Macroscopic and microscopic study of the brain structure of the common kestrel (Falco tinnunculus)

Abstract

This study was conducted to examine the macroscopic and light microscopic structures of the brain in kestrels (Falco tinnunculus). In the study, brains from three adult kestrels that were brought in for treatment but could not be rescued, one from Keçiören Municipality Veterinary Affairs Directorate and two from Afyon Kocatepe University Wildlife Rescue and Rehabilitation Centerwere used. The brains were properly removed and subjected to macroscopic and light microscopic examination procedures. The average brain weight was measured as 3.23 g, total length as 22.5 mm, and total width as 23.5 mm. The cerebrum, cerebellum, lobus opticus, and medulla oblongata were the prominent regions of the brain. A well-developed lobus opticus was observed, and  small and rudimentary bulbus olfactorius structures were present on both sides of the midline  at  the  rostroventral  part  of the cerebral hemispheres. In the cerebellum, transverse protrusions called folia cerebelli, varying in number between 9 and 10, and the fissura cerebelli separating them were seen. On the sides of the cerebellum and behind the lobus opticus, auricula cerebelli were identified. At the caudal part of the brain, the pons and medulla oblongata were present and separated by a slightly prominent transverse groove. In the light microscopic examination, small neurons located beneath the piamater in the cerebral cortex and irregularly distributed glial cells among them were observed. In the deeper cortical regions, large neurons with vesicular nuclei were identified. In the cerebellum, a typical three-layered structure consisting of molecular, Purkinjecell, and granular layers was present. In addition, numerous multipolar neurons and supporting glial cells were found in the medulla oblongata, and ependymal cells were identified in the fourth ventricle. In the optic lobe, medium-sized spherical neurons containing few glial cells attracted attention. With this study, the macroscopic and light microscopic structures of the brain in kestrels were revealed. The data obtained were compared with the morphological structures of the brains of other avian species, and similarities and differences were discussed.The findings are expected to contribute to the literature on the morphological characteristics of raptors and serve as a foundation for comparative anatomical and histological studies on wild bird species.