Morphological and Histological study of the Harderian gland in the Striated Scops Owl (Otus brucei)

This research focused on examining the anatomical and histological features of the Harderian gland in seven Striated Scops Owls. Seven different Birds models were utilized, with the birds being euthanized following established protocols. The Harderian gland was subsequently removed for anatomical and histological analysis. The anatomical observations indicated that the gland is situated behind the eyeball in the dorsomedial area and has one central excretory duct that connects to the lacrimal duct. Hematoxylin-eosin staining demonstrated the general architecture of the gland, whereas Masson's trichromatic stain illustrated the arrangement of collagen fibers and PAS-Alcian blue was utilized to identify the characteristics of the glandular secretions. Histologically, the gland was observed to be encased in a fibrous capsule and made up of two primary lobes of different sizes: a smaller lobe and a larger lobe. The sizable lobe displayed thick glandular tissue with distinct intercellular connections partitioning it into smaller lobules. A significant density of collagen fibers was noted in the capsule encasing the gland, showcasing a blue hue, while the collagen concentration was reduced in the interstitial tissue, which appeared green. The findings from the small lobe exhibited a positive response with Alcian blue, showing blue coloration, the secretion was of the acidic mucopolysaccharides variety. The large lobe exhibited a mixed response; regions of acini reacted with Alcian blue and turned blue, whereas the gland's center showed a positive reaction with PAS and appeared pink, the presence of neutral mucopolysaccharides. Cells in the central areas also displayed a purple hue from the combination of blue and pink, suggesting that their secretions were of a hybrid nature (acidic and neutral). These findings suggest a distinct structural and functional verity between the two lobes of the horny gland in owls, highlighting a range in the characteristics of glandular secretions and their roles.