Histological changes of liver in overfed young nile tilapia

Abstract

We investigated histopathologically liver structural responses of Nile Tilapia Oreochromis niloticus towards overfeeding. Mixed population of O. niloticus with mean weight of 55±3.83 g was 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% of fish body weight, respectively. Fish were dissected at three time intervals. Tissues were fixed, re-fixed, processed, embedded with paraffin and sectioned. Sectioned tissue ribbons were stained with hematoxylin and eosin technique for light microcopy. Hepatosomatic Index (HSI) and Hepatohypertrophic Index (HHI) were calculated. Irregular shaped hepatocytes with circular, conspicuous and centrally located nuclei were found from all control groups. Large hypertrophic hepatocytes with nuclei dislocated to the cell periphery observed after three weeks of overfeeding. Lipid vacuolation and atrophy were found after five weeks of overfeeding. Fish overfed for three weeks showed significantly (p<0.05) higher HSI and HHI values. Whereas, fish which were under third week control group showed the second significantly (p<0.05) higher HSI value. Significant (p<0.05) differences in HSI as well as HHI were not found between zero and fifth week control groups. We conclude that overfeeding may cause liver histological alterations in O. niloticus and in turn lower aquaculture profitability by making the fish susceptible to disease. © 2014 Academic Journals Inc.