Detection of substrate vibrations by salamanders: inner ear sense organ activity

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Abstract
Microphonic potentials were recorded from the inner ear of anesthetized adult and juvenile Notophthalmus viridescens, adult Plethodon cinereus and larval Ambystoma maculatum lying prostrate in air on a horizontally vibrating platform. At temperatures of 15-17.degree. C, responses were obtained from all groups over the frequency range 20 Hz to 500-650 Hz. At 20-22.degree. C, adult N. viridescens responded to 1100 Hz. Microphonics were produced over a maximum vibration amplitude range of 0.011-35 .mu.m peak-to-peak displacement, but the range limits varied at individual frequencies. A lower range limit, or higher sensitivity, was found for adult N. viridescens at 20-22.degree. C than at 15-17.degree. C. The amplitude of the response increased nonlinearly with increasing vibration amplitude and did not adapt to a steady-state vibration. Microphonics were double the stimulus frequency, indicating that the receptors have hair cells of opposite polarization. Inner ear sense organ activity can occur in salamander ears in response to gross substrate vibration. The variety of response characteristics indicates a versatile sensory system.