Season related ultrastructural features of the parotid, submandibular and von Ebner's glands in hibernating bats

The parotid, submandibular and the von Ebner's salivary glands of hibernating insectivorous bats (Pipistrellus pipistrellus, Rhinolophus f. e. and Eptesicus serotinus) were studied by transmission electron microscopy and by histochemical methods during various seasons of the year. We report the seasonal ultrastructural changes that occur in the cytoplasmic organelles and the secretory granules of the serous and mucous cells and in the intercalated and striated ducts of the major glands. It previously has been hypothesized that the heterogeneity of the inclusions in the serous granules is closely related to the varying seasonal levels of proteinaceous and glycidic constituents. Lymphatic vessels are present only in the perivascular and periductal connective tissue. Morphofunctional and comparative studies seem to confirm a relationship between secretory activity and nutritional status as well as a likely involvement of the intercalated and striated ducts in determining the composition of the saliva.