ULTRASTRUCTURE AND FUNCTION OF SETAE-BEARING CUTANEOUS SENSORY ORGANS IN TARENTOLA-MAURITANICA L (REPTILIA-GEKKONIDAE)

The ultrastructural organization of the setae-bearing sensilla was elucidated with regard to their position on the scales, their surface structure and their presumable functions. These sensilla had a thickened basis caused by enveloping epithelial cells. Each organ was situated above the appropriate nerve. Entering the organ, this nerve ramified into axons, which continued between 2 great central-positioned cells of epidermal origin as far as to the top of them. The central cells ended beneath the distal layer of the outer epidermal generation. Leaving the central cells at their top, the axons invaginated into this layer and formed, corresponding to the number of axons, 10-15 terminal vesicles. The terminals are, according to recent ultrastructural findings, presumably able to transduce (mechanical) stimuli. The terminals were embedded in masses of tonofibrils, especially at their bases. At the flattened top of the organ long setae were situated centrally but without any direct contact to lower parts of the organ. Mechanical bending of the setae deforms the top of the sensillum which is recorded by the terminal receptors described. The movement of the toes was controlled by the sensilla of the scales surrounding the toes, which was important for climbing. A decisive function of these organs was the perception of water or other wet substrata. When touching this, the geckos will immediately roll up their toes thus protecting their bristles of the footpads from sticking together.