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Sublethal effects of chlorpyrifos (CPF) and monocrotophos (MCP) on fish biochemical constituents were investigated along with the assessment of recovery response after cessation of intoxication. The fish, Clarias batrachus were exposed to 1.656 mg(-l) and 2.114 mg(-l) of CPF and MCP for 28 days. After 28 days, they were released in freshwater and allowed to recover for 21 days. The CPF exposure resulted in the decrease of carbohydrate and glycogen content, whereas MCP intoxication caused mixed response. Pyruvate and lactate contents were altered under the stress of CPF and MCP. Recovery of these alterations was observed after the cessation of toxicity. Exposure of C. batrachus to CPF and MCP resulted in decreased activity of lactate dehydrogenase in the kidney, liver and muscle but its activity increased in the gills. The CPF caused inhibition of succinate dehydrogenase enzyme in all tissues. Induction in the activity of malate dehydrogenase was caused by both insecticides. Glycogen phosphorylase a was induced in all tissues, whereas glycogen phosphorylase ab showed both induction and inhibition. Of the two insecticides, CPF was more toxic and the recovery response was less. These results are important in the assessment of the risk caused by organophosphate insecticides on nontarget organisms, especially the food fish.

The sublethal stress of the organophosphate insecticide chlorpyrifos was investigated in different tissues of the freshwater crab (Barytelphusa guerini). Crabs were exposed to 1/3 of LC50 concentrations for 7, 14, 21, and 28 days. After 28 days, they were released into fresh water and kept for 18 days for recovery. The study was conducted by estimating total proteins, amino acids, ammonia, urea, and glutamine levels, and protease, transaminases, and phosphatases activities. Total proteins level was decreased whereas amino acids and ammonia were increased. The urea content was decreased in all tissues and glutamine exhibited a mixed response. Protease activities and those of alanine and aspartate aminotransferase, respectively, were elevated. Acid phosphatase activity was reduced in hepatopancreas and brain and induced in gills and muscle. Alkaline phosphatase activity was enhanced in gills and hepatopancreas and reduced in muscle and brain. The crabs recovered from the biochemical stress caused by chlorpyrifos after their release into fresh water