Toxicity of cypermethrin on the embryo and larvae of Gangetic mystus, Mystus cavasius.

The objective of the present study was to elucidate the effects of cypermethrin on the embryo and the larvae of Gangetic mystus, Mystus cavasius. Therefore, fertilized eggs (n = 100) and 1-day-old larvae (n = 100) were exposed to six different concentrations of cypermethrin (0, 2, 4, 8, 16 and 32 μg L-1) in each of the 18 plastic bowls. Each of the treatment and control was maintained in three replicates. The LC10 and LC50 values for Gangetic mystus embryos and larvae were calculated using probit analysis. Results showed the mortality of embryos significantly increased with increasing cypermethrin concentrations. The 24-h LC10 and LC50 (with 95% confidence interval) values of cypermethrin for embryo were 0.42 (0.14-0.81) and 5.60 (4.16-7.19) μg L-1, respectively. Hatching success decreased and mortality of larvae increased significantly with increasing cypermethrin concentrations. The 24-h LC10 and LC50 values (with 95% confidence limits) of cypermethrin for larvae were 1.72 (1.24-2.20) and 11.57 (10.09-13.42) μg L-1, respectively; the 48-h LC10 and LC50 for larvae were 1.34 (0.83-1.89) and 8.25 (6.87-9.91) μg L-1, respectively; the 72-h LC10 and LC50 for larvae were 1.13 (0.63-1.66) and 6.12 (4.91-7.47) μg L-1, respectively. Furthermore, results showed several malformations in embryos and larvae when exposed to the two highest concentrations of cypermethrin. The findings of the study suggest that 2 μg L-1 cypermethrin concentration in the aquatic environment may have deleterious effects on the development and the reproduction of Gangetic mystus.