Structure of the temporal organ of the Japanese house centipede, Thereuonema hilgendorfi Verhoeff.

The ultrastructure of the temporal organ of the Japanese house centipede, Thereuonema hilgendorfi Verhoeff (Chilopoda), has been examined. The temporal organ of this species is known to be a carbon dioxide receptor. It appears externally as a small protuberance with a small opening (5 μm) on its summit. There is a small cuticle-lined cavity beneath the protuberance, and a mushroom-shaped projection protrudes from the base of the cavity into its interior. Below the cavity is an encapsulated, bulb-shaped cellular mass (sensory bulb), which contains about ten receptor cells and 100 supporting cells. Nuclei of both receptor and supporting cells occur basally in the sensory bulb. Each receptor cell has a single dendrite, which gives rise to a pair of sensory cilia. The cilia enter the mushroom-shaped projection, and course along the inner surface of its calyx. The supporting cells have distal processes, which accompany the cilia into the calyx. The surface cuticle of the calyx consists of a fabric of fibrils, but in not layered like the cuticular integument. The fabric is permeable to water. The observed structure is discussed in relation to carbon dioxide reception and in comparison with the structure of olfactory receptors and hygroreceptors.