23 0 0 0 OA イソアワモチ背眼のレンズ細胞のレンズ構築と光受容能
Cellular composition of the lens of the dorsal eye in Onchidium verruculatum (Opisthobranch, Gastropoda) was investigated by light microscope and the photoresponsiveness of the lens cells and their identities were examined by means of a fluorescent dye microelectrode technique. A pear-shaped lens located in the center of the dorsal eye was composed of several lens cells and ensheathed entirely with connective tissue. Number, shape, size and arrangement of constituent cells were considerably varied in individual lenses. In most lenses, an upper principal part and a lower accessory part could be distinguished, each of which was composed of a group of lens cells and surrounded by glia-like cells. The principal part with a flat bottom contained 1-8 cells and occupied more than half of the lens, beneath which the accessory part containing 0-9 cells adjoined and formed the spherical bottom of the whole lens. The size of the lens was almost linearly related to that of the dorsal eye itself, and it was noted that the larger the lens, the more complex the cell composition. In 63% of the lenses, the principal part was formed by a single large lens cell. Occasionally, free lens cells occurred outside the lens proper. All the lens cells, independent of their location, were provided with rhabdomerric microvilli and responded to light with a characteristic pattern of slow depolarization. It was suggested that lens cells in the Onchidium dorsal eye play double roles, that of a photoreceptor individually and of a dioptric apparatus en masse.