References of "Thomé, Jean-Pierre"
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See detailMultiscale approach of fish responses to different types of environmental contaminations: A case study
Mayon, N.; Bertrand, Annick ULg; Leroy, Delphine ULg et al

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 ▲]

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See detailFEEDING SELECTIVITY OF THE ROTIFER BRACHIONUS CALYCIFLORUS: EVIDENCE OF THE ROLE OF CHEMICAL CUES.
Joaquim-Justo, Célia ULg; Ayala-Andrés, N; Thomé, Jean-Pierre ULg

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 ▲]

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See detailMercury, polychlorobiphenyls and stable isotopes in the blood of harbour seals (Phoca vitulina) from the southern North Sea
Das, Krishna ULg; Lepoint, Gilles ULg; Fonfara, Sonja et al

Poster (2005)

The harbor seal (Phoca vitulina) is one of the most widely distributed seal species and the North Sea contains around 10 % of the world population. The harbour seal population in the North Sea was ... [more ▼]

The harbor seal (Phoca vitulina) is one of the most widely distributed seal species and the North Sea contains around 10 % of the world population. The harbour seal population in the North Sea was estimated at 36 000 individuals between 1994 and 1996). However, recurrent Phocine Distemper Virus (PDV) epizooties have affected the North Sea seal population. Recently, 21 500 harbor seals were killed by PDV in the North Sea and adjacent waters in 2002. Some intriguing questions about the interaction between PDV and immunotoxic contaminants, such as mercury (Hg) and polychlorinated biphenyls (PCBs) remain unanswered. In this framework, circulating levels of Hg and PCBs (PCBs 28, 52, 101, 118, 138, 153, 180) were measured in the blood of 24 harbour seals captured on a sandbank between 2001 and 2004 (Schleswig-Holstein, Germany). As pollutant level may be linked to the trophic position in the food web, carbon and nitrogen isotopic ratios (δ13C and δ15N) were measured in clotted blood cells. The average concentration of mercury in these living seals did not differ significantly from those observed previously in stranded harbour seals (94 ± 41 vs 146 ± 71 µg.l-1 respectively). Mean blood concentrations of total PCBs (∑PCBs) were 11 ng/ml. CB 153 clearly dominated the mix (45%) followed by PCB 138 (31%). The average isotopic composition measured in the blood cells was –15.6 ± 0.3 0/00 and 18.7 ± 0.6 0/00 for δ13C and δ15N respectively, similar to that obtained previously in muscle of stranded individuals, confirming the high position of the harbour seal in the North Sea trophic chain. Further investigations are obviously needed on a larger sampling but our preliminary results suggest that blood is an interesting substrate for both trophic and pollutant long-term monitoring of the harbour seal in the North Sea. [less ▲]

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See detailFeeding of planktonic rotifers on ciliates: a method using natural ciliate assemblages labelled with fluorescent microparticles
Joaquim-Justo, Célia ULg; Detry, Cédric ULg; Caufman, F. et al

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 ▲]

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See detailAn unexpected parallelism between Vitamin A and PCBs in seal milk
Debier, C.; Pomeroy, P. P.; Thomé, Jean-Pierre ULg et al

in Aquatic Toxicology (2004), 68(2), 179-183

Bioaccumulating pollutants such as polychlorinated biphenyls (PCBs) induce a range of adverse effects in mammals. Vitamin A metabolism is prone to such pollutant disruption which may be particularly ... [more ▼]

Bioaccumulating pollutants such as polychlorinated biphenyls (PCBs) induce a range of adverse effects in mammals. Vitamin A metabolism is prone to such pollutant disruption which may be particularly harmful for young animals. During lactation, maternal PCBs are transferred to the offspring through the milk. Seal milk is very fatty and consequently contains large amounts of these persistent lipophilic contaminants. In the present study, we investigated the relationships between PCBs and Vitamins A and E during lactation, in free-ranging grey seals, using longitudinal samples of milk and blubber. We discovered that, unlike Vitamin E or triglycerides, the dynamics of Vitamin A matches closely those of PCBs in milk throughout lactation. Levels of Vitamin A and PCBs remain constant during the first half of lactation and then increase at late lactation, indicating that pups ingesting higher levels of PCBs also ingest higher amounts of Vitamin A. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailEffects of atrazine on sex steroid dynamics, plasma vitellogenin concentration and gonad development in adult goldfish (Carassius auratus)
Spano, L.; Tyler, C. R.; van Aerle, R. et al

in Aquatic Toxicology (2004), 66(4), 369-379

Sexually mature goldfish (Carassius auratus) of both sexes were exposed to two doses (100 and 1000 mug/l) of the widely used herbicide atrazine (2-chloro-4-ethylamino-6-isolropylamino-s-triazine) for a ... [more ▼]

Sexually mature goldfish (Carassius auratus) of both sexes were exposed to two doses (100 and 1000 mug/l) of the widely used herbicide atrazine (2-chloro-4-ethylamino-6-isolropylamino-s-triazine) for a period of 21 days and effects on the concentrations of gonad and plasma sex steroids (testosterone (T), 17beta-estradiol (E2) and 11-ketotestosterone (11-KT)), plasma vitellogenin (VTG) and gonad histo-morphology assessed. Atrazine did not show any obvious estrogenic effect in males, as determined by a lack of vitellogenin induction. There were, however, effects of atrazine on plasma androgen concentrations (androgen dynamics) and tissue (plasma and gonad) estrogen concentrations in male goldfish; exposure to 1000 mug/l atrazine induced suppression in both testosterone and 11-ketotestosterone, and resulted in elevated 17beta-estradiol, after 21 day of exposure. Further, these suppressive effects on plasma androgens and the induction in estrogen were dose- and time-related. The highest atrazine exposure dose induced structural disruption in the testis and both 100 and 1000 mug/l induced elevated levels of atresia in ovaries. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailTrophic links in the lowland river Meuse (Belgium): importance of the predation exerted by rotifers on bacterio- and protozooplankton.
Joaquim-Justo, Célia ULg; Pirlot, S; Viroux, Laurent et al

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 ▲]

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See detailDynamics of PCB transfer from mother to pup during lactation in UK grey seals Halichoerus grypus: differences in PCB profile between compartments of transfer and changes during the lactation period
Debier, Cathy; Pomeroy, Paddy P.; Dupont, Cédric et al

in Marine Ecology-Progress Series (2003), 247

The composition of the PCB mixture which is transferred from mother to pup in grey seals Halichoerus grypus throughout lactation was measured in the successive compartments of transfer: maternal blubber ... [more ▼]

The composition of the PCB mixture which is transferred from mother to pup in grey seals Halichoerus grypus throughout lactation was measured in the successive compartments of transfer: maternal blubber, maternal serum, milk and pup serum. Mother-pup pairs were captured regularly between birth and weaning on the Isle of May, Scotland. The PCB profiles of the different compartments of transfer consisted mainly of congeners 153, 138, 180, 187, 170 and 101, which made up 85% of the total PCB burden. Outer blubber contained higher relative concentrations (R-153) Of hepta-, octa-, and nona-chlorinated congeners (higher chlorinated congeners) than inner blubber, at both early (less than or equal to 5 d) and late (greater than or equal to 11 d) lactation. There was no change in the composition of the outer blubber layer between early and late lactation, while in the inner blubber, there was a slight increase in the R153 of higher chlorinated congeners at late lactation. In maternal serum, profiles changed towards having a higher proportion of higher chlorinated congeners as lactation progressed, but in milk, the PCB pattern stayed constant throughout lactation. Surprisingly, in pup serum profiles also changed towards higher R153 of higher chlorinated congeners at late lactation compared to early lactation, which was different to the pattern observed in milk. In all body compartments, higher proportions of higher chlorinated congeners were associated with higher concentrations of total PCBs. Maternal blubber and pup serum contained a higher R153 of higher chlorinated congeners than milk and, to a lesser extent, maternal serum. Thus biomagnification of the higher chlorinated congeners was recorded in pup serum. [less ▲]

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See detailQuantitative dynamics of PCB transfer from mother to pup during lactation in UK grey seals Halichoerus grypus
Debier, Cathy; Pomeroy, Paddy P.; Dupont, Cédric et al

in Marine Ecology-Progress Series (2003), 247

PCB contamination was measured in the milk and serum of grey seal Halichoerus grypus mothers and in the serum of their pups sampled from 2 to 5 times between parturition and weaning on the Isle of May ... [more ▼]

PCB contamination was measured in the milk and serum of grey seal Halichoerus grypus mothers and in the serum of their pups sampled from 2 to 5 times between parturition and weaning on the Isle of May, Scotland, in 1998 and 2000. Blubber biopsies were also taken from the lactating females at early and late lactation in 2000. Concentrations of PCBs in milk stayed constant during the first part of lactation (0.31 +/- 0.17 mug g milk(-1)) and then increased at late lactation (0.67 +/- 0.42 mug g milk(-1)). Curiously, it did not follow the changes of milk lipid content, which increased at early lactation and then stayed constant until the end of the nursing period. As a result, even when expressed per unit of milk lipids, PCBs underwent a rise at the end of lactation. The changes in milk PCBs were accompanied by similar dynamics in maternal serum as well as in pup serum. Increased concentrations of PCBs at late lactation in serum and milk may be explained in part by the changes observed in maternal blubber. PCB levels increased significantly between early and late lactation in inner blubber, suggesting that PCBs are less easily mobilised from blubber than lipids. At late lactation, the retention capacity of the reduced blubber layer for PCBs might have reached its maximum. The mobilization of less polar lipids from blubber might also occur at this stage. In both cases, this could result in a higher mobilization of PCBs at this time. While inner blubber was significantly less concentrated than outer blubber at early lactation (1.26 +/- 0.72 mug g lipids(-1) in inner blubber vs 3.16 +/- 1.34 mug g lipids(-1) in outer blubber), these variations disappeared at late lactation (3.24 +/- 2.60 mug g lipids(-1) in inner blubber vs 3.59 +/- 1.46 mug g(-1) lipids in outer blubber). Newborn pups already had significantly higher serum levels of PCBs than their mothers, revealing an important placental transfer (11.9 +/- 7.0 ng ml serum(-1) in pups vs 6.7 +/- 3.5 ng ml serum(-1) in mothers). These differences were even greater in late lactation, due to the ingestion of milk (27.9 +/- 18.1 ng ml serum(-1) in pups vs 12.2 +/- 7.2 ng ml serum(-1) in mothers). As lactation progressed, PCB levels in pup serum increased exponentially as compared to the levels in the serum of their mothers. [less ▲]

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See detailPCB trends and patterns in the plankton of the river Meuse (Belgium).
Joaquim-Justo, Célia ULg; Schockert, Vincianne ULg; Deguée, N et al

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 ▲]

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See detailPotential of using Daphnia magna (crustacea) developing in an aerated waste stabilisation pond as a commercial source of chitin
Cauchie, Henry-Michel ULg; Versali, Marie-France ULg; Hoffmann, L. et al

in Aquaculture (2002), 205(1-2), 103-117

The potential of using the planktonic crustacean Daphnia magna as a commercial source of chitin was studied on the basis of the estimation of the amount of chitin produced annually by this species and the ... [more ▼]

The potential of using the planktonic crustacean Daphnia magna as a commercial source of chitin was studied on the basis of the estimation of the amount of chitin produced annually by this species and the specifications of this kind of chitin. D. magna was found to have a significant chitin content, ranging from 3% to 7% of the body dry weight. During three consecutive years, chitin biomass (B) and daily somatic chitin production (daily P-SOM) were monitored in a 59,000-m(2) aerated waste stabilisation pond located in the Grand-Duchy of Luxembourg (Western Europe). These variables were found to vary a lot seasonally. Maximum values were observed in summer (B > 40 kg chitin; daily P-SOM > 20 kg chitin day(-1)). Annual somatic chitin production reached on average 1200 kg chitin year(-1). The amount of chitin generated by the moulting of the daphnids (i.e. chitin contained in the exuviae) can also constitute a significant source of chitin, reaching about 1220 kg chitin year(-1). Chitin was isolated from D. magna, following three different processing routes. The specifications of the isolated and purified chitin were similar to those of commercial chitin extracted from crabs and shrimps. The average molecular weight varied from 600,000 to 2,600,000 depending on the processing route, The isolated chitin had a low N content indicating a high degree of acetylation. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailIN SITU MEASUREMENTS OF METAZOOPLANKTON PREDATION ON PROTOZOOPLANKTON: USE OF FLUORESCENTLY LABELLED PROTISTS.
Joaquim-Justo, Célia ULg; Caufman, F; Thomé, Jean-Pierre ULg

Poster (2001, February 04)

The importance of trophic relationships between metazooplankton and protozoans in rivers are not yet well known, but as some authors have shown during the last decade, the predation exerted by ... [more ▼]

The importance of trophic relationships between metazooplankton and protozoans in rivers are not yet well known, but as some authors have shown during the last decade, the predation exerted by metazooplankton on these organisms might be of importance in the transfer of energy from the pico- and nanoplankton to the metazooplankton. Fluorescent carboxylate microspheres of 0.5 µm in diameter were used to label natural protozooplankton. Different combinations of labelling times and concentrations of microspheres were tested to achieve an optimal labelling of the protists (i.e. a maximal proportion of individuals labelled with an identical number of microspheres); the most appropriate labelling conditions were with short incubations (10 minutes) and relatively low microsphere concentrations (1.105 FMP/ml). Live labelled protozooplankton was used to determine ingestion rates of the natural metazooplankton of the river Meuse (Belgium). It could be showed for all abundant species (i.e. the rotifers Brachionus calyciflorus, Brachionus angularis and Keratella cochlearis) that the predation exerted on protozooplankton was high (from 34 to 182 protists.rotifer-1.h-1) in in situ conditions. [less ▲]

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See detailA note on the use of fluorescently labelled algae for the determination of gut passage time in Bosmina and Daphnia
Cauchie, Henry-Michel ULg; Deguée, N.; Joaquim-Justo, Célia ULg et al

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

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See detailUSE OF FLUORESCENTLY LABELLED PROTOZOANS TO INVESTIGATE THE PREDATION OF ROTIFERS ON PROTOZOOPLANKTON
Joaquim-Justo, Célia ULg; Detry, Cédric ULg; Thomé, Jean-Pierre ULg

Conference (2000, January 16)

The importance of trophic relationships between rotifers and protozoans in rivers are not yet well known, but as some authors have shown during the last decade, the predation exerted by rotifers on these ... [more ▼]

The importance of trophic relationships between rotifers and protozoans in rivers are not yet well known, but as some authors have shown during the last decade, the predation exerted by rotifers on these organisms might be of importance in the transfer of energy from the pico- and nanoplankton to the metazooplankton. Fluorescent polycarbonate beads of 0.45 µm in diameter were used to label the ciliate Tetrahymena pyriformis. Different combinations of labelling times and concentrations of microspheres were tested to achieve an optimal labelling of the ciliates (i.e. a maximal proportion of individuals having ingested the same number of microspheres). Live labelled Tetrahymena pyriformis were used to determine both the gut passage time and the ingestion rate of the rotifer Brachionus calyciflorus. The ingestion rates measured with relatively high densities of ciliates (from 30 to 500 cells.ml-1) were on average of 30 cells.ind-1.day-1. The ingestion rates yielded by this method were compared with ingestion rates measured by assessing the disappearance of the ciliates in experimental media during 5-6 hour incubations. Results from both methods were comparable but the use of fluorescently labelled prey items produced less variable results. [less ▲]

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See detailTrophics relationships between planktonic micro-organisms in the river Meuse (Belgium): a carbon budget
Servais, Pierre; Gosselain, Véronique; Joaquim-Justo, Célia ULg et al

in Arch. Hydrobiol (2000)

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