Renewal Acute Toxicity of Broad-Spectrum Herbicide, Paraquat Dichloride in Channa punctatus (Bloch)

Abstract

Paraquat dichloride (PD) is a major contaminant in aquatic environment and is a cause of concern to different organisms, especially to fishes, as it causes different changes in behavioral and morphological to aquatic creatures. Hence, the objectives of the study are to examine the acute toxicity, behavioral and morphological alterations in air-breathing teleost fish, Channa punctatus (CP) (Bloch). Renewal acute toxicity was performed to calculate the lethal concentration (LC50) by Finney’s probit analysis to CP by exposure to wide range of PD concentrations (30, 60, 90, 120, 150 mg/L) for 24, 48, 72 and 96 h. The LC50 values determined are 93.36, 82.22, 67.93 and 65.87 mg/L for 24, 48, 72 and 96 h, respectively. Maximum allowable toxicant concentrations (MATC) defined by LC50 value is found to be 0.6587 mg/L. The upper and lower 95 percent confidence limit (Fiducial limit) are in narrow range for 24, 48, 72 and 96 h, respectively, and thus results of the experiments are considered good. Fiducial limit calculated helps us to state that the LC50 falls within the specified limit and helps in constructing of toxicity curve. LC50 value gradually decreases with increase in time. Mortality rate was dose-time dependent and increased with increase in concentration. The behavioral changes provide biologically relevant endpoints in evaluating toxicity testing. Deviation from baseline behavior was noticed. Morphological deformities were also seen. The present study provides a clear indication of the toxicity of PD, and is highly toxic even at low level. Hence, it is recommended that appropriate eco-toxicological risk assessment should be made and indiscriminate use of PD by farmers should be discouraged particularly in areas close to aquatic environment.