COMPLEX TIBIAL ORGANS IN THE FORELEGS, MIDLEGS, AND HINDLEGS OF THE BUSH-CRICKET GAMPSOCLEIS-GRATIOSA (TETTIGONIIDAE) - COMPARISON OF THE PHYSIOLOGY OF THE ORGANS

Complex tibial organs are found in all three pairs of legs of tettigon iids and consist of the subgenual organ, the intermediate organ, and t he crista acoustica. In the forelegs of most tettigoniids, the tibial organs in association with tympanic membrane, tracheal tube, and spira cle are highly developed sound transmitting structures (tympanal organ s), but not so in the mid and hind pairs of legs (tympanal organs). We have studied the electrophysiology of the atympanal organs and in par ticular of the intermediate organ and the crista acoustica using extra cellular recordings to obtain summed responses to vibratory and acoust ic stimuli and single cell recordings from the different receptor cell s.Significant differences in the responses of the receptor cells of th e tympanal and atympanal organs were found predominantly in the case o f sound stimulation. Whereas the crista acoustica and the distal part of the intermediate organ of the foreleg are very sensitive auditory r eceptor organs, the same organs in the mid- and hindlegs appear to res pond not at all or only unspecifically to airborne sound stimuli. By c ontrast, the responses to vibratory stimuli are similar if not identic al. The functions of the subgenual organs in all six legs are basicall y identical, but the function of the middle and distal parts of the cr ista acoustica in the mid- and hindlegs remains to be characterized. ( C) 1994 Wiley-Liss, Inc.