Biophysical heterogeneity in the tympanic membrane of the Asian water monitor lizard, Varanus salvator

摘要

The tympanic membrane of the Asian water monitor lizard (Varanus salvator) is functionally divided into dorsal, more pliant, and ventral, stiffer regions. The ventral portion is smaller and vibrates significantly (up to 12x) more to the same stimuli. The pattern of tympanic membrane response is frequency-dependent with a peak response centered around 2.5 kHz, and a lower response at 0.5 kHz. This pattern of tympanic membrane frequency response coincides with the high- and low-frequency ranges of the varanid auditory response. The functional relationship between the tympanic heterogeneity and the internally coupled ears of the varanid auditory system is uncertain, as is the exact role of the tympanum in modulating pharyngeal pressure. The middle ear dynamics of Varanus salvator, and likely those of other squamates, are more complex than previously reported.