Leukocyte Profiles in Odontophrynus carvalhoi (Amphibia: Odontophrynidae) Tadpoles Exposed to Organophosphate Chlorpyrifos Pesticides

Abstract

We analyzed the toxic effects of the organophosphate insecticide chlorpyrifos (Klorpan® 480 EC formulation) on the blood leukocyte profiles of Odontophrynus carvalhoi tadpoles, a neotropical species endemic to Brazil, exposed to four different concentrations of that insecticide (10, 100, 200, and 400 μg L−1) for 192 h. The tadpoles were anesthetized and their blood was collected by cardiac puncture, with subsequent cell smears and staining with May–Grunwald–Giemsa and Wright. The numbers and types of leukocytes were determined after different periods of exposure (24 h, 48 h, 96 h, and 192 h) by analyzing 100 leukocytes from each tadpole (under 1000× magnification). The tadpoles exposed to different concentrations of chlorpyrifos exhibited reductions in their numbers of lymphocytes, monocytes, and basophils, but increases in the numbers of neutrophils and eosinophils. As such, exposure to chlorpyrifos altered cell type proportions, which could alter the capacity of those tadpoles to respond to environmental stresses, make them more susceptible to infection by diverse pathogens, and thus compromise their chances of survival. That scenario would be even more serious for species having restricted distributions, as population declines would be more severe and impacting. Therefore, the use of chlorpyrifos constitutes a serious risk for anuran amphibians that occur in or near agricultural fields by contributing to immunosuppression and threatening their survival.