Ultrastructure of major intraglandular ducts in the parotid gland of the African mole-rat.

The parotid gland of a female African mole-rat, Tachyoryctes splendens, was examined by light and electron microscopy. A pure seromucous gland of conventional histology, its striated and excretory ducts contain prominent cytoplasmic inclusions that are lightly stained with toluidine blue. At the ultrastructural level, the inclusions are seen to consist of a light to moderately dense structureless matrix in which are suspended scattered, randomly oriented filaments that either are 4-7 nm or approx 14 nm thick. A few multivesicular bodies or putative lipid droplets are sparsely distributed in the inclusions. Even though the inclusions lack an encompassing membrane, all other formed cytoplasmic structures are excluded. These inclusions are not present in the ducts of the submandibular gland of the mole-rat. The inclusions may confer special properties on the parotid gland of this fossorial animal that permit it to cope with the exigencies of a subterranean existence.