Anatomical and histological changes associated with hibernation in the stomachs of Anatolian ground squirrels

This study investigated the anatomical and histological characteristics of the stomach in Anatolian ground squirrels ( Spermophilus xanthoprymnus ) during hibernation (H) and non-hibernation (NH) periods. Stomach tissues from hibernating and non-hibernating animals were examined using stereo microscopy and light microscopy. Scanning electron microscopy was also used to characterize the surface morphology of the gastric mucosa. Histochemical staining, including Mallory’s Modified Triple, Alcian Blue-Periodic Acid Schiff (AB-PAS), and High Iron Diamine-Alcian Blue (HID-AB), together with immunohistochemical detection of Microtubule Associated Protein-2 (MAP-2) and Proliferation Associated Nuclear antigen Ki-67 (Ki-67), was performed to characterize structural, secretory, and proliferative dynamics. The Anatolian ground squirrel possessed a simple, single-compartment stomach comprising the cardia, fundus, corpus, and pylorus, with the corpus divided into two morphologically distinct subregions. Hibernation was associated with marked reductions in stomach dimensions and region-dependent alterations in the thickness of the gastric wall layers. Histomorphometric analysis revealed differences in gastric gland dimensions and epithelial, parietal, and principal cell sizes between H and NH animals. AB-PAS and HID-AB staining demonstrated that animals in the hibernating state exhibited the distribution and staining intensity of gastric mucosubstances. MAP-2 immunohistochemistry revealed differences in immunoreactivity within the enteric plexuses between H and NH stomachs, whereas qualitative Ki-67 assessment showed less frequent immunopositive nuclei in H stomachs, predominantly localized within the neck/isthmus region of the gastric glands. These findings provide a morphological basis for understanding the association between the hibernating state and gastric structure of this species; however, the functional significance and underlying mechanisms of these alterations require further physiological and molecular investigation.