Ultrastructure of the Submandibular Gland in the Big White-Toothed Shrew, Crocidura lasiura

Abstract

The ultrastructure and histochemical characteristics of the submandibular gland was examined in the big white-toothed shrew, Crocidura lasiura. A submandibular gland of Crocidura lasiura was a mixed gland composed of serous and mucous acinar cells. Secretory granules from the acini were discharged through the intercalated duct, the granular duct and the striated duct into the oral cavity. Serous and mucous acinar cells and granular duct cells had large amount of rough endoplasmic reticulum, free ribosome and prominent Golgi apparatus at the basal cytoplasm of the cell, and many granules at the apical cytoplasm. Oval type serous granules had a homogeneously pale round shape of bead at the center. Mucous granules were distinct from those of the other mammalian species having variety patterns with several dense bands into homogeneous pale matrix. A serous-like secretory granules and myelin-like body were observed in the cytoplasm and the lumen of granular duct cells. The myelin-like body is a characteristic structure only reported in the salivary glands of two shrews, Suncus murinus and C. dsinezumi. Striated duct cell had numerous well-developed mitochondria but secretory granule was not shown at all.