ORIGINAL ARTICLE Seasonal Changes in the Histochemical Properties of the Olfactory Epithelium and Vomeronasal Organ in the Japanese Striped Snake, Elaphe quadrivirgata D. Kondoh 1,2 , Y. Yamamoto 1,3 , N. Nakamuta 1,2 , K. Taniguchi 4 and K. Taniguchi 1,2 * Addresses of authors: 1 Department of Basic Veterinary Science, The United Graduate School of Veterinary Science, Gifu University,1-1 Yanagido, Gifu, Gifu 501-1193, Japan; 2 Laboratory of Veterinary Anatomy, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan; 3 Laboratory of Veterinary Biochemistry and Cell Biology, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan; 4 Laboratory of Veterinary Anatomy, Kitasato University School of Veterinary Medicine, 23-35-1 Higashi, Towada, Aomori 034-8628, Japan Introduction In many tetrapods, the olfactory system is divided into two systems: the main olfactory system and the vomero- nasal system; the former senses odoriferous molecules, and the latter detects species-specific substances (e.g. pheromones) (Brennan, 2001). The peripheral receptor organs of the olfactory system and vomeronasal system are the olfactory epithelium and vomeronasal epithelium projecting to the main olfactory bulb and accessory olfac- tory bulb, respectively (Taniguchi et al., 2011). The olfac- tory and vomeronasal epithelia are covered with mucous layers to prevent these epithelia from drying and infec- tion. In addition, odoriferous molecules are perceived as olfactory stimuli after being dissolved in the mucous layers. Among all tetrapods, snakes have the most developed vomeronasal organ (Halpern, 1987; Døving and Trotier, 1998). Unlike many other tetrapods, the snake vomerona- sal system perceives not only species-specific substances but it is also perceptive of odoriferous molecules from their preys and thus mediates predatory activities (Halpern, 1987; Martı´nez-Marcos et al., 2002). Snakes sample envi- ronmental substances by the tongue-flicking and deliver concentrated chemicals to the vomeronasal organ (Halp- ern, 1987; Martı´nez-Marcos et al., 2002). In snakes, the vomeronasal epithelium is unique, consisting of four cell types, viz. the receptor cells, supporting cells, basal cells *Correspondence: Tel.: +(81) 19 621 6207; fax: +(81) 19 621 6209; e-mail: anatomia@iwate-u.ac.jp With 5 figures and 5 tables Received April 2011; accepted for publication July 2011 doi: 10.1111/j.1439-0264.2011.01101.x Summary Seasonal changes in the histochemical properties of the vomeronasal and olfac- tory epithelia of the Japanese striped snake were examined in four seasons, viz. the reproductive, pre-hibernating, hibernating and post-hibernating seasons. In the vomeronasal and olfactory supporting cells, secretory granules were much more abundant in the hibernating season than in the other seasons. In the vomeronasal and olfactory receptor cells, the lipofuscin granules were much fewer in the post-hibernating season than in the other seasons. In histochemi- cal studies with 21 lectins, several lectins stained the vomeronasal and olfactory epithelia (receptor cells, supporting cells and free border) more weakly in the hibernating season than in the reproductive season. However, all lectins stained both epithelia in the hibernating season after sialic acid removal in a similar manner as in the reproductive season after sialic acid removal. These lectin his- tochemical studies indicate that sialic acid residues in the vomeronasal and olfactory epithelia are more numerous in the hibernating season than in the reproductive season. The results suggest that during hibernation, the vomero- nasal and olfactory receptor cells possibly undergo rapid cell turnover, and that during this time, the vomeronasal and olfactory epithelia are securely protected from pathogens by an innate immune defence system. Anatomia Histologia Embryologia ª 2011 Blackwell Verlag GmbH 41 Anat. Histol. Embryol. 41 (2012) 41–53