Chemical Senses Advance Access originally published online on July 20, 2009
Chemical Senses 2009 34(7):581-593; doi:10.1093/chemse/bjp040
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Histological Properties of the Nasal Cavity and Olfactory Bulb of the Japanese Jungle Crow Corvus macrorhynchos
1 Department of Comparative and Behavior Medicine, Nippon Veterinary and Life Science University, Tokyo, Japan 2 School of Agriculture, Utsunomiya University, Utsunomiya, Japan 3 Laboratory of Neurobiology, National Institute of Agrobiological Sciences, Tsukuba, Japan 4 Department of Basic Techniques and Facilities, Tokyo Metropolitan Institute for Neuroscience, Tokyo, Japan
Correspondence to be sent to: Makoto Yokosuka, Department of Comparative and Behavior Medicine, Faculty of Veterinary Medicine, Nippon Veterinary and Life Science University, 1-7-1 Kyonan-Cho, Musashino, Tokyo 180-8602, Japan. e-mail: mayokosuka{at}nvlu.ac.jp
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Abstract |
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The nasal cavity and olfactory bulb (OB) of the Japanese jungle crow (Corvus macrorhynchos) were studied using computed tomography (CT) and histochemical staining. The nasal septum divided the nasal cavity in half. The anterior and maxillary conchae were present on both sides of the nasal cavity, but the posterior concha was indistinct. A small OB was present on the ventral surface of the periphery of the cerebrum. The OB–brain ratio—the ratio of the size of the OB to that of the cerebral hemisphere—was 6.13. The olfactory nerve bundles projected independently to the OB, which appeared fused on gross examination. Histochemical analysis confirmed the fusion of all OB layers. Using a neural tracer, we found that the olfactory nerve bundles independently projected to the olfactory nerve layer (ONL) and glomerular layer (GL) of the left and right halves of the fused OB. Only 4 of 21 lectins bound to the ONL and GL. Thus, compared with mammals and other birds, the jungle crow may have a poorly developed olfactory system and an inferior sense of olfaction. However, it has been contended recently that the olfactory abilities of birds cannot be judged from anatomical findings alone. Our results indicate that the olfactory system of the jungle crow is an interesting research model to evaluate the development and functions of vertebrate olfactory systems.
Key words: computed tomography, fused olfactory bulb, jungle crow, juxtaglomerular cells, lectin, nasal cavity
Accepted 10 June 2009