title: Unexpected dynamic up-tuning of auditory organs in day-flying moths.
abstract: In certain nocturnal moth species the frequency range of best hearing shifts to higher frequencies during repeated sound stimulation. This could provide the moths with a mechanism to better detect approaching echolocating bats. However, such a dynamic up-tuning would be of little value for day-flying moths that use intra-specific acoustic communication. Here we examined if the ears of day-flying moths provide stable tuning during longer sound stimulation. Contrary to our expectations, dynamic up-tuning was found in the ear of the day-flying species Urania boisduvalii and Empyreuma pugione. Audiograms were measured with distortion-product otoacoustic emissions (DPOAEs). The level of the dominant distortion product (i.e. 2f1-f2) varied as a function of time by as much as 45 dB during ongoing acoustic stimulation, showing a systematic decrease at low frequencies and an increase at high frequencies. As a consequence, within about 2 s of acoustic stimulation, the DPOAEs audiogram shifted from low to high frequencies. Despite the up-tuning, the range of best audition still fell within the frequency band of the species-specific communication signals, suggesting that intra-specific communication should not be affected adversely. Up-tuning could be an ancestral condition in moth ears that in day-flying moths does not underlie larger selection pressure.
authors.affiliation: Research Group in Bioacoustics and Neuroethology, Faculty of Biology, Havana University, 25 St. No. 455, Vedado, CP. 10400, Havana, Cuba, emanuel_mora@yahoo.com.
authors.forename: Emanuel C
authors.initials: EC
authors.lastname: Mora
authors.forename: Ariadna
authors.initials: A
authors.lastname: Cobo-Cuan
authors.forename: Frank
authors.initials: F
authors.lastname: Macías-Escrivá
authors.forename: Manfred
authors.initials: M
authors.lastname: Kössl
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D004423:Ear / Q000502:physiology; D005260:Female; D005426:Flight, Animal; D006309:Hearing / Q000502:physiology*; D008297:Male; D009036:Moths / Q000502:physiology*; D017440:Photoperiod; D013018:Sound Spectrography; D013045:Species Specificity