Record Details

Werner, Yehudah L
Temperature effects on inner-ear sensitivity in six species of iguanid lizards
Journal of Herpetology
Journal Article
Dipsosaurus dorsalis
Temperature effects on the function of the inner ear in Anolis lionotus, Crotaphytus collaris, Dipsosaurus dorsalis, Sceloporus occidentalis, Uma scoparia and Uta stansburiana are defined and correlated to the same lizards' known ecological temperature preferenda. Pure tones (50·15,000 Hz) were presented to the anaesthetized lizard's external ear. The sound intensity required to elicit a standard response of the alternating potentials of the cochlea was plotted (db versus frequency). A total of 348 curves were obtained, mostly within 20-40 c. In all species, the basic shape of the sensitivity curve persists at all temperatures, showing the greatest sensitivity in a central region that varies with the species within a range of 400-4000 Hz. In this region multiple peaks of sensitivity occur at low temperatures. With a rise in temperature the sensitivity at high frequencies improves markedly, that at low frequencies somewhat deteriorates. Between these regions, the peak of sensitivity and adjacent maxima and minima become more sensitive and shift to higher frequency. A unimodal curve results – “the II optimal sensitivity function”. In each species the lowest temperature yielding the optimal sensitivity function equals the ecological preferred body temperature. Similar temperature effects occur when, after extirpation of the middle ear apparatus, the stapedial footplate is stimulated directly by aerial or mechanical vibrations. Hypotheses for their origin are discussed. Hearing appears to be best at ecological optimal temperature. Greater care in regulating and reporting experimental temperatures and other biological parameters is advocated.