Distortion-product otoacoustic emissions from the tympanic organ in two noctuoid moths

• Published in: Journal of Comparative Physiology 1998-10, Vol.183 (4), p.525-531
• Main Authors: Coro, F., K ssl, M.
• Format: Article
• Language: English
• Subjects: Auditory organs; Auditory system; Butterflies & moths; Distortion; Emission measurements; Emissions; Mechanical properties; Organs; Otoacoustic emissions; Physical characteristics; Species; Spectral emissivity; Spectral sensitivity; Vertebrates
• ISSN: 0340-7594; 1432-1351
• DOI: 10.1007/s003590050278

Distortion-product otoacoustic emissions were measured from the tympanic organ of Ascalapha odorata (Noctuidae, Erebinae) and Empyreuma affinis (=pugione) (Arctiidae, Ctenuchinae) during stimulation with two pure tones of different frequency ( f1, f2) within a frequency range between 5 and 60 kHz. The cubic distortion-product that appears at a frequency of 2f1-f2 showed the largest amplitude and could be used to obtain “distortion audiograms”. In such audiograms, the maximal distortion-product otoacoustic emission levels were measured for stimulus frequencies that correspond to lowest A1-cell thresholds in each of the two species. Newly emerged E. affinis showed very low levels of the 2f1-f2 distortion, most of which were within the noise range. In contrast to vertebrate distortion-product otoacoustic emissions, in neither of the species could an optimum f2/f1 ratio be easily defined, and small ratios were sufficient to induce the distortions. We conclude that the ears of the two moth species exhibit distinctly non-linear mechanical properties. Distortion-product otoacoustic emissions are a good non-invasive method for studying the spectral response characteristics of the mechanics of their auditory organs, despite the fact that their morphological characteristics are very different from those in vertebrates.