Methyl parathion (O-O-dimethyl O-4-nitrophenyl thiophosphate) effects on whole-body and tissue respiration in the teleost, Tilapia mossambica (Peters).

The respiratory parameters of a freshwater teleost, Tilapia mossambica Peters, were studied under sublethal intoxication of methyl parathion. The rate of oxygen consumption by whole fish and selected tissues decreased during a 48-hr time-course study. The activities of the respiratory enzymes succinate dehydrogenase, malate dehydrogenase, and cytochrome-c oxidase also decreased considerably under methyl parathion exposure in muscle, gill, liver, and brain tissues. These results suggest that methyl parathion has a profound effect on the oxidative metabolism of the fish which results in low ATP turnover, possibly due to its influence on the respiratory center of the brain.