Ultrastructure of the parotid gland in two species of naked-backed bats

Naked-backed bats of the genus Pteronotus (family Mormoopidae) occur in the Neotropics from Mexico through northern South America. These are relativel y small-sized insectivorous species that frequently roost in caves. Eight s pecimens of naked-backed bats (Pteronotus parnellii) were live-trapped in S uriname and one in Cuba (P. quadridens). Their parotid glands were fixed in an aldehyde mixture designed for field work and postfixed in the laborator y with osmium tetroxide. Tissues were further prepared for electron microsc opy by conventional means. The parotid glands of the two species of Pterono tusclosely resemble each other except for the substructure of their serous secretory granules. Serous granules in P. parnellii are bizonal, with a mod erately dense inner matrix and an outer, denser corona or crescent. The mat rix is occupied by laminae, flakes, and filaments in random array. In contr ast, serous granules in P. quadridens consist of a uniform matrix that cont ains dense, usually stacked toroids or tubules either in random array or pa cked in bundles. A parotid gland from one specimen of P. parnellii containe d an endpiece that consisted of cells that contained giant (up to 9 mu m in diameter) serous granules. Serous cells in both species contain aggregates of small, uniformly dense, rod-like, membrane-delimited organelles as well as occasional bundles of cytofilaments. The endpieces are separated from i ntercalated ducts by a ring of granulated cells that contain secretory gran ules that often have a bull's-eye configuration. Intercalated and striated ducts are typical in appearance, except that many of the cells in the latte r contain small, dense secretory granules in their apical cytoplasm. The pa rotid glands in the two species of naked-baked bats differ slightly in term s of acinar secretory granule ultrastructure, but otherwise are fairly cons ervative. It is thought that the glands in these particular bats might repr esent the "basal" condition of the salivary glands of insectivorous bats an d thus can serve as a reference point for making comparisons to the highly diversified (in terms of diet) phyllostomid bats. Anat Rec 255:105-115, 199 9. (C) 1999 Wiley-Liss, Inc.