Sublethal toxicity of deltamethrin in relation to sex: Enzymatic studies in the freshwater fish Channa punctatus.

ABSTRACT

One of the most widely used active ingredients in the world (for pest control) is deltamethrin, a synthetic pyrethroid. Deltamethrin is popular not only because of its effectiveness, but also for characteristics that allow the insecticide to work efficiently at low doses. Deltamethrin is a Type-II pyrethroid compound that is however highly toxic to fish, while being less toxic to birds and mammals. In the present study, Channa punctatus was used as an animal model to determine the toxicity of deltamethrin. Males weighing 10 ± 2g and females weighing 12 ± 2g were divided into groups of ten each and were exposed to different concentrations of deltamethrin ranging from 0.02 ppm to 0.2 ppm, for five exposure periods, i.e., 1, 7, 15, 20 and 30 days. The acetylcholinesterase (AChE) activity and actylcholine (ACh) content were estimated. The levels of AChE activity rose at 24 h relative to control in all the organs, whereas the ACh content dipped. Thereafter, the levels of AChE activity progressively decreased through 7 days, and continued upto the 15th day, mirroring the steady increase in ACh. From 15th day onwards, the levels of AChE activity gradually increased, and approached that of the control at 30 day exposure, whereas the levels of ACh content displayed an opposite trend.