Effects of Lambda-Cyhalothrin on Behavioural, Hepatosomatic Indices, Gonad Histopathology and Oxidative Stress Biomarkers of Clarias Gariepinus

Abstract

This study investigated the effects of Lambda-cyhalothrin on behavioural, hepatosomotic indices, gonad histopathology and oxidative stress biomarkers on Clarias gariepinus. It was carried out in the Fisheries wet Laboratory, Department of Zoology and Environmental Biology University of Nigerian Nsukka. A total of 300 Clarias gariepinus with standard length and weigh that ranged from 16 to 40cm and 80 to 250g, respectively were used for the experiment. They comprised fingerlings and adult fishes of reproductive age. Prior to the experiment, determination of median lethal concentration, LC24-96 h, of Lambda-cyhalothrin, a total of 150 Clarias gariepiuns were used. They were exposed to five treatments: 0.00, 5.0 x 10-4, 6.25 x 10-4, 7.5 x 10-4 and 8.75 x 10-4 µg/L (A-E). While during sublethal determination, four treatments were exposed to: 0.00, 2.5 x 10-4, 5.0 x 10-4 and 6.25 x 10-4 µg/L (A-D). Each group was replicated three times. Acute toxicity was carried out and the percentage mortality and survival were recorded. The 96 hours LC50 value of Lambda-cyhalothrin on Clarias gariepinus was calculated to be 8.163 x 10-4 µg/L. The water parameters observed showed no changes on the temperature. pH levels were all within the range of 6.8 to 5.7 while dissolved oxygen ranged from 5.80 to 5.55. Nitrite and Nitrate were not present in the water used for the study. Behavioural changes observed after 24-96 hours of fish exposure to different concentrations of Lambda-cyhalothrin showed uncoordinated jerky movement and loss of equilibrium balance. The safe levels obtained varied from 8.163 x 10-5 to 8.163 x 10-9 µg/L. Hepatosmatic index (HIS) of the control group showed minimal variation, while HIS of the groups exposed to various doses of Lambda-cyhalothrin exhibited significant decline along duration of exposure. The results of the present study on antioxidant parameters revealed that malondialdehyde (MDA) significantly increased in radical activities on day 28 when compared to day 1 of the groups exposed to different concentrations of Lambda-cyhalothrin. Catalase (CAT), Superoxide dismutase (SOD), Glutathione peroxidase (GPx) and Glutathione reductase (GR) antioxidant activities also increased slightly during the exposure periods. The findings indicated that changes in biomarkers oxidative stress of MDA CAT, SOD, GPx and GR were all duration and concentration dependent of the exposure. The testes of the fish exposed to low concentrations of the Lambda-cyhalothrin demonstrated abundant spermatogenic cells in all the groups. Also the testes of the groups exposed to toxicant graded concentration displayed necrotic condition in the spermatogenic cells with nuclear pyknosis and cytoplasmic swelling. The ovary of the control group showed no structural and functional damage, while those fishes exposed to higher concentrations of the toxicant exhibited flabby oocytes, vacuolation and degenerative ovarian changes. The liver of Clarias gariepinus exposed to lower concentration showed indistinct cords of hepatocytes while those exposed to highest concentrations exhibited severe cytoplasmic swelling, eccentric displacement of the nucleus (pyknosis) and massive necrosis of the hepatocytes. The present study revealed that Lambda-cyhalothrin is toxic to Clarias gariepinus and should be used carefully. Therefore, biological method of controlling insects and pests should be adopted by farmers especially those around riverine and coastal regions to minimize the effects of insecticides on aquatic organisms.