Study of endocrine disruption in seabass (Dicentrarchus labrax)

Conference (2006, October 28)

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine ... [more ▼]

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine system of many fish species and mammals and are thus qualified as endocrine disruptors. The objective of this project aims a better understanding of the effects of these compounds on the thyroid function of European seabass (Dicentrarchus labrax). Thyroid tissue and muscle of 46 seabass from the Aegean Sea in Greece (fished and aquaculture, n=15 and n=31, respectively) were sampled. The levels in PCBs, DDT and DDE were evaluated in the muscles of 30 individuals. The diameter of follicles and the epithelial cell heights were measured in each individual by optical microscopy. The concentration of the thyroid hormone T4 (thyroxin) was measured by Radio-Immuno-Assay (RIA). Finally, the potential relationships between these thyroid parameters and these organic compounds were investigated using factor analysis and multiple regressions. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T4 levels) could be observed. We cannot exclude the assumption that an endocrine disruption of thyroid gland related to these pollutants could be the origin of the modifications of these thyroid parameters. [less ▲]

Multiscale approach of fish responses to different types of environmental contaminations: A case study

in Science of the Total Environment (2006), 367(2-3), 715-731

In order to study the responses of wild fish to environmental contaminations, different sites (two references and three contaminated) were sampled across the Walloon hydrographical network (southern ... [more ▼]

In order to study the responses of wild fish to environmental contaminations, different sites (two references and three contaminated) were sampled across the Walloon hydrographical network (southern Belgium). The status of fish communities was characterized according to an index of biotic integrity (1131). Furthermore, population structure, reproductive parameters and biochemical assays were performed on chub (Leuciscus cephalus) as sentinel species. The results showed impaired responses in fish sampled downstream paper mill effluents (BKME), in a polychlorinated biphenyls (PCB) contaminated site, and in a river receiving pesticides (i.e. atrazine and hexachlorocyclohexane). High level of hepatic 7-ethoxyresorufin-Odeethylase (EROD) activity were evidence of direct toxicant exposure, while population structures showed unbalanced size-frequency distributions. Moreover, in the pesticide contaminated site, a higher proportion of atretic oocytes was found in females and abnormally high plasma alkali-labile phosphorus (ALP) values were noticed in males, compared to reference sites, suggesting that chubs were exposed to estrogenic compounds. IBI scores from both sites were also lower than in reference sites. On the other hand, no particular response was found in hepatic glutathione-S-transferase (GST) activities, hepatic heat-shock protein HSP70 concentrations and plasma sex steroids (estradiol-17 beta, 11-ketotestosterone and testosterone) in chubs from any sites. By using a multiparametric approach, a better understanding of response mechanisms to pollution in fish may be achieved in order to improve the ecological status of river ecosystems. (c) 2006 Elsevier B.V All rights reserved. [less ▲]

Le dépérissement de l'abeille domestique, Apis mellifera L., 1758 ( Hymenoptera : Apidae) : faits et causes probables.

in Notes Fauniques de Gembloux (2006), 59(1), 3-21

FEEDING SELECTIVITY OF THE ROTIFER BRACHIONUS CALYCIFLORUS: EVIDENCE OF THE ROLE OF CHEMICAL CUES.

Poster (2005, June 19)

The rotifer Brachionus calyciflorus is a ubiquitous species that often dominates river zooplankton. It has been described as a species that selects its food mainly on the basis of the size of food ... [more ▼]

The rotifer Brachionus calyciflorus is a ubiquitous species that often dominates river zooplankton. It has been described as a species that selects its food mainly on the basis of the size of food particles and not on the basis of their taste. Nevertheless, experiments carried out with a green algae, 3,5 microns in diameter, showed that the ingestion rate of rotifers on DTAF (5-(4,6-dichlorotriazin-2-yl)aminofluorescein) stained algae is much lower than on untreated algae. The impact of all steps of the staining procedure was tested to determine the factor that elicits a negative selection against stained algae. Moreover, impact of algal abundance and light on selection was tested. Results clearly show the selection is triggered by chemical cues, DTAF itself inducing the strongest avoidance. Algal abundance influenced the degree of selectivity of rotifers; analysis of ingestion rate of treated and untreated algae throughout all treatments provide information on selection mechanisms and support the hypothesis that B. calyciflorus can detect chemical cues in the buccal funnel, even when feeding on small preys, and select its food accordingly. [less ▲]

Feeding of planktonic rotifers on ciliates: a method using natural ciliate assemblages labelled with fluorescent microparticles

in Journal of Plankton Research (2004), 26(11), 1289-1299

A method was developed to allow direct measurements of predation exerted by metazooplankton on ciliates. The method relied on the use of ciliates labelled with fluorescent microparticles (FMP). Optimal ... [more ▼]

A method was developed to allow direct measurements of predation exerted by metazooplankton on ciliates. The method relied on the use of ciliates labelled with fluorescent microparticles (FMP). Optimal labelling conditions were determined with ciliates from cultures (Tetrahymena pyriformis) and with natural ciliate assemblages sampled in a river. Labelled T. pyriformis were used as tracer food to determine gut passage time (GPT) and ingestion rates of the rotifer Brachionus calyciflorus in the laboratory. Predation of metazooplankton from the lowland river Meuse (Belgium) was determined by labelling natural assemblages of ciliates and using them as tracer food for metazooplankters sampled in the river. Optimal labels of ciliates, i.e. sharp distribution of FMP in cells, were obtained with short incubations (10 min) and low FMP concentrations (1 x 10(5) mL(-1)). GPT varied between 30 and 45 min for B. calyciflorus and from 25 up to >35 min for rotifers from the river. The ingestion rate of B. calyciflorus fed with T. pyriformis was 3.3 +/- 0.6 ciliate rot(-1) h(-1), i.e. 1.4 +/- 0.3 ngC rot(-1) h(-1). Metazooplankton species for which the ingestion of ciliates could be measured were the rotifers Keratella cochlearis, Euchlanis dilatata and Synchaeta spp. Ingestion rates measured ranged from 0.4 to 12.5 ngC rot(-1) h(-1). The method proposed proved to be useful in estimating the predation of microplankton on ciliates in semi- in situ conditions; in further developments, labelled natural assemblages of ciliates could be used for in situ incubations with the Haney chamber. [less ▲]

Trophic links in the lowland river Meuse (Belgium): importance of the predation exerted by rotifers on bacterio- and protozooplankton.

Conference (2003, June 07)

Trophic interactions within the plankton of the lowland river Meuse (Belgium) were measured in Spring and Summer (2001). Consumption of bacteria by protozoa was measured by monitoring the radioactivity ... [more ▼]

Trophic interactions within the plankton of the lowland river Meuse (Belgium) were measured in Spring and Summer (2001). Consumption of bacteria by protozoa was measured by monitoring the radioactivity disappearance of 3H-thymidine labelled bacteria. The proportion of protozoan bacterivory attributable to flagellates and ciliates was determined with fluorescently labelled bacteria (FLB). Metazooplankton bacterivory was assessed with 0.5 µm fluorescent microparticles (FMPs) and predation of metazooplankton on ciliates was measured by using natural ciliate assemblages labelled with FMPs as tracer food. Grazing of metazooplankton on flagellates was determined through in situ incubations with manipulated metazooplankton densities. flagellates were the main bacterial consumers their grazing being 91  10 % of total bacterial grazing. Metazooplankton, essentially rotifers, grazing on bacteria was negligible compared to grazing by protozoa and to bacterial production. Protozoa grazing balanced bacterial production in early samplings but was lower in July. Predation of rotifers on heterotrophic flagellates (HF) was generally low (1.765 3.432 mg C m-3 d-1 ), the higher contribution of HF in the diet of rotifers being observed when Keratella cochlearis was the dominant metazooplankter. Predation of rotifers on ciliates was low in the first samples (0.557  0.004 mg C m-3 d-1) in contrast to measurements performed in July (8.722  1.363 mg C m-3d-1). The proportion of protozoa in the diet of rotifers was generally low compared to phytoplankton (< 30% of total carbon ingestion) except when phytoplankton biomass decreased below the incipient limiting level (ILL) of the main metazooplantonic species. In such conditions, protozoa (mainly ciliates) constituted ca. 50% of total rotifer food. These results give evidence that microbial organisms play an important role within the plankton of the river Meuse, ciliates providing an alternative food for metazooplankton when phytoplankton becomes scarce. [less ▲]

PCB trends and patterns in the plankton of the river Meuse (Belgium).

Poster (2002, May 12)

PCB concentrations were monitored in the river Meuse (Belgium) from 1993 to 1998; compartments sampled were water, suspended matter (mainly phytoplankton), zooplankton and sediment. The PCB patterns were ... [more ▼]

PCB concentrations were monitored in the river Meuse (Belgium) from 1993 to 1998; compartments sampled were water, suspended matter (mainly phytoplankton), zooplankton and sediment. The PCB patterns were compared to those of Aroclors and found to best match a mixture of 30 to 40% of Aroclor 1254 and 60 to 70% of Aroclor 1260 for all compartments with the exception of suspended matter where the proportions were of 50% of both Aroclor 1254 and 1260. These patterns together with the average total concentrations did not show any trends throughout the monitoring period nor did they show any particular seasonal pattern variations. Mean total PCBs concentrations were of 0.029 ng/g in the water, 3408 ng/g D.W. in suspended matter, 862 ng/g D.W. in zooplankton and 387 ng/g D.W. in the sediment. Bioconcentration factors for phytoplankton (suspended matter) and zooplankton were respectively of 118 000 and 30 000 indicating there is no biomagnification between these two trophic levels. These results will be commented on the basis of in vitro contamination experiments with planktonic organisms. [less ▲]

A note on the use of fluorescently labelled algae for the determination of gut passage time in Bosmina and Daphnia

in Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie = Proceedings of the International Association of Theoretical and Applied Limnology (2001), 27

Trophics relationships between planktonic micro-organisms in the river Meuse (Belgium): a carbon budget

in Arch. Hydrobiol (2000)

Calcul des niveaux et charges critiques des polluants acidifiants pour les eaux de surface en Région wallonne. Ecosystèmes aquatiques : réservoirs de barrage et lacs.

Report (2000)

Cette étude visait à estimer les niveaux et charges critiques des polluants acidifiants pour les eaux de surface en Région Wallonne. Elle faisait suite à une étude préliminaire réalisée en 1997. Ces ... [more ▼]

Cette étude visait à estimer les niveaux et charges critiques des polluants acidifiants pour les eaux de surface en Région Wallonne. Elle faisait suite à une étude préliminaire réalisée en 1997. Ces estimations ont été réalisées pour 7 lacs situés en Région Wallonne par différentes méthodologies (modèle SSWC, la méthode empirique et le modèle FAB). Une évaluation de l'importance des fluctuations saisonnières, ainsi que de l'importance des apports anthropiques en azote a également été réalisée. [less ▲]