Neurobiology and modeling of cuticular hair sensilla of scorpions: Response characteristics and implications for biomimetic design

In this thesis, the neurobiology of mechanoreceptive sensilla on the pectines of the scorpion Pandinus cavimanus was examined. The morphology of the pectines, the innervation and morphology of the sensilla as well as their response characteristics were analyzed. Based on the neurobiological results, mechanoreceptive bristles of arthropods were characterized from a technical point of view. A biomimetic, physical model of the mechanoreceptive hairs was developed that exhibited several important characteristics of the biological examples. Following main results were achieved: 1. On the pectines of scorpions, several types of cuticular receptors are located. Of these receptors, only the chemoand mechanosensory peg sensilla have been studied in detail so far. This thesis extends the knowledge of the pectines by an analysis of the mechanoreceptive long hair sensilla (pectinal hair sensilla, PHS). A detailed description of their morphology, innervation and response characteristics is given. • The morphological studies showed that the hairs are robust sensilla with lengths of 300-1400 μm and diameters of 30 μm at the base, tapering to about 10 μm at the tip. The sockets allow wide range of movements, certainly within the range of 20-30 degrees. • Each sensillum is associated with a cluster of 4-6 bipolar sensory cells, approximately 70-100 μm below the hair socket. • It was possible to record up to three different action potential classes (units) which could be distinguished by size, response characteristics and conduction velocity. Two of these units were analyzed in more detail. The response characteristics showed two phasic units, one large (L) and one small (S), coding the velocity of a stimulus. One medium-sized unit (M) showed phasictonic characteristics, also coding the duration of a stimulus. The deflection threshold for all units was determined to be approximately 1◦. The velocity response curves showed that the M-unit responded best to angular velocities