Interest of threespine stickleback (Gasterosteus aculeatus) digestive enzymes as new biomarkers in ecotoxicology field

chemical and physical disruption of the aquatic ecosystems. Regulations, such as the EU Water Framework Directive, for the protection of the aquatic environment, encourage the development of new sensitive and predictive tools to evaluate the effects of contaminants on aquatic living organisms. In this context, energy metabolism biomarkers are of interest given the central place of energy in all physiological processes (i.e. defense, growth and reproduction). In this study, we addressed for the first time three digestive enzymes (amylase, trypsin and intestinal alkaline phosphatase) and evaluated their interest as novel biomarkers in the threespine stickleback (Gasterosteus aculeatus), a model species in multidisciplinary fields of biology, and recently in ecotoxicology. The interest of the two digestive enzymes as biomarkers was evaluated in comparison with other parameters, usually applied in ecotoxicology studies: biometric parameters, reproduction parameters, antioxidant parameters, and other energy metabolism parameters. For that, juvenile sticklebacks were exposed for 3 months in semi-static conditions to cadmium at 0.5 μg.L-1 (chemical stress), and two water temperatures 16°C and 21°C (physical stress). Results showed that the high temperature (21 °C) was the major stress factor on stickleback physiology. The very low cadmium concentration used in this study had no effect on most of the studied parameters (i.e. growth parameters, antioxidant parameters and parents' reproduction parameters). However, digestive enzymes showed an interesting sensitivity to cadmium exposure which was emphasis at 21 °C (significant decrease). Although cadmium had no effect on parental reproduction, negative consequences on their offspring survival were observed after in vitro fertilization trials (decreased survival capacity). Compared to conventional measurements, digestive enzymes responded rapidly, which could be an important advantage for their use as early warning tool, to reflect organism’s health