Comparative morphology of the lingual papillae and their connective tissue cores in the tongue of the Abyssinian black-and-white colobus (Colobus guereza).

ABSTRACT

We observed the morphology of the lingual papillae (filiform, fungiform, foliate, and vallate) and their underlying connective tissue cores (CTCs) in Abyssinian black-and-white colobus monkeys using light and scanning electron microscopy. The tongues of both juvenile and senescent individuals were relatively short in the rostro-caudal direction, with a rounded apex. Lingual tori were absent. Numerous filiform papillae were distributed over the entire tongue, except at the lingual root. A pair of foliate papillae was present on both the lateral and caudal margins of the corpus. Three vallate papillae were distributed on the boundary between the caudal part of the body and the root in both juvenile and senescent individuals. Based on scanning electron microscopy observations, the morphologies of the filiform papillae differed between juvenile and senescent individuals. The epithelial surface of juvenile filiform papillae had a main process, but the associated processes were weak and the underlying CTCs displayed immature morphology. In contrast, the epithelial surface of senescent filiform papillae was associated with several accessory processes, and their underlying CTCs consisted of several auxiliary cores that nearly encircled the main core, forming a concavity in the papilla. CTCs of the filiform papillae showed variable morphology. Juvenile filiform CTCs exhibited a rather primitive morphology, resembling those of the hamster, mole, and Cape hyrax while, conversely, despite the basically folivorous diet of the Abyssinian black-and-white colobus, senescent filiform CTCs resembled those found in omnivorous primates, including members of the Callitrichinae and Homoidea, and also those in Carnivora (e.g., Canidae and Felidae).