References of "Das, Krishna"
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See detailEVALUATION OF FISH EXPOSURE TO POP-LIKE (ORGANOTIN) COMPOUNDS IN SEPETIBA BAY (RIO DE JANEIRO STATE, BRAZIL) THROUGH HEPATIC TOTAL TIN CONCENTRATIONS
Paiva, TC; Schilithz, PF; Bisi, TL et al

in Organohalogen Compounds (2016, August)

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See detailIsolation and identification of anthropogenic particles in fish stomachs by Raman spectroscopy: a new method
Collard, France ULg; Gilbert, Bernard ULg; Eppe, Gauthier ULg et al

in Organohalogen Compounds (2015, August)

Microplastic particles (MP) contaminate oceans and affect marine organisms in several ways. Ingestion combined with food intake is generally reported. However, data interpretation is often circumvented by ... [more ▼]

Microplastic particles (MP) contaminate oceans and affect marine organisms in several ways. Ingestion combined with food intake is generally reported. However, data interpretation is often circumvented by the difficulty to separate MP from bulk samples. Visual examination is often used as one or the only step to sort these particles. However, color, size and shape are insufficient and often unreliable criteria. Here we present an isolation method of MP specially adapted to a subsequent analysis by Raman spectroscopy. This method avoids fluorescence problems allowing the identification anthropogenic particles (AP) from stomach contents of fish by Raman spectroscopy. It was validated with commercial samples of microplastics and cotton along with stomach contents from three different Clupeiformes fishes: Clupea harengus, Sardina pilchardus and Engraulis encrasicolus. The optimized digestion and isolation protocol showed no visible impact on microplastics and cotton particles while the spectroscopic analysis allowed precise identification of microplastics and textile fibers. This approach allowed us to isolate 35 particles. These were analyzed by Raman spectroscopy: eleven were microplastics and thirteen were made of cellulose or lignin, or both (mostly fibers). Some particles were not identified but contained artificial colorants. This isolation protocol will help to assess the presence, quantity and composition of AP in planktivorous fish stomachs. [less ▲]

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See detailDo Triclosan affect hearing development of Cyprinodon variegatus larvae?
Schnitzler, Joseph ULg; Benichou, Farida; Pinte, Nicolas et al

Poster (2015, August)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Thyroid hormones are critical to the development of the brain and auditory system. Thus, TCS could affect the development of the brain and hearing. The aims of this study were: to investigate hearing development in sheepshead minnows (Cyprinodon variegatus) using the ABR technique (Auditory Brainstem Response) and to investigate the effects of triclosan on hearing development. Exposure to TCS was conducted from fertilization of eggs on at concentrations likely to be found in the environment: 20, 50 and 100 µgl-1. We characterized previously the ontogenic variation of thyroid hormones in embryos and larvae of sheepshead minnows. We observed an increase of thyroid hormones level around the 12th and the 15th day post hatching (dph), that may be associated with the transition from larval to juvenile stage during the development of this species. We concluded, that this period could be defined as a critical exposure window to pollutants. We determined hearing thresholds for sheepshead minnows of different ages. Our sheepshead minnows show ontogenic variations in the hearing ability during their development. At 30 days post hatching, their hearing ability is quite bad, with a narrow bandwidth of detected frequencies. But their hearing ability considerably enhance during their development to reach the adult hearing ability at around 80 days post hatching when this species reach sexual maturity. So we observe during the developmental phase of this fish species clear ontogenic improvements of the hearing ability and they showed an ontogenetic expansion in the frequency bandwidth they were able to detect. The effects of TCS in this development have yet to be determined but will be fully discussed. This study proposes an interesting new endpoint in thyroid disruption research. [less ▲]

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See detailThe effects of triclosan exposure in shape changes of sheepshead minnow (Cyprinodon variegatus) during early development and metamorphosis
Schnitzler, Joseph ULg; Frederich, Bruno ULg; Dussenne, Mélanie et al

Conference (2015, August)

Thyroid hormones are essential for normal development, and for maintenance of normal physiological functions in vertebrates [1, 2]. In fish, thyroid hormones are involved in the control of osmoregulation ... [more ▼]

Thyroid hormones are essential for normal development, and for maintenance of normal physiological functions in vertebrates [1, 2]. In fish, thyroid hormones are involved in the control of osmoregulation, metabolism, somatic growth and post-hatching metamorphosis [1, 3, 4]. The regulation of thyroid hormone bioavailability in tissues and cells represents a very complex and unique web of feedback systems [2]. In fish and other vertebrates the thyroid cascade involves two components. First, thyroxine (T4) biosynthesis and secretion are largely under central control by the brain–pituitary–thyroid axis [5]. Second, there is the conversion of T4 to its biologically active form 3,5,3-triiodothyronine (T3) and its metabolism and receptor-mediated actions that seems largely to be under peripheral control in extra-thyroidal tissues [6]. The accumulation in the aquatic environment of anthropogenic chemicals, among which are endocrine disrupting chemicals (EDCs) that alter normal hormonal regulation, is having dramatic consequences for humans and wildlife. Numerous chemicals disrupt thyroid homeostasis affecting thyroid hormone (TH) synthesis and transport, and cellular uptake and metabolism [7, 8]. Triclosan (TCS) is a synthetic chlorinated phenolic compound with a generalized use as an antimicrobial and preservative in many personal care and household products [9-11]. As a result of disposal of TCS through sewage systems and insufficient/variable removal by wastewater treatment plants (WWTP) [9], widespread contamination with TCS has been detected in several countries, particularly in aquatic ecosystems, WWTP influents and effluents; sludges and biosolids; surface or ground water; drinking water; and aquatic sediments [9-11]. TCS and its metabolites have been detected in tissues and body fluids of aquatic organisms including fish, revealing they are accumulating in the food chain [9-11] and TCS has also been detected in human blood, breast milk and urine [9-11]. The structural similarity of TCS with THs [9] suggest it may have adverse effects on the thyroid system. However, little is known about the mechanisms by which TCS disrupts the thyroid axis. TCS effects on fish thyroid axis have not been investigated. It is possible, that the TCS toxic effects reported in fish embryos, larvae and adults [9-11] might be caused, at least in part, through its effect on the thyroid system. We determined how TCS affect ontogenic variations of thyroid hormones in developing sheepshead minnow larvae. Knowing that thyroid hormones are involved in somatic growth and post-hatching metamorphosis, we also tested the hypothesis that TCS alter the development of these larvae. To do this, we used landmark-based geometric morphometric methods. These methods allowed us to analyse the pure shape variations of our developing larvae, regardless orientation, position, and size. [less ▲]

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See detailEstrogenic Evaluation and Organochlorine Identification in Blubber of North Sea Harbour Porpoise (Phocoena phocoena) Stranded on the North Sea Coast
Didimo Imazaki, Pedro Henrique ULg; Brose, François ULg; Jauniaux, Thierry ULg et al

in BioMed Research International (2015), 2015

Thirteen individual organochlorine compounds at 3 concentrations (80, 400, and 2000 ng/mL culture medium), as well as mixtures, were assayed for the estrogen receptor (ER) activation or inhibition, using ... [more ▼]

Thirteen individual organochlorine compounds at 3 concentrations (80, 400, and 2000 ng/mL culture medium), as well as mixtures, were assayed for the estrogen receptor (ER) activation or inhibition, using a luciferase reporter gene assay (RGA). None of the PCB 138, 153, or 180 or their mixture induced a response in the RGA. o,p'-DDT was the most potent xenoestrogen fromthe DDT group, inducing a response already at 80 ng/mL. From the HCH and HCB group, only 𝛽-HCH (at 400 and 2000 ng/mL) and 𝛿-HCH (at 2000 ng/mL) displayed estrogenic activities.These 13 organochlorines were determined by GC-MS in 12 samples of North Sea harbor porpoise blubber. The PCBs were the main contaminants. Within each group, PCB 153 (6.0 × 102∼4.2 × 104 𝜇g/kg), p,p'- DDE (5.1 × 102∼8.6 × 103 𝜇g/kg), and HCB (7.6 × 101∼1.5 × 103 𝜇g/kg) were the compounds found in highest concentrations.The hormonal activity of the porpoise blubber samples was also assayed in RGA, where two samples showed estrogenic activity, seven samples showed antiestrogenic activity, and one sample showed both estrogenic and antiestrogenic activity. Our results suggest that the 13 POPs measured by GC-MS in the samples cannot explain alone the estrogenicity of the extracts. [less ▲]

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See detailTHE EFFECTS OF TRICLOSAN ON HEARING DEVELOPMENT OF CYPRINODON VARIEGATUS LARVAE
Schnitzler, Joseph ULg; Benichou, Farida; Pinte et al

Conference (2015, May)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Thyroid hormones are critical to the development of the brain and auditory system. Thus, TCS could affect the development of the brain and hearing. The aims of this study were: to investigate hearing development in sheepshead minnows (Cyprinodon variegatus) using the ABR technique (Auditory Brainstem Response) and to investigate the effects of triclosan on hearing development. Exposure to TCS was conducted from fertilization of eggs on at concentrations likely to be found in the environment: 20, 50 and 100 μgl-1. We characterized previously the ontogenic variation of thyroid hormones in embryos and larvae of sheepshead minnows. We observed an increase of thyroid hormones level around the 12th and the 15th day post hatching (dph), that may be associated with the transition from larval to juvenile stage during the development of this species. We concluded, that this period could be defined as a critical exposure window to pollutants. We determined hearing thresholds for sheepshead minnows of different ages. Due to the small size of larvae, first measurements were only possible at 30 dph. Audiograms showed that the hearing ability is not yet completely established at 30 dph compared to adults. So we pursued our experiments in older larvae of 40, 60, 70, and 80 dph when sexual maturity is attained. First results indicate that the hearing ability considerably improves between 50 and 60 dph. The effects of TCS in this development have yet to be determined but will be fully discussed. This study proposes an interesting new endpoint in thyroid disruption research. [less ▲]

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See detailApplications of stable isotopes in environmental studies at the University of Liege
Sturaro, Nicolas ULg; Borges, Alberto ULg; Das, Krishna ULg et al

Poster (2015, March 26)

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed ... [more ▼]

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed within the Laboratory of Oceanology and, more recently, within the Chemical Oceanography Unit. In the Laboratory of Oceanology, one research axis is the measurement of stable isotope composition (C, N, S) in organic matter to delineate trophic web structure and to study animal diet, their trophic niches and their alteration by human activities. This methodology has been successively applied worldwide in different habitats and ecosystems (marine, freshwater, terrestrial) in temperate and tropical areas. Mediterranean food web and fish trophic ecology have received a particular attention. Coupling between trophic ecology and ecotoxicology is another area of investigation. This has been applied mainly to marine vertebrates and freshwater ecosystems. Stable isotope labelling is also used in our laboratory to study and quantify various ecological processes such as inorganic nitrogen incorporation and trophic transfers. The laboratory facilities, renewed in 2012 and managed by Dr. Gilles Lepoint, are composed of an elemental analyser (EA, vario MICRO cube, Elementar) and a gas chromatography (GC, Agilent) coupled to an isotope ratio mass spectrometer (IRMS, Isoprime 100). The GC is also equipped with a quadrupole mass spectrometer. In 2014, the Chemical Oceanography Unit, headed by Dr. Alberto Borges, has acquired and implemented an off-axis cavity ring-down spectroscopy (CRDS) for the measurements of δ15Nα, δ15Nβ, δ18O of N2O. This enables characterization of the N2O origin in a variety of aquatic environments including groundwater in Wallonia, rivers and lakes in Wallonia and Africa, coastal environments (Scheldt estuary, Lake Grevelingen, North Sea), Mediterranean seagrass beds, and Antarctic and Arctic sea-ice. [less ▲]

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See detailPOPs in free-ranging pilot whales, sperm whales and fin whales from the Mediterranean Sea: Influence of biological and ecological factors
Pinzone, Marianna ULg; Budzinski, Hélène; Tasciotti, Aurélie et al

in Environmental Research (2015), 142

The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are ... [more ▼]

The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are subjected to numerous anthropogenic threats, such as exposure to high levels of contaminants. Therefore, selected persistent organic pollutants, POPs (29 PCBs, 15 organochlorine compounds, nine PBDEs and 17 PCDD/Fs), were analysed in the blubber biopsies of 49 long-finned pilot whales, 61 sperm whales and 70 fin whales collected in the north-western Mediterranean Sea (NWMS) from 2006 to 2013. The contamination profile and species feeding ecology were combined through the use of stable isotopes. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS, respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2 ± 1.3‰ for sperm whales, 10.5 ± 0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, which positions sperm whales at higher trophic levels. δ13C of the two odontocetes were similar and amounted to −17.3±0.4‰ for sperm whales and −17.8±0.3‰ for pilot whales, whereas the result for fin whales reflected more depleted (−18.7±0.4‰). This outcome indicates a partial overlap in the feeding habits of toothed whales and confirms the differences in feeding behaviour of the mysticete. Pilot whales had higher concentrations than sperm whales for ΣPCBs (38666 ± 25731 ng.g-1 lw and 22849 ± 15566 ng.g-1 lw, respectively), ΣPBDEs (712±412 ng.g-1 lw and 347±173 ng.g-1 lw, respectively) and ΣDDTs (46081±37506 ng.g-1 lw and 37647±38518 ng.g-1 lw, respectively). Fin whales had the lowest values, which reflected its trophic position (ΣPCBs: 5721±5180 ng.g-1 lw, ΣPBDEs: 177±208 ng.g-1 lw and ΣDDTs: 6643±5549 ng.g-1 lw). Each species was characterized by large inter-individual variations that are more related to sex than trophic level. Males presented a higher contaminant burden than females. The discriminant analysis (DA) confirmed how DDTs and highly chlorinated PCBs could differentiate the three species. The pollutant concentrations of our species were significantly higher than both their southern hemisphere and North Atlantic counterparts. This result is possibly due to Mediterranean geomorphology, which influences the distribution and recycling of pollutants. Dioxin-like PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) the pollutants of Mediterranean cetaceans often surpassed the estimated threshold toxicity value of 17000 ng.g−1 lw for blubber in marine mammals and (2) how the final pollutant burden in these animals is strongly influenced not only by trophic position but also by numerous other factors, including sex, age, body size and geographical distribution. [less ▲]

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See detailDiurnal and Seasonal Variation in the Behaviour of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els; Holsbeek, Ludo; Das, Krishna ULg

in Aquatic Mammals (2015)

Diurnal and seasonal patterns in the behaviour of a small population of bottlenose dolphins were assessed in Bahía San Antonio (BSA), Patagonia, Argentina, between 2006 and 2011. Results indicated that ... [more ▼]

Diurnal and seasonal patterns in the behaviour of a small population of bottlenose dolphins were assessed in Bahía San Antonio (BSA), Patagonia, Argentina, between 2006 and 2011. Results indicated that dolphins used the study area mainly to rest, travel, and forage, with a marked diurnal and seasonal pattern in their activity. During the early morning, most dolphin groups were resting, while towards the afternoon and evening, surface feeding and social activities peaked. During winter, social activities and surface feeding increased notably; during summer, diving behaviour reached its peak, presumably associated with a tail-out/peduncle-dive foraging strategy. The observed seasonal variation in foraging strategies is hypothesised to be related to the seasonal behavioural changes of prey species in the area that are linked to spawning. The variation in group size further appears to reflect the regulation of feeding competition while reconfirming the low predation risk within the study area. Results of this study indicate the behavioural and social flexibility of bottlenose dolphins in BSA and suggest a link to the seasonal variations in prey availability. Considering the general bottlenose dolphin population declines in Argentina presumably related to prey depletion, it could be argued that the temporal occurrence of spawning shoals and a general low presence of other top predators directly and indirectly make this a favourable area for this population. Additional information is required to more comprehensively address this hypothesis. The information presented herein serves as vital baseline data for future conservation management protocols. [less ▲]

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See detailAssessment of contaminant levels and trophic relations at a World Heritage Site by measurements in a characteristic shorebird species
Schwemmer, Philipp; Covaci, Adrian; Das, Krishna ULg et al

in Environmental Research (2015), 136

The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB ... [more ▼]

The River Elbe is responsible for influxes of contaminants into the Wadden Sea World Heritage Site. We investigated levels of polychlorinated biphenyls (PCBs), oxychlordane (OxC), hexachlorobenzene (HCB), hexachlorocyclohexanes (α-, β-, γ-HCHs), dichlorodiphenyltrichloroethane (DDT) and its metabolites, and polybrominated diphenyl ethers (PBDEs) in blood and feathers from Eurasian oystercatchers (Haematopus ostralegus; n=28) at the Elbe and compared it with a non-riverine site about 90 km further north. (1) Mean levels of all contaminants in feathers and serum were significantly higher at the river (ƩPCBs: 27.6 ng/g feather, 37.0 ng/ml serum; ƩDDTs: 5.3 ng/g feather, 4.4 ng/ml serum) compared with the non-riverine site (ƩPCBs: 6.5 ng/g feather, 1.2 ng/ml serum; ƩDDTs: 1.4 ng/g feather, 0.5 ng/ml serum). Mean ƩHCH and HCB levels were <1.8 ng/g in feather and <1.8 ng/ml in serum at both sites. (2) Levels of most detectable compounds in serum and feathers were significantly related, but levels were not consistently higher in either tissue. (3) There was no significant relationship between trophic level in individual oystercatchers (expressed as δ15N) or the degree of terrestrial feeding (expressed as δ13C) and contaminant loads. (4) PBDEs were not detected in significant amounts at either site. The results of this study indicate that the outflow from one of Europe’s largest river systems is associated with significant historical contamination, reflected by the accumulation of contaminants in body tissues in a coastal benthivore predator. [less ▲]

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See detailMaternal transfer of organohalogenated compounds in sharks and stingrays
Weijs, Liesbeth; Briels, Nathalie; Adams, Douglas et al

in Marine Pollution Bulletin (2015)

Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study ... [more ▼]

Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study provides preliminary data on the POP transfer from pregnant females to offspring of three species (Atlantic stingrays, bonnethead, blacktip sharks) with different reproduction modes (aplacental, placental viviparity). Polychlorinated biphenyl (PCB) levels were generally higher than any other POPs. Stingrays and blacktip shark embryos contained the lowest POP concentrations while bonnetheads and the blacktip adult female had the highest concentrations. Results suggest that are more readily transferred from the mother to the embryo compared to what is transferred to ova in stingrays. Statistically significant differences in levels of selected POPs were found between embryos from the left and right uterus within the same litter as well as between female and male embryos within the same litter for bonnetheads, but not for the blacktip sharks. [less ▲]

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See detailBioaccumulation of organohalogenated compounds in sharks and rays from the southeastern USA
Weijs, Liesbeth; Briels, Nathalie; Adams, Douglas et al

in Environmental Research (2015), 137

Organohalogenated compounds are widespread in the marine environment and can be a serious threat to organisms in all levels of aquatic food webs, including elasmobranch species. Information about the ... [more ▼]

Organohalogenated compounds are widespread in the marine environment and can be a serious threat to organisms in all levels of aquatic food webs, including elasmobranch species. Information about the concentrations of POPs (persistent organic pollutants) and of MeO-PBDEs (methoxylated polybrominated diphenyl ethers) in elasmobranchs is scarce and potential toxic effects are poorly understood. The aims of the present study were therefore to investigate the occurrence of multiple POP classes (PCBs, PBDEs, DDXs, HCB, CHLs) and of MeO-PBDEs in various elasmobranch species from different trophic levels in estuarine and marine waters of the southeastern United States. Overall, levels and patterns of PCBs, PBDEs, DDXs, HCB, CHLs and of MeO-PBDEs varied according to the species, maturity stage, gender and habitat type. The lowest levels of POPs were found in Atlantic stingrays and the highest levels were found in bull sharks. As both species are respectively near the bottom and at top of the trophic web, with juvenile bull sharks frequently feeding on Atlantic stingrays, these findings further suggest a bioaccumulation and biomagnification process with trophic position. MeO-PBDEs were not detected in Atlantic stingrays, but were found in all shark species. HCB was not found in Atlantic stingrays, bonnetheads or lemon sharks, but was detected in the majority of bull sharks examined. Comparison with previous studies suggests that Atlantic stingrays may be experiencing toxic effects of PCBs and DDXs on their immune system. However, the effect of these compounds on the health of shark species remains unclear. [less ▲]

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See detailSpatial variation in the concentrations of mercury and persistent organic pollutants in free-ranging bottlenose dolphins (Tursiops truncatus) from South Florida
Damseaux, France ULg; Kiszka, Jeremy; Heithaus et al

Poster (2014, December 12)

The bottlenose dolphin (Tursiops truncatus) is an abundant apex predator found in nearshore waters of South Florida, especially in the Lower Florida Keys (Key West) and the coastal waters of Everglades ... [more ▼]

The bottlenose dolphin (Tursiops truncatus) is an abundant apex predator found in nearshore waters of South Florida, especially in the Lower Florida Keys (Key West) and the coastal waters of Everglades National Park (ENP). The objective of this study was to assess variation in contamination levels of total mercury (T-Hg) and persistent organic pollutants (NDL-PCBs, PBDEs, DDT, HCH, HCB, PCDD/Fs and DL-PCBs) in bottlenose dolphins found offshore of the densely populated Key West (n = 27) and from undeveloped ENP (n = 20). T-Hg and POPs were analysed in skin and blubber, respectively, by the mean of Direct Mercury analyser (for THg), GC-ECD (POPs) and GC-HRMS (DLCs). The 7 ICES PCBs were the main compounds found in bottlenose dolphins from Key West (8229 ng.g-1 lipids) and the ENP (2289 ng.g-1 lipids), while the concentrations of PCDD/Fs remained low (Key West: 104 pg.g-1 lipids, ENP: 102 ng.g-1 lipids). POP concentrations were higher in individuals from Key West compared to those from the ENP. However, POPs concentrations in Key West dolphins were lower than those from other locations in Florida and around the world. Unlike organic pollutants, T-Hg concentrations were significantly higher in ENP dolphins (Key West: 2941 ng.g-1 dw versus ENP: 9314 ng.g-1 dw) highlighting the specific cycle of Hg in mangrove ecosystems. To conclude, sources of T-Hg and POPs differed between Key West and ENP as reflected by their concentrations in skin and blubber of free-ranging bottlenose dolphins highlighting their role as sentinels of their environment. [less ▲]

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See detailImpact of triclosan on behaviour and neural development of Cyprinodon variegatus
Benichou, Farida; Rahmouni, Chahrazed; Denoël, Mathieu ULg et al

Poster (2014, December)

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems ... [more ▼]

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems, which can act as endocrine disruptor, mainly by modifying thyroid functioning. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Exposure to TCS was conducted at fertilization of eggs at concentrations likely to be found in the environment: 20, 50 and 100 μg.l-1. The analysis of growth parameters of C. variegatus showed no effect of TCS on the fertility of eggs, survival and larval weight. Subsequently, THs concentrations were measured on 15 days post hatching larvae. THs are initially produced as T4 (thyroxine) cells and then converted in the bioactive form of T3 (triiodothyronine) cells. The observed increase of T4 and T3 cells in larvae exposed to 50 and 100 μg.l-1 suggests an increase in THs synthesis as a consequence of TCS exposure. Auditory thresholds of larvae were determined using ABR (Auditory Brainstem Response) technique, and finally larval mobility was measured. For both parameters no significant differences were observed among the three different treatments. Audiograms showed that the auditory system is not yet completely established at 30 days post hatching. However, these results allowed us to consider C. variegatus as an “hearing generalist” because this species have a hearing sensitivity lower than 2000 Hz. Regarding locomotion, our result summarized short time experiences targeting only swimming speed, distance and degree of mobility. It would be interesting to expand the behavioural aspects on other parameters of locomotion and integrate Cyprinodon reaction to different stress (light or touch). In conclusion, our results require an extensive long-term study on the full life cycle of C. variegatus, in order to evaluate the impact of triclosan on neural function and behaviour through several generations. [less ▲]

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See detailEvaluation of the impact of Triclosan on the functioning of the thyroid system in Cyprinodon variegatus L., 1803.
Rahmouni, Chahrazed; Benichou, Farida; Klaren, PHM et al

Poster (2014, December)

Triclosan (5-chloro-2-[2, 4-dichlorophenoxy] phenol) is an antimicrobial widely used in various industrial products such as textiles, cosmetics and body care products. It is often detected in aquatic ... [more ▼]

Triclosan (5-chloro-2-[2, 4-dichlorophenoxy] phenol) is an antimicrobial widely used in various industrial products such as textiles, cosmetics and body care products. It is often detected in aquatic environments. The presence of the main biotransformation product, methyl TCS, indicates that this compound is not only degraded, but also persistent and accumulates in aquatic organisms. In this study, the effects of TCS on the thyroid system during embryonic and larval stages in Cyprinodon variegatus were evaluated. In particular, whole body thyroid hormone levels and the activity of deiodinases, enzymes involved in the activation of the thyroid prohormone T4, were measured. Couples of three females and two males were placed in breeding chambers designed for this experiment from which 3832 eggs were obtained by reproduction in the laboratory. Eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope, randomly assigned to each of five treatment groups: Control, DMSO control (vehicle), 20 μg/L TCS, 50 μg/L TCS and 100 μg/L TCS and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L dishes. The larvae were fed on artemia and on flaked fish food till day 15 post hatching when the fish were analyzed. The fertilization and survival rate, as well as the larval dry weight did not vary significantly between individuals exposed to 20, 50 and 100 μg/L TCS. T3 and T4 concentrations increased significantly in larvae exposed to 50 and 100 μg/L TCS. The study of the activity of enzymes involved in the deiodination of thyroid hormones (ORD) represents a new aspect in the study of endocrine disruption in C. variegatus. Unfortunately, we were not able to detect a net enzymatic T4 deiodination activity, most likely due to the very small amounts of protein and low specific enzyme activity in brain homogenates, carcass and liver. [less ▲]

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See detailThe thyroid gland and thyroid hormones in sheepshead minnow (Cyprinodon variegatus) during early development and metamorphosis
Schnitzler, Joseph ULg; Benichou, Farida; Klaren, PHM et al

Poster (2014, December)

The sheepshead minnow is widely used in ecotoxicological studies that recently, begin to focus on potential disruption of the thyroid axis by xenobiotics and endocrine disrupting compounds. However ... [more ▼]

The sheepshead minnow is widely used in ecotoxicological studies that recently, begin to focus on potential disruption of the thyroid axis by xenobiotics and endocrine disrupting compounds. However, reference levels of thyroxin (T4) and 3,5,3’-triiodothyronine (T3) and their developmental patterns are unknown. This study set out to describe the ontogeny and morphology of the thyroid gland in sheepshead minnow, and correlate these with whole body concentrations of thyroid hormones during early development and metamorphosis. Couples of three females and two males were placed in breeding chambers designed for this experiment. More than 1000 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L beakers. For one week after hatching, larvae were fed on artemia, and from 8 to 30 days post-hatch they were fed on flaked fish food. Embryos were sampled on day 0, 3, 6 post-fertilization and larvae and juveniles were sampled every three days from day 0 to 28 days post-hatch. The pooled samples were taken from several incubation dishes and divided in three replicate batches of 10-30 individuals. T4 and T3 were extracted from whole fish bodies and an enzyme-linked immunoassay was used to measure whole-body hormone levels. At each sampling point 5 individuals were placed in formalin fixative for histology. Length and body mass were measured. Hatching success, gross morphology, thyroid hormone levels and histology data were recorded. The onset of metamorphosis at 12 days post-hatching coincided with surges in whole body T4 and T3 concentrations. Thyroid follicles were first observed in pre-metamorphic larvae at hatching, and were detected exclusively in the subpharyngeal region, surrounding the ventral aorta. Follicle size and epithelial cell heights varied during the developmental phase, indicating fluctuations in thyroid hormone synthesis activity. The increase in the whole body T3/T4 ratio was indicative of an increase in outer ring deiodination. This study establishes a baseline for thyroid hormones in sheepshead minnows, which will be vital for the understanding of thyroid hormone functions and in future studies of thyroid toxicants in this species. [less ▲]

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See detailThe effects of Triclosan on the metabolism of developing Sheepshead minnow (Cyprinodon variegatus) larvae
Lallemand, Lise; Voisin, Anne-Sophie; Darchambeau, François ULg et al

Poster (2014, December)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Thyroid hormones are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Thyroid hormones are involved in the control of metabolism, so changes in hormone levels induced by triclosan may affect respiratory rates and antioxidant stress in exposed fish. Couples of three females and two males were placed in breeding chambers designed for this experiment. Eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope, randomly assigned to each of five treatment groups: Control, DMSO control, 20 μg/L TCS, 50 μg/L TCS and 100 μg/L TCS and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L dishes. The larvae were fed on artemias and on flaked fish food till day 15 and 30 post hatching when the fish were analyzed. Respiratory rate measurements were carried out by respirometry and assays of antioxidant enzymes, Glutathionreductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were conducted to determine the presence of oxidative stress. Respirometry showed that TCS exposed fish exhibited decreased the metabolism at 15 dph, whereas no differences in respiration rate could be observed between control and exposed larvae at 30 dph. At 15 dph no difference was observed for any of the antioxidant enzymes, whereas at 30 dph a sharp increase in the activity of GR was observed between the control and TCS exposed fish. The activity of GST and Gpx remained stable. Thyroid hormones are major factors controlling the metabolic rate related to respiration and oxidative stress. TCS reduced the metabolism at 15 dph that corresponds to the moment where larvae to juvenile transition of Sheepshead minnows occur. Previous experiments showed that TCS induces an increase in thyroid hormone concentrations and hyperthyroidism induces oxidative stress. So our observed increase of antioxidant protection mechanisms could be a way to compensate oxidative stress. On the other hand, the changes in GR activity observed at 30 dph, may also be related to the reduced metabolism at 15 dph. [less ▲]

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See detailHarbour seals as sentinels for the marine environment
Das, Krishna ULg

Scientific conference (2014, November 25)

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See detailSeals as sentinels for the marine environment
Das, Krishna ULg

Scientific conference (2014, November 25)

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