Morphologie évolutive et fonctionnelle des hémichordés

L’embranchement Hemichordata regroupe les classes Enteropneusta et Pterobranchia. Hemichordata constitue, avec l’embranchement Echinodermata, le groupe-frère des chordés. Les entéropneustes sont des organismes vermiformes solitaires qui vivent sous ou à la surface du substrat et s’alimentent généralement par déposivorie, alors que les ptérobranches sont des organismes coloniaux filtreurs habitant dans un réseau de tubes appelé coenecium. Ce mémoire présente trois études dont le point commun est l’utilisation des hémichordés actuels pour répondre à des questions concernant l’évolution des hémichordés, des chordés, et du super-embranchement qui les regroupe, Deuterostomia. Notre première étude démontre que les fentes pharyngiennes, l’organe pré-oral cilié (POCO) et le pharynx de l’entéropneuste Protoglossus graveolens sont utilisés pour l’alimentation par filtration. Le système de filtration de P. graveolens permet la capture de particules jusqu’à 1.3 um, à un débit de 4.05 mm.s-1, pour une demande énergétique de 0.009 uW. Les similarités structurales et fonctionnelles avec le système de filtration des céphalochordés suggèrent que la filtration pharyngienne est ancestrale aux deutérostomes. Lors de notre deuxième étude, nous avons exploré l’hypothèse selon laquelle le POCO des entéropneustes, une structure ciliée pré-buccale au rôle possiblement chémorécepteur, serait homologue au « wheel organ » des céphalochordés et à l’adénohypophyse des vertébrés. Pour cela, nous avons déterminé par immunohistochimie l’expression de Pit-1, un facteur de transcription spécifique à ces deux structures, chez l’entéropneuste Saccoglossus pusillus. Pit-1 est exprimé dans des cellules sensorielles du POCO, mais aussi dans des cellules épithéliales distribuées dans le proboscis, collet et tronc. Ce patron d’expression ne permet pas de confirmer ou rejeter l’homologie du POCO et de l’adénohypophyse des vertébrés. Lors de notre troisième étude, nous avons caractérisé l’ultrastructure du coenecium des ptérobranches Cephalodiscus hodgsoni, Cephalodiscus nigrescens et Cephalodiscus densus par microscopie électronique à transmisison et à balayage. Cephalodiscus est le groupe frère de Graptolithina, un groupe qui inclut les graptolithes éteints ainsi que les ptérobranches du genre Rhabdopleura. Nous avons décrit les types de fibrilles de collagène présents, leur taille et leur organisation, ainsi que l’organisation globale du coenecium. Nous avons ainsi démontré la présence chez Cephalodiscus d’une organisation similaire au paracortex, pseudocortex et eucortex des graptolithes. La présence chez Cephalodiscus de ce type d’organisation suggère que le cortex est ancestral à la classe Pterobranchia. Ces trois études illustrent plusieurs axes importants de la recherche sur les hémichordés, qui en intégrant des données morphologiques, fonctionnelles et moléculaires permet de reconstruire certains évènements clés de l’évolution des deutérostomes.

Intranuclear crystalloids of Antarctic sea urchins as a biomarker for oil contamination

Because of human actions, biomarkers have become important to detect and mitigate pollution. This study showed that crystalloids can be a biomarker for analyses of low levels of water-soluble fractions of oil (WSF). Antarctic sea urchins (Sterechinus neumayeri) from regions free of pollution were exposed for 2, 5, 10 and 15 days at different levels of WSF (0.4, 0.8 and 1.2 ppm). No significant differences were observed in the phagocytic rates or the germicide capacity for the yeast Saccharomyces cerevisiae; however, there was a significant increase in the quantity of intranuclear iron crystalloids in phagocytic amoebocytes of urchins exposed to higher levels of WSF. This study characterizes histological alterations in crystalloids of S. neumayeri that could be used as a biomarker for oil contaminants, with a simple and inexpensive protocol.

Bioecologia da ictiofauna marinha descartada pelo arrasto camaroeiro em praias da Bacia Potiguar, Brasil

The composition of ichthyofauna discarded by trawling shrimping, their reproductive status and feeding ecology were studied on the beaches of Basin Rio Grande do Norte, Brazil. Fish were collected monthly in the year of 2012. During biometrics, portions of the digestive tract and of gonads were removed, fixed in formalin 10% and Bouin, respectively, for be submitted to histological processing by the techniques of hematoxylin-eosin. Stomach content analyzes were performed using the methods of Frequency of Occurrence and Volumetric and was calculated the repletion index. Throughout the study period were recorded a total of 49 species. The fish assemblages differed between sections monitoring, with the highest abundance, biomass and indices of richness and diversity in sections B, D and C. Already the excerpt A, showed higher values for dominance and equitability. In the cluster analysis according to the faunal similarity was observed the formation of three groups: group I formed by excerpts B and D, group II by excerpt C and group III formed by excerpt A. The assessment of reproductive stage revealed that the fish assemblages discarded by trawling are composed mainly of juveniles. Regarding the feeding ecology, the species Larimus breviceps, Menticirrhus littoralis and Pomadasys corvinaeformis characterized as carnivorous with tendency to carcinofagia. Already Conodon nobilis characterized as carnivorous with tendency to piscivory, but all proved generalist-opportunistic with increase of feeding activity during drought. The dendrogram of grouping of the species developed based on the food items used shows the formation of four groups: Group I consists of species that feed mainly of "gastropod" and "sediment"; group II of "teleost fish"; the group III of "crustacea" and group IV of "echinodermata" and "bivalve". The anatomical and histological characteristics of the digestive tract were consistent with the dietary habits of the analyzed species. In this context, the Costa Branca of Rio Grande do Norte can be considered a feeding site and recruitment for juveniles, which, opportunistically, utilize resources associated with the background

Invertebrates from the Low Head Member (Polonez Cove Formation, Oligocene) at Vaureal Peak, King George Island, West Antarctica

Eight taxa of marine invertebrates, including two new bivalve species, are described from the Low Head Member of the Polonez Cove Formation (latest early Oligocene) cropping out in the Vaureal Peak area, King George Island, West Antarctica. The fossil assemblage includes representatives of Brachiopoda (genera Neothyris sp. and Liothyrella sp.), Bivalvia (Adamussium auristriatum sp. nov., ?Adamussium cf. A. alanbeui Jonkers, and Limatula (Antarctolima) ferraziana sp. nov.), Bryozoa, Polychaeta (serpulid tubes) and Echinodermata. Specimens occur in debris flows deposits of the Low Head Member, as part of a fan delta setting in a high energy, shallow marine environment. Liothyrella sp., Adamussium auristriatum sp. nov. and Limatula ferraziana sp. nov. are among the oldest records for these genera in King George Island. In spite of their restrict number and diversification, bivalves and brachiopods from this study display an overall dispersal pattern that roughly fits in the clockwise circulation of marine currents around Antarctica accomplished in two steps. The first followed the opening of the Tasmanian Gateway at the Eocene/Oligocene boundary, along the eastern margin of Antarctica, and the second took place in post-Palaeogene time, following the Drake Passage opening between Antarctic Peninsula and South America, along the western margin of Antarctica.

Dermatologia ambiental: Manifestações dermatológicas de acidentes por animais aquáticos (invertebrados)

Contact between humans and coastal areas has increased in recent decades, which has led to an increase in injuries from aquatic animals. The majority of these present dermatological manifestations, and some of them show typical lesions. The highest percentages of injuries that occur in marine environments are associated with invertebrates such as sea urchins, jellyfish and Portuguese men-of-war (echinoderms and cnidarians). In this review, we discuss the clinical, therapeutic and preventive aspects of injuries caused by marine and freshwater invertebrates, focusing on first aid measures and diagnosis for dermatologists and professionals in coastal areas. © 2013 by Anais Brasileiros de Dermatologia.

Resposta comportamentiais do ouriço-do-mar preto a pistas químicas que indicam risco de predação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O uso do vídeo como recurso didático para o ensino de Ciências e Biologia

As características dos animais do Filo Echinodermata e seus principais representantes são conteúdos abordados no ensino médio, na disciplina de Biologia. Dessa maneira, é importante a produção de um material didático que favoreça o entendimento dos alunos frente a esse tema. Sendo assim, os objetivos do trabalho foi elaborar um material didático na forma de vídeo para professores e alunos do ensino médio, que facilite a visualização e compreensão das principais características dos animais representantes do Filo Echinodermata e um guia de utilização do recurso para os professores, propondo a formas de abordar os conteúdos, utilizando as fotos e esquemas contidos no vídeo e o desenvolvimento de atividades como mais uma forma de avaliar os alunos. Todo o conteúdo abordado foi retirado de livros didáticos específicos de zoologia de invertebrados, a fim de prevenir a ocorrência de erros conceituais

Differences in diversity, structure, and variability between intertidal and subtidal meiofaunal assemblages

[EN] Meiofaunal assemblages from intertidal and shallow subtidal seabeds were studied at two sites (one dominated by volcanic sands and the other by organogenic sands) at Tenerife (Canary Islands, NE Atlantic Ocean) throughout an entire year (May 2000?April 2001). Specifically, we aimed (i) to test for differences in diversity, structure, and stability between intertidal and subtidal meiofaunal assemblages, and (ii) to determine if differences in the meiofaunal assemblage structure may be explained by environmental factors (granulometric composition, availability of organic matter, and carbonate content in sediments). A total of 103,763 meiofaunal individuals were collected, including 203 species from 19 taxonomic groups (Acari, Amphipoda, Cnidaria, Copepoda, Echinodermata, Gastrotricha, Isopoda, Insecta, Kinorrhyncha, Misidacea, Nematoda, Nemertini, Oligochaeta, Ostracoda, Polychaeta, Priapulida, Sipuncula, Tanaidacea, and Turbellaria). Nematodes were the most abundant taxonomic group. Species diversity was higher in the subtidal than in the intertidal zone at both sites, as a result of the larger dominance of a few species in the intertidal zone. The meiofaunal assemblage structure was different between tidal levels at both sites, the intertidal presenting greater temporal variability (multivariate dispersion) in the meiofaunal assemblage structure than the subtidal. Sediment grain size, here quantified by the different granulometric fractions, explained the variability in meiofaunal assemblage structure to a greater extent than the percentage of carbonates, a variable linked to sediment origin. This study revealed differences in diversity, assemblage structure, and variability between intertidal and subtidal meiofauna.

Spatio-temporal diversity of Megistozoobenthos in the Antalya Gulf and relationships with environmental features

Antalya Gulf is situated in the Levantine Sea, the second biggest and most eastern basin in the Mediterranean Sea. This area is an ultra-oligotrophic basin, strongly affected by anthropogenic inputs, in particular in the fishing areas. For this characteristic, in the Levantine Sea, there is a strong pressure on the natural resources and benthic assemblages. Furthermore, many alien species enter from Suez Canal and are well established in the area. All these pressures are leading to a degradation of the Levantine Sea. For this reason it is important to have tools to study and monitoring the functioning of the marine ecosystem. Benthic organisms are superior to many other biological groups for their response to environmental stresses. The variability of benthic assemblages on a site can reflect, in an integrative mode, the entire functioning of the marine ecosystem. In this study, that wants to analyze the spatial and temporal distribution of the benthic macrofaunal assemblages of Antalya Gulf, 90 benthic species divided in 8 taxa (Annelida, Cnidaria, Echinodermata, Echiura, Mollusca, Porifera, Sipunculida and Tunicata) were found. All the analyses conducted on the entire benthic class and later on Mollusca and Echinodermata separately highlighted the importance of depth on structuring benthic community.

Diversity and faunal composition of benthic foraminifera in Hole 44-390A on the Blake Nose Plateau

Benthic foraminiferal assemblages are a widespread tool to understand changes in organic matter flux and bottom-water oxygenation and their relation to paleoceanographic changes in the Upper Cretaceous oceans. In this study, assemblage data (diversity, total number, and number per species and gram) from Deep Sea Drilling Project (DSDP) Site 390 (Blake Nose, western North Atlantic) were processed for the lower Maastrichtian (Globotruncana falsostuarti - Gansserina gansseri Planktic Foraminiferal Zone). These data document significant changes in nutrient flux to the sea floor as well as bottom-water oxygenation during this time interval. Parallel to the observed changes in the benthic foraminiferal assemblages the number of inoceramid shells decreases, reflecting also a significant increase in bottom-water oxygenation. We speculate, that these data could reflect the onset of a shift from warmer low-latitude to cooler high-latitude deep-water sources. This speculation will predate the major reorganization of the oceanic circulation resulting in a circulation mode similar to today at the Early/Late Maastrichtian boundary by ~1 Ma and therefore improves our understanding of Late Cretaceous paleoceanography.