Taste Buds on the Lingual Papillae of the Lesser Japanese Mole and the Large Japanese Mole

Lesser Japanese mole (Mogera imaizumii) and large Japanese mole (Mogera wogura) are mammals belonging to the family Talpidae of the order Eulipotyphla, which feed mainly on earthworms and insects. The tongue is the first digestive organ to take in food, and many taste buds are distributed on the lingual papillae of the tongue. It has been reported that three types of lingual papillae are present on the tongue of Talpidae: fungiform papillae with taste buds, vallate papillae, and filiform papillae without taste buds. It is said that there is a difference in the distribution of fungiform papillae on the tongue between the lesser Japanese mole and the large Japanese mole. In addition, characteristics such as the number and size of taste buds across the tongue of these species have not yet been investigated. In this study, we investigated the morphological characteristics of the taste buds on the lingual papillae of the lesser Japanese mole and the large Japanese mole by using external morphological and histological observations, and compared the differences between the two species and those of other mammals to verify the characteristics of the taste buds of the Talpidae. Morphological observation of the lingual papillae of the large Japanese mole revealed that the fungiform papillae were scattered from the apex linguae to the corpus linguae, and were also found in the central part of the dorsum linguae, which was not observed by Kobayashi et al. (1983). The number of taste buds was confirmed to be 796 in the lesser Japanese mole and 459 in the large Japanese mole. The number of taste buds was very small compared to that of herbivorous mammals. The average size of the taste buds of the lesser Japanese mole was 37.9×28.1 µm for the fungiform papillae and 48.5×28.5 µm for the vallate papillae, while the average size of the taste buds of the large Japanese mole was 35.0×24.5 µm for the fungiform papillae and 40.1×30.2 µm for the vallate papillae. A comparison of the size of the taste buds of these two species revealed that the height of the vallate papillae was different, but the size of the taste buds was almost the same. However, the taste bud size of the two species in this study was clearly smaller than that of the mouse, but it is thought that the ratio of taste cells in the taste bud as well as the taste bud size reflects differences in taste processing. In the future, it is necessary to investigate the expression of gustatory receptors in the taste buds using immunohistochemical staining, and to compare it with other species of Soricidae and Erinaceidae species that have similar feeding habits.

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