Effect of cadmium on the hatching of Metaphire posthuma cocoons

Earthworms are considered ideal soil organisms for use in terrestrial ecotoxicology. Due to their susceptibility of heavy metals, the effect of cadmium on the hatching of M. posthuma cocoons was studied. The hatching was observed by the water incubation method and the doses of Cd were 0, 1.25, 2.5, 5.0, 10.0 and 40.0 ppm. The 0 and 1.25 ppm treated cocoons hatched within 45-60 days at 20 degrees C with 80% hatching rate and one juvenile per cocoon; no hatching was observed at higher concentrations. Furthermore, there was a linear increase in Cd residue in the treated cocoons. These results are apparently ill effects of Cd on embryonic development of the earthworms.