The Use of Terrestrial Life-stages of European Amphibians in Toxicological Studies
Increasing pesticide use is suggested to contribute to amphibian population declines. Most European species have terrestrial life-stages after aquatic development. Many species that occur in the cultivated landscape have a high risk of coming into contact with pesticides, either by exposure to residues on food (oral uptake) or by dermal uptake (owing to direct over-spraying or contact with contaminated plant material or soil). Although species-specific differences in sensitivity are well known in amphibian toxicology, only 8% of European amphibian species have ever been used as test organisms in toxicological studies and urodele species are especially underrepresented. Birds and mammals, which are currently serving as surrogate species for pesticide toxicity to terrestrial life-stages of amphibians, dramatically differ in their biology and ecology. In particular, the fast dermal uptake of xenobiotics by amphibians questions the unique use of data obtained by oral administration of pesticides to surrogate species in pesticide approval. Furthermore, indirect effects (mainly strong reduction of food resources owing to pesticide applications) are not considered in current risk assessments and, finally, added substances in the formulations (adjuvants), which are often more toxic than the active ingredient, are not adequately assessed.