Morphological and histochemical characteristics of the tongue of the hystricomorph rodent Lagostomus maximus and its comparison with other mammals

The mammalian tongue performs several relevant functions, including food capture and its mechanical and chemical modification, swallowing, taste perception, vocalization, and also thermoregulation. Most of these functions are related to the morphology of the organ. In this work, we described for the first time the morphological, histochemical and lectin-histochemical characteristics of the tongue of the hystricomorph rodent Lagostomus maximus (plains viscacha). The viscacha's tongue was classified as type I and exhibited features typical of herbivorous mammals. Its histological characteristics were similar to those reported for other mammals with comparable diets, showing filiform, fungiform and vallate papillae. Particularly, the number of vallate papillae varied from what has been observed in other hystricomorphs and eutherians, suggesting that this feature may be species-specific. Foliate papillae were absent. Lingual glands consists of serous acini superficially located, and mucous acini which were situated more deeply. These glandular locations also varied among different hystricomorphs. The glycosylation pattern of the acini in the viscacha's tongue resembles those reported in other species; however, since there is currently no available data related to the lectin-histochemical pattern for eutherian species, comparisons were not possible. The glandular secretions may participate in food mastication and breakdown, as well as in the cleaning of certain papillae. Our results contribute to a better understanding of diverse digestive features of this species, including diet and mastication.