Intraspecific and interspecific tolerance to copper sulphate in five Iberian amphibian species at two developmental stages.

Intraspecific and interspecific variations have been observed across many taxa with respect to resistance to natural environmental stressors. It has already been well documented that amphibians are sensitive to habitat degradation and are regarded as bioindicators of aquatic and agricultural ecosystems. In southern Spain, different toxic substances, including copper sulphate, which is used to control Cycloconium oleaginum (Fungi, Ascomycota, Venturiaceae) during spring and autumn, are used in intensive olive tree agriculture. In this context, many wetlands are affected by a diffuse pollution process. Thus, toxicological studies using different species living in wetlands surrounded by agricultural activity are needed to understand the alterations suffered by these ecosystems. To achieve this understanding, individuals of five amphibian species (Bufo bufo, Epidalea calamita, Discoglossus jeanneae, Pelobates cultripes, and Pelophylax perezi) at Gosner developmental stages 19 and 25 were exposed to different copper sulphate concentrations in 96 h acute toxicity tests. Exposure to copper sulphate had a negative effect on total larval length reached at the end of the experimental period and generated approximately 30% of growth reduction respect to control treatments. P. perezi was the most tolerant species studied and showed no mortality at the maximum concentration tested (0.20 mg Cu L(-1)), whereas the most sensitive species (B. bufo, E. calamita, and D. jeanneae) showed approximately 90% mortality at the same concentration. These results indicates that the sole presence in wetlands of P. perezi, the most abundant species in southeast of Iberian Peninsula, might be correlated with its high tolerance to agrochemicals.