STIMULATING EFFECTS OF LOW LEAD CONCENTRATIONS ON GROWTH AND COCOON PRODUCTION OF EISENIA-FETIDA (OLIGOCHAETA)

Earthworms form an important component of the soil biota in many soils and are very sensitive to various types of contaminants. Their protec tion may therefore provide a margin of safety for other fauna once com parative toxicological-data are available. The effects of lead on grow th, maturation, cocoon viability and cocoon production of the vermicom posting earthworm species Eisenia fetida were studied by exposing worm s experimentally to a sublethal concentration of lead (2000 mu g.g(-1) ) for a period of 76 days. Growth rate as well as cocoon production we re monitored every 14 days and cocoons were incubated to determine the ir hatching success. Lead content of worms was also analysed. Exposed wens grew noticably better and produced more cocoons than control worm s. Cocoon viability was, however, affected detrimentally. It is conclu ded that, although lead is known to be toxic at higher concentrations, sublethal concentrations close to the predicted EC50 and NOEC-values have a stimulating pr hermetic effect on growth and cocoon production.