Monocrotophos: Toxicity Evaluation and Respiratory Responses of Cyprinus carpio (Linnaeus)

Abstract

Static rencval bioassay method was used to determine the 96 hr LC₅₀ of monocrotophos on Cyprinus carpio. Oxygen consumption and behavioral responses were recorded at lethal and at two sublethal (1/10^th and 1/15^th) concentrations.  Oxygen consumption responses were concentration dependent. The data indicated maximum decrease in oxygen consumption at lethal exposure (86.4 µg/L) over control on 4^th day followed by 2^nd, 3^rd, 1^st days.  At 1/10^th of lethal concentration (8.64 µg/ L) continuous decrease on 1^st, 10^th and 20^th day but decrease was reduced on 30^th day. Similar variations were observed at 1/15^th of lethal exposure (5.76 µg/ L) from day 1 to day 10. The decrease continued on 30^th day which was witnessed to be very less amongst all. Behavioral responses were significant in lethal exposures due to intoxication.  Fish showed hyper excitation, erratic swimming, jumping, and lethargy due to low breathing frequency followed by muscular rigidity and abundant mucous secretion over the gills.