Ultrastructure of gastric mucosa was studied comparatively in six species representing four microchiropteran genera, Pteronotus parnellii, Phyllostomus hastatus, P. elongatus, Carollia perspicillata, Artibeus lituratus, and A. concolor, which have different diets. Overall, the ultrastructural comparisons were shown to have systematic value as well as value for determination of evolutionary patterns at the cellular and tissue levels. Generic differences were found in numbers and types of entero-endocrine cells; a glucagonproducing A cell was the only type common to all four genera. Generally, entero-endocrine cell types could be correlated with both diet and systematics and the specific composition of cell types could be explained in terms of potential interactions with other cell types within individual species. Intergeneric ultrastructural differences also were found among chief cells and their secretory products and among mucous neck cells. The chief cell differences were related to diet and it was clear that stenodermatine chief cells are functionally divergent and, therefore, might be useful to an understanding of evolution of cell types. Interfamilial histochemical analyses of mucous neck cell product appeared to loosely match diet (insectivore-omnivore versus strict frugivore), whereas ultrastructural features of these cells were more nearly indicative of systematic relationships among

The fundic mucosa in Trachops cirrhosus, Chiroderma trinitatum, and C villosum (Suborder Microchiroptera) was studied comparatively by transmission electron microscopy. Trachops is an animalivorous species that mainly feeds on Neotropical frogs, whereas both species of Chiroderma are frugivorous. In Trachops, two types of enteroendocrine cells (A and D cells) that possibly produce glucagon and somatostatin, respectively, were identified ultrastructurally. In Chiroderma examples of possible A, EC^, Di(H), and G cells were identified. The product in possible G-cells in Chiroderma ultrastructurally matched that found in the pylorus of another stenodermatine bat, Ariteus flavescens, which has been shown to exhibit gastrin-like immunoreactivity. In Trachops