Changes in tissue lipid levels in the freshwater catfishClarias batrachus associated with the reproductive cycle.
The levels of free fatty acid (FFA), monoglyceride (MG), diglyceride (DG), triglyceride (TG), phospholipid (PL), free cholesterol (CF) and esterified cholesterol (CE) were measured in the liver, plasma, ovary, abdominal fat and muscle during different phases of the annual reproductive cycle in femaleClarias batrachus. During the preparatory phase, hepatic lipogenic activity predominated over mobilization and consumption. In the prespawning season, an increased hepatic lipogenic activity was maintained, but lipids were transferred from the liver to the ovary. In the spawning phase, the diminished food intake, and enhanced caloric demand for spawning behaviour and activity limited hepatic lipogenic activity, and TG lypolysis was increased as was the production of more FFA. Maximum accumulation of vitellogenin, as reflected by maximum rise in ovarian PL titre was characteristic of this phase. Marked reductions in ovarian lipid occurred during the postspawning phase. In the resting phase, there was a recovery of lipogenic activity, but PL synthesis was still inhibited. In contrast to other investigated teleosts, there were extremely high level of FFA in liver, plasma, ovary and muscle throughout the annual reproductive cycle inC. batrachus. FFA appears to be the main lipid metabolite which had a very high turnover. As evidenced by the high TG content, abdominal fat seems to be the main fat depot, not the liver and muscle.
Fish Endocrinology Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India.
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Singh