Comparative Study of the Gastric Mucosa of Risso's Dolphin ( Grampus griseus ) and Bottlenose Dolphin ( Tursiops truncatus ): A Key to Manage the Diet in Captive Conditions.

To histologically evaluate the gastric compartments of Risso's ( Grampus griseus ) and bottlenose dolphins ( Tursiops truncatus ) and provide suggestions for the diet of Risso's dolphins in captivity, we examined 12 stomachs from both species. While slight differences in keratinization were observed in the forestomach, significant differences came to light in the second stomach's mucosa. At this level, in Risso's dolphin, the principal cells are markedly reduced in size and located externally to the parietal cells, not interspersed between them, compared to bottlenose dolphins; differences were also observed in the structure and concentration of the parietal and principal cells of the gastric body glands ( p < 0.0001). The quantitative results of G- and D-cell counts in the gastric mucosa show a clear difference, with a higher concentration of G cells in the mucosa of Risso's dolphin (t = 7.334; p < 0.0001) and a higher level of D cells in bottlenose dolphin mucosa (t = 3.123; p = 0.0049). These results suggest that parietal cells undergo greater stimulation by gastrin produced by G cells, with greater acid secretion in G. griseus . Further studies are needed to understand whether an inappropriate diet could lead to severe clinical signs due to gastric acidity in Risso's dolphin.