Effects of metals on earthworm life cycles: a review.

Earthworms are abundant and ecologically very important organisms in the soil ecosystem. Impacts by pollutants on earthworm communities greatly influence the fertility of the terrestrial environment. In ecotoxicology, earthworms are good indicators of metal pollution. The observed median lethal concentrations (LC50) and the effective concentrations that cause 50% reduction of earthworm growth and reproduction (EC50) are referred to as toxicity concentrations or endpoints. In addition, the 'no observed effective concentration' (NOEC) is the estimation of the toxicity of metals on earthworms expressed as the highest concentration tested that does not show effects on growth and reproduction compared to controls. This article reviews the ecotoxicological parameters of LC50, EC50 and NOEC of a set of worms exposed to a number of metals in various tested media. In addition, this article reviews metal accumulation and the influences of soil characteristics on metal accumulation in earthworms. Morphological and behavioural responses are often used in earthworm toxicity studies. Therefore, earthworm responses due to metal toxicity are also discussed in this article.