Use of Gammarus fossarum (Amphipoda) embryo for toxicity testing: A case study with cadmium


The effects of environmental contaminants on arthropod embryo stages have been poorly investigated in ecotoxicology. Moreover, many of these tests used hatching success as the sole metric, while many more subtle effects could be detected. In the present study, after having finely described embryogenesis in Gammarus fossarum, sublethal effects of cadmium (Cd) exposure during the embryonic development of G. fossarum were studied. For this purpose, embryos were first directly exposed in multiwell plates throughout the entire embryo cycle (i.e. 23 days) to increasing Cd concentrations (0, 1.5 µg/L and 3.0 µg/L; 120 embryos per concentration). Second, to assess the representativeness of the gammarid embryo assay performed in multiwell plates, embryos were exposed to similar Cd concentrations through the maternal open brood pouch. Third, to pinpoint sensitive periods of development, embryos were directly exposed to 3.0 µg/L of Cd for shorter periods of time: during gastrulation, organogenesis and hatching. After hatching, i) body mass, ii) activity of the enzyme phenoloxidase, a key enzyme of the arthropod immune system, and iii) locomotor activity were measured in the newborn individuals. Phenoloxidase activity was strongly inhibited in newborn individuals of embryos exposed – either in multiwell plates or in the maternal brood pouch – to 3.0 µg/L Cd throughout embryonic development. Furthermore, strong detrimental locomotor effects were observed in newborn individuals of embryos directly exposed to 3.0 µg/L. Exposures for shorter periods of time were not sufficient to induce such effects; no sensitive period could be determined. By bringing new insights into a critical time window of exposure, the gammarid embryo assay could provide a novel and interesting addition to existing bioassays in gammarids.