Comparación de la respuesta auditiva del tallo cerebral entre rana Catesbiana (Anura: Ranidae) y Sceloporus torquatus (Sauria: Phrynosomatidae)

Abstract

The sense of hearing in reptiles and amphibians is poorly understood. The auditory end-organ has undergone major evolutionary changes related to transition from an aquatic to a terrestrial environment. Therefore, terrestrial reptiles show an efficient auditory system in comparison with amphibians. The present study was carried out in order to compare the auditory responses between Rana catesbiana and Sceloporus torquatus. Using brainstem auditory evoked potentials (BAEP) auditory responses were obtained in both specimens. BAEP were recorded by means of one active needle electrode placed on the vertex. The common and ground electrodes were located on the opposite side of the head around the external opening of the ear. Stimuli consisted of alternated clicks delivered in a sound-buffered chamber through a loudspeaker placed at distance of 70 cm in front of the head of the animal. The animals were anesthetized by temporary cooling to 4°C. Differences in the pattern of BAEP responses were observed between R. catesbiana and S. torquatus. These results suggest that the sense of hearing is certainly under evolutionary changes.