Seasonal effects on the diel changes in circulating thyroid hormones in the freshwater catfishClarias batrachus

Modulatory effect of temperature on the influence of dietary linolenic (18 : 3 n‐3) and linoleic (18 : 2 n‐6) acids on the gonadal recrudescence in Clarias batrachus (L.)

“…Similarly, Corrazze et al (1991) discussed the role of rearing temperature on lipid content of eggs in rainbow trout brood stock. The variation in seasonal temperature influences the feeding activity of fishes including C. batrachus (Sinha et al, 1992) with higher feeding activity at higher temperatures (Hora & Pillai, 1962;Khanna, 1986). High temperature also promotes gonadal growth (Saxena & Sandhu, 1984;Lal et al, 1999).…”

Variability in the characteristics of ultradian and circadian rhythms in plasma levels of growth hormone in the Indian walking catfish,Clarias batrachus

“…As reported by Sinha et al (1992), this fish feeds twice daily; once shortly after sunrise and again shortly before sunset. One of the ultradian peaks of GH also occurred in the early light phase and another shortly after sunset.…”

“…On the annual scale, this fish consumes very little food during winter (December and January). With the rise in temperature and lengthening of photoperiod from March onwards, feeding activity increases gradually and attains its maximum during May and June, then declines in July and becomes moderate in the late part of August and September (Sinha et al 1992). This fish is also a seasonal breeder, starting with mild reproductive preparation with a rising photoperiod and temperature from March to peak preparation in May and June when the temperature and photoperiod attain maxima and then breeding in the latter half of July when the temperature drops along with the onset of monsoon showers.…”

“…From August onward it enters into gonadal quiescence until January and February (Lal and Singh 1987). The seasonal changes in daily rhythm of maturational gonadotropin (Harikrishnan et al 2002), different sex steroids and thyroid hormones (Sinha et al 1992) have been studied in this fish as a function of the status of feeding and reproduction, photoperiod, and water temperature.…”

“…The rhythmic secretory pattern makes them physiologically more effective and relevant. A good number of reports are available on the rhythmic secretory pattern of gonadotropin (de Vlaming and Vodicnik 1977;Hontela and Peter 1978;Khan and Thomas 1994;Harikrishanan et al 2002), sex steroids (Lamba et al 1983;Singh and Singh 1987) and thyroid hormones (Stacey et al 1984;Cook and Eales 1987;Sinha et al 1992). Plasma levels of GH are also reported to undergo seasonal and diurnal variation in fishes (Marchant and Peter 1986;Le Bail et al 1991;Bjornsson et al 1994;Zhang et al 1994;Gomez et al 1996;Bjornsson et al 2002;Einarsdottir et al 2002;Mingarro et al 2002;Canosa and Peter 2005), but the results are highly inconclusive and debatable.…”