Morphological analysis of the sloth tongue: Bradypus variegatus (Schinz, 1825)

Sloths are arboreal folivores and rely on an efficient digestive system to thrive in Neotropical forests. This study was performed to evaluate the morphological aspects of the tongue of the brown-throated sloth (Bradypus variegatus). Five adult specimens (three males and two females) were obtained from the collection of the Anatomy Laboratory at the Academic Center of Vitória de Santo Antão, Universidade Federal de Pernambuco. The tongues were dissected and analyzed for their macroscopic characteristics. They were also subjected to histological analysis, in which sections were stained using hematoxylin–eosin, 1% toluidine blue, Masson’s trichrome, picrosirius–hematoxylin, and mucicarmine. The average tongue length was 4.12 ± 0.17 cm, width was 1.50 ± 0.05 cm, and thickness was 2.00 ± 0.11 cm. The tongue consisted of an apex, body, and root. Numerous filiform and fungiform papillae were present on the dorsum of the tongue, and only two vallate papillae were observed. Microscopic examination revealed that the dorsal surface of the tongue was lined with keratinized stratified squamous epithelium, with melanin in the basal layer. The tongue predominantly consisted of skeletal striated muscle fibers. Occasional mast cells were scattered in the connective tissue. Numerous mucous glands were observed, but no serous glands were found. These morphological findings of the tongue of B. variegatus are partially unique to this species and are influenced by its diet and feeding habits.