Download Anatomical and functional recovery of the goldfish saccule following

PHYSIOLOGY AND BIOCHEMISTRY
Mapping frequency-dependent hair cell loss in the goldfish saccule
JULIE B. SCHUCK*1, BRIAN D. ROGERS1, MICHAEL E. SMITH1, 1Department of Biology,
Western Kentucky University, Bowling Green, KY 42101
Mammalian and avian auditory hair cells display tonotopic mapping of frequency along the
length of the cochlea and basilar papilla. It is not known whether the auditory hair cells of fish
possess a similar tonotopic organization in the saccule, the primary auditory receptor in many
teleosts. To investigate this question, we determined the location of hair cell damage in fish
saccules following exposure to specific frequencies. We exposed groups of six goldfish
(Carassius auratus) to one of four pure tones (100 Hz, 800 Hz, 2000 Hz, and 4000 Hz) at 176 dB
re: 1 µPa for 48 hrs. The saccules of each fish were labeled with phalloidin in order to visualize
hair cell bundles. The hair cell bundles were counted at 19 specific points in each saccule to
determine the extent and location of hair cell loss. All noise-exposed fish exhibited significant
hair cell loss following noise exposure. The location of hair cell loss varied along the length of
the saccule in a graded manner with the frequency of noise exposure, with lower and higher
frequencies damaging the more caudal and rostral regions of the saccule, respectively. This data
suggests that the frequency discrimination ability of goldfish is at least partially driven by
peripheral tonotopy in the saccule.
In a previous study, goldfish exposed to white noise exhibited significant hair cell loss in the
central and caudal saccule, as well as significant hearing loss across most of their hearing
bandwidth. Birds and mammals have a tonotopic relationship in the sensory epithelia of their
ears (ie. hair cell regions are frequency-specific). It is not known whether the auditory hair cells
of fish possess a similar tonotopic organization in the saccule, the primary auditory receptor in
many teleosts, but recent data suggest that this is the case for goldfish.