ASA 125th Meeting Ottawa 1993 May

4pAB1. Effect of intense tone stimulation on the anatomy of the peripheral auditory system in bony fishes.

Mardi C. Hastings

Dept. of Mech. Eng., Ohio State Univ., 206 W. 18th Ave., Columbus, OH 43210

Results of current and previous studies by M. C. Hastings et al. [J. Acoust. Soc. Am. Suppl. 1 79, S80 (1986); J. Acoust. Soc. Am. Suppl. 1 80, S75 (1986); and J. Acoust. Soc. Am. Suppl. 1 81, S7 (1987)] and P. S. Enger [Hearing and Sound Communication in Fishes (Springer-Verlag, New York, 1981), pp. 243--255] to determine the effect of intense tone stimulation on the anatomy of the peripheral auditory system in bony fishes are summarized. In these studies different species of fish were exposed to pure tones at frequencies between 200 and 1000 Hz at different sound pressure levels for 1 to 4 h. The sensory epithelia in the saccule and legena were then examined using scanning electron microscopy to assess damage to hair cells. These experimental evaluations indicated (1) the possibility of a gross place-type mechanism for frequency discrimination and (2) a possible breakdown of the Weberian apparatus in goldfish (Carassius auratus) at extremely high sound pressure levels because the primary site of hair cell damage switched from the saccule to lagena. A mathematical model for the dynamic motion of the swimbladder and Weberian ossicles has been developed based on the work of R. McN. Alexander [J. Exp. Biol. 38, 747--757 (1961)], which includes viscoelastic properties of the tissue. The model supports previous experimental observations and indicates that motion is no longer transmitted to the saccule when the system is excited by sufficiently high sound pressure levels. [Work supported in part by ONR and NIH.]