Lectin histochemical study on the olfactory bulb of the newt, Cynops pyrrhogaster

The function and/or morphological features of the vomeronasal olfactory system remain unclear in aquatic animals, although the system appeared first in urodeles based on phylogenic data. We examined the lectin binding patterns in the olfactory bulb of a semi-aquatic urodele, the Japanese red-bellied newt, Cynops pyrrhogaster, using 22 different lectins. Eleven of the lectins showed specific binding to the nerve fibres and glomeruli in the olfactory bulb. Among these, Wheat germ agglutinin, pokeweed and peanut agglutinin preferentially bound the main olfactory bulb, reflecting variation in the expression of glycoconjugates between the main and accessory olfactory bulbs. By contrast, the types of lectins bound to the Cynops olfactory bulb were considerably different from those reported in other urodele families. These results suggest a histochemical distinction between the main and accessory olfactory bulbs, and that glycoconjugate expression may differ significantly among urodele families.