Neuroethology of the katydid T-cell. II. Responses to acoustic playback of conspecific and predatory signals.
Although early work on the tettigoniid T large fiber suggested that it might mediate early-warning and escape behavior in katydids, the majority of research thereafter has focused on the ability of the T-cell to detect, localize and/or discriminate mate-calling song. Interestingly, T-cell responses to conspecific song are rarely examined for more than a few seconds, despite the fact that many katydids sing for minutes or hours at a time. In this paper, the second of a pair examining the physiology of the T-cell in Neoconocephalus ensiger, we recorded T-cell responses using longer-duration playbacks (3 min) of conspecific song (Katydid signal 30 ms syllables, 9-25 kHz bandwidth, 12-15 kHz peak frequency) and two types of bat-like ultrasound, a 10 ms, 80->30 kHz frequency-modulated sweep (Bat 10 signal) and a 30 ms, 80->30 kHz frequency-modulated sweep (Bat 30 signal). Spiking responses were distinctly biased towards the short-duration ultrasonic signal, with more spikes per pulse, at a shorter spike latency and at a higher instantaneous firing frequency to the Bat 10 signal than to the Katydid signal or, surprisingly, to the Bat 30 signal. The ability of the T-cell to encode the temporal pattern of the stimulus was particularly striking. Only for the predatory bat signals did T-cell spiking faithfully copy the stimulus; playbacks of conspecific song resulted in significantly weaker spiking responses, particularly in male katydids. The results demonstrate that responses from the T-cell alone may be sufficient for katydids to discriminate biologically relevant signals pertinent to the phonotactic behavior patterns involved in mate attraction and predator avoidance.
Faure
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Section of Neurobiology and Behavior, Cornell University, Seeley G. Mudd Hall, Ithaca, NY 14853-2702, USA. paul4@u.washington.edu
Hoy
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D000161:Acoustic Stimulation; D000818:Animals; D002685:Chiroptera; D005260:Female; D006110:Grasshoppers / Q000166:cytology / Q000502:physiology*; D006309:Hearing / Q000502:physiology*; D007395:Interneurons / Q000502:physiology; D008297:Male; D011235:Predatory Behavior; D012726:Sexual Behavior, Animal; D014828:Vocalization, Animal