ELECTROPHYSIOLOGY OF LIZARD COCHLEA

The cochlear potentials of several species of lizard were measured, in particular Trachysaurus rugosus. Auditory responses were measured both at the round window and in scala tympani. The round window membrane was found to have considerable effect on the recorded potentials causing an attenuation and differentiation of summating potential (SP). Geckos and pygopodids produced a large (30 μv) neural response and smaller SP and cochlear microphonics (CM) while skinks, varanids and agamids produced a large SP (20 μv) and smaller neural response and CM. In T. rugosus, frequency response for a constant SP indicated a probable best hearing range of 750-3000 cycle/sec. The Q10 for SP varied from 1.5 at high sound pressures to 3.5 at low sound pressures. When pairs of tone pips were applied to T. rugosus the amplitude and latency of the neural response to the second tone pip were greatly increased. The SP in T. rugosus was very sensitive to season, increasing ten-fold during spring. © 1969.