Modes of stimulation of the teleost ear

Microphonic potentials were recorded from the inner ears of a catfish (Ictalurus punctatus) and an African mouthbreeder (Tilapia macrocephala) in response to underwater sound stimulation and direct vibration of the head. The shape of the vibratory isopotential functions of frequency was similar in both species up to 600 HZ. Above 600 HZ, the sensitivity of Ictalurus continued to increase to 4000 HZ while the sensitivity of Tilapia declined. Deflation of the swim bladder did not affect the response to vibration in either species, the response of Tilapia to the underwater sound stimulus being minimal and unaffected by removal of the swim bladder. Ictalurus was pressure-sensitive to above 4000 HZ, ther being a significant dedline in the response with deflation of the swimbladder.