Histological anomalies and alterations in enzyme activities of the earthworm Glyphidrillus tuberosus exposed to high concentrations of phosphogypsum.

Phosphogypsum (PG) is the major solid waste generated by phosphate fertilizer plants and is used worldwide as sulfur and calcium supplement in agricultural soil. Considering the probability of elevated doses of PG during agricultural applications, this study was carried out to assess its impact on the connective tissue, tissue cholinesterase (ChE) activity, lactate dehydrogenase (LDH) activity, and lipid peroxidation (LPX) level of the tropical earthworm Glyphidrillus tuberosus (Stephenson) found in abundance in the rice fields in India. Consistent loss of connective tissue and sloughing of the intestinal epithelium were observed in worms exposed to 10%, 15%, and 20% concentrations of PG in soil over an incubation period of 30 days. ChE, LDH activities, and the level of LPX indicated highly significant variation (p < 0.01) between pre and postclitellar regions of the worm and concentrations of treatment. ChE activity was higher in postclitellar with respect to preclitellar region; however, the values for LDH activity and LPX level were higher in preclitellar region in comparison to postclitellar region in both PG treated and control worms. It was concluded that PG concentration at and beyond 10% could cause damage to muscle fibers and bring about significant alterations in these enzyme activities in G.tuberosus thus affecting the physiology and ecological functions of these worms.