ULTRASTRUCTURE OF THE SALIVARY-GLANDS IN THE MIDTONGUE OF THE COMMON VAMPIRE BAT, DESMODUS-ROTUNDUS

Background: All examined mammals have at least two sets of lingual sal ivary glands: von Ebner's glands and Weber's glands. A third set, the glands of Blandin and Nuhn, is present in the tongues of some but not all mammals. Vampire bats, Desmodus rotundus, are unusual in that they possess another set of lingual glands, these being in the midtongue r egion. Methods: The anterior half of the tongue was extirpated from se veral adult vampire bats, dissected, and tissue blocks derived from th e midregions of the body of the tongue prepared for transmission elect ron microscopy by conventional means. Results: The midlingual glands a re in the form of long, tubular secretory endpieces that are succeeded by ducts of simple morphology. In general, the secretory portions con sist of two cell types, which may be intermingled in the same tubule o r may form tubules that consist wholly of one cell type or the other. Seromucous cells usually have one or several rough endoplasmic reticul um cisternae that are hugely distended by a homogeneously dense materi al. Their granules have a bizonal substructure: one or several dense b ands are embedded in a lighter matrix. Mucous cells are rather typical in structure, but their secretory product is different from run-of-th e-mill mucous droplets. These droplets vary in density from cell to ce ll. In some cells, these droplets have a relatively light matrix; in o ther cells, the droplet is unusually dense, consisting mainly of a dar k, structureless matrix with marginal lenticular lacunae of low densit y in which some short, irregular filaments are scattered. A rare findi ng is the presence of ciliated cells intermingled with secretory endpi ece cells. The cilia are of conventional morphology. Secretory tubules are succeeded by ducts that resemble intercalated ducts; the epitheli um of these ducts gradually increases in height to form a kind of excr etory duct, without the intervention of striated ducts. As the ducts a pproach the lingual surface, the epithelium changes to stratified squa mous. Conclusions: Saliva produced by the midlingual glands may be an aid in the reciprocal grooming behavior of vampire bats. Based on thei r morphology, the excurrent ducts may not modify the initial. saliva e laborated by these glands and might act simply as pipelines by which t he saliva reaches the mouth. (C) 1997 Wiley-Liss, Inc.