Les peuplements de poissons démersaux de la pointe de Bretagne : environnement, biologie, structure démographique, relations trophiques.

About sixty species of demersal fishes are living in the coastal waters of the bay of Douarnenez, the road of Brest, the bay of Audierne and the nearby waters of Iroise Sea. They are mainly distributed according to the bio-sedimentary structure of the bottom. The seasonal study of catches shows the influence of the hydro-climatic conditions, particularly in the bay of Douarnenez. Analysis of correspondences on the occurrence of the species allow to separate the winter populations from the summer one. This alternance is also connected with the spawning periods of the characteristic species. On the intertidal nurseries, the study of the physico-chemical factors shows the great influence on the distribution of the fishes, particularly for the Pleuronectiforms juveniles, of the continental fresh-water feeds, and the exposure of the beaches. The monthly evolution of the catches shows the same pattern in the different stations : an increase whenthe sea-water temperatures rises, from May onwards, and the decrease due to an escape of the young fishes into deeper waters in November. The analysis of the demographic structures suggests a double origin for the young plaices in the northern part of the surveyed area. As for Solea lascaris, however the bimodalism of the 0 group could be accounted for by a confusion between two species whose spawning periods could be different. Finally, the study of diets of principal predators shows the large diversity of preys and their variability, particularly as for as the size of fishes are concerned. These facts, completed by ethological analysis, emphasize the main aspects of the predator-prey connections. Several dues show that inter-specific competition between predators is very low.Une soixantaine d'espèces de poisons démersaux fréquentent les eaux sub-littorales de la baie de Douarnenez, de la rade de Brest, de la baie d'Audierne et de la proche Iroise. Elles s'y répartissent surtout en fonction de la nature du fond. L'étude de l'évolution saisonnière des captures a, cependant, montré une influence des conditions hydro-climatiques, en particulier en baie de Douarnenez. L'utilisation de l'analyse des correspondances sur les fréquences d'apparition des espèces permet de différentier les peuplements hivernaux de ceux d'été. Cette alternance est également en rapport avec les périodes de reproduction de leurs espèces caractéristiques. Sur les nourriceries intertidales, l'étude des caractères physico-chimiques de l'eau montre l'extrême dépendance de la répartition des espèces, en particulier des juvéniles de Pleuronectiformes, vis-à-vis des arrivées d'eau douce continentale et de l'exposition de ces estrans par rapport au large. L'évolution mensuelle des quantités capturées montre le même schéma, quel que soit le lieu ; un accroissement des prises lors de l'élévation de la température de l'eau à partir de mai, suivi d'une diminution traduisant une fuite en profondeur des jeunes poissons en novembre. L'analyse des structures démographiques tendrait à montrer une double origine géographique des jeunes plies au Nord de la zone étudiée. Par contre, chez Solea lascaris, le bi modalisme du groupe 0 pourrait être attribué à la confusion de deux espèces dont les périodes de ponte seraient distinctes. Enfin, l'étude des contenus stomacaux des principaux prédateurs montre la grande variété des proies consommées ainsi qu'une variabilité des régimes, particulièrement en fonction de la taille des poissons. Ces observations, complétées par une analyse éthologique des régimes, permettent la mise en évidence des aspects primordiaux de la relation prédateur-proie. Plusieurs indices montrent que la compétition interspécifique entre les prédateurs est faible

A novel family of diversified immunoregulatory receptors in teleosts is homologous to both mammalian Fc receptors and molecules encoded within the leukocyte receptor complex

Three novel and closely related leukocyte immune-type receptors (IpLITR) have been identified in channel catfish (Ictalurus punctatus). These receptors belong to a large polymorphic and polygenic subset of the Ig superfamily with members located on at least three independently segregating loci. Like mammalian and avian innate immune regulatory receptors, IpLITRs have both putative inhibitory and stimulatory forms, with multiple types coexpressed in various lymphoid tissues and clonal leukocyte cell lines. IpLITRs have an unusual and novel relationship to mammalian and avian innate immune receptors: the membrane distal Ig domains of an individual IpLITR are related to fragment crystallizable receptors (FcRs) and FcR-like proteins, whereas the membrane proximal Ig domains are related to several leukocyte receptor complex encoded receptors. This unique composition of Ig domains within individual receptors supports the hypothesis that functionally and genomically distinct immune receptor families found in tetrapods may have evolved from such ancestral genes by duplication and recombination events. Furthermore, the discovery of a large heterogeneous family of immunoregulatory receptors in teleosts, reminiscent of amphibian, avian, and mammalian Ig-like receptors, suggests that complex innate immune receptor networks have been conserved during vertebrate evolution. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at http://dx.doi.org/10.1007/s00251-006-0134-1 and is accessible for authorized users

Domaine vital, utilisation de l'espace et des ressources (les grands dauphins, Tursiops truncatus, de l'île de Sein)

BREST-BU Droit-Sciences-Sports (290192103) / SudocSudocFranceF

Cinétique de l'ovogenèse et stratégie de ponte chez la limande,

Pour décrire la cinétique de l'ovogenèse et la stratégie de ponte chez la limande, Limanda limanda (L., 1758) les ovaires de 74 femelles capturées en baie de Douarnenez et en baie de Seine en 1990 et 1991 ont fait l'objet de prélèvements. Une échelle de développement ovocytaire en six stades a été utilisée pour classer les ovocytes. L'apparition d'alvéoles corticaux à la périphérie du cytoplasme est le premier signe de la vitellogenèse. Ils sont visibles dans les ovocytes dont le diamètre est de 120 μm, taille limite à utiliser lors d'études de la fécondité. Chez les femelles à ponte précoce un hiatus existe avant les pontes entre les ovocytes prévitellogéniques et vitellogéniques. Ceci permet de classer la limande parmi les espèces à fécondité déterminée. Chez ces femelles l'intensité de l'atrésie est faible et leur fécondité annuelle est proche de la fécondité potentielle. Par contre chez les femelles à ponte tardive tous les ovocytes vitellogéniques ne parviendront pas à maturité et ceux non encore émis à la fin du printemps dégénèreront

Responses of Pacific oyster Crassostrea gigas populations to abiotic stress in environmentally contrasted estuaries along the Atlantic coast of France

International audienceGenetic and ecophysiological responses of oyster, Crassostrea gigas, populations to environmental stress were investigated in three highly contaminated French estuaries (the Gironde, Loire and Vilaine) and compared to a control, the Belon estuary. A strong response in both metallothionein CgMT4 mRNA expression, as determined by semi-quantitative RT-PCR, and amount of protein, as determined by ELISA tests, was demonstrated in estuarine populations subjected to differential contamination, with an inhibition in the area most highly contaminated with metals. In these same estuarine populations, we found polymorphisms of the metallothionein CgMT4 gene and three other genes (glutamine synthetase - GS, delta-9 desaturase - D9 and phosphoglucomutase - PGM) involved in stress response of C. gigas. We showed that genetic differentiation was observed for MT4 and PGM genes in the Gironde estuary which is highly contaminated with metals. A strong seasonal effect was observed. Phenotype-genotype coupling revealed that one particular MT4 allele and one PGM allele seemed to be associated with metal sensitivity expressed as lower detoxification efficiency and higher metal bioaccumulation. The MT4 gene is a good physiological and genetic marker of stress response and susceptibility

Responses of juvenile European flounder (Platichthys flesus) to multistress in the Vilaine estuary, during a 6-month survey

International audiencePhysiological and genetic responses of age 0+ Platichthys flesus were investigated in the eutrophicated and moderately contaminated Vilaine estuary, during a 6-month survey. The main objective of this study was to explore the biological responses of fishes during their juvenile period in an estuarine system in order to detect a possible selective pressure induced by the environmental stress. Our results showed a general convergence in physiological responses along the survey: an increase in genotoxicity was associated with an increase in mRNA expression of ATPase and betaine homocysteine methyltransferase. These results could suggest an increase of cellular damage, energetic request, and detoxification rate related to the growing exposure time to stress. Considering the aging of the cohort, the genetic characteristics of the Vilaine flounder cohort came closer to the one observed in a highly stressed system, the Seine estuary, suggesting a potential selective pressure mainly induced by the chemical stress

Comparisons of liver proteomes in the European flounder Platichthys flesus from three contrasted estuaries

International audienceEstuaries are important areas highly susceptible to anthropogenic degradations like pollution. Estuarine species have thus to cope with many types of constraints depending on the estuaries' characteristics. The European flounder Platichthys flesus is considered as a sentinel species for the monitoring of estuarine water quality. In this study, juvenile flounders (0+ group) were sampled from three contrasted Channel estuaries, i.e. the Seine, the Canche and the Tamar, and we characterized their liver proteomes by using a two-dimensional electrophoresis based proteomic approach. We showed that 27 protein spots differentially accumulated between the 3 populations. Six of these proteins were identified by MALDI TOF-TOF mass spectrometry. Flounders from the Seine and from the Tamar, two highly polluted estuaries, displayed common differences, i.e. an increase of the energetic- and the glutathione-metabolism. The most accumulated protein in the Seine's samples (6.7-fold) was a Vitelline Membrane Outer layer protein 1 homolog, suggesting oogenesis deregulation in these juvenile (sexually immature) flounders. Future works applying this kind of proteomic approach on flounders experimentally exposed to conditions that mimic environmental constraints will help to better understand the significance of these environmental proteomic signatures

Comparative study of three analysis methods (TTGE, flow cytometry and HPLC) for xenobiotic impact assessment on phytoplankton communities

International audienceThe impacts of the fungicide Opus® (epoxiconazole) on marine phytoplankton communities were assessed in a 12-day field experiment using in situ microcosms maintained underwater at 6 m depth. Three community analysis methods were compared for their sensitivity threshold in fungicide impact detection. When phytoplankton communities were exposed to 1 μg l−1 of epoxiconazole, no effects could be demonstrated using TTGE (Temporal Temperature Gradient gel Electrophoresis), flow cytometry or HPLC. When exposed to 10 μg l−1, TTGE fingerprints from PCR amplified 18S rDNA of communities exhibited significant differences compared with controls (ANOSIM, P = 0.028). Neither flow cytometry counts, nor HPLC pigment profiles allowed to show significant differences in microcosms exposed to 10 μg l−1 of epoxiconazole. When exposed to 100 μg l−1, all three methods allowed to detect significant differences in treated microcosms, as compared to controls. The TTGE analysis appears in this study as the most sensitive method for fungicide impact assessment on eukaryote microbial communities

Impacts of mixtures of herbicides on molecular and physiological responses of the European flounder Platichthys flesus

International audienceThe widespread use of pesticides results in a growing contamination of the aquatic environment. The effects of (1) a simple mixture of a glyphosate-based formulation and AMPA (Aminomethylphosphonic acid -- a primary metabolite of glyphosate) and of (2) a more complex mixture of herbicides (glyphosate/AMPA/mecoprop/acetochlor/2,4D) were explored on the molecular and physiological responses of the European flounder Platichthys flesus, considering a long-term and environmentally realistic contamination. Molecular responses were identified using suppression subtractive hybridization on liver samples: the level of gene transcription was significantly different between contaminated fishes vs control ones for 532 sequences, after a 62-day contamination. Among them, 222 sequences were identified by homology with data-based sequences; they encoded several metabolic pathways including: methionine and lipid metabolism, immunity, protein regulation, coagulation and energetic metabolism. Expression pattern of nine transcripts in the liver was confirmed by real-time PCR. The molecular study underlined that potential markers of liver injury were expressed for both mixtures, in particular betaine homocysteine methyl transferase and chemotaxin. Physiological responses were analysed considering blood parameters and condition factor; after the two months contamination period; no significant physiological difference was detected between contaminated and control fish

Proteomic analysis of the European flounder Platichthys flesus response to experimental PAH–PCB contamination

International audiencePlatichthys flesus is often used as a sentinel species to monitor the estuarine water quality. In this study, we carried out an experimental contamination of fish using a PAHs/PCBs mixture, which was designed to mimic the concentrations found in the Seine estuary (C1) and 10 times these concentrations (C2). We used a proteomic approach to understand the molecular mechanisms implied in the response of P. flesus to these xenobiotics. We showed that 54 proteins were differentially accumulated in one or several conditions, which 34 displayed accumulation factors higher than two. 18 of these proteins were identified by MALDI TOF-TOF mass spectrometry. The results indicated the deregulation of oxidative stress- and glutathione metabolism-(GST, GPx) proteins as well as of several proteins belonging to the betaine demethylation pathway and the methionine cycle (BHMT, SHMT, SAHH), suggesting a role for these different pathways in the P. flesus response to chemical contamination