Chronic toxicity bioassay and effect of endosulfan, HCH, copper and zinc on the survival and intermoult duration of larvae of mangrove crab Macrophthalmus erato De Man.

The effects of insecticides (endosulfan, HCH) and heavy metals (copper and zinc) were studied on survival and duration of the moult cycle of larvae and megalopa of a common mangrove crab, Macrophthalmus erato, that inhabits Pitchavaram mangroves, southeast coast of India. In chronic toxicity test, percentage of survival from hatchling to megalopa stage at different concentrations of endosulfan (0.048 to 0.36 microg/L), HCH (0.32 to 2.4 microg/L), copper (9.0 to 67.5 microg/L) and zinc (15.2 to 139.0 microg/L) were 6, 12, 8 and 12 respectively. Endosulfan, HCH, copper and zinc considerably increased the total period in development from first zoea to megalopa stage from 18 days in the control to 23, 21, 20 and 22 days in the treated specimens. It is concluded that concentrations well below the observed chronic concentrations, may prove to be more deleterious to larva of this species in natural environment leading to reduction in the success of recruitment to the adult population.