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/s00359-014-0914-202554nas 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.05646502386nas a2200229 4500008004100000245010400041210006900145520161400214653001401828653001001842653002201852653002901874653002201903653000901925100001701934700001801951700002301969700001401992700001602006700001402022856012002036 2013 eng d00aMechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations0 aMechanical tuning of the moth ear distortionproduct otoacoustic 3 a

The mechanical tuning of the ear in the moth Empyreuma pugione was investigated by distortion-product otoacoustic emissions (DPOAE) and laser Doppler vibrometry (LDV). DPOAE audiograms were assessed using a novel protocol that may be advantageous for non-invasive auditory studies in insects. To evoke DPOAE, two-tone stimuli within frequency and level ranges that generated a large matrix of values (960 frequency–level combinations) were used to examine the acoustic space in which the moth tympanum shows its best mechanical and acoustical responses. The DPOAE tuning curve derived from the response matrix resembles that obtained previously by electrophysiology, and is V-shaped and tuned to frequencies between 25 and 45 kHz with low Q10dB values of 1.21±0.26. In addition, while using a comparable stimulation regime, mechanical distortion in the displacement of the moth’s tympanal membrane at the stigma was recorded with a laser Doppler vibrometer. The corresponding mechanical vibration audiograms were compared with DPOAE audiograms. Both types of audiograms have comparable shape, but most of the mechanical response fields are shifted towards lower frequencies. We showed for the first time in moths that DPOAE have a pronounced analogy in the vibration of the tympanic membrane where they may originate. Our work supports previous studies that point to the stigma (and the internally associated transduction machinery) as an important place of sound amplification in the moth ear, but also suggests a complex mechanical role for the rest of the transparent zone.

10aAudiogram10aDPOAE10aEmpyreuma pugione10alaser Doppler vibrometry10amechanical tuning10amoth1 aMora, E., C.1 aCobo-Cuan, A.1 aMacias-Escriva, F.1 aPerez, M.1 aNowotny, M.1 aKossl, M. uhttp://jeb.biologists.org/cgi/doi/10.1242/jeb.085902https://syndication.highwire.org/content/doi/10.1242/jeb.08590202072nas a2200205 4500008004100000245008700041210006900128520133100197653001601528653002001544653002201564653001901586653002901605653001801634100002101652700002101673700002001694700002101714856013101735 2014 eng d00aProcessing of simple and complex acoustic signals in a tonotopically organized ear0 aProcessing of simple and complex acoustic signals in a tonotopic3 a

Processing of complex signals in the hearing organ remains poorly understood. This paper aims to contribute to this topic by presenting investigations on the mechanical and neuronal response of the hearing organ of the tropical bushcricket species Mecopoda elongata to simple pure tone signals as well as to the conspecific song as a complex acoustic signal. The high-frequency hearing organ of bushcrickets, the crista acustica (CA), is tonotopically tuned to frequencies between about 4 and 70 kHz. Laser Doppler vibrometer measurements revealed a strong and dominant low-frequency-induced motion of the CA when stimulated with either pure tone or complex stimuli. Consequently, the high-frequency distal area of the CA is more strongly deflected by low-frequency-induced waves than by high-frequency-induced waves. This low-frequency dominance will have strong effects on the processing of complex signals. Therefore, we additionally studied the neuronal response of the CA to native and frequency-manipulated chirps. Again, we found a dominant influence of low-frequency components within the conspecific song, indicating that the mechanical vibration pattern highly determines the neuronal response of the sensory cells. Thus, we conclude that the encoding of communication signals is modulated by ear mechanics.

10abushcricket10acrista acustica10aElectrophysiology10ainsect hearing10alaser Doppler vibrometry10aTettigoniidae1 aHummel, Jennifer1 aWolf, Konstantin1 aKössl, Manfred1 aNowotny, Manuela uhttps://royalsocietypublishing.org/doi/10.1098/rspb.2014.1872https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2014.187202436nas a2200229 4500008004100000022001400041245008800055210006900143260001600212300001600228490000800244520157900252653002701831653001901858653002701877653002901904653002001933653002301953100002501976700001902001856018602020 2016 eng d a0022-094900aFunctional relevance of acoustic tracheal design in directional hearing in crickets0 aFunctional relevance of acoustic tracheal design in directional  cMar-10-2017 a3294 - 33000 v2193 a

Internally coupled ears (ICEs) allow small animals to reliably determine the direction of a sound source. ICEs are found in a variety of taxa, but crickets have evolved the most complex arrangement of coupled ears: an acoustic tracheal system composed of a large cross-body trachea that connects two entry points for sound in the thorax with the leg trachea of both ears. The key structure that allows for the tuned directionality of the ear is a tracheal inflation (acoustic vesicle) in the midline of the cross-body trachea holding a thin membrane (septum). Crickets are known to display a wide variety of acoustic tracheal morphologies, most importantly with respect to the presence of a single or double acoustic vesicle. However, the functional relevance of this variation is still not known. In this study, we investigated the peripheral directionality of three co-occurring, closely related cricket species of the subfamily Gryllinae. No support could be found for the hypothesis that a double vesicle should be regarded as an evolutionary innovation to (1) increase interaural directional cues, (2) increase the selectivity of the directional filter or (3) provide a better match between directional and sensitivity tuning. Nonetheless, by manipulating the double acoustic vesicle in the rainforest cricket Paroecanthus podagrosus, selectively eliminating the sound-transmitting pathways, we revealed that these pathways contribute almost equally to the total amount of interaural intensity differences, emphasizing their functional relevance in the system.

10aacoustic communication10ainsect hearing10aInternally coupled ear10alaser Doppler vibrometry10aMatched filters10aSound localization1 aSchmidt, Arne, K. D.1 aRömer, Heiner uhttp://jeb.biologists.org/lookup/doi/10.1242/jeb.145524https://syndication.highwire.org/content/doi/10.1242/jeb.145524https://syndication.highwire.org/content/doi/10.1242/jeb.14552402345nas a2200265 4500008004100000022001400041245013100055210006900186260002000255300001600275490000800291520145900299653002301758653001701781653001701798653002901815653002901844653003001873100002001903700002401923700002401947700002001971700002801991856006002019 2017 eng d a0022-094900aChamber music: an unusual Helmholtz resonator for song amplification in a Neotropical bush-cricket (Orthoptera, Tettigoniidae)0 aChamber music an unusual Helmholtz resonator for song amplificat cSep-15-20172153 a2900 - 29070 v2203 a

Animals use sound for communication, with high-amplitude signals being selected for attracting mates or deterring rivals. High amplitudes are attained by employing primary resonators in sound producing structures to amplify the signal (e.g., avian syrinx). Some species actively exploit acoustic properties of natural structures to enhance signal transmission by using these as secondary resonators (e.g., tree-hole frogs). Male bush-crickets produce sound by tegminal stridulation and often use specialised wing areas as primary resonators. Interestingly, Acanthacara acuta, a Neotropical bush-cricket, exhibits an unusual pronotal inflation, forming a chamber covering the wings. It has been suggested that such pronotal chambers enhance amplitude and tuning of the signal by constituting a (secondary) Helmholtz resonator. If true, the intact system – when stimulated sympathetically with broadband sound – should show clear resonance around the song carrier frequency which should be largely independent of pronotum material, and change when the system is destroyed. Using laser Doppler vibrometry on living and preserved specimens, micro computed tomography, 3D printed models, and finite element modelling, we show that the pronotal chamber not only functions as a Helmholtz resonator due to its intact morphology but also resonates at frequencies of the calling song on itself, making song production a three-resonator system.

10aacoustic resonator10abioacoustics10abush-cricket10afinite element modelling10alaser Doppler vibrometry10amicro computed tomography1 aJonsson, Thorin1 aBrown, Kate, Robson1 aSarria-S, Fabio, A.1 aWalker, Matthew1 aMontealegre-Z, Fernando uhttp://jeb.biologists.org/lookup/doi/10.1242/jeb.160234