Embryotoxic, Developmental and Genotoxic Evaluations of a Endosulfan and Deltamethrin Mixture on the African Sharptooth Catfish (Clarias gariepinus)

Abstract

The evaluation of pesticides using early life stages of fish yields high throughput results that can inform one about the developmental effects of these toxicants. The effects of sublethal concentrations of a commercial mixture of endosulfan and deltamethrin (ratio 280:2) were evaluated in the embryos and juveniles of Clarias gariepinus. Embryotoxic and developmental evaluations were conducted in the embryos from 0 - 26 hours post fertilization. Genotoxic effects were assessed in the erythrocytes of the juveniles using the micronucleus assay over a period of 28 days. The acute toxicity studies revealed that the 24 hLC₅₀ and 26 hEC₅₀ (non-hatching) values for embryos were 25.25 µg/L and 12.96 µg/L respectively while the 96 hLC₅₀ value for fingerlings was 12.67 µg/L. Hatching success was lower in the exposed embryos compared to the control. The percentage developmental abnormalities and number of heartbeats per minute were statistically higher (p<0.05) in the exposed embryos compared to the control. Developmental abnormalities observed included pericardial and yolk sac oedema, scoliosis and tail curvature. The genotoxicity studies showed that there was a significant increase (p<0.05) in micronuclei in the erythrocytes of the exposed juveniles by days 14 and 28 compared to the control animals. These results imply that the pesticide mixture can cause a decline in the population of non-target organisms such as fish at sub-lethal or environmentally realistic concentrations. A review of the use of this pesticide formulation and development of environmentally friendly methods for pest management are recommended to safeguard non-target organisms such as the African sharptooth catfish.