Turtle shells as an auditory receptor.

Evoked responses were obtained from the brainstem of seven box turtles (T. carolina) using air conducted stimuli and also vibratory stimuli applied directly to the carapace. Both stimuli elicited similar neural electrical responses that differed chiefly in sensitivity. The vibratory responses were lower in threshold and higher in amplitude than responses to air conducted clicks. Further, simultaneous masking of vibratory clicks by air conducted noise had negligible effects, whereas vibratory masking completely suppressed the responses to airborne sound, suggesting that the turtle ear is differentially sensitive to sound and vibration. Spinal blocking of somatic pathways had negligible effects on the vibratory-evoked responses, suggesting that the latter originate in the auditory system and are stimulated by bone conduction.