Different Concentrations of Nanoencapsulated Geraniol Induce Lethargy and Acetylcholinesterase Activity in Aquarana catesbeiana Tadpoles.

Abstract

Nanoencapsulated geraniol (nGER) may be a promising alternative to currently used synthetic pesticides, as it combines the pesticidal effects of geraniol with the protection against environmental degradation provided by zein nanocapsules. Anurans are non-target organisms that are highly harmed by the effects of pesticides; however, studies investigating the effects caused by alternatives to pesticides in amphibians are scarce. Thus, this study aimed to evaluate the toxicity of nGER through behavioral analyses and muscle acetylcholinesterase (AChE) activity in Aquarana catesbeiana tadpoles exposed to different concentrations of nGER (1, 5, 10, and 20 mg L^-1). Characterization of the nanoparticles in the aquarium water over the exposure time (96 h) revealed similar sizes among the different groups. However, the concentration of particles in the higher concentrations (10 and 20 mg L^-1) decreased, indicating a process of aggregation and precipitation. The results of the biomarkers showed that these higher nGER concentrations induce lethargy in animals within 96 h of exposure. Though, induction of muscle AChE was only observed in animals exposed to 5 mg L^-1. Thus, the neuro-depressive effect of nGER appears to be unrelated to AChE activity in bullfrog tadpoles. Therefore, the hypothesis of this study was partially accepted since higher concentrations of nGER significantly altered the behavior of A. catesbeiana. However, this was not related to changes in AChE. As this is the first investigation into nGER toxicity in amphibians, the findings emphasize the importance of evaluating non-target organisms before considering alternative pesticides as sustainable.