Copper-driven avoidance and mortality in temperate and tropical tadpoles

Amphibians have experienced an accentuated population decline in the whole world due to many factors, one of them being anthropogenic contamination. The present study aimed to assess the potential effect of copper, as a worldwide and reference contaminant, on the immediate decline of exposed population due to avoidance and mortality responses in tadpoles of three species of amphibians across climatic zones: a South American species, Leptodactylus latrans, a North American species, Litho bates catesbeianus, and a European species, Pelophylax perezi. A non-forced exposure system with a copper gradient along seven compartments through which organisms could freely move was used to assess the ability of tadpoles to detect and avoid copper contamination. All species were able to avoid copper at a concentration as low as 100 mu g L-1. At the lowest (sublethal) concentrations (up to 200 mu g L-1) avoidance played an exclusive role for the population decline, whereas at the highest concentrations (>450 mu g L-1) mortality was the response determining population decline. The median concentrations causing exposed population immediate decline were 93, 106 and 180 mu g L-1 for Le. latrans, Li. catesbeianus and P. perezi, respectively. Contaminants might, therefore, act as environmental disruptors both by generating low-quality habitats and by triggering avoidance of tadpoles, which could be an important response contributing to dispersion patterns, susceptibility to future stressors and decline of amphibian populations (together with mortality). (C) 2013 Elsevier B.V. All rights reserved.