Measuring the impacts of Roundup Original® on fluctuating asymmetry and mortality in a Neotropical tadpole

Abstract

Amphibian larvae are highly susceptible to contamination, which can lead to lethal and sublethal effects. This impact can be measured by fluctuating asymmetry (FA), which is based on differences between the sides of organisms with bilateral symmetry. We evaluated the effect of acute and chronic exposure to Roundup Original® on Physalaemus cuvieri tadpoles. We measured tadpole survival and estimated the LC5096h. We also evaluated whether a sublethal concentration increases the FA. In acute exposure, survival was reduced and the LC50 was 2.13 mg a.i./l. In chronic exposure, nostril–snout distance and eye width had a significantly higher FA in contaminated tadpoles. The chronic exposure to contaminants could lead to several sublethal effects, which would be used in biomonitoring surveys. Morphological traits affected by contaminants, such as malformations or FA, would be relatively more easily measured from field samples. Because it is cost effective, easy to measure, and can be obtained without tagging or housing field-caught animals, we suggest that FA is a promising marker for monitoring the environmental impacts of contaminants like Roundup. However, additional studies are necessary to understand what additional environmental stressors might impact FA, and how this might alter its utility for use in biomonitoring.