Toxic effects of Carbofuran on Duttaphrynus Melanostictus Larvae

This study investigated effects of the carbamate pesticide carbofuran on larvae of the Asian Common Toad Duttaphrynus melanostictus. Tadpoles were continuously exposed to four concentrations of carbofuran (50 -500 μgl⁻¹) for 15 days during which mortality, growth, development, and swimming activity were monitored. In a separate trial, the liver and tail muscle tissues were examined for histopathological changes after one week of exposure to 250 and 500 μgl⁻¹. The study revealed that carbofuran at the tested concentrations induced significantly high levels of mortality in D. melanostictus tadpoles. Trends in mortality depicted a bellshaped curve indicating a hormetic response. The LC50_{1–15 days} ranged from 1865 – 152 μgl⁻¹. Effects on growth, development and swimming were transient. A few tadpoles exposed to 250 μgl ¹ and above showed swelling of the head region. Exposure to carbofuran also caused severe histological alterations in the tail muscle tissues, while the liver tissue was also affected, but to a lesser extent. Greater vacuolation in hepatocytes, sinusoidal dilations and the formation of bile plugs were observed in the liver of treated larvae whilst tail muscles were substantially disintegrated as a result of exposure to carbofuran. The observed harmful effects induced by carbofuran in the present study suggest that D. melanostictus populations may face detrimental consequences as a result of exposure to this pesticide.