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ABSTRACT
This study was conducted to investigate the effect of chlorpyrifos on the embryonic development of Clarias gariepinus. Freshly fertilized eggs of C. gariepinus were exposed to 0.01µg/l, 0.1µg/l, 1.0µg/l, c of chlorpyrifos through embryogenesis in a static renewal bioassay. The effect of chlorpyrifos was investigated on three of the seven broad stages of embryogenesis: gastrulation, segmentation and hatching. At gastrulation stage, germ rings, caudal edge and cephalic edge were observed across the treatment and control groups. Results from the segmentation stage showed complete somite blocks across treatments groups and control. At hatching, it was observed that optic primordial, myotomal muscle, yolk sac, notochord and mouth gape were fully formed at 24hrs post hatching in the control and treatments except at the highest concentration (10µg/l) where hatching was not observed. Thus there was no significant aberration during the period of embryogenesis across the treatments. Results of the physicochemical parameters observed across control and various treatments of chlorpyrifos during this study shows that mean temperature ranged from 27.37 oC to 27.46oC, pH (7.00 to 7.04), Conductivity (101.10 to 102.30 µS/cm), Turbidity (0.23 to 0.24mg/l), Alkalinity (7.43 to 7.50 mg/l and Dissolved oxygen (8.11 to 8.14mg/l). Results of hatchability test showed that at the least concentration of chlorpyrifos (CHL1), hatched about 60% of the thirty (30) fertilized eggs, CHL2 hatched about 40% of the thirty (30) fertilized eggs, CHL3 hatched about 20% of the thirty (30) fertilized eggs. The mere presence of pesticide calls for continuous monitoring of water quality so as to check the effects of toxicants on developing eggs and larvae of fish and other fauna in the aquatic environment
