Exposure of Eisenia andrei (Oligochaeta; Lumbricidea) to Cadmium Polluted Soil Inhibits Earthworm Maturation and Reproduction but not Restoration of Experimentally Depleted Coelomocytes or Regeneration of Amputated Segments.

Abstract

Lumbricid earthworms are often exposed to polluted soil. They are also commonly subjected to various stimuli and attacks by predators that induce extrusion of coelomocyte-containing coelomic fluid and/or the loss of body segments followed by the renewal of immune-competent cells and regeneration of tissues/organs. The aim of our investigations was to test the effects of exposure of the earthworm Eisenia andrei to cadmium-polluted soil, combined with electrostimulation-induced depletion of coelomocytes (i.e. amoebocytes and chloragocyte-derived eleocytes) or the surgical amputation of posterior segments, on earthworm maturation, reproductive output, and regenerative processes. Experimental worms were maintained up to 7 weeks either in unpolluted soil or in soil spiked with cadmium chloride (500 mg/kg air-dried soil). In juvenile worms, sexual maturation (measured by clitellum formation) was delayed and cocoon production was inhibited in Cd-exposed worms. Coelomocytes were significantly depleted by electrostimulation and the kinetics of their recovery was similar in worms kept in clean and cadmium polluted soils, in both exposure conditions amoebocyte recovery was faster than recovery of riboflavin-storing eleocytes. In adult worms, soil cadmium exposure inhibited reproduction but, at macroanatomical level, had a negligible effect on regeneration of amputated posterior segments, visible only on histological cross-sections.