Effect of Chronic Dietary Copper Exposure on Haematology and Histology of Common Carp (Cyprinus carpio L.)

Abstract

Effects of exposure of common carp (Cyprinus carpio L.) to dietary copper and its recovery rate were investigated with the aim of determining the haematological and histological impact. In this study, fish were fed elevated copper diets (1000mgCukg^-1 and 2000 mgCukg^-1 as diet 2 and diet 3 respectively,) and control diet (5mgCukg^-1, diet 1) for 42days and were then fed the control diet for a further 21days.To make dietary preparations of the copper concentrations,1.1722g and 2.3503g of CuSO₄.5H₂ O(AnalaR grade), dissolved in 35ml deionised water, were mixed with each of 300g of the commercially available pellet diet, which contained 5mgCu/kg of feeds, to make 1000mgCu/kg and 2000mgCu/kg of feed , respectively. Fish fed diet 2 (1000 mgCukg^-1) showed significant increase (p<0.05) in haematocrit, red blood cell, white blood cell and neutrophil and a significant decrease (p<0.05) in lymphocyte and mean cell haemoglobin compared to diet 1 and diet 3. This increase in blood indices is indicative of stress onset to which fish fed diet 2 (1000 mgCukg^-1) is subjected. Fish fed diet 3 (2000 mgCukg^-1) showed significant reduction in haematocrit, red blood cell, white blood cell and increased lymphocyte (p<0.05) and became anaemic with severe skin discoloration, indicative of a worsening effect of excess dietary copper exposure on the fish. Gills and intestines of both diet 2 and diet 3 were normal during and after exposure, but fatty change was observed throughout the experiment. This was confirmed by a 4.4 and 7.1-fold increase in the liver copper of fish fed diet 2 and  diet 3 respectively compared to control (p<0.05) and a further 1.8- and 1.2-fold increase post exposure, indicative of delayed hepatotoxicity. In conclusion, increasing the copper level of common carp beyond tolerable dose impacted negatively on the fish. @JASEM

J. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 39 - 45