畑中 恒夫

Odor responses of the single olfactory cells on the antennae in the dung beetle (Geotrupes auratus) were studied. The receptor cells well responded respectively to a part or all of the five characteristic odors (2-butanone, phoenol, p-cresol, indole, skatole) from cattle's dung. The olfactory cells could be divided into the following two types of responses. (1)R-Type I: Only 2-butanone was effective for all cells of this type. The impulse frequency increased with increase of stimulus concentration. The slope of the dose-resoonse curve was relatively steep. Threshold concentration of the individual olfactory cells varied in the value. Impulse discharges of some of the cells to 2-butanone disappeared of decreased by stimulus of the mixture with other four odors. (2s) R-Type II: All cells in this type responded to 2-butanone but the responses to the other four odors were different with cells. The dose-response curve to 2-butanone of this type of cells resembled with that of R-Type I. Threshold values of the cells to the odors were differed from each other. 2-butanone in the dung may be volatilized faster than the other four odors, it is thus suggested that the dung beetles may be oriented to 2-butanone odor contained in their food.動物の生得的行動を開発する「鍵刺激」として、視覚的に単純な形や色、聴覚的な一定周波数の音、また、物理的な接触刺激などの存在が知らされている。一方、化学的、特に嗅覚的な匂いも鍵刺激として重要であり、鱗翅目昆虫の性フェロモンは、配偶行動を開発する、種に固有な匂いであることは良く知られている。・・・

The fine structure of the vomeronasal mucosa in the Reeve's turtle which lives in water and sometimes on land was observed with an electron microscope. The mucosa was situated in the ventral region of the nasal cavity. The terminal end of the vomeronasal receptor cell dendrites extending to the mucosal surface did not protrude from the mucosal free surface as in the case of olfactory cells; the dendrites contained many mitochondria. The dendrites had only microvilli in the distal part; these were 0.1-0.2 μm in thickness and 3-5 μm in length. The number of microvilli considered to arise from one dendrite was from 15-100. The functional role of the vomeronasal organ in the Reeve's turtle was discussed.