Efeitos letais e subletais de cipermetrina e deltametrina em larvas de Physalaemus gracilis (Anura: Leptodactylidae)

Abstract

Agrochemicals have been widely used in agriculture, ensuring food supply for a constantly growing population. One of the groups of pesticides most used today are pyrethroid insecticides, however, these compounds have brought risks to non-target species such as amphibians. This study evaluated the toxicological effects caused to the native species of amphibian Anuran, Physalaemus gracilis, exposed to two insecticides, cypermethrin and deltamethrin. For this, total spawnings were collected in the natural environment, and transported to the laboratory where they were kept under controlled conditions for their larval development. Toxicity tests were performed on larvae at stages 24-25 of Gosner. An acute test was performed to determine the LC50 96h and chronic test, where the mortality, swimming activity and oral morphology of larvae exposed to sublethal concentrations were evaluated. The LC50 96h was determined by the Trimmed Spearman-Karber method, for cypermethrin was 5.4 mg/L and 0.46 mg/L for deltamethrin. Chronic tests were defined as 1/50; 1/75, 1/100, 1/200, 1/300 and 1/500 of the LC50 96h, ie 0.1, 0.07, 0.05, 0.03, 0.02 and 0.01 mg/L cypermethrin and 0.009, 0.006, 0.004, 0.003, 0.0015 And 0.001 mg/L deltamethrin. There was a significant influence of mortality in relation to time and increase of concentrations (p<0.001). Observed the effect of mortality, the unobserved effect concentration (CENO) for cypermethrin was 0.02 mg/L and the observed effect concentration (CEO) was 0.01 mg/L. For deltamethrin CENO = 0.004 mg/L and CEO = 0.003 mg/L. The chronic value for mortality effect was 0.015 mg/L cypermethrin and 0.003 mg/L deltamethrin. The effects of exposure also influenced swimming activity, where cypermethrin immobilized individuals. In the oral morphology both pesticides presented alterations like absence of denticles and mandible. It is concluded that pyrethroids with active principle cypermethrin and deltamethrin have toxicological effects for non-target species, such as Physalis gracilis larvae.