Diurnal and infradian rhythms in lipid parameters of Indian catfish, Heteropneustes fossilis

Twentyfour-hour variation in (C-14) acetate incorporation in the liver lipi d, and lipid concentrations in the liver and muscle tissues were studied du ring different phases of the annual reproductive cycle in the female freshw ater catfish, H. fossilis. A 24-h rhythm in hepatic lipogenic activity was validated. Lipid concentration in liver and muscle also varied in a rhythmi c fashion (tau = 24 h). The mesor and amplitude of these rhythms appeared t o be modulated by the phase of the annual gonadal cycle of H. fossilis. All three lipid parameters, in addition, exhibited low frequency rhythms with a tau = 6 months or 3 months. The results indicate that the time of the day and month of the year for sampling in any experiment involving examination of lipid metabolism are of critical importance.