Post-hatch development of preen gland in the duck (anas platyrhynchos)

Abstract

The study on the post-hatch development of the preen gland in ducks was conducted using 44 ducks from the day of hatch to 150 days of age. The project was taken up to trace the structure and development of the glands and their relationship with the age and body weight. After recording gross relations and measurements, the material was fixed using various fixatives for studying the cellular details, arrangement of cells, connective tissue framework, micrometry and histochemistry. The preen gland was a paired organ with two gland and a common cylindrical papilla together formed a ‘V’ shaped structure. Each gland was pear shaped and pale yellow in colour, in fresh state. They were located on the dorsal surface of the pygostyle. The two glands had separate ducts. The uropygial circlet was seen at the tip of the papilla. The glands were vascularized through a pair of branches from the caudal artery and innnervated through the medial caudal nerve. The weight of the preen glands increased progressively from the day of hatch to 150 days of age. This weight was positively correlated with the age and body weight. The proportion of the gland weight to body weight showed a decreasing trend. The right gland was slightly heavier, longer, wider and thicker than the left. The length, breadth and thickness were positively correlated with age and body weight. Simple, branched, tubular and holocrine type of glands was covered by highly vascular connective tissue capsule composed of collagen and reticular fibres. Elastic and smooth muscle cells were absent. The secretory tubules showed two zones, an outer zone or zone I, near the capsule and an inner zone or zone II, towards the primary cavity. The epithelium of the tubules consisted of basal, intermediate and transitional cell layers. The papilla had two ducts, which were lined by glandular epithelium initially and keratinized type of stratified stratified squamous epithelium at the tip. The glandular epithelium was surrounded by longitudinally arranged smooth muscle fibres and skin. Lamellar corpuscles and circlet feather follicles were noticed in the papilla. Capsule, trabeculae and the parenchyma were PAS positive. Acid mucopolysaccharides and glycogen were not detected in the gland. Lipids were evident uniformly in all the cell layers. The acid phosphatase activity was moderate in the basal and intermediate layers and strong in the transitional layer. The alkaline phosphatase activity was moderate in the basal and intermediate layers and weak in transitional layer of outer zone. It was moderate in the basal and intermediate layers and intense in the transitional layer of inner zone. Micrometrical findings on the capsule thickness, width of outer and inner zones and the primary cavity increased with the advancement of age.