The three-dimensional analysis of gustatory papillae and its taste buds on the tongue of the wild-living hare (Lepus europaeus), European rabbit (Oryctolagus cuniculus), and domestic rabbit (Oryctolagus cuniculus f. domestica)

Abstract

Correlative light microscopy (LM), scanning electron microscopy (SEM), and three-dimensional (3D) analysis in two wild-living species, i.e. hare and European rabbit, and domesticated rabbit, provide the first microstructural characteristics of fungiform papillae (Fu's), vallate papillae (Vp), and foliate papillae (Fo). The 3D reconstruction method of 2D histosections revealed types of internal connective tissue cores (CTCs) and allowed visualisation of spatial distribution and number of taste buds (Tbs). By the almost even morphology of Fu, in the wild-living lagomorphs, CTCs were columnar- or ballon-like, while in the domestic rabbit, balloon-like. CTCs of Vp were flower-like with some species variation. The Fo displayed the structure of three collagenous laminae across all species. 3D models of papillae revealed the species-specific traits in the distribution of Tbs in rows, stripes or kinds of dispersion. Quantitative data showed that in the wild-living lagomorphs, there was a higher number of Tbs on the ventral surface of the apex, the area of first contact with food, and its preselection. Among the species studied, the hare exhibited the highest number of Tbs in Vp and Fo, while within rabbits, domestic rabbits had more Tbs than their wild counterparts. Notably, the posterior part of the tongue, containing approximately 96 % of total Tbs, reflects the importance of intensive taste perception during chewing. The total number of Tb estimated in gustatory papillae in hares was 17,509, whereas in domestic and European rabbits was approximately 25 % and 43 % lower, respectively. Our finding contrasts with 3D analyses conducted previously on wild-living and domesticated ruminant herbivores.

Keywords: 3D reconstruction; LM and SEM; gustatory papillae; lagomorphs; taste buds.