Unexpected dynamic up-tuning of auditory organs in day-flying moths
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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.
KeywordsAudiogram DPOAEs Dynamic tuning Moths
Distortion-product otoacoustic emissions
Fast Fourier transform
Laser Doppler vibrometry
Sound pressure level
We thank students at Havana University for collecting animals in the field. We thank the three anonymous reviewers for their helpful comments. This work was supported by the Institute Partnership Stipendium from the Alexander von Humboldt Foundation to the Research Groups of ECM and MK. Capture, holding and experimental procedures used in this study were approved by the animal care committees of the University of Frankfurt and University of Havana.
Conflict of interest
The authors declare that they have no conflict of interest.
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- Adams WB (1972) Mechanical tuning of the acoustic receptor of Prodenia eridania (Cramer) (Noctuidae). J Exp Biol 57:297–304Google Scholar
- Barro A, Vater M, Pérez M, Coro F (2009) Surface structure of sound emission organs in Urania moths. In: Gorb SN (ed) Functional surfaces in biology. Springer, pp 189–199Google Scholar
- Coro F (1986) El órgano timpánico de Urania boisduvalii (Lepidoptera: Uraniidae). Cien Biol 15:3–17Google Scholar
- Fernández Y, Pérez M, Mora EC (2013) Is accoustic communication essential in the mating behavior of Empyreuma pugione (Erebidae: Arctiinae)? Revista Cubana de Ciencias Biológicas 2:32–37Google Scholar
- Fullard JH, Otero LD, Orellana A, Surlykke A (2000) Auditory sensitivity and diel flight activity in neotropical Lepidoptera. Ann Entomol Soc Am 93:956–965. doi:10.1603/0013-8746(2000)093[0956:ASADFA]2.0.Co;2Google Scholar
- Pérez Álvarez M, Barro A (2014) Functional characteristics of the tympanic organ of Urania boisduvalii (Lepidoptera: Geometroidea: Uraniidae) and its behavioral role. Revista Cubana de Ciencias Biológicas 3:81–94Google Scholar
- StatSoft Inc. (2001) STATISTICA for Windows 6.0. Statsoft Inc., Tulsa, OklahomaGoogle Scholar
- Takanashi T, Nakano R, Surlykke A, Tatsuta H, Tabata J, Ishikawa Y, Skals N (2010) Variation in courtship ultrasounds of three Ostrinia moths with different sex pheromones. PloS One 5. doi: 10.1371/journal.pone.0013144