Effects of combinations of malathion and cypermethrin on survivability and time of metamorphosis of tadpoles of Indian cricket frog (Fejervarya limnocharis)

Abstract

This study was undertaken to determine the effect of environmentally realistic concentrations of two commonly used pesticides viz., malathion and cypermethrin, using a fully 3 × 3 factorial experiments on the survivability and time of metamorphosis in a common rice paddy field frog (cricket frog) Fejervarya limnocharis under laboratory conditions. The results suggest that cypermethrin is more toxic than malathion and combinations of higher concentrations of cypermethrin (50 μg/L) with malathion (250 and 500 μg/L) are more deleterious to the survivability of tadpoles. With increasing cypermethrin concentration, the survivability of tadpole decreased (r = −0.986, P = 0.108). But cypermethrin alone induced early metamorphosis among the surviving tadpoles. However, there was a delay in the time required for metamorphosis induced by malathion and its combination with cypermethrin. The delay in metamorphosis may indicate the altered physiological fitness of the individual. The emergent froglets will be subjected to environmental stressors like high temperature and less humidity of post-monsoon tropical climate that could enhance negative influence triggered by pesticides.

Keywords:

• Pesticide combinations
• tadpole
• survivability
• time of metamorphosis
• common paddy field frog

Acknowledgments

Makkimane B. Nataraj would like to acknowledge the support, help, & cooperation rendered by Dr.Girish Janney, and Mr. Vivek Gunaga of the Dept. of Environmental Science, Kuvempu University. Thanks to Mr. Dinesh J.K. for assisting with photography of the tadpoles.