@article {58010,
	title = {A Tympanal Insect Ear Exploits a Critical Oscillator for Active Amplification and Tuning},
	journal = {Current Biology},
	volume = {23},
	year = {2013},
	month = {Jan-10-2013},
	pages = {1952 - 1957},
	abstract = {<p>A dominant theme of acoustic communication is the partitioning of acoustic space into exclusive, species-specific niches to enable efficient information transfer. In insects, acoustic niche partitioning is achieved through auditory frequency filtering, brought about by the mechanical properties of their ears [1]. The tuning of the antennal ears of mosquitoes [2] and flies [3], however, arises from active amplification, a process similar to that at work in the mammalian cochlea [4]. Yet, the presence of active amplification in the other type of insect ears\&mdash;tympanal ears\&mdash;has remained uncertain [5]. Here we demonstrate the presence of active amplification and adaptive tuning in the tympanal ear of a phylogenetically basal insect, a tree cricket. We also show that the tree cricket exploits critical oscillator-like mechanics, enabling high auditory sensitivity and tuning to conspecific songs. These findings imply that sophisticated auditory mechanisms may have appeared even earlier in the evolution of hearing and acoustic communication than currently appreciated. Our findings also raise the possibility that frequency discrimination and directional hearing in tympanal systems may rely on physiological nonlinearities, in addition to mechanical properties, effectively lifting some of the physical constraints placed on insects by their small size [6] and prompting an extensive reexamination of invertebrate audition.</p>
},
	issn = {09609822},
	doi = {10.1016/j.cub.2013.08.028},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0960982213010348https://api.elsevier.com/content/article/PII:S0960982213010348?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0960982213010348?httpAccept=text/plain},
	author = {Mhatre, Natasha and Daniel Robert}
}
@article {57643,
	title = {Low-pass filters and differential tympanal tuning in a paleotropical bushcricket with an unusually low frequency call},
	year = {2013},
	abstract = {<p>Low-frequency sounds are advantageous for long-range acoustic signal transmission, but for small animals they constitute a challenge for signal detection and localization. The efficient detection of sound in insects is enhanced by mechanical resonance either in the tracheal or tympanal system before subsequent neuronal amplification. Making small structures resonant at low sound frequencies poses challenges for insects and has not been adequately studied. Similarly, detecting the direction of long-wavelength sound using interaural signal amplitude and/or phase differences is difficult for small animals. Pseudophylline bushcrickets predominantly call at high, often ultrasonic frequencies, but a few paleotropical species use lower frequencies. We investigated the mechanical frequency tuning of the tympana of one such species, Onomarchus uninotatus, a large bushcricket that produces a narrow bandwidth call at an unusually low carrier frequency of 3.2 kHz. Onomarchus uninotatus, like most bushcrickets, has two large tympanal membranes on each fore-tibia. We found that both these membranes vibrate like hinged flaps anchored at the dorsal wall and do not show higher modes of vibration in the frequency range investigated (1.5\&ndash;20 kHz). The anterior tympanal membrane acts as a low-pass filter, attenuating sounds at frequencies above 3.5 kHz, in contrast to the high-pass filter characteristic of other bushcricket tympana. Responses to higher frequencies are partitioned to the posterior tympanal membrane, which shows maximal sensitivity at several broad frequency ranges, peaking at 3.1, 7.4 and 14.4 kHz. This partitioning between the two tympanal membranes constitutes an unusual feature of peripheral auditory processing in insects. The complex tracheal shape of O. uninotatus also deviates from the known tube or horn shapes associated with simple band-pass or high-pass amplification of tracheal input to the tympana. Interestingly, while the anterior tympanal membrane shows directional sensitivity at conspecific call frequencies, the posterior tympanal membrane is not directional at conspecific frequencies and instead shows directionality at higher frequencies.</p>
},
	keywords = {auditory, katydid, laser vibrometry, Onomarchus uninotatus, Orthoptera, pseudophylline, tettigoniid, trachea, tympanum},
	doi = {10.1242/jeb.078352},
	url = {http://jeb.biologists.org/cgi/doi/10.1242/jeb.078352https://syndication.highwire.org/content/doi/10.1242/jeb.078352},
	author = {Rajaraman, K. and Mhatre, N. and Jain, M. and Postles, M. and Rohini Balakrishnan and Daniel Robert}
}
