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, although it is possible to detect many more subtle effects. After a detailed description of embryogenesis in Gammarus fossarum, the present study reports on the sublethal effects of cadmium (Cd) exposure during embryonic development in G. fossarum. Embryos were first directly exposed in multiwell plates throughout the entire embryonic cycle (23 d) to increasing Cd concentrations (0, 1.5, and 3.0 µg/L; 120 embryos/concentration). Then, 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. Next, 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, the following parameters were measured in the newborn individuals: 1) body mass; 2) activity of the enzyme phenoloxidase, a key enzyme of the arthropod immune system; and 3) locomotor activity. 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. Environ Toxicol Chem 2017;36:2436-2443. © 2017 SETAC.

New method to discriminate sedative and analgesic effects of drugs in the automated formalin test in rats.

We developed an automated technique based on the detection of pain-related behaviours (like licking or biting) and small activities (mostly grooming) in the formalin pain test. By comparing automated and manual scoring, we determined that the interphase score was mostly independent of pain-related behaviours and it was used as an index of sedative events. The non-pain-related behaviours, still present during the second phase, were eliminated in order to visualize only pain-related behaviours. This new method, validated using classical analgesic (morphine) and sedative drugs (diazepam) could be used to discriminate sedative from analgesic effects of pharmacological treatments in the formalin test.