Malathion-induced endocrine disruption leads retardation in fish growth

Abundant reports on stunted growth in fishes following pesticides exposure are available; however, mechanism underlying it is rarely studied. Since hormones are well known to play vital role in regulation of metabolic activities and general body growth, present study was conducted to investigate the effects of malathion (an organophosphorous pesticide) on metabolic hormones, responsible for promotion of body growth as well as somatic and ovarian growth of the freshwater catfish, Clarias batrachus. Malathion treatment drastically reduced the body weight as well as food intake. Malathion-treated catfish exhibited avoidance to food to a great degree. This pesticide also suppressed the secretions of thyroxine (T 4 ), triiodothyronine (T 3 ), growth hormone (GH), insulin like growth factor-I (IGF-I), testosterone (T) and estradiol-17â (E 2 ) significantly, in a dose dependent manner, in general, except that the low dose of malathion increased the secretion of growth hormone. Significant reduction in muscle and hepatic protein content was also noted in malathion-treated fish. Malathion induced lipolysis in liver and muscle. Study, thus, revealed that malathion disrupted the entire endocrine mechanism and olfactory sensation responsible for gustatory feeding behavior, food intake and metabolism, which ultimately resulted in retardation in general growth.