Light microscopic observations of the vomeronasal organ of Habu, Trimeresurus flavoviridis.

Light microscopic observations of the vomeronasal organ (VNO) (Jacobson's organ) of Habu, Trimeresurus flavoviridis, revealed that the organ was encased in the os vomeris and the vomeronasal cartilage on either side of the nasal septum. Habu VNO was divided into a dome-shaped portion mainly composed of a sensory epithelium (SE) and a hemispherical mushroom body covered with a ciliated epithelium. A narrow lumen, leading to the oral cavity via the vomeronasal duct, was made between the mushroom body and the SE. The SE consisted of a supporting cell layer facing the lumen and the underlying sensory cell layer where a large number of cells piled up in columns. Vascular plexuses were found around the neck and bottom of the columns. Along the antero posterior axis of the VNO, the height of the columns reached its maximum in the middle of the dorsal and the median parts (over 300 micron), and gradually decreased toward lateral. Each column contained undifferentiated basal cells, sensory cells and satellite cells. Sensory cells had a round nucleus and prominent lipofuscin granules. The sensory cells were arrayed in a string-like arrangement. Cells situated in the neck region of columns contained a larger amount of lipofuscin granules. Distal processes of sensory cells passed through the cytoplasmic meshwork of supporting cells and terminated as small swellings. Aggregates of heterogeneous cell populations were observed in the antero lateral region of the dome. A number of pigment cells were seen in the epineurium and the perivascular regions of the dorsal and lateral VNOs. Goblet cells were present in the lateral boundary between the dome portion and the mushroom body. Present findings clarify the complex organization of the Habu VNO, and the occurrence of the sensory columns similar to those reported in other snakes.