Pesticide-induced alterations in the oxygen uptake rate of a freshwater major carp Labeo rohita

Abstract

In one of the series of experiments, regular oxygen consumption ( VO 2) was determined in six continuous-flow respirometers in water containing different concentrations of pesticides, i.e., chlordane (organochlorine), Metasystox (organophosphorus), and Sevin (carbamate). The concentrations which were selected for the experiment were 1, 1 2 , 1 4th , 1 8th , and 1 12th of the TL 50 values of each pesticide and VO 2 was determined after intervals of 2, 4, 6, 8, 10, 12, 24, 36, 48, 60, 72, 84, and 96 hr. At the TL 50 values of the pesticides an all or none response was observed, but at all other concentrations the period of VO 2 was observed in three different but clear phases: (a) sensitization phase (b) responsive phase; and (c) normalization phase. Every said phase has shown marked differential persistence for different time periods probably depending on the different concentrations of the pesticides used in experiment. Further the oxygen uptake data show that in general there is a critical threshold time for the hyperactivity response: between 6 and 24 hr for chlordane; from the very beginning up to 6 hr for Metasystox, and between 2 and 24 hr for Sevin. It was also noted that animals which took the longest time to show the hyperactive response exhibited the lower initial rates of VO 2. Hence it is axiomatic that respiratory changes are good indicators of environmental stressors.