Respiratory performance and behavioral responses of the freshwater fish, Cyprinus carpio (Linnaeus) under sublethal exposure to chlorpyrifos

Abstract

A short-term definitive test by static renewal bioassay method was conducted to determine the acute toxicity (LC50) of an organophosphate insecticide, chlorpyrifos on the fish, Cyprinus carpio. Carp fingerlings were exposed to different concentrations (0.120 to 0.200 mg/L) of chlorpyrifos for 96 h. The acute toxicity of chlorpyrifos was found to be 0.160 m g/L. One-seventh (1/7th, 0.0224 mg/L) and one-fourteenth (1/14th, 0.0112 mg/L) of the acute toxicity value were selected as sublethal concentrations for subchronic studies. The fish were exposed to both the sublethal concentrations for 1, 7, and 14 days and allowed to recover in toxicant-free medium for 7 days. Behavioral responses and respiratory rate were studied in experimental periods. Fish in toxic media exhibited irregular, erratic, and darting swimming movements, hyperexcitability, and loss of equilibrium and sinking to the bottom. Caudal bending was the chief morphological alterations during the exposure tenures. The behavioral and morphologic changes might be due to the inhibition of acetylcholinesterase (AChE) activity. The carp were found under stress but mortality was insignificant at both the sublethal concentrations. Considerable variation in respiratory rates (-71.85 to 119.52%; -75.65 to 17.58%) were observed in the 1/7th and 1/14th of lethal concentration of chlorpyrifos respectively. The alteration in respiratory rate is due to respiratory distress, this may be a consequence of impaired oxidative metabolism and elevated physiological response during chlorpyrifos exposure. The impairments in fish respiratory physiology and behavioral responses even under recovery periods may be due to slow release of sequestered chlorpyrifos from storage tissues.