Systematic Implications of Comparative Ultrastructure of Secretory Acini in the Submandibular Salivary Gland in Artibeus (Chiroptera: Phyllostomidae)

Abstract

The principal submandibular salivary gland in four species of the stenodermatine genus Artibeus was examined ultrastructurally to determine the possible intrageneric systematic value of salivary gland morphology. In terms of general architecture, the submandibular glands are similar in Artibeus cinereus, the previously studied A. phaeotis, A. jamaicensis, A. lituratus, and A. concolor. The secretory acini in all five species consist of serous cells that often are capped by a seromucous demilune. Secretory granules in the serous cells are large and uniformly electron-dense. In contrast, secretory granules in the seromucous cells have a complex substructure that varies from species to species. The most highly organized seromucous granules are found in A. cinereus and closely resemble those in A. phaeotis. The secretory granules in Artibeus jamaicensis and A. lituratus differ slightly from these other two species, but are extremely similar to one another. Artibeus concolor differs from all of the other four in having seromucous granules that are ultrastructurally distinctive. Similarities and differences in seromucous secretory granules thus match independently derived genic data, showing that the ultrastructure of salivary gland secretory product can have systematic significance. This also is the first reported instance in which ultrastructural differences in a cell product have been correlated with intrinsic genic differences as opposed to functional state or some other factor.