THE EFFECTS OF DIELDRIN ON THE SPERM ULTRASTRUCTURE OF THE EARTHWORM EUDRILUS-EUGENIAE (OLIGOCHAETA)

Earthworms of the species Eudrilus eugeniae were exposed to dieldrin, using the contact filter paper method, to study the sublethal effects of the pesticide, which is still widely used in many parts of Africa, on the ultrastructure of spermatozoa. The concentrations ranged from 0.154 to 1.54 mu g/cm(2) and exposures lasted 48 h. The spermathecae were dissected out and prepared for electron microscopy. Dieldrin was extracted from the worms by steam distillation and analysed by ECD-gas chromatography. A description of the sperm ultrastructure is presented. This study showed that dieldrin at relatively low concentrations caused structural damage, especially to the nucleus of the sperm. It is argued that this finding could contribute toward the development of a model for predicting environmental quality, based on sperm morphology, sperm motility, and sperm density. The sublethal effects of dieldrin on sperm morphology could provide a subanimal test for ecotoxicity since its effects will most probably be manifested at the population level.