Papers by Célia Joaquim-justo
Many substances released in aquatic ecosystems have been reported to disrupt endocrine systems in... more Many substances released in aquatic ecosystems have been reported to disrupt endocrine systems in vertebrates and invertebrates. In the rotifer Brachionus calyciflorus, studies show that chemicals characterized by a high affinity to the vertebrate androgen receptor depress sexual reproduction at concentrations one to two orders of magnitude below those that affect asexual reproduction. We studied the effect of cyproterone acetate, an anti-androgen of steroid like structure, and of the pesticide fenitrothion, a non steroidal molecular which has a high affinity to the vertebrate androgen receptor, on the sexual reproduction of rotifers. In mating experiments we crossed control females with exposed males and vice versa to determine whether anti-androgens affected males, females or both. Fertilization rate and number of resting eggs produced were affected by both substances tested. With fenitrothion, depression of these endpoints was observed exclusively when males were treated. Cyproterone acetate enhanced production of resting eggs whereas fertilization rate was not significantly affected. Increased production of resting eggs was observed both with treated females and males. Parameters of male fertility were compared in control and in exposed males. We report impacts on spermatozoa numbers, morphology and fertilizing potential, and on male morphology, longevity and mating behaviour for the two substances tested
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Verhandlungen, May 1, 1998
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Environmental Science and Pollution Research, Jun 29, 2019
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Iranica journal of energy and environment, 2015
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Knowledge on the impacts of endocrine disruptors on gastropods is scarce and their mechanism of a... more Knowledge on the impacts of endocrine disruptors on gastropods is scarce and their mechanism of action poorly understood especially the impacts of androgenic and antiandrogenic compounds. In this study effects of 5 androgenics and antiandrogenics endocrine disruptors were investigated on the reproduction and life traits of the freshwater pulmonate gastropod Lymnaea stagnalis. The chemicals tested were Tributyltin, Cyproterone acetate, Methyltestosterone, Vinclozolin and Fenitrothion. Tributyltin was used as androgenic positive control. The other compounds tested are androgenic and antiandrogenic compounds either steroids or non steroids. Adult snails were exposed to 3 concentrations of each chemical for 30 days. The size and reproductive organs development were monitored throughout exposure. The number of clutches, the number of eggs per clutch were assessed during the first 10 days. The clutches were kept individually in clear water except for the clutches of the eighth day which were divided in two. Half was kept individually in clear water and the other half was individually reared in contaminated water following the same exposure as their parents. The percentage of hatching per clutch of these clutches was measured. The development size, mortality, and development of reproductive organs of the juveniles were assessed until their first clutch was laid
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Putative endocrine disruptors affect rate of fertilization of sexual females by males. Preston et... more Putative endocrine disruptors affect rate of fertilization of sexual females by males. Preston et al. (2000) reported a decrease in fertilization rate following exposition to, notably, flutamide at 10µg/l. We observed similar effects with fenitrothion. Cross mating experiments showed that the decrease in fertilization rate is due to an impact on males exclusively. We studied the impact of anti-androgens on spermatogenesis and observed a decrease in the spermatozoa production with concentrations down to 0,5 mg L-1.We also report a detailed description of the morphology of the male reproductive apparatus in B. calyciflorus based on optic and electronic microscopy analysis and we describe the effect of anti-androgens on males and spermatogenesis in males
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The importance of trophic relationships between rotifers and protozoans in rivers are not yet wel... 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
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Grazing of metazooplankton on phytoplankton and protozooplankton has been widely studied using th... more Grazing of metazooplankton on phytoplankton and protozooplankton has been widely studied using the radiotracer technique. An interesting alternative to radioactive label is the use of fluorescent dies. Indeed, the use of fluorescently labelled algae (FLA) or protozoans does not imply particular security measures or equipment; moreover they allow the visualisation of the labelled prey in the predator sometimes providing useful informations on the variability between individuals and on the mechanism of feeding processes. Prior to the use of this method in ingestion rate measurements with Brachionus calyciflorus discrimination experiments were performed. The FLAs were Chlorella-like algae (Dictyosphaerium ehrenbergianum) labelled with DTAF (5-(4,6-dichlorotriazin-2-yl) aminofluorescein). The ingestion rate of the rotifer on the FLAs was 3 to 15 times lower than the ingestion rate on non labelled. Evidence was gathered that the staining procedure (heat-killing of the algae) was mainly responsible for the discrimination of the rotifer rather than the dye itself. Other technical considerations will be discussed like the occurrence of crashed algae in the rotifers gut and the inter-individual variability
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Knowledge on the impacts of endocrine disrupting chemicals (EDCs) on gastropods is scarce and the... more Knowledge on the impacts of endocrine disrupting chemicals (EDCs) on gastropods is scarce and their mechanisms of action are still poorly understood. In this study, effects of 3 androgens (tributyltin, testosterone and fenitrothion), 2 anti-androgens (cyproterone acetate and vinclozolin) and 1 estrogen (chlordecone) on growth and reproduction were investigated in the hermaphrodite gastropod Lymnaea stagnalis
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The rotifer Brachionus calyciflorus is a ubiquitous species that often dominates river zooplankto... 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
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Chemosphere, Feb 1, 2018
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Ecotoxicology and Environmental Safety, Dec 1, 2015
Very few ecotoxicological studies have considered differences in toxic effects on male and female... more Very few ecotoxicological studies have considered differences in toxic effects on male and female organisms. Here, we investigated protein expression differences in caeca of Gammarus pulex males and females under control conditions (unexposed) and after 96h exposure to BDE-47. Using gel-free proteomic analysis, we have identified 45 proteins, of which 25 were significantly differently expressed according to sex and/or BDE-47 exposure. These proteins were involved in several biological processes such as energy metabolism, chaperone proteins, or transcription/translation. In unexposed amphipods, 11 proteins were significantly over-expressed in females, and 6 proteins were over-expressed in males. Under BDE-47 stress, 7 proteins were differently impacted according to sex. For example, catalase was over-expressed in exposed females and under-expressed in exposed males, as compared to respective controls. Conversely, proteins involved in energy metabolism were up-regulated in males and down-regulated in females. Our proteomic study showed differences in responses of males and females to BDE-47 exposure, emphasizing that sex is a confounding factor in ecotoxicological assessment. However, due to the limited information existing in databases on Gammarids, it was difficult to define a BDE-47 mechanism of action. The gel-free proteomic seems to be a promising method to develop in future ecotoxicological studies and thus, to improve our understanding of the mechanism of action of xenobiotics.
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Ecotoxicology and Environmental Safety, Jul 1, 2017
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Many substances released in the aquatic environment have been reported to have disruptive effects... more Many substances released in the aquatic environment have been reported to have disruptive effects on endocrine systems of vertebrates and invertebrates. In rotifers, some of these chemicals have been shown to depress sexual reproduction at concentrations one to two orders of magnitude below those that affect asexual reproduction. The anti-androgen flutamide impacts sexual reproduction of rotifers at particularly low concentrations. We studied the effect of different types of putative endocrine disruptors on sexual reproduction of Brachionus calyciflorus. Contaminants tested were cyproterone acetate, an anti-androgen with a steroid-like structure, the pesticides fenitrothion and linuron which both have high affinity to the androgen receptor in vertebrates, although they are nonsteroidal molecules, and lindane a widely used pesticide that binds weakly to the androgen receptor in vertebrates. A series of endpoints relative to different steps of sexual reproduction were monitored to define critical functions affected and to get information on mechanisms of action. Fenitrothion, had the strongest impact on the sexual reproduction of rotifers. We observed a decrease in the proportion of mictic females among the ovigerous individuals and in the production of fertilized eggs per female that was proportional to the dose. The most sensitive parameter was the number of males produced per mictic female which was considerably higher in treated animals even at concentrations 10 times lower than the NOEC of asexual reproduction
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Papers by Célia Joaquim-justo