Neuromuscular activity during stridulation in the cricketTeleogryllus commodus

Abstract

The central nervous control of singing behavior in male crickets (Teleogryllus commodus) has been investigated using electromyograms (EMG) and intracellular recording techniques. A preparation is described in which the species-specific stridulatory behavior can be elicited with the normal chirp and trill pattern. Stridulation was induced routinely in intact crickets as well as in crickets prepared for intracellular analysis (Fig. 1). p] 1. EMG recordings were taken from opener muscle 99 (subalar) and closer muscle 90 (remotor coxae) of intact singing animals. The intervals between bursts in both opener and closer muscles vary with cycle duration (opener to opener) and maintain their phase constancy. During the chirp the closer muscle activity (burst duration, number of spikes per burst) increases considerably as compared with the trill, but opener muscle activity remains unchanged (Fig. 2). 2. The preparation necessary for the intracellular analysis of motor patterns involved deafferentation of the thoracic ganglia, in which the stridulatory pattern generator resides. This resulted in an increase of the period duration in chirp and trill by about 20% (Fig. 3). Otherwise, only minor changes in the motor pattern were noted after deafferentation except for a marked increase in opener burst duration (Fig. 3), which did not affect the phase relationship described for the intact preparation. 3. The investigation of synaptic input to identified motoneurons 99 (opener) and 90 (closer) revealed differences in the burst patterns in these neurons during the chirp as compared with the trill, but also some common synaptic components (Figs. 6 and 7). This suggests that some interneurons are activated during the chirp and trill, whereas others are only activated during the chirp.