Influences of length of photoperiod on the adrenocortical activity of the male blossomheaded parakeet Psittacula cyanocephala.

Abstract

Adult male Blossomheaded Parakeets were exposed to very long (22 h) and very short (2 h) daily photoperiods for 45 days during different phases of the annual testicular cycle. Adrenocortical activity of the experimental photoperiodic birds were compared with that of parallely held natural photoperiodic birds with the use of different histophysiological parameters. These parameters are believed to be faithful indices of secretory functions in the steroidogenic part of avian adrenal gland. The study revealed that very short (2 h/day) day-length does not influence the activity of adrenocortical tissue in any phase of the annual cycle. Adrenocortical tissue of very long photoperiodic (22 L : 2 D) birds (i) remains unaffected during breeding phase, (ii) shows the features of inactiveness in the subcapsular zone (SCZ) during late preparatory, early progressive and prebreeding phases of treatment, and (iii) becomes atrophied in both the SCZ and IZ (inner zone) when the birds were exposed during early preparatory and late progressive phases of the annual gonadal cycle. The results of this study are discussed in the light of previous studies into photoperiodic effects on adrenocortical activity in parakeets.