Published Paper Details:

The present study was carried out to demonstrate a comparative account of distinctive histological features of the thyroid gland in male and female redheaded buntings (Emberiza bruniceps) maintained under natural and artificial laboratory conditions, during pre-breeding and breeding seasons, with respect to their physiological indices. 48 adult birds were procured during the over-wintering season in India and divided into two groups each of 24 birds (12 birds/ sex). One set of birds was housed in an outdoor aviary, while the other set was transferred to an indoor aviary. In both aviaries, six birds/ sex were used for collecting data on physiological indices and histomorphometry. Gonadosomatic index (GSI) and fatness index were significantly different between NDL/ artificial conditions, pre-breeding/ breeding seasons, and male/ female birds. GSI was also influenced by the condition of the study. Histologically, the thyroid gland was observed to be enclosed by a thin capsule that showed sex-dependent differences. Follicular area and follicular density were significantly different between pre-breeding and breeding season. The cross-sectional area of the thyroid gland was significantly affected by the interaction between condition x sex and season x sex. These results suggest that surrounding condition, life history state (LHS), and sex of the birds play a key determining role in regulating the seasonal phenotypic plasticity at the level of physiology and organ plasticity. Histomorphometric changes in the thyroid gland are suggestive of its season-dependent differential activity.