Meeting Abstract

3.5  Monday, Jan. 4  A Neuroethological Analysis of Ultrasonic Communication in an Endemic Bornean Frog ARCH, V.S.*; GRAFE, T.U.; SIMMONS, D.D.; NARINS, P.M.; University of California, Los Angeles; University of Brunei Darussalam; University of California, Los Angeles; University of California, Los Angeles varch@ucla.edu

Huia cavitympanum, an endemic Bornean frog, is the first amphibian known to emit exclusively ultrasonic (i.e., > 20 kHz) vocal signals. To test the hypothesis that these frogs use purely ultrasonic vocalizations for intraspecific communication, we performed playback experiments with male frogs in their natural calling sites. We found that the frogs respond with increased calling to broadcasts of conspecific calls containing only ultrasound. The field study was complemented by electrophysiological recordings from the auditory midbrain. These measurements revealed that the frog’s auditory system is broadly tuned over a wide frequency range, with peak sensitivity occurring above 20 kHz. Our results demonstrate that H. cavitympanum is the first non-mammalian vertebrate described to communicate with purely ultrasonic acoustic signals. To explore the morphological underpinnings of the species’ extraordinary high-frequency sensitivity, we are using immunohistochemistry to fluorescently label hair cell components of the frogs’ inner-ear auditory organs. With confocal microscopy, we are able to visualize the labeled organs in 3-dimensions. Comparisons between the auditory epithelia of H. cavitympanum and Rana pipiens, a frog with a more typical anuran hearing range, reveal differences in a number of inner-ear morphometrics including hair cell number and length. These differences may permit insights into the mechanistic foundations of amphibian high-frequency detection.