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PW08 Aquatic Ecotoxicology II
(PW138) Short-term toxicity assays with a small fish (Brachydanio rerio) based on avoidance and postexposure feeding.
Moreira-Santos, M1, Donato, C1, Ribeiro, R1, 1 Instituto do Ambiente e Vida, Departamento de Zoologia da Universidade de Coimbra, Coimbra, Portugal
ABSTRACT- Fish are key test organisms in aquatic toxicology, for ecological reasons and because of their sensitivity to many toxicants. In particular, small fish are generating more interest because they are easy to handle, require less laboratory space, and have short generation times enabling to shorten assay duration. Behavioral endpoints, such as avoidance and feeding, are being increasingly recognized as ecologically relevant sublethal responses because they result from the integration of complex biochemical and physiological processes, and are a major component of important life functions with implications at the population, community and ecosystem levels. Yet, they have not been implemented in the decision making process, mainly because of the lack of standardized assay procedures. The objective of this study was to develop ecologically relevant and cost-effective short-term assays with the small fish Brachydanio rerio using behavioral responses as assay endpoints. Two assays were proposed, one based on postexposure feeding and the other on avoidance. The feeding assay consisted of a 96-h exposure period followed by a 30-min postexposure feeding period under controlled conditions to assess effective concentrations. The avoidance assay consisted also of a 96-h exposure period to a gradient of contaminant concentrations, and avoidance was monitored at 24-h intervals. Exposure was conducted in a flow-through system which was demonstrated to allow the free and random distribution of the organisms and the establishment of a stable contamination gradient. Assays were evaluated by exposing organisms to essential (Cu and Cd) and non-essential metals (Zn and Cr), and to a field sample contaminated with acid mine drainage. Both endpoints were sensitive, easy and rapid to quantify and consequently amenable to standardization. Results are also discussed in light of differences in assay-sensitivity and on the relevance of incorporating information from both types of assays in risk assessment studies.
Key words: postexposure feeding, short-term sublethal assays, avoidance, small fish
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