Impact of cadmium on the ecdysteroids production in Gammarus fossarum.

Gammarus fossarum is an important test organism which is currently used as a bio-indicator as well as in ecotoxicological tests. Nevertheless, data on ecdysteroids in endocrine toxicity test are not yet available for these species, despite its crucial role in molting and reproduction. In the present paper, ecdysteroids concentrations were studied during the molt cycle (in females) and embryonic development in G. fossarum (Crustacea, Amphipoda) in order to propose an ecdysteroids toxicity test. Ecdysteroids levels in G. fossarum showed a single peak during premolt at stage Dl-D2. In embryos, ecdysteroids levels progressively increased over stages 3 and 4, with peak levels at stage 4. A Cadmium toxicity test was proposed to examine if the molting and embryogenesis disturbances previously observed after cadmium exposure (Geffard et al. 2010) could be attributed to changes in ecdysteroids titers. Exposure to the different cadmium concentrations (3; 9; 300; 900 µg/l) increased ecdysteroids secretion by Y-organs in vitro, but it had no significant effect on exposed embryos (in vivo). Based on previous findings, we are led to conclude that the molting impairments in cadmium-exposed females of G. fossarum is connected to the changes in ecdysteroids concentrations.