A UNIQUE PAROTID-GLAND IN HARTS LITTLE FRUIT BAT, ENCHISTHENES HARTII

Background: Hart's little fruit bat, Enchisthenes hartii, is uncommon and, although it has been the subject of recent molecular genetic stud ies, is little known biologically, Because chiropteran salivary glands vary interspecifically in ways that reflect evolutionary history and ecology, we examined the parotid gland in E. hartii to ascertain the e xtent to which it resembles homologous glands in species to which this bat presumably is related, Methods: The parotid glands were prepared for electron microscopic examination by conventional means, Results: T he parotid gland off. hartii is structurally unique among all previous ly studied species of bats (>230 species examined) and other mammals, In contrast to the same gland in other mammals, the parotid gland in E . hartii lacks secretory endpieces, In their place, there is a type of striated duct, Thus, in this species single secretory elements consis t of (proceeding in the direction of salivary how): striated duct-inte rcalated duct-and a conventionally located striated duct, The proximal ducts possess microvillus-lined intercellular canaliculi, whereas the walls of the distal ducts include occasional dark cells, Some small s erous-like granules may be present in the intercalated duct cells, Con clusions: The function(s) and biological role of the unique parotid gl and in E, hartii are unknown. Nevertheless, the presence of two sets o f striated ducts provides two separate glandular components seemingly capable of electrolyte transport, This might be of adaptive significan ce in enabling this species to make use of tropical nutrient resources that otherwise would be unavailable, The uniqueness of its parotid gl ands lends support to the current hypothesis that E, hartii should be classified as a monotypic genus rather than as a species of Artibeus, whose members it resembles morphometrically. (C) 1997 WiIey-Liss, Inc.