No neural evidence for dynamic auditory tuning of the A1 receptor in the ear of the noctuid moth, Noctua pronuba

Asi, Navdeep S.; Fullard, James H.; Whitehead, Scott; Dawson, J. W.

doi:10.1007/s00359-009-0471-2

Cited by 4 publications

(4 citation statements)

References 17 publications

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“…However, this phenomenon would represent a significant adaptation only if the biophysical responses were reflected by similar shifts in neural responses as encoded by the auditory receptors. Unfortunately, a previous attempt to find a neuronal correlate of the tympanal uptuning of the ear in N. pronuba failed to find any changes in the moth's auditory frequency sensitivity [Asi et al, 2009]. So far, the moth auditory system seems unable to follow frequency shifts and two-tone bats could profit from this.…”

Section: Discussionmentioning

confidence: 97%

Tone-Deaf Ears in Moths May Limit the Acoustic Detection of Two-Tone Bats

et al. 2014

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Frequency alternation in the echolocation of insectivorous bats has been interpreted in relation to ranging and duty cycle, i.e. advantages for echolocation. The shifts in frequency of the calls of these so-called two-tone bats, however, may also play its role in the success of their hunting behavior for a preferred prey, the tympanate moth. How the auditory receptors (e.g. the A₁ and A₂ cells) in the moth's ear detect such frequency shifts is currently unknown. Here, we measured the auditory responses of the A₁ cell in the noctuid Spodoptera frugiperda to the echolocation hunting sequence of Molossus molossus, a two-tone bat. We also manipulated the bat calls to control for the frequency shifts by lowering the frequency band of the search and approach calls. The firing response of the A₁ receptor cell significantly decreases with the shift to higher frequencies during the search and approach phases of the hunting sequence of M. molossus; this could be explained by the receptor's threshold curve. The frequency dependence of the decrease in the receptor's response is supported by the results attained with the manipulated sequence: search and approach calls with the same minimum frequency are detected by the moth at the same threshold intensity. The two-tone bat M. molossus shows a call frequency alternation behavior that may enable it to overcome moth audition even in the mid-frequency range (i.e. 20-50 kHz) where moths hear best.

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Section: Discussionmentioning

confidence: 97%

Tone-Deaf Ears in Moths May Limit the Acoustic Detection of Two-Tone Bats

et al. 2014

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“…The observed up-tuning could be an inherent consequence of the biophysics of the auditory receptor organ and is not related to the relevance of sounds, or it could serve a general energy saving function. It has been suggested that the dynamic changes observed in the tympanic resonance could be a result of changes in the vibrational characteristics of the tympanum after the tensioning of thoracic musculature upon hearing loud sounds (Asi et al 2009). In addition, active sensillar processes or flight musculature that might affect tympanal tension or respiratory oscillations that affect the air pressure behind the tympanum could cause an upward shift in the auditory characteristic frequencies of the moth ear.…”

Section: Discussionmentioning

confidence: 99%

“…The discovery of a dynamic up-tuning of the tympanum in the moth Noctua pronuba (Windmill et al 2006) when exposed to bat-like acoustic signals indeed suggested that predation pressure could have resulted in an evolutionary response of the prey. Tympanal dynamic tuning, however, was not obvious in the neuronal auditory responses of N. pronuba (Asi et al 2009) and different physiological conditions during experiments (i.e. changes on the tracheal system or muscular control) could be an explanation for the discrepancy between the mechanical and the neuronal responses of this ear.…”

Section: Introductionmentioning

confidence: 87%

Unexpected dynamic up-tuning of auditory organs in day-flying moths

et al. 2015

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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.

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“…In characterizing moth audition, however, it is important to keep in mind that not every mechanical event implicates a neuronal correlate. For example, the dynamic tuning in resonant frequency that takes place in the mechanical vibration response of the stigma in N. pronuba when stimulated with high-intensity sounds does not seem to affect the neuronal response of the A1 auditory receptor (Asi et al, 2009). There is no doubt that further research into the tympanum of the moth will continue to demonstrate that it is not a simple system.…”

Section: Using the Distortion-products Mechanical Audiograms To Charamentioning

confidence: 99%

Mechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations

Mora

Cobo-Cuan

Macías-Escrivá

et al. 2013

Journal of Experimental Biology

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SUMMARYThe 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 Q 10dB 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.

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No neural evidence for dynamic auditory tuning of the A1 receptor in the ear of the noctuid moth, Noctua pronuba

Cited by 4 publications

References 17 publications

Tone-Deaf Ears in Moths May Limit the Acoustic Detection of Two-Tone Bats

Tone-Deaf Ears in Moths May Limit the Acoustic Detection of Two-Tone Bats

Unexpected dynamic up-tuning of auditory organs in day-flying moths

Mechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations

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