Detection of sound and substrate vibration is crucial for the survival and reproduction of many animals, particularly insects. Bushcrickets (Orthoptera, Tettigoniidae), developed a large mechanosensory organ complex in their legs to detect such stimuli. As demonstrated by various studies in the past, sensilla in distinct functional groups form specialized vibratory organs (the subgenual organ and the accessory organ), respond sensitively to both vibration and sound (in the intermediate organ [IO]), or mediate hearing (in the crista acustica [CA]; the tympanal hearing organ). In their recent publication, Zhantiev and Korsunovskaya addressed auditory and vibratory sensitivity in the IO and the CA in two species of bushcrickets, using single-cell recording and staining of sensory neurons from their soma in an isolated foreleg. Their main finding was that not only the IO but also the complete CA contains bimodal sensilla responding with high sensitivity to both sound and vibration, which would be a true change in the paradigm of how the auditory/vibratory sense in Orthoptera works. In addition, they revealed vibratory tuning of the IO sensilla, which differs largely from that in previous studies. We propose three major experimental causes of such discrepancies: calibration, experiments with isolated legs, and differences in the sites of recording. To judge the causes of these discrepancies more adequately, a detailed comparison of methods and a number of control experiments are needed. This will deepen our understanding of sensory adaptations and specialization of insect mechanosensory organs to stimuli entering the system by different input pathways.
Keywords: Ensifera; hearing; insect; mechanical coupling; neurophysiology; vibration sense.
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