ITHACA, N.Y. -- Without enough estrogen-like hormone in their systems, female plainfin midshipman fish turn a deaf ear to the alluring love songs of the males. And, according to Cornell University biologists, a similar steroid-sensitive response could underlie changes in the hearing sensitivity of humans. The biologists experimentally boosted levels of the steroid hormone in non-reproductive females of the fish species Porichthys notatus, temporarily altering their inner-ear auditory mechanism so they could hear the males' hum-like advertisement call that says, essentially: "I have prepared a nest under a rock in shallow water, so deposit your eggs for me to fertilize, and together we'll make beautiful small fry."

Altering steroid hormone levels did not change the reproductive status of the females; the eggs they carried were still immature and were not ready to be deposited, even if the hearing-enhanced females had been attracted to the males' nests. Rather, the Cornell biologists found a hormonal trigger for a complex auditory system.

Andrew H. Bass, the Cornell professor of neurobiology and behavior who led the research team that reported the findings in the July 16, 2004, issue of Science ("Steroid-dependent Auditory Plasticity Leads to Adaptive Coupling of Sender and Receiver") comments: "We suspected that enhancing the sensitivity of the females' ears to the upper harmonics of the males' hums should improve detection of their vocalizations. Upper harmonics propagate farther in shallow water environments like those where midshipman males build nests and sing their love song to attract females.

"But the females can't process this vital information and respond appropriately if they can't hear it. Steroid hormones appear to provide a key molecule that leads to shifts in the hearing sensitivity of females," Bass said.

Paul M. Forlano, a graduate student in Bass's lab, and David L. Deitcher, one of Bass's colleagues at Cornel
'"/>

Contact: Roger Segelken
hrs2@cornell.edu
607-255-9736
Cornell University News Service
15-Jul-2004

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