Development of the Bowman's and Jacobson's glands in the Japanese reddish frog, Rana japonica.

The olfactory organs are equipped with their own associated glands, Bowman's glands (BG) of the olfactory epithelium (OE), and Jacobson's glands (JG) of the vomeronasal organ (VNO). Histology and ultrastructure of these glands in the adult were investigated in the Japanese reddish frog, Rana japonica, along with their development from hatching to the end of metamorphosis. In the adult, BG cells contained large, electron-opaque secretory granules, intensely PAS-positive by light microscopy, while JG cells contained middle-sized secretory granules with moderate electron density, only faintly PAS-positive. Embryologically, BG appeared within the OE at 44 days after hatch, increased in number and were situated in the lamina propria under the OE at 52 days after hatch. BG cells contained large, electron-opaque granules, and well-developed rER at this time. While, JG appeared much earlier than BG. The VNO appeared as a concave of the ventral part of the OE at 4 days after hatch, and JG appeared under the VNO at 10 days after hatch. JG cells contained well-developed rER at 12 days after hatch. Secretory granules appeared in a small number in JG at 24 days after hatch, and increased thereafter. These findings suggest that JG may take part in secretion earlier than BG in ontogeny.