ABSTRACT

The continuous indiscriminate use of pesticides raises a number of environmental concerns. The present study evaluated the effects of chlorpyrifos on the early developmental stages of the African catfish, which are considered to be one of the most sensitive stages in the fish life cycle to the toxic effects of chemical contaminants. Eggs were artificially fertilized and exposed to varying concentrations of chlorpyrifos of 0.01, 0.1, 1.0 and 10µg/l. Histological studies was carried out on the samples collected at specific stages and microscopic slides were viewed with the use of a light microscope. Morphological malformations such as distortions in the germ cell layers were observed to during the gastrulation stages of the developing embryos. The embryo exposure to chlorpyrifos also resulted to decreasing rates in the survivability and hatchability of the developing embryos with increasing concentrations of the pesticide. Mortality was also recorded across all the treatment groups at every developmental stage of the fish with increasing concentration of chlorpyrifos. The findings show that chlorpyrifos even at low doses could result to adverse developmental effects in the embryonic stages of Clarias gariepinus which will ultimately lead to decline population of Clarias gariepinus and other non-target organisms in the wild.