Page 73 - Summer2022

and testosterone be involved in the maintenance of high- frequency hearing sensitivity in humans? Studies of the effects of estrogen on midshipman hearing might provide the answer someday. What inspired you to work in this area of scholarship? I became inspired to work in the research area of hor- mones and behavior during my PhD working in the lab of Timothy “Tim” Tricas at FIT. I had the opportunity to travel to Mexico with Tim to investigate the role of electroreception during mating in the round stingray (Urobatis halleri). We found that male stingrays use their extremely sen- sitive electric sense to detect and locate reproductive females buried in the shallow lagoons, which were the breeding grounds for this species. Females emit a complex weak bioelectric field from their gills that is modulated during ventilation by the rhythmic move- ments of their gill slits and spiracles (a muscular valve that intakes water into the gill chamber). We discovered that the electroreceptor system of male stingrays was “tuned” to 1-2 Hz, which matched the low-frequency “signature” signal produced by buried females during ventilation. This matched filter of the male’s electrore- ceptor system with the female’s electrical signal only occurs during the mating season when androgen levels are elevated. These studies that combined animal behav- ior and electrophysiology piqued my interest in learning more about the neural basis of behavior and initiated my career path on becoming trained as a neuroethologist. Of all your contributions during your career, which are you most proud of and why? Perhaps I am most proud of the research that was per- formed during my postdoc training in the laboratory of Andrew “Andy” Bass at Cornell University, Ithaca, New York. What started as an “odd observation” eventually led to an important discovery of the mechanism that is responsible for seasonal changes in hearing sensitivity in the plainfin midshipman. The purpose of my postdoc was to work on the audi- tory system of the plainfin midshipman fish. My initial interests were to examine how the auditory sensitivity of the midshipman changes during development from early juvenile to adult stages. During my first full summer in the Bass lab, I trav- eled to the University of California, Davis, Bodega Marine Laboratory in Bodega Bay to collect juvenile midshipman and characterize ontogenetic changes in the auditory sensitivity of the midshipman sac- cule. Unfortunately, I arrived too early in the summer season to collect fish that were large enough to obtain recordings from. This enabled an alternative fortunate opportunity. Instead of waiting around for my fish to grow large enough to record from, Andy suggested that I try to characterize the sensitivity of the sac- cule in adult females that had recently spawned and from females that were still gravid (full of eggs) to determine if the presence of eggs affected the auditory sensitivity of the saccule. Earlier, Andy had shown in midshipman behavioral experiments that reproductive gravid females perform phonotaxis to the playback and sound source of a syn- thetic male midshipman advertisement (mate) call because gravid females are highly motivated to spawn. However, females that had recently spawned showed no interest in the call. Could it be that “spent” females (void of eggs) are just no longer motivated to respond to the call or could there be a change in their auditory sensitivity to the call? As I started collecting data on the auditory sensitivity of saccule in reproductive females, I noticed something odd. The auditory tuning profiles of the saccule in reproduc- tive females did not match the saccular tuning profiles that the Bass lab had obtained in a previous study on midshipman fish that had been housed over the winter back at Cornell. The saccule of reproductive females (whether gravid or not) appeared to have a greater sen- sitivity to higher frequencies within their hearing range compared with previous recordings of “winterized” fish. After many calibration checks and the retesting of my equipment, we concluded that it wasn’t the equipment but something different about the fish! Could there really be seasonal changes in midshipman auditory sensitivity related to the female’s reproductive cycle? The observed seasonal changes in the electrosen- sitivity of adult elasmobranch fishes and in other fishes such as weakly electric fishes were one thing, but in the auditory system? Such changes in the auditory sensitiv- ity of adult animals had never been documented before. Summer 2022 • Acoustics Today 73