Quantitative histomorphology of the blind mole rat harderian gland.

Anatomical, histological and morphometric studies have been performed on the harderian gland and its surroundings in the blind mole rat (Spalax ehrenbergi). The gland is tubuloalveolar with no true duct system. All ducts within the gland are formed by a single epithelial cell type and drain into a wide secretory duct. This opens into the conjunctival sac which serves as a reservoir for harderian secretions. Drainage from the conjunctival sac follows 2 possible routes: one through the nasolacrimal duct to the external nasal cavity, the other through a unique excretory duct that emerges from the anteromedial part of the conjunctival sac and runs through the dermis to the skin, opening at the base of a hair follicle. The function of this newly described duct is discussed. Morphometric studies revealed that the lumen volume fraction in the female, slightly smaller than that of the male during the summer, becomes significantly greater during the winter breeding season. The dimorphism and seasonal variations found in the gland acini suggests that the gland may be implicated in pheromone production.