In search of diVerences between the two types of sensory cells innervating spider slit sensilla (Cupiennius salei Keys.)

摘要

The metatarsal lyriform organ of the spider Cupiennius salei is a vibration detector consisting of 21 cuticular slits supplied by two sensory cells each, one ending in the outer and the other at the inner slit membrane. In search of functional diVerences between the two cell types due to diVerences in stimulus transmission, we analyzed (1) the adaptation of responses to electrical stimulation, (2) the thresholds for mechanical stimulation and (3) the representation of male courtship vibrations using intracellular recording and staining techniques.Single- and multi-spiking receptor neurons were found among both cell types,which showed high-pass Wlter characteristics. Below 100-Hz threshold, tarsal deXections were between 1° and 10°. At higher frequencies, they decreased down to values as small as 0.05°, corresponding to 4.5-nm tarsal deXection in the most sensitive cases. DiVerent slits in the organ and receptor cells with slow or fast adaptation did not diVer in this regard. When stimulated with male courtship vibrations,both types of receptor cells again did not diVer signiWcantly regarding number of action potentials, latency and synchronization coeYcients. Surprisingly, the diVerences in dendrite coupling were not reXected by the physiological responses of the two cell types innervating the slits.