Abstract :
[en] Endocrine disruptors (EDCs) are well known to disrupt the development and the reproduction of exposed organisms. Although this point has been studied in vertebrate models, the limited knowledge of the endocrine system of invertebrates makes the evaluation of EDCs effects difficult. However, invertebrates represent the major part of aquatic ecosystems, such as amphipods Gammaridae, which are crucial for their functioning (e.g. litter degradation, food resource). Moreover, gammarids are hosts of hidden parasites such as vertically-transmitted microsporidia (microsporidia VT), which could be confounding factors in assessment of EDC effects, since microsporidia VT could feminize juvenile males in some Gammarus sp. Consequently, currently, no biomarkers (assessment tools) are available to assess the endocrine disruption in gammarids.
The present work focused on EDC effects on the molt process of Gammarus pulex, by researching the DNA sequences of two main proteins in the endocrine system of amphipods: the molt-inhibiting hormone (MIH) and the ecdysteroid receptor (EcR). Next, the expression variations of these two genes have been measured by RT-qPCR after an exposure of four EDCs: ethinylestradiol (EE2), 4-hydroxitamoxifen (4HT), 17α-methyltestosterone (17MT) and the cyproterone acetate (CPA), all commonly studied in vertebrates.
Sequence research allowed to obtain a 204 bp length and 255 bp length amplimers for EcR and MIH, respectively. The EcR sequence encodes for 68 amino acid fragment while the MIH sequence encodes for an 85 amino acid fragment. Exposure of G. pulex males at each EDC highlighted an increased of the MIH expression, whatever the parasitic status. However, a tend to increase was observed for the EcR expression only in uninfected gammarids.
This work allowed to identify two main proteins involved in the endocrine system of amphipods. Exposure to each ECD highlighted EDCs affecting vertebrates could also impact invertebrates species. In addition, the presence of microsporidia VT appeared to be a confounding factor which could lead to misinterpretation the endocrine risk assessment. Finally, results the results are promising in the development of PE biomarkers in invertebrates, since this is a tool that is currently missing. However, further studies will be needed to study the variations of these genes and understand their regularization, before to use them as biomarkers.
