Investigation of Glandula Uropygialis in Different Avian Species Using Morphometric and Histological Methods

The aim of this study was to identify the glandula uropygialis's macroanatomical and histological structure in male and female birds (stork, goose, eagle, pigeon, crow and sparrowhawk) that belong to different populations. A total of 58 specimens were used in the study. The study materials were delivered to our laboratory by nature conservation and national parks, and no animals were euthanised for this study. The longitudinal and transversal lengths, dorsoventral heights and feather length of the glandula uropygialis and papilla uropygialis were measured with a digital calliper. Haematoxylin–eosin and Masson trichrome staining were performed for histological examinations. The shape of the glandula uropygialis was found to be pear-shaped in pigeons and sparrowhawks, heart-shaped in geese, kidney-shaped in eagles and oval-fascule-shaped in storks. In the crow, the shape of the glandula uropygialis was different from the other species in that it was located dorso-caudally. Histomorphological examination of the glands of these species revealed that the gland generally consisted of two lobes, right and left, surrounded by connective tissue from the outside. The parenchyma of these lobes consisted of tubulo-alveolar secretory glands with a radial arrangement from the periphery to the centre. The glands within the lobes differed from the periphery to the centre and although the general histomorphological appearance was similar between bird species, some differences were observed between species. Similar stromal structure was observed in all bird species evaluated in the study. However, the reticular connective tissue forming the roof of the gland was found to be more developed in pigeons, especially in Masson's trichroma staining. The degenerative layer in the glands was more prominent in the eagle, followed by the goose and crow. Although a common general histological structure was observed among bird species, simple histomorphological differences were found between these formations, but no differences were found between the sexes. The results obtained will be compared with the findings of the aves class and will provide a data source for this special gland specific to birds. It is thought that the results obtained may help to determine the functional properties of the gland and contribute to the science of ornithology.