The scentmarking glands of the anal pouch, penile pad, and the forefoot of the aardwolf (Proteles cristatus) were studied by histological, histochemical, immunohistochemical methods, and by electron microscopy. The morphological observations are correlated with eco-ethological aspects of this nocturnal animal. In all studied regions there was a superficial layer of holocrine sebaceous glands and a deeper layer of apocrine scent glands; these two types of glands apparently function in concert. Only in the forefoot were additional tubular glands, resembling eccrine sweat glands found, which may improve the frictional capacities of the paw, while apocrine and holocrine glands serve scent-marking functions of the forefoot. Penile pad and anal pouch are exclusively scent marking organs. The secretion modus of the apocrine glands is both via exocytosis and apocrine mechanism. Homogeneous apical, secretory granules, which contain glycoproteinaceous material, represent evidence for exocytosis. In the anal pouch, additional variably sized granules contain endogenous pigments which are probably responsible for the brownish coloration of the secretory product of the male animals. Variable heights of the glandular cells, frequent apical tall protrusions as well as pinched-off pieces of cytoplasm in the glandular tubules support the concept of an apocrine secretion in the scent glands. The immunohistochemical staining pattern of actin points to the involvement of actin filaments in the pinching-off process of the apical cell protrusion, which does not contain any cell organelles. The variable actin staining patterns suggest a dynamic process during which actin filaments form a ring or sheet at the basis of the pinching-off bleb. Proliferative and apoptotic phenomena show no preference for active and inactive glandular cells suggesting that replacement of cells occurs independently of the functional status of the glands.
Copyright 2000 Wiley-Liss, Inc.