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(and unbeknownst to Dick), was it known that goldfish had a wider hearing range (to over 3 kHz) and better hearing sensitivity than most other fish species.
Over the course of his career, Dick conducted a wide range of investigations using psychophysical and physiological methods to ask a plethora of questions that sought to com- pare hearing of the goldfish with that of other vertebrates. Indeed, Dick was among the early investigators of hearing who combined psychophysical with neurophysiological measures to explore auditory processing. Of course, Dick also delved into other species (Fay et al., 1974; Lombard et al., 1981), making especially important contributions to understanding hearing in the toadfish (Opsanus tau; e.g., Zeddies et al., 2012; Edds-Walton et al., 2015), but those are other stories, some of which are described by Sisneros (2016) and by Yost and Popper (2016).
The Goldfish Auditory Periphery
Dick viewed his studies of auditory function in the gold- fish as providing crucial information about the peripheral neural contribution to hearing. The inner ear of most fishes is typical of that of other vertebrates in having three semicircular canals as well as otolith organs. Of the latter, goldfish have a saccule and utricle as well as a third oto- lith organ, the lagena, which is not present in amniotes (reptiles, birds, and mammals). Each of the otolith organs has sensory hair cells that are the same as found in other vertebrates, and it is clear that these cells evolved in the earliest fishes (e.g., Coffin et al., 2004).
However, unlike most other vertebrates, the majority of bony fishes do not have otoconia in their otolith organs. Instead, the otoconial material in each end organ is in the form of a solid mass, the otolith, composed of calcium carbonate. These otoliths sit above the cilia of the sensory hair cells, separated by an otolithic membrane.
The fish inner ear does not have the biomechanical struc- tures found in mammals. Stimulation of the hair cells comes from relative motion between the otolith mass, which is far denser than other fish tissues, and the rest of the fish’s body, including the sensory epithelia (for a dis- cussion of fish hearing and inner ear function see Popper and Hawkins, 2018, 2019; Schulz-Mirbach et al., 2019).
What the Ear Tells the Brain
The mammalian biomechanical structures provide a pow- erful form of the spectral/temporal processing of sound, which is transduced via the vibration of the stereocilia of cochlear hair cells into neural action potentials in the auditory nerves that synapse with the hair cells. Dick argued that because his data showed that goldfish tend to respond to changes in the parameters of sound such as frequency and intensity in ways similar to how mam- mals respond, then the biomechanical properties of the mammalian ear are probably not the only way for vibra- tion to be transduced into useful information for hearing (e.g., Fay, 1969, 1970a,b, 1972). Dick also showed that auditory nerve responses measured in goldfish were very similar to those measured in mammalian auditory nerve fibers (e.g., Fay, 1978a,b; Fay and Olsho, 1979). Thus, his work revealed those aspects of the auditory nerve responses (i.e., the temporal pattern of action potentials) that provided the basis for hearing in the goldfish and in vertebrates in general.
The Databook
The view that goldfish hearing shared many similarities with that of other vertebrates eventually led to Dick’s now
famous book, Hearing in Vertebrates: A Psychophysical Databook (Fay, 1988). Over many years, Dick gathered all of the articles that he could find related to psychophysical measures of auditory function in all vertebrates (and as far as we know, he found them all). He then developed a system to provide a standard format for presenting what Dick believed to be the relevant psychophysical data from each and every one of these studies. He devoted thou- sands of hours to using a clever, manual caliber system designed to trace the data from figures in articles, resulting in numbers in a spread sheet that formed the basis of his structured presentation of the results. Bill Yost has vivid memories of Dick hunched over the apparatus hours on end, tracing the figures from an article he had just received.
As this project developed and Dick published the Data- book, he began to appreciate that his earlier observations of the similarity in goldfish “hearing” data with that from other vertebrates was not unique to the goldfish. He was firmly convinced that vertebrates shared many common features in hearing sound. Dick compiled figures comparing
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