of the former temperate Gondwana: South America, Africa, Australia, New Caledonia and New Zealand. Despite decades of morphological study of this unique fauna, it has been difficult reconciling the classic species of the group (some described over a century ago) with recent cladistic morphological work and previous molecular work. Here we attempted to investigate the pattern and timing of diversification of Neopilionidae by sampling across the distribution range of the family and sequencing three markers commonly used in Sanger-based approaches (18S rRNA, 28S rRNA and cytochrome-c oxidase subunit I). We recovered a well-supported and stable clade including Ballarra (an Australian ballarrine) and the Enantiobuninae from South America, Australia, New Caledonia and New Zealand, but excluding Vibone (a ballarrine from South Africa). We further found a division between West and East Gondwana, with the South American Thrasychirus/Thrasychiroides always being sister group to an Australian–Zealandian (i.e. Australia + New Zealand + New Caledonia) clade. Resolution of the Australian–Zealandian taxa was analysis-dependent, but some analyses found Martensopsalis, from New Caledonia, as the sister group to an Australian–New Zealand clade. Likewise, the species from New Zealand formed a clade in some analyses, but Mangatangi often came out as a separate lineage from the remaining species. However, the Australian taxa never constituted a monophyletic group, with Ballarra always segregating from the remaining Australian species, which in turn constituted 1–3 clades, depending on the analysis. Our results identify several generic inconsistencies, including the possibility of Thrasychiroides nested within Thrasychirus, Forsteropsalis being paraphyletic with respect to Pantopsalis, and multiple lineages of Megalopsalis in Australia. In addition, the New Zealand Megalopsalis need generic reassignment: Megalopsalis triascuta will require its own genus and M. turneri is here transferred to Forsteropsalis, as Forsteropsalis turneri (Marples, 1944), comb. nov.