References of "Das, Krishna"
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See detailStable isotopes of captive Cetaceans (Killer Whales and Bottlenose dolphins)
Caut, Stéphane; Laran, Sophie; Garcia-Hartmann, Emmanuel et al

in Journal of Experimental Biology (2011), 214

There is currently a great deal of interest in using stable-isotope methods to investigate diet, trophic level and migration movement in wild cetaceans. Fundamental to the interpretation of these methods ... [more ▼]

There is currently a great deal of interest in using stable-isotope methods to investigate diet, trophic level and migration movement in wild cetaceans. Fundamental to the interpretation of these methods is the need to understand how diet isotopic values are reflected in consumer tissues. In this study, we investigated patterns of isotopic discrimination between diet and blood constituents of two species of cetaceans (killer whale, Orcinus orca and 19 bottlenose dolphin, Tursiops truncutus) fed with controlled diets during 350 days. Diet discrimination factors ( ) for plasma were estimated to 13C =2.3‰ and 1520 N =1.8‰ respectively for both species and to 13C =2.7‰ and 1521 N =0.5‰ for red blood cells (RBC). Delipidation had no significant effect on carbon and nitrogen isotopic values of blood constituents, confirming that cetacean blood no serving as reservoirs of lipids. In contrast, carbon isotopic values are higher in delipidated samples of blubber, liver and muscle of orca tissues. The mean half life for plasma was 32.9 days for killer whales and 27.2 days for bottlenose dolphin and for RBC was greater than 175 days. The potential for conflict between fisheries and cetaceans has heightened the need for trophic information about this taxa within those ecosystems. These results provide the first published stable isotope turnover rates and discrimination factors for cetaceans, which are essential if conclusions are to be drawn on issues concerning trophic structures, carbon sources and diet reconstruction. [less ▲]

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See detailRelationship between PCB 153 and stable nitrogen in a Guiana dolphin (Sotalia guianensis) food weeb, Gunabara Bay, Brazil
Vidal, L. G.; Bisi, T. L.; Dorneles, P. R. et al

in Organohalogen Compounds (2011)

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See detailPCBs versus PBDEs: how similar compounds can behave differently in harbour porpoises
Weijs, Liesbeth; Yang, R. S. H.; Das, Krishna ULg et al

in Organohalogen Compounds (2011)

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See detailMaternal transfer of PCBs, PBDEs and their hydroxylated metabolites in grey seal (Halichoerus grypus) from the Isle of May, Scotland
Vanden Berghe, Marie; Weijs, Liesbeth; Habran, Sarah ULg et al

in Organohalogen Compounds (2011)

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See detailToothed whales in the northwestern Mediterranean: Insight into their feeding ecology using chemical tracers
Praca, Emilie; Laran, Sophie; Lepoint, Gilles ULg et al

in Marine Pollution Bulletin (2011), 62(5), 1058-1065

Risso’s dolphins, pilot whales and sperm whales rarely strand in the northwestern Mediterranean. Thus, their feeding ecology, through the analysis of stomach contents, is poorly known. The aim of this ... [more ▼]

Risso’s dolphins, pilot whales and sperm whales rarely strand in the northwestern Mediterranean. Thus, their feeding ecology, through the analysis of stomach contents, is poorly known. The aim of this study was to gain further insight into the segregation/superposition of the diet and habitat of Risso’s dolphins, pilot whales and sperm whales using chemical tracers, namely, stable isotopes (d13C, d15N) and orga- nochlorines. Significantly different d15N values were obtained in Risso’s dolphins (11.7 ± 0.7‰), sperm whales (10.8 ± 0.3‰) and pilot whales (9.8 ± 0.3‰), revealing different trophic levels. These differences are presumably due to various proportions of Histioteuthidae cephalopods in each toothed whale’s diet. Similar d13C contents between species indicated long-term habitat superposition or corroborated impor- tant seasonal migrations. Lower congener 180 concentrations (8.20 vs. 21.73 lg.g􏰀1 lw) and higher tDDT/ tPCB ratios (0.93 vs. 0.42) were observed in sperm whales compared with Risso’s dolphins and may indi- cate wider migrations for the former. Therefore, competition between these species seems to depend on different trophic levels and migration patterns. [less ▲]

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See detailUse of stable isotopes to study pollutants in marine vertebrates
Das, Krishna ULg

Conference (2010, November 11)

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See detailEssential and non-essential elements in the eggs of sea turtles from the Lesser Antilles
Leroy, Céline; Dyc, Christelle ULg; Bouquegneau, Jean-Marie ULg et al

Poster (2010, October)

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See detailAssessment of gestation, lactation and fasting on stable isotope ratios in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Crocker, Dan E. et al

in Marine Mammal Sciences (2010), 26(4), 880-895

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in ... [more ▼]

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring transfer of nutrients was generated between mother and offspring during gestation and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6‰ to +1.3‰ in blood cells and from +1.1‰ to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using δ15N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues. [less ▲]

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See detailMethylmercury and selenium in vitro effects on harbor seal (Phoca vitulina) lymphocytes : a multidisciplinary approach
Dupont, Aurélie ULg; Bouquegneau, Jean-Marie ULg; Das, Krishna ULg et al

Poster (2010, May 26)

Methylmercury (MeHg) bioaccumulates along the food web, leading to the highest levels in tissues of predatory species. It constitutes the predominant form present in the blood of marine mammals. The blood ... [more ▼]

Methylmercury (MeHg) bioaccumulates along the food web, leading to the highest levels in tissues of predatory species. It constitutes the predominant form present in the blood of marine mammals. The blood cells, including the immune cells, are therefore exposed to the toxic properties of that chemical. Nevertheless, selenium (Se) is an essential element absorbed concomitantly to MeHg which seems to modulate this toxicity. The goal of this study is to evaluate the immunotoxicity of MeHg on the harbor seal (Phoca vitulina) T lymphocytes, highly important in the adaptive immune response, and to investigate the modulating effect of Se on that toxicity. In parallel, the concentrations of MeHg, total mercury (T-Hg) and Se are determined in free-ranging harbour seal blood in order to follow their contamination levels. The T lymphocytes were isolated from the whole blood, exposed to various MeHg and Se concentrations and the exposure effects were estimated by functional tests including the evaluation of viability, proliferation, metabolic activity, DNA and protein synthesis, and by morphological analysis by transmission electron microscopy. The mean T-Hg concentration was 172 ± 143 µg/l of whole blood. The T lymphocytes cultures in vitro displayed a decreasing number of viable cells with increasing concentrations of MeHg, and numerous ultrastructural defects. The cells exposed to MeHg notably displayed distortion of the plasmic membrane, nucleus fragmentations, chromatin compaction, swelling mitochondrias and cytoplasmic vacuolisations. Those results highlighted various immunotoxic effects of MeHg, both at the functional and ultrastructural levels. The antagonistic role of Se on MeHg immunotoxicity is discussed. [less ▲]

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See detailMaternal transfer of trace metals to offspring in grey seals
Habran, Sarah ULg; Pomeroy, Paddy; Debier, Cathy et al

Conference (2010, May 25)

Marine mammals may display high heavy metal levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Some lactating female phocids fast during ... [more ▼]

Marine mammals may display high heavy metal levels in their tissues, which raises the question of the importance of toxic metal transfer from mother to offspring. Some lactating female phocids fast during the suckling period. This fasting period involves not only an important mobilization of energy reserves, but also mobilization of potentially associated contaminants. We studied maternal transfer of trace metals to offspring in the grey seal (Halichoerus grypus). Trace metal concentrations were measured in whole blood, milk and hair of mother-pup pairs in early and late lactation. Metal levels in blood decreased according to the following pattern: Fe > Zn > Se > Cu > Hg > Pb > Cr > V in mothers and pups. Cd and Ni were not detected and V, Cr and Pb levels were very low in maternal and pup blood. However, Ni and Pb levels were detected in the milk showing a transmammary transfer of these metals. Hg levels in blood and milk were higher than levels of previous metals and levels varied significantly throughout lactation. The increasing maternal levels over lactation were likely due to the remobilization of energy reserves during fasting and milk production in mothers causing a Hg release in blood. All metals were detected in hair and lanugo according to the following pattern: Fe > Zn > Hg > Cu > Se > Ni > V > Pb > Cd > Cr in mothers and Zn > Fe > Hg > Se > Cu > Pb > Ni > V > Cr > Cd in pups. Pb levels were relatively high in comparison with other phocid species. Only Hg showed a significant relationship between hair/lanugo and blood levels. This study highlights (i) a transplacental and transmammary transfer of metals in grey seals, and shows that (ii) physiological processes such as lactation and/or fasting can modify trace metal levels in the blood of mothers and pups. [less ▲]

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See detailOrganochlorine pollutants in sea turtles and their association with vitamin A
Dyc, Christelle ULg; Debier, Cathy; Thomé, Jean-Pierre ULg et al

Poster (2010, May)

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See detailMaternal transfer of chlorinated contaminants in the leatherback turtles, Dermochelys coriacea, nesting in French Guiana
Guirlet, Elodie ULg; Das, Krishna ULg; Thomé, Jean-Pierre ULg et al

in Chemosphere (2010), 79(7), 720-726

We examined the maternal transfer of organochlorine contaminants (OCs), pesticides (DDTS and HCHs) 26 and polychlorinated biphenyls (PCBs), and the temporal variation of blood and eggs concentrations from ... [more ▼]

We examined the maternal transfer of organochlorine contaminants (OCs), pesticides (DDTS and HCHs) 26 and polychlorinated biphenyls (PCBs), and the temporal variation of blood and eggs concentrations from 27 38 leatherback turtles (Dermochelys coriacea) nesting in French Guiana. PCBs were found to be the dom- 28 inant OCs with respective mean concentrations of 55.14 ng g 1 lipid-mass for egg and 1.26 ng mL 1 wet- 29 mass for blood. OC concentrations were lower than concentrations measured in other marine turtles 30 which might be due to the lower trophic position (diet based on gelatinous zooplankton) and to the loca- 31 tion of their foraging and nesting grounds. All OCs detected in leatherback blood were detected in eggs, 32 suggesting a maternal transfer of OCs. This transfer was shown to depend on female blood concentration 33 for RDDTs and for the most prevalent PCB congeners, since significant relationships were found between 34 paired blood–egg concentrations. During the nesting season, OC concentrations in eggs and the percent- 35 age of lipid in eggs were found to decline in successive clutches, highlighting a process of offloading from 36 females to their eggs and a decreasing investment of lipid from females into their clutches. OCs in eggs 37 tended to be higher in females spending 3 years in the foraging grounds between two nesting seasons 38 than in those spending 2 years, suggesting an impact of time spacing two breeding seasons, called remi- 39 gration interval, and of location of the foraging grounds. [less ▲]

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See detailAnthropogenic and naturally-produced organobrominated compounds in marine mammals from Brazil
Dorneles, Paulo R; Lailson-Brito, José; Dirtu, Alin C et al

in Environment International (2010), 36(1), 60-67

Liver samples from 51 cetaceans, comprising 10 species, stranded between 1994 and 2006 in a highly industrialized and urbanized region in Southeast Brazil, were analyzed for polybrominated diphenyl ethers ... [more ▼]

Liver samples from 51 cetaceans, comprising 10 species, stranded between 1994 and 2006 in a highly industrialized and urbanized region in Southeast Brazil, were analyzed for polybrominated diphenyl ethers (PBDEs) and methoxylated-PBDEs (MeO-PBDEs). A concentration range of PBDEs (3-5960 ng/g lw) similar to that observed in Northern Hemisphere dolphins was found. MeO-PBDE concentrations in continental shelf (CS) dolphins from Brazil are among the highest detected to date in cetaceans (up to 250 µg/g lw). Higher [Sigma]MeO-PBDE concentrations were measured in CS and oceanic dolphins than in estuarine dolphins. The [Sigma]PBDE/[Sigma]MeO-PBDE ratio varied significantly ranging from a mean value of 7.12 to 0.08 and 0.01 for estuarine, CS and oceanic species, respectively. A positive correlation was observed between [Sigma]PBDE and year of stranding of male estuarine dolphins (Sotalia guianensis), which suggests temporal variation in the exposure. Placental transfer of organobrominated compounds was also evidenced in S. guianensis. [less ▲]

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See detailPersistent organic pollutants and methoxylated PBDEs in harbour porpoises from the North Sea from 1990 until 2008. Young wildlife at risk?
Weijs, Liesbeth; van Elk, Cornelis; Das, Krishna ULg et al

in Science of the Total Environment (2010), 409

n the European North Sea, harbour porpoises are top predators with relatively long life spans and a limited capacity for metabolic biotransformation of contaminants compared to some other marine mammal ... [more ▼]

n the European North Sea, harbour porpoises are top predators with relatively long life spans and a limited capacity for metabolic biotransformation of contaminants compared to some other marine mammal species. As such, they are exposed to a mixture of persistent pollutants, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), DDT and metabolites (DDXs), hexachlorobenzene (HCB) and chlordanes (CHLs) that bioaccumulate in their tissues. We report here on the levels of persistent organic pollutants and of the naturally-produced methoxylated PBDEs (MeO-PBDEs) in blubber, liver and kidney of harbour porpoise neonates (n = 3), calves (n = 15), juveniles (n = 6) and adults (n = 4) of the southern North Sea. Concentrations of almost all contaminant classes decrease slightly in all age groups over the period 1990–2008. For some classes (e.g. PCBs and DDXs) however, levels seem to increase little in harbour porpoise calves. In all animals, blubber had the highest concentrations, followed by liver and kidney, whereas liver and kidney were the preferred tissues for several compounds, such as octa- and deca-PCBs. Our data suggest that harbour porpoises calves are exposed to higher or comparable concentrations of POPs and of MeO-PBDEs and somewhat different patterns of selected POPs than adults, potentially placing them, and the entire population, at a disproportionate risk for exposure-related health effects. [less ▲]

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See detailOccurrence of anthropogenic and naturally-produced organohalogenated compounds in tissues of Black Sea harbour porpoises
Weijs, Liesbeth; Das, Krishna ULg; Neels, Hugo et al

in Marine Pollution Bulletin (2010), 60

Harbour porpoises are one of the three cetacean species inhabiting the Black Sea. This is the first study to report on polybrominated diphenyl ethers (PBDEs) and naturally-produced compounds, methoxylated ... [more ▼]

Harbour porpoises are one of the three cetacean species inhabiting the Black Sea. This is the first study to report on polybrominated diphenyl ethers (PBDEs) and naturally-produced compounds, methoxylated PBDEs (MeO-PBDEs) and polybrominated hexahydroxanthene derivatives (PBHDs), in tissues (kidney, brain, blubber, liver, muscle) of male harbour porpoises (11 adults, 9 juveniles) from the Black Sea. Lipid-normalized concentrations decreased from muscle > blubber > liver > kidney > brain for the sum of polychlorinated biphenyls (PCBs) and for the sum of PBDEs. Among the naturally-produced compounds, levels of PBHDs were higher than of MeO-PBDEs, with tri-BHD and 6-MeO-BDE 47 being the dominant compounds for both groups, respectively. Concentrations of naturally-produced compounds decreased from blubber to brain, similarly to the sum of DDT and metabolites (DDXs). Concentrations of DDXs were highest, followed by PCBs, HCB, PBHDs, PBDEs and MeO-PBDEs. Levels of PCBs and PBDEs in blubber were lower than concentrations reported for harbour porpoises from the North Sea, while concentrations of DDXs were higher. [less ▲]

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See detailPolychlorinated Biphenyls affect Histological Appearance of European sea bass (Dicentrarchus labrax) Thyroids
Schnitzler, Joseph ULg; Klaren, Peter; Celis, Niko et al

Conference (2010)

Polychlorobiphenyls (PCBs) are well-described endocrine disrupters and of particular interest are effects on thyroid function. We propose here a thorough approach to assess effects of these compounds on ... [more ▼]

Polychlorobiphenyls (PCBs) are well-described endocrine disrupters and of particular interest are effects on thyroid function. We propose here a thorough approach to assess effects of these compounds on the thyroid function of European sea bass (Dicentrarchus labrax). An experimental exposure of sea bass to commercial PCB mixtures has been designed to understand underlying toxicity mechanisms and effects on the thyroid system. After 120 days of exposure histological appearance of thyroid tissue was assessed by light and electron microscopy. The follicle area, perimeter, diameter, length and with of every follicle cross section were interactively measured. The shape of the follicles was described with three dimensionless shape descriptors: roundness, form factor and aspect ratio. The histomorphometrical analysis showed a greater heterogeneity of thyroid follicle diameter and especially higher epithelial cell heights in sea bass exposed to environmental relevant doses of PCB (from 0.3 to 0.9 μg g-1 [7 ICES PCB]). Ultrastructural histological investigations showed that the epithelial cells surrounding the bigger follicles present an higher accumulation of colloid droplets. This was interpreted to be the result of increased stimulation of follicular cells. No differences in shape could be identified among the different treatment groups The size of the follicles and the form of the follicular cells gives an indication of the secretary activity of the gland. These observations support the hypothesis that the contamination of PCB mixtures can induce a hyperactivity of the thyroid tissue. These observations were confirmed by measurements of muscular thyroid hormone concentrations and activity thyroid hormone metabolism. [less ▲]

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