A Comparative Ultrastructural Study of the Parotid Gland Acinar Cells of Nine Wild Ruminant Species (Mammalia, Artiodactyla)

Abstract

The ultrastructural similarities and differences of the parotid gland acinar cells of nine wild ruminants (roe deer, nyala, tahr, Eld's deer, red deer, Pere David's deer, European mouflon, African buffalo, sable antelope) representing three feeding types i.e. concentrate selectors (CS), grass and roughage eaters (GR) and intermediate feeders (IM) were compared. The parotid acinar cells of the CS contained more granular endoplasmic reticulum, Golgi-complexes and secretory granules than those of the GR. The acinar cells of the latter were characterized by numerous mitochondria, folded plasma membranes and intercellular secretory canaliculi. The ultrastructure of the secretory granules varied in different species but their morphology was not related to feeding type. An unusual feature of the parotid acinar cells of all feeding types was the evidence of an apocrine-like mode of secretion. A typical morphological change of some parotid acinar cells was the compression of the nucleus by large vacuoles. No distinctive differences were found in the ultrastructure of the parotid gland of wild and captive ruminants.