01910nas a2200181 4500008004100000245007300041210006900114520135500183653001001538653001101548653002901559653001101588653001301599100002001612700002101632700002001653856005501673 2014 eng d00aMechanical basis of otoacoustic emissions in tympanal hearing organs0 aMechanical basis of otoacoustic emissions in tympanal hearing or3 a

Tympanal hearing organs of insects emit dis- tortion–product otoacoustic emissions (DPOAes), which in mammals are used as indicator for nonlinear cochlear amplification, and which are highly vulnerable to manipu- lations interfering with the animal’s physiological state. Although in previous studies, evidence was provided for the involvement of auditory mechanoreceptors, the source of DPOAe generation and possible active mechanisms in tympanal organs remained unknown. Using laser Dop- pler vibrometry in the locust ear, we show that DPOAes mechanically emerge at the tympanum region where the auditory mechanoreceptors are attached. Those emission- coupled vibrations differed remarkably from tympanum waves evoked by external pure tones of the same frequency, in terms of wave propagation, energy distribution, and loca- tion of amplitude maxima. Selective inactivation of the auditory receptor cells by mechanical lesions did not affect the tympanum’s response to external pure tones, but abol- ished the emission’s displacement amplitude peak. These findings provide evidence that tympanal auditory recep- tors, comparable to the situation in mammals, comprise the required nonlinear response characteristics, which during two-tone stimulation lead to additional, highly localized deflections of the tympanum.

10aDPOAE10aInsect10alaser Doppler vibrometry10alocust10atympanum1 aMöckel, Doreen1 aNowotny, Manuela1 aKössl, Manfred uhttp://link.springer.com/10.1007/s00359-014-0914-201444nas a2200205 4500008004100000245006500041210006500106520072400171653002400895653002900919653001200948653002900960653001300989100001901002700002501021700002001046700002201066700001901088856013101107 2014 eng d00aEnergy localization and frequency analysis in the locust ear0 aEnergy localization and frequency analysis in the locust ear3 a

Animal ears are exquisitely adapted to capture sound energy and perform signal analysis. Studying the ear of the locust, we show how frequency signal analysis can be performed solely by using the structural features of the tympanum. Incident sound waves generate mechanical vibrational waves that travel across the tympanum. These waves shoal in a tsunami- like fashion, resulting in energy localization that focuses vibrations onto the mechanosensory neurons in a frequency-dependent manner. Using finite element analysis, we demonstrate that two mechanical properties of the locust tympanum, distributed thickness and tension, are necessary and sufficient to generate frequency-dependent energy localization.

10aenergy localization10afrequency discrimination10atension10atravelling flexural wave10atympanum1 aMalkin, Robert1 aMcDonagh, Thomas, R.1 aMhatre, Natasha1 aScott, Thomas, S.1 aRobert, Daniel uhttps://royalsocietypublishing.org/doi/10.1098/rsif.2013.0857https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2013.085702554nas a2200193 4500008004100000245007500041210006900116520185900185653001702044653004502061653001202106653002902118653001102147653001302158100001702171700002602188700002602214856012002240 2011 eng d00aNo evidence for DPOAEs in the mechanical motion of the locust tympanum0 aNo evidence for DPOAEs in the mechanical motion of the locust ty3 a

Distortion-product otoacoustic emissions (DPOAEs) are present in non-linear hearing organs, and for low-intensity sounds are a by-product of active processes. In vertebrate ears they are considered to be due to hair cell amplification of sound in the cochlea; however, certain animals lacking a cochlea and hair cells are also reported to be capable of DPOAEs. In the Insecta, DPOAEs have been recorded from the locust auditory organ. However, the site of generation of these DPOAEs and the physiological mechanisms causing their presence in the locust ear are not yet understood, despite there being a number of potential places in the tympanal organ that could be capable of generating DPOAEs. This study aimed to record locust tympanal membrane vibration using a laser Doppler vibrometer in order to identify a distinct place of DPOAE generation on the membrane. Two species of locust were investigated over a range of frequencies and levels of acoustic stimulus, mirroring earlier acoustic recording studies; however, the current experiments were carried out in an open acoustic system. The laser measurements did not find any evidence of mechanical motion on the tympanal membrane related to the expected DPOAE frequencies. The results of the current study therefore could not confirm the presence of DPOAEs in the locust ear through the mechanics of the tympanal membrane. Experiments were also carried out to test how membrane behaviour altered when the animals were in a state of hypoxia, as this was previously found to decrease DPOAE magnitude, suggesting a metabolic sensitivity. However, hypoxia did not have any significant effect on the membrane mechanics. The location of the mechanical generation of DPOAEs in the locust’s ear, and
therefore the basis for the related physiological mechanisms, thus remains unknown.

10abioacoustics10adistortion-product otoacoustic emissions10ahearing10alaser Doppler vibrometry10alocust10atympanum1 aMoir, H., M.1 aJackson, Joseph, Curt1 aWindmill, James, F.C. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.056465https://syndication.highwire.org/content/doi/10.1242/jeb.05646500422nas a2200109 4500008004100000245011500041210006900156300001200225490000600237100002800243856004100271 2017 eng d00aMorphological observations on a gynandromorph of Anacridium aegyptium (Linnaeus, 1764) (Orthoptera Acridiidae)0 aMorphological observations on a gynandromorph of Anacridium aegy a827-8320 v81 aAldini, Rinaldo, Nicoli uhttps://bio.acousti.ca/es/node/52765