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Brain Behav Evol

Title:		Histological Properties of Main and Accessory Olfactory Bulbs in the Common Hippopotamus
Author(s):		Kondoh D; Watanabe K; Nishihara K; Ono YS; Nakamura KG; Yuhara K; Tomikawa S; Sugimoto M; Kobayashi S; Horiuchi N; Kobayashi Y; Sasaki M; Kitamura N;
Address:		"Laboratory of Veterinary Anatomy, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan"
Journal Title:		Brain Behav Evol
Year:		2017
Volume:		20170830
Issue:		3
Page Number:		224 - 231
DOI:		10.1159/000479180
ISSN/ISBN:		1421-9743 (Electronic) 0006-8977 (Linking)
Abstract:		"The olfactory system of mammals comprises a main olfactory system that detects hundreds of odorants and a vomeronasal system that detects specific chemicals such as pheromones. The main (MOB) and accessory (AOB) olfactory bulbs are the respective primary centers of the main olfactory and vomeronasal systems. Most mammals including artiodactyls possess a large MOB and a comparatively small AOB, whereas most cetaceans lack olfactory bulbs. The common hippopotamus (Hippopotamus amphibius) is semiaquatic and belongs to the order Cetartiodactyla, family Hippopotamidae, which seems to be the closest extant family to cetaceans. The present study evaluates the significance of the olfactory system in the hippopotamus by histologically analyzing the MOB and AOB of a male common hippopotamus. The MOB comprised six layers (olfactory nerve, glomerular, external plexiform, mitral cell, internal plexiform, and granule cell), and the AOB comprised vomeronasal nerve, glomerular, plexiform, and granule cell layers. The MOB contained mitral cells and tufted cells, and the AOB possessed mitral/tufted cells. These histological features of the MOB and the AOB were similar to those in most artiodactyls. All glomeruli in the AOB were positive for anti-Galphai2, but weakly positive for anti-Galphao, suggesting that the hippopotamus vomeronasal system expresses vomeronasal type 1 receptors with a high affinity for volatile compounds. These findings suggest that the olfactory system of the hippopotamus is as well developed as that of other artiodactyl species and that the hippopotamus might depend on its olfactory system for terrestrial social communication"
Keywords:		Animals Artiodactyla/*anatomy & histology Male Neurons Olfactory Bulb/*anatomy & histology/*cytology Olfactory Nerve/physiology Olfactory Pathways/anatomy & histology/physiology Smell/physiology Accessory olfactory bulb Cetartiodactyla G protein Glomeruli;
Notes:		"MedlineKondoh, Daisuke Watanabe, Kenichi Nishihara, Kaori Ono, Yurie S Nakamura, Kentaro G Yuhara, Kazutoshi Tomikawa, Sohei Sugimoto, Miki Kobayashi, Saori Horiuchi, Noriyuki Kobayashi, Yoshiyasu Sasaki, Motoki Kitamura, Nobuo eng Switzerland 2017/08/30 Brain Behav Evol. 2017; 90(3):224-231. doi: 10.1159/000479180. Epub 2017 Aug 30"