Tongue morphology of the red-nosed mouse (Wiedomys pyrrhorhinos Wied-Neuwied, 1821) and adaptive implications.

Morphological tongue studies are an interesting tool for assessing feeding habits and understanding evolutionary processes. In this context, this study aimed to describe the tongue morphology of the red-nosed mouse Wiedomys pyrrhorhinos, to establish a standard model for the species and infer potential morphological associations with feeding habits. Five tongues from adult females were obtained, stored in 4% paraformaldehyde and 2.5% glutaraldehyde, and analyzed both macroscopically and using light microscopy, histochemistry, and scanning electron microscopy techniques. Tongue areas are categorized as apex, body, and root. Different types of papillae, that is, filiform (mechanical), fungiform, foliate, and vallate (taste), were identified. Filiform papillae vary morphologically, with both long and short pointed, long bifurcated, long trifurcated, and broad multifurcated papillae. The epithelium is organized in layers, including keratinized, granular, spinous, and basal, with a thin and slender lamina propria and well-developed musculature containing clusters of mucous and serous glands on the tongue root. The tongue morphology of W. pyrrhorhinos is, thus, characterized by filiform, fungiform, foliate, and vallate papillae, an adaptive pattern consistent with its omnivorous habit. Moreover, similarities with phylogenetically close species, such as the bank vole Clethrionomys glareolus, reinforce the hypothesis of an evolutionarily conserved anatomical configuration within the Cricetidae family.