Toxicity and Effect of Cypermethrin onTotal Protein and Nucleic Acid Content in the Tissues of Cirrhinus mrigala

Contamination of aquatic ecosystems is the inevitable and burning issue of concern all over the world due to usage of chemicals both in agri and aqua practices. Such usage as environmental pollutants can cause alterations in the biochemical parameters of non-target organisms like fish and can react with each other as synergistic effect on aquatic biota [1]. Among them, pesticides are one of the toxicants take the lion’s share known to affect fish and other aquatic fauna. Pesticides are the class of toxic compounds designed to kill unwanted organisms, despite of their benefits but when applied on land, they may be washed into the surface water and kill, or at least adversely influence, the life of aquatic organisms by producing wide range of toxic effects and pose potential hazards to the environment [2, 3]. The contamination of aquatic bodies by pesticides is mainly due to intensive agriculture combined with surface runoff and subsurface drainage, usually within a few weeks after application [4]. The continuous presence of pesticides in aquatic ecosystems is the consequence of their use (timing, rate, frequency) and the rainfall during the application period [5]. The use of pesticides in agriculture may also lead to contamination of surface and ground waters by drift, runoff, drainage and leaching [6]. Omnipresence of pesticides in surface waters due to application in disease management of aquaculture requires that sensitive biological tests be developed to study relative occurrence and toxicity to the ambient organisms [7]. Aquatic invertebrates and fish thus become targets of toxic substances at potentially hazardous concentrations and this is of special concern if sensitive larval and developmental stages are affected [8]. 

Pyrethroids are among the most widely used pesticides, due to their low environmental persistence and low mammalian and bird toxicity [9, 10], viable substitutes for organochlorine and organophosphate pesticides in pest-control programs. In fish farms they are applied to control ectoparasites and biological vectors especially lice, as well as insects in nursery and growout systems as alternatives for the more toxic organophosphates [11]. Fish are one of the most important aquatic organisms and ideal sentinels for a wide range of toxicity bioassays of various stress factors and toxic chemicals such as pesticide exposure due to their economic value of edibility and culturability, sensitivity to contaminants, ecological relevance in many natural systems [9, 12]. Pyrethroids insecticides present low water solubility, low residence time in water and high absorbance into particulate matter [13, 14], which may decrease its toxicity in field conditions. However, these pesticides are very toxic even at low concentrations, posing risks to non-target aquatic populations. Fish are very susceptible to pyrethroid contamination [15] and the rate of toxicity to fishes is in a range of micrograms per liter [16]. The purpose of this study was to evaluate the acute toxicity of cypermethrin using a non-target aquatic organism, Cirrhinus mrigala in order to assess its sensitivity towards the toxicant with reference to total protein and nucleic acid content.