EPIDERMAL FINE-STRUCTURE OF THE TOE TIPS OF SPHAERODACTYLUS-CINEREUS (REPTILIA, GEKKONIDAE)

This paper deals with epidermal structures of the sphaerodactyline gec ko Sphaerodactylus cinereus: adhesive pads, cutaneous sensilla and int raepidermal axon terminals. The adhesive pad is restricted to a single terminal scale and bears approximately 6,000 setae. The setae are com plex, hair-like structures which branch and sub-branch up to five time s. The terminal ends are shaped like inverted cones. They provide the friction which enables the gecko to walk even on vertical glass-plates . Cutaneous sensilla of supposed mechanoreceptive function are found i n groups of three or four at the anterior free edge of all dorsal and distal scales of the digit. The sensillum consists of a circular plate let in an epidermal depression bordered by an annular furrow and two o r three bristles in a central position. Discoid axon terminals in the digital scales are located between relatively stiff structures: the co rneous layers of the epidermis and a layer of tonofibrillar bundles. T he axon terminals are hypothesized to be sensitive to the internal pre ssure depending on hyperextension of the toe.