HISTOPATHOLOGICAL STUDIES OF EARTHWORM (Aporrectodea longa) EXPOSED TO CADMIUM

The histopathological studies of earthworm (Aporrectodea longa) exposed to cadmium was investigated. The earthworm was exposed to 0.25, 0.5, 1, 2 and 4 mg/kg of cadmium for 30 days in the laboratory. The procedure for the exposure was according to the Organisation for Economic Cooperation and Development (OECD) #207 recommended method for testing of chemicals. There were three replicates per treatment and 5 earthworms per jar of soil spiked with cadmium. Control groups were also prepared. Bioaccumulation of cadmium increased (p<0.05) with increase in cadmium concentration. The histopathological alterations were carried out in the clitellum and gizzard of earthworms. Mild to severe necrosis and distortion of muscles were observed in the cadmium concentrations of 0.25, 0.5, 1, 2, and 4 mg/kg and the effects increased with increase in concentration of the metal in the clitellum and gizzard. Vacuolisation and clearing of epithelial cells were observed in the clitellum. The results of this study revealed the effect of cadmium on the histological composition of Aporrectodea longa. The discharge of cadmium into terrestrial ecosystems should be discouraged as this could affect the health of earthworms whose ecological roles as ecosystem engineers could be impaired.