Histological Changes of Liver in Overfed Young Nile Tilapia Oreochromis niloticus

Abstract

The adverse effect of overfeeding has been explained only from water quality deterioration perspective so far. Direct influence of overfeeding on liver of fish was given little attention. This study aimed to investigate histopathologically structural responses of liver of Nile tilapia Oreochromis niloticus towards overfeeding. Mixed population of O. niloticus with mean weight of 55+3.83g obtained from Pukyong National University fish farm and acclimated for one week. Then, the fish were separated into control and treatment groups. Glass aquariums with external biofilters and artificial heaters were used. Control and treatment groups were fed commercial tilapia diet at 3 % and 6 % per body weight feeding level, respectively. Fish were dissected at three time intervals. Tissues were fixed, re-fixed, processed, embedded with paraffin, sectioned and stained with Hematoxylin & Eosin technique for light microcopy. Occurred morphological changes were explained semi-quantitatively using indices. Significant differences (p<0.05) of indices were found between control and treatment groups of different weeks. Livers with normal brown and pale brown color were observed from control groups and treatment groups, respectively. Normal hepatocytes with circular, conspicuous and centrally located nuclei were found from all control groups. Hepatocyte hypertrophy was observed after three weeks of overfeeding. Large hepatocytes with nuclei dislocated to the periphery of the cell dominated in the third week treatment group. Hepatocytes with lipid vacuoles and inconspicuous nuclei were found after five weeks of overfeeding. Some atrophic livers were also observed among fish from the fifth week treatment group. Hence, the findings of this study suggested that overfeeding indeed can cause liver histological alterations in O. niloticus.