Histological, histochemical and immunohistochemical aspects of the intestine and pancreas of bats of the Phyllostomidae family (Mammalia, Chiroptera)

The present study aims to describe the intestine and pancreas of both Dryadonycteris capixaba and Pygoderma bilabiatum. Furthermore, it aims to identify the enteroendocrine cells that produce serotonin (5-HT), somatostatin (SST), and cholecystokinin (CCK) in the intestine and CCK, SST, glucagon (CGC) and insulin (INS) in the pancreas, relating histological characteristics with feeding habits, besides contributing to basic research on aspects of the diffuse neuroendocrine system of mammals. Histologically, the intestinal wall of the species D. capixaba and P. bilabiatum was similar to that of other mammals. The height of the villi in the small intestine was different among the species studied. In the duodenum and ileum, PAS positive secretion was observed. The duodenal gland present only in P. bilabiatum showed intense reaction for PAS stain, indicating neutral glycosaminoglycans (GAGs). The frequency and distribution of 5-HT Immunoreactive (IR) cells varied among the species. In D. capixaba, these cells were evident only in the ileum (11.8 ± 2.9 μm) and large intestine region. In P. bilabiatum were different among the segments, with the highest frequency in the duodenum (13.3 ± 2.8 μm), jejunum (8.1 ± 2.3 μm) and ileum (10.1 ± 1.9 μm). CCK-IR cells were not observed in D. capixaba. In P. bilabiatum these cells were observed in the ileum (9.5 ± 1.3 μm). SST-IR cells were not found throughout the intestine of the studied species. The pancreas of bats presents islets with differentiated cellular composition. All the antibodies used (CCK, SST, GCG and INS) obtained positive staining in the pancreatic islets of both the species studied. The INS-IR cells marked the entire islet in both species, whereas the CGC-IR cells were visualized throughout the islet in D. capixaba and preferentially in the periphery in P. bilabiatum. CCK and SST-IR cells were located in the peripheral region of the islets in both species. In our study we observed similarities in the intestinal and pancreatic morphology of the studied species, although there were interspecific differences in the distribution of intestinal GAGs and enteroendocrine cells. This suggests that these differences may be more related to the distinct feeding habits of each species than to their phylogeny, as they belong to the same family.