Effect of malathion on the male reproductive organs of earthworms, Eisenia foetida

Aim: To observe the cytotoxic effect of the organophosphate insecticide malathion in the reproductive tissues of the earthworms, Eisenia foetida. Methods: Worms were nourished in soil treated with malathion at single sub-lethal doses of 0, 80, 150, 300 and 600 mg·kg^-1 soil. (LD50 = 880 mg·kg^-1 soil) and evaluated on days 1, 5, 15 and 30 after exposure. The body weights were recorded and male reproductive organs evaluated. Results: Malathion-treated animals showed a significant reduction in body weight in a dose-dependent manner. Malathion treatment modified the disposition of spermatozoa in the basal epithelium of the spermatheca. The Br-deoxyuridine test showed a significant rise in cells in phase S on days 5 and 15. Also, a higher percentage of spermatogonia with fragmented DNA were observed by means of the TdT-mediated dUTP nick-end labeling (TUNEL) technique in the spermatheca of treated animals. Conclusion: Treatment with malathion decreased the body weight and the spermatic viability in spermatheca, altering the cell proliferation and modifying the DNA structure of spermatogonia.