Toxic Effects of Chlorpyrifos on Early Developmental Stages of Fish Anabas testudineus (Bloch 1972)

Chlorpyrifos is one of the most widely used insecticide in and around Northeast, Assam, India. In this study an experiment was conducted to examine the effects of chlorpyrifos on embryonic development of Anabas testudineus. From the fertilized eggs and hatched larvae LC50 value was calculated at 24 h, 48 h and 72 h. Four sub-lethal concentration was selected for the toxicity treatment on embryological and larval stages i.e., 0.1 μgL−1, 0.2 μgL−1, 0.4 μgL−1 and 0.6 μgL−1. About 100 numbers of fertilized eggs were introduced to each mention sub-lethal concentration of chlorpyrifos. The LC50 values of chlorpyrifos pesticide for embryo and larvae of Anabas testudineus at 24 h was 0.261 μgL−1 respectively. Results showed increasing concentrations decreased hatching success and increased embryonic mortality rate. In embryos, various abnormalities were observed including egg shell broken, yolk sac damage, yolk sac elongation. The LC50 values of chlorpyrifos pesticide for larvae of Anabas testudineus 24, 48, 72 h were 0.6 μgL−1, 0.39 μgL−1 and 0.311 μgL−1 respectively. Various physical deformities, including inflammation of swim bladder, abnormalities in notochord, yolk sac edema, lordosis, tail ulceration and irregular caudal region were evident in larvae in response to different concentrations of chlorpyrifos. The finding of the current study indicates that chlorpyrifos pesticide exerts various developmental toxicity to Anabas testudineus embryos and larvae.