Phonotactic specificity of the cricketTeleogryllus oceanicus: intensity-dependent selectivity for temporal parameters of the stimulus

Summary

We have investigated the effects of alterations of several temporal parameters of auditory stimuli, as well as of stimulus intensity changes, on the attractiveness of these stimuli to femaleTeleogryllus oceanicus, as measured by monitoring sound-elicited flight steering responses. AlthoughT. oceanicus has a rhythmically complex calling song, females are attracted by a simpler model consisting of regularly repeating sound pulses. We have found that the two major temporal features of this model, sound pulse duration and pulse repetition rate, are both important for eliciting phonotactic steering responses.

Stimuli with altered temporal features had intensity thresholds indistinguishable from the control stimulus (Fig. 3). The majority of crickets, however, ceased to respond to the altered stimuli when the stimulus intensity was sufficiently increased (Figs. 4–7). In some cases, intensity increases resulted in a reversal of the steering response from positive to negative (Fig. 10). Effects of altered temporal parameters were also apparent at lower stimulus intensities, where the amplitudes of steering responses to stimuli with altered parameters were smaller than those in response to the control stimulus (Figs. 8, 9).

We considered the possibility that the cessation of responsiveness to stimuli with altered temporal features was due to a temporal pattern-specific diminution of binaural cues for sound localization at high intensities. Experiments performed with unilaterally deafened crickets (Fig. 11) led us to conclude that this was not the case, and that our findings instead reflect the properties of the song recognition mechanism.