Effects of the pesticide dieldrin on incubation of the earthwonn <I>Eisenia letitia</I> (Oligochaeta)

Abstract

The effects of a long-term exposure of newly hatched earthworms to a dieldrin-treated culture medium were examined with regard to the determination of incubation period and hatching success of cocoons ultimately produced by the exposed worms. Dieldrin concentrations in exposed worms and in cocoons produced by these worms were also examined. Eisenia fetida (Savlgny 1826) were exposed for 90 days to various concentrations of dieldrin ranging from 10 to 100 mg kg ^-1 in an organic substrate. The study was undertaken to determine possible sub-lethal and accumulative effects of dieldrin. This chemical was still widely used in southern Africa when this study commenced and is generally considered to be non-toxic to earthworms, based on acute toxicity tests (Edwards 1981). The presence of dieldrin significantly prolonged the incubation period of cocoons at relatively high concentrations and the hatching success was similarly influenced. The amount of dieldrin in the worms and cocoons was determined by gas chromatograph and was correlated with that in the substrate. Sufficient evidence was obtained to conclude that dieldrin has a detrimental influence on the life cycle of Eisenia fetida.

S. Afr. J. Zool. 1987. 22(2)