Effects of photoperiod alterations on adrenocortical, pineal and gonadalactivity in nocturnal bird, Athene brama and diurnal bird, Perdiculaasiatica

摘要

Present study showed the influence of photoperiod alterations on adrenal gland weight, adrenal lipids and plasma corticosterone profiles (adrenocortical function), and pineal and gonadal weights of two Indian tropical male and female birds belonging to nocturnal (Spotted owlet, Athene brama) and diurnal (Jungle bush quail, Perdicula asiatica) habitats. Exposure of both sexes of nocturnal birds to long photoperiod (Lf, 16L:8D, light between 6:00 to 22:00hr) and continuous illumination (CL) during reproductive recrudescence and active phases, respectively, increased adrenal weight, adrenal lipids, such as phospholipids, free and esterified cholesterol, as well as plasma corticosterone levels. Concomitantly, the LP treatment elevated the gonado-somatic index while decreased the pineal gland weight, however, the CL treatment was ineffective to alter gondal and pineal activity. Exposure of both sexes of nocturnal birds to short photoperiod (SP, 8L:16D, light between 9:00 to 17:00hr) and continuous darkness (CD) during reproductive recrudescence and/or active phases inhibited adrenocortical function and gonadal activity while elevated the pineal gland weight. Exposure of both sexes of diurnal birds to SP and CD during the reproductive active phase produced similar changes on these variables like that of the nocturnal birds while the CL treatmet was ineffective. These results indicated that adrenocortical function and gonadal weights are photoperiod-dependent in both sexes of birds, irrespective of their habitats and can be positively correlated. Pineal gland activity showed an inverse pattern of changes with adrenocortical function and gonadal activity when exposed to different photoperiod regimes, irrespective of the habitat or sex of birds. Present study together with previous reports further indicate that pineal gland may mediate photic signals. Direct evidence is, however, required to support this hypothesis.