Application of multimedia models to evaluate the behavior of Rhinella arenarum tadpoles (Anura, Bufonidae) exposed to the insecticide spirotetramat

Abstract

In recent decades, new active substances with a more specific effect and lower toxicity for non-target organisms have been developed. This is the case of spirotetramat (STM), for which little ecotoxicological information is currently available. The aim of this work was to generate ecotoxicological information on STM by using Rhinella arenarum tadpoles as a model, applying simple multimedia models and computer simulations to describe behavioral effects, and correlating modeled values with experimental ones. Acute exposure (96 h) of 10 larvae per replicate to 1000 ml of the corresponding STM solution was carried out in glass chambers. Twenty-one concentrations ranging from 0.1875 to 33 mg a.i./l were tested in quadruplicate. A negative control was also performed and all solutions were completely renewed every 24 h. Swimming alterations occurred at concentrations much lower (< 2 mg/l) than those leading to mortality (LC50: 6.07 mg/l), and showed an increase in mean position, speed, and time at the edge of the tadpoles at low concentrations, followed by a transition to a more static regime at higher concentrations, resembling a hormesis response. The application of a Vicsek model with a waiting effect that simulated the effect of STM showed good agreement with the experimental results. This model could be used in the future as a predictive and alternative tool to assess the effects on environmentally stressed larvae. This work is the first report on the lethal and sublethal effects of STM on a native anuran species representative of local amphibian communities in Argentina.