Structure of and energy reserves in the liver of wild and cultured yellowtail flounder, Limanda ferruginea

Abstract Knowledge of the structure and energy re-serves, in the liver of commercially important fish spe-cies, is important in understanding metabolic processes and in assessing the impact of potential environmental physical and chemical stressors in both wild and cul-tured stocks. The present study investigated the micro-scopic morphology and histochemistry (total and neutral lipids, glycogen) of liver tissue of wild (3+) and cultured (1+) sexually immature female and male yel-lowtail flounder (Limanda ferruginea Storer), sampled in late April 2001. Hepatosomatic indices [HSI: (liver weight/body weight)liver weight)·100] of cultured fish were significantly higher than those of wild fish. Females in the cultured group had significantly lower HSIs than males. The liver of both wild and cultured L. ferruginea was interspersed with pancreatic tissue. The main com-ponents of the liver tissue were irregular cords of he-patocytes arranged in tubules which surrounded vascular sinusoids. The hepatocytes contained an abundance of lipid, much of which appeared to be neutral lipids, in both sexes of the cultured fish. Total and neutral lipid droplets were larger, and the area occupied by these droplets was significantly greater in both cultured females and males compared to the wild fish, suggesting lipidosis in the cultured fish. In the cul-tured fish these differences were sex-dependent, the fe-males having significantly more total and neutral lipids in hepatocytes than the males. This suggests a poten-tially greater storage capacity in females and/or a higher lipid metabolism in males. There were no statistically significant differences in glycogen content between the cultured and wild fish, or between the sexes in both sampling groups