Behavioral determination of frequency resolution in the ear of the cricket,Teleogryllus oceanicus

Abstract

1. We used the flying phonotactic behavior of tethered female Australian field crickets,Teleogryllus oceanicus, to measure frequency filtering (determined from CR-bands, critical bands, and “effective” bandwidths) in the auditory system at frequencies of 4.5, 20, 40 and 70 kHz. Till now such measurements have been made only in vertebrates. 2. In CR-band determinations the spectrum level of the noise at the masked threshold increased monotonically with increasing tone level (Fig. 2). At 20, 40 and 70 kHz the regression lines had slopes very close to 1 indicating that, at least over the intensity range tested (5–20 dB above tone threshold), the masking process is linear. At 4.5 kHz, however, the slope of the regression line was only 0.56 showing a strong non-linearity in the masking process at this frequency. Such a nonlinearity has not been found in vertebrates. 3. At 4.5 kHz the three measures of filter bandwidths, CR-band, critical band and “effective” bandwidth, were not significantly different from each other, whereas at 40 kHz the “effective” bandwidth was significantly smaller than CR-band and critical band. 4. The width of the CR-band filter around 4.5 kHz increases with tone intensity, an effect which has not been observed in vertebrates. 5. Both CR-bands and critical bands indicate that the cricket auditory system is sharply tuned around 4.5 kHz, may show some tuning at 40 kHz, and is completely untuned at 20 and 70 kHz. 6. These results are discussed with respect to frequency tuning at the single unit level in crickets.