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William E. Conner - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of tiger moth (Erebidae: Arctiinae) anti-bat sounds can be predicted from Tymbal morphology.
Frontiers in zoology, 2019Co-Authors: Nicolas J. Dowdy, William E. ConnerAbstract:Acoustic signals are used by many animals to transmit information. Variation in the acoustic characteristics of these signals often covaries with morphology and can relay information about an individual’s fitness, sex, species, and/or other characteristics important for both mating and defense. Tiger moths (Lepidoptera: Erebidae: Arctiinae) use modified cuticular plates called “Tymbal organs” to produce ultrasonic clicks which can aposematically signal their toxicity, mimic the signals of other species, or, in some cases, disrupt bat echolocation. The morphology of the Tymbal organs and the sounds they produce vary greatly between species, but it is unclear how the variation in morphology gives rise to the variation in acoustic characteristics. This is the first study to determine how the morphological features of Tymbals can predict the acoustic characteristics of the signals they produce. We show that the number of striations on the Tymbal surface (historically known as “microTymbals”) and, to a lesser extent, the ratio of the projected surface area of the Tymbal to that of the thorax have a strong, positive correlation with the number of clicks a moth produces per unit time. We also found that some clades have significantly different regression coefficients, and thus the relationship between microTymbals and click rate is also dependent on the shared ancestry of different species. Our predictive model allows the click rates of moths to be estimated using preserved material (e.g., from museums) in cases where live specimens are unavailable. This has the potential to greatly accelerate our understanding of the distribution of sound production and acoustic anti-bat strategies employed by tiger moths. Such knowledge will generate new insights into the evolutionary history of tiger moth anti-predator defenses on a global scale.
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Characteristics of tiger moth (Erebidae: Arctiinae) anti-bat sounds can be predicted from Tymbal morphology
Frontiers in Zoology, 2019Co-Authors: Nicolas J. Dowdy, William E. ConnerAbstract:Background Acoustic signals are used by many animals to transmit information. Variation in the acoustic characteristics of these signals often covaries with morphology and can relay information about an individual’s fitness, sex, species, and/or other characteristics important for both mating and defense. Tiger moths (Lepidoptera: Erebidae: Arctiinae) use modified cuticular plates called “Tymbal organs” to produce ultrasonic clicks which can aposematically signal their toxicity, mimic the signals of other species, or, in some cases, disrupt bat echolocation. The morphology of the Tymbal organs and the sounds they produce vary greatly between species, but it is unclear how the variation in morphology gives rise to the variation in acoustic characteristics. This is the first study to determine how the morphological features of Tymbals can predict the acoustic characteristics of the signals they produce. Results We show that the number of striations on the Tymbal surface (historically known as “microTymbals”) and, to a lesser extent, the ratio of the projected surface area of the Tymbal to that of the thorax have a strong, positive correlation with the number of clicks a moth produces per unit time. We also found that some clades have significantly different regression coefficients, and thus the relationship between microTymbals and click rate is also dependent on the shared ancestry of different species. Conclusions Our predictive model allows the click rates of moths to be estimated using preserved material (e.g., from museums) in cases where live specimens are unavailable. This has the potential to greatly accelerate our understanding of the distribution of sound production and acoustic anti-bat strategies employed by tiger moths. Such knowledge will generate new insights into the evolutionary history of tiger moth anti-predator defenses on a global scale.
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Acoustic Aposematism and Evasive Action in Select Chemically Defended Arctiine (Lepidoptera: Erebidae) Species: Nonchalant or Not?
PLOS ONE, 2016Co-Authors: Nicolas J. Dowdy, William E. ConnerAbstract:Tiger moths (Erebidae: Arctiinae) have experienced intense selective pressure from echolocating, insectivorous bats for over 65 million years. One outcome has been the evolution of acoustic signals that advertise the presence of toxins sequestered from the moths’ larval host plants, i.e. acoustic aposematism. Little is known about the effectiveness of tiger moth anti-bat sounds in their natural environments. We used multiple infrared cameras to reconstruct bat-moth interactions in three-dimensional (3-D) space to examine how functional sound-producing organs called Tymbals affect predation of two chemically defended tiger moth species: Pygarctia roseicapitis (Arctiini) and Cisthene martini (Lithosiini). P. roseicapitis and C. martini with intact Tymbals were 1.8 and 1.6 times less likely to be captured by bats relative to those rendered silent. 3-D flight path and acoustic analyses indicated that bats actively avoided capturing sound-producing moths. Clicking behavior differed between the two tiger moth species, with P. roseicapitis responding in an earlier phase of bat attack. Evasive flight behavior in response to bat attacks was markedly different between the two tiger moth species. P. roseicapitis frequently paired evasive dives with aposematic sound production. C. martini were considerably more nonchalant and employed evasion in fewer interactions. Our results show that acoustic aposematism is effective at deterring bat predation in a natural context and that this strategy is likely to be the ancestral function of Tymbal organs within the Arctiinae.
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Acoustic Aposematism and Evasive Action in Select Chemically Defended Arctiine (Lepidoptera: Erebidae) Species: Nonchalant or Not? - Fig 1
2016Co-Authors: Nicolas J. Dowdy, William E. ConnerAbstract:Morphology and acoustic emissions of Pygarctia roseicapitis (A-F) and Cisthene martini (G-L). The moths (A, G) and their corresponding Tymbal organs (B, H), oscillogram (C, I), spectrogram (D, J), power spectral density plot (E, K), and the spectrogram of their response to simulated bat cries (F, L) are shown. Tymbal images are oriented with anterior on the left and ventral on the top with some scales removed. Insets show the relative position, orientation, and size of the Tymbal (yellow) organ and microTymbals (red) on the thorax of each species. Insets are oriented with anterior on the left and dorsal on the top. Oscillogram, spectrogram, and power spectral density plots (C-E, I-K) show a single activation and relaxation (modulation cycle) of the Tymbal organ. Moth responses to simulated bat cries (F, L) show each species’ earliest response and do not correspond to the same segment of time. Bat cries are brightest and sweep from higher to lower frequencies within a single call. Moth clicks are broadband and cluster in groups of clicks.
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Ultrasonic signals in the defense and courtship ofEuchaetes egle Drury andE. bolteri Stretch (Lepidoptera: Arctiidae)
Journal of Insect Behavior, 1996Co-Authors: Rebecca B. Simmons, William E. ConnerAbstract:Euchaetes egle Drury and E. bolteri Stretch produce ultrasound using paired thoracic Tymbal organs in both defensive and sexual contexts. The defensive ultrasound produced in response to tactile stimulation is fully characterized. The sounds are sexually monomorphic and species specific in the number of sound pulses produced during each flexion and relaxation of the Tymbal, peak frequency, peak intensity, and duration of the interval between flexion and relaxation. Ultrasonic signals play a role in the courtship of both species. Males produce ultrasound just prior to contact with females, and it is shown to be important to courtship success in E. egle . Ultrasonic courtship communication is mapped on a recently proposed cladogram for the family Arctiidae. The use of ultrasound in courtship has evolved on at least three occasions within the family.
R. M. Hennig - One of the best experts on this subject based on the ideXlab platform.
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Directional characteristics of the auditory system of cicadas: is the sound producing Tymbal an integral part of directional hearing?
Physiological Entomology, 2004Co-Authors: Paulo J. Fonseca, R. M. HennigAbstract:. Directional hearing is investigated in males of two species of cicadas, Tympanistalna gastrica (Stal) and Tettigetta josei Boulard, that are similar in size but show different calling song spectra. The vibrational response of the ears is measured with laser vibrometry and compared with thresholds determined from auditory nerve recordings. The data are used to investigate to what extent the directional characteristic of the tympanal vibrations is encoded by the activity of auditory receptors. Laser measurements show complex vibrations of the tympanum, and reveal that directional differences are rather high (>15 dB) in characteristic but limited frequency ranges. At low frequencies, both species show a large directional difference at the same frequency (3–5 kHz) whereas, above 10 kHz, the directional differences correspond to the different resonant frequencies of the respective Tymbals. Consequently, due to the mechanical resonance of the Tymbal, the frequency range at which directional differences are high differs between the two species that otherwise show similar dimensions of the acoustic system. The directional differences observed in the tympanal vibrations are also observed in the auditory nerve activity. These recordings confirm that the biophysically determined directional differences are available within the nervous system for further processing. Despite considerable intra as well as interindividual variability, the ears of the cicadas investigated here exhibit profound directional characteristics, because the thresholds determined from recordings of the auditory nerve at 30° to the right and left of the longitudinal axis differ by more than 5 dB.
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PHASIC ACTION OF THE TENSOR MUSCLE MODULATES THE CALLING SONG IN CICADAS
The Journal of Experimental Biology, 1996Co-Authors: Paulo J. Fonseca, R. M. HennigAbstract:The effect of tensor muscle contraction on sound production by the Tymbal was investigated in three species of cicadas (Tettigetta josei, Tettigetta argentata and Tympanistalna gastrica). All species showed a strict time correlation between the activity of the Tymbal motoneurone and the discharge of motor units in the tensor nerve during the calling song. Lesion of the tensor nerve abolished the amplitude modulation of the calling song, but this modulation was restored by electrical stimulation of the tensor nerve or by mechanically pushing the tensor sclerite. Electrical stimulation of the tensor nerve at frequencies higher than 3040 Hz changed the sound amplitude. In Tett. josei and Tett. argentata there was a gradual increase in sound amplitude with increasing frequency of tensor nerve stimulation, while in Tymp. gastrica there was a sudden reduction in sound amplitude at stimulation frequencies higher than 30 Hz. This contrasting effect in Tymp. gastrica was due to a bistable Tymbal frame. Changes in sound pulse amplitude were positively correlated with changes in the time lag measured from Tymbal motoneurone stimulation to the sound pulse. The tensor muscle acted phasically because electrical stimulation of the tensor nerve during a time window (010 ms) before electrical stimulation of the Tymbal motoneurone was most effective in eliciting amplitude modulations. In all species, the tensor muscle action visibly changed the shape of the Tymbal. Despite the opposite effects of the tensor muscle on sound pulse amplitude observed between Tettigetta and Tympanistalna species, the tensor muscle of both acts by modulating the shape of the Tymbal, which changes the force required for the Tymbal muscle to buckle the Tymbal.
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FUNCTION OF THE TENSOR MUSCLE IN THE CICADA TIBICEN LINNEI
The Journal of experimental biology, 1994Co-Authors: R. M. Hennig, Theo Weber, Thomas E. Moore, Franz Huber, Hans Ulrich Kleindienst, A. V. PopovAbstract:The calling song and the disturbance squawk of the cicada Tibicen linnei (Insecta: Homoptera) are described in terms of their physical parameters. The calling song is composed of quiet parts, which are very similar to the disturbance squawk, and loud parts, which are amplitude- and rate-modulated. The role of the tensor muscle acting on the Tymbal frame in modulating the sound pulse amplitude was investigated. We demonstrate by tensor nerve recordings, by mechanical mimicking of the tensor muscle action and by electrical stimulation of the tensor nerve, that the contraction of the tensor muscle is responsible for (a) initiating sound production and (b) modulating the sound pulse amplitude. These results allow us to construct a model which suggests that the tensor shifts the Tymbal into a mechanical working range that enables sound production and modulation of the sound pulse amplitude.
Paulo J. Fonseca - One of the best experts on this subject based on the ideXlab platform.
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© 2008 AB Academic Publishers THE EVOLUTION OF CICADA SONGS CONTRASTED WITH THE RELATIONSHIPS INFERRED FROM MITOCHONDRIAL DNA
2016Co-Authors: Paulo J. Fonseca, Ester A. Serrão, Francisco Pina-martins, Sara Mira, Jose Alberto Quartau, Pedro Silva, Octávio S. PauloAbstract:The molecular phylogeny of nine Palaearctic species of cicadas (Hemiptera, Cicadoidea) was inferred using two mitochondrial DNA genes, Cytochrome Oxidase I and II. The two main groups detected, namely species within Tettigetta and Tympanistalna, as well as the two species investigated in the genus Cicada, are robustly supported across the analytical methods. The structure of the song syllables, generated during single Tymbal cycles of males of the analysed group of species is remarkably consistent in these two phyletic lines. This reflects the morphology and the mechanics of the Tymbal. However the higher level song patterns, which depend on the activity of the central nervous system and have evolved to advertise receptive mates, do not seem to be consistent with either the inferred molecular topology or the basic Tymbal cycle. The observed similarities between the molecular phylogeny and the basic Tymbal cycles seem to reflect the basic conservative nature of the Tymbal structure, while the discrepancy between the former and the calling song pattern is probably related to the high plasticity of the pattern generator in the central nervous system and dependent on species-specific selection
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THE EVOLUTION OF CICADA SONGS CONTRASTED WITH THE RELATIONSHIPS INFERRED FROM MITOCHONDRIAL DNA (INSECTA, HEMIPTERA)
Bioacoustics, 2008Co-Authors: Paulo J. Fonseca, Ester A. Serrão, Francisco Pina-martins, Pedro C. Silva, Sara Mira, Jose Alberto Quartau, Octávio S. Paulo, Leonor CancelaAbstract:ABSTRACT The molecular phylogeny of nine Palaearctic species of cicadas (Hemiptera, Cicadoidea) was inferred using two mitochondrial DNA genes, Cytochrome Oxidase I and II. The two main groups detected, namely species within Tettigetta and Tympanistalna, as well as the two species investigated in the genus Cicada, are robustly supported across the analytical methods. The structure of the song syllables, generated during single Tymbal cycles of males of the analysed group of species is remarkably consistent in these two phyletic lines. This reflects the morphology and the mechanics of the Tymbal. However the higher level song patterns, which depend on the activity of the central nervous system and have evolved to advertise receptive mates, do not seem to be consistent with either the inferred molecular topology or the basic Tymbal cycle. The observed similarities between the molecular phylogeny and the basic Tymbal cycles seem to reflect the basic conservative nature of the Tymbal structure, while the disc...
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Directional characteristics of the auditory system of cicadas: is the sound producing Tymbal an integral part of directional hearing?
Physiological Entomology, 2004Co-Authors: Paulo J. Fonseca, R. M. HennigAbstract:. Directional hearing is investigated in males of two species of cicadas, Tympanistalna gastrica (Stal) and Tettigetta josei Boulard, that are similar in size but show different calling song spectra. The vibrational response of the ears is measured with laser vibrometry and compared with thresholds determined from auditory nerve recordings. The data are used to investigate to what extent the directional characteristic of the tympanal vibrations is encoded by the activity of auditory receptors. Laser measurements show complex vibrations of the tympanum, and reveal that directional differences are rather high (>15 dB) in characteristic but limited frequency ranges. At low frequencies, both species show a large directional difference at the same frequency (3–5 kHz) whereas, above 10 kHz, the directional differences correspond to the different resonant frequencies of the respective Tymbals. Consequently, due to the mechanical resonance of the Tymbal, the frequency range at which directional differences are high differs between the two species that otherwise show similar dimensions of the acoustic system. The directional differences observed in the tympanal vibrations are also observed in the auditory nerve activity. These recordings confirm that the biophysically determined directional differences are available within the nervous system for further processing. Despite considerable intra as well as interindividual variability, the ears of the cicadas investigated here exhibit profound directional characteristics, because the thresholds determined from recordings of the auditory nerve at 30° to the right and left of the longitudinal axis differ by more than 5 dB.
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Asymmetry of Tymbal action and structure in a cicada: a possible role in the production of complex songs
The Journal of Experimental Biology, 1998Co-Authors: Paulo J. Fonseca, H-c Bennet ClarkAbstract:The type 1 echeme of the song of the small European cicada Tympanistalna gastrica consists of a pair of loud IN-OUT pulses followed by a train of soft IN-OUT pulses. In all nine insects investigated, the right and left Tymbals buckled inwards and outwards alternately, but the echeme started with the buckling of the right Tymbal. Both the inward and the outward buckling movements produced single discrete sound pulses. The loud IN pulses were produced with the Tymbal tensor muscle relaxed. They were approximately 10 dB louder than the loud OUT pulses and than the soft IN and OUT pulses. The period between the right loud IN and OUT pulses (3.75+/-0.31 ms) (mean +/- s.d.) was significantly shorter than between the left loud IN and OUT pulses (4.09+/-0.28 ms). The period between the loud IN and OUT pulses was significantly shorter than the period between the soft IN and OUT pulses, which was similar on both sides (mean for the right Tymbal 5.54+/-0.20 ms, mean for the left Tymbal 5.30+/-0.51 ms). Measured at the Tymbal, the power spectrum of the right loud IN pulses showed major components between 4 and 8 kHz as well as around 11.7 kHz. That of the left loud IN pulse had approximately 10 dB less power at 4 kHz and similar power at 7-8 kHz, with a further louder peak at around 10.8 kHz. The loud OUT pulses and all subsequent IN and OUT soft pulses showed very little power at 4 and 8 kHz, but all showed a spectral peak at approximately 13 kHz. The soft OUT pulses had similar pulse envelopes to the preceding IN pulses, which they closely mirrored. Measured at the fourth abdominal sternite, only the right loud IN pulse produced peak power at 4 kHz. The transfer function between the Tymbal sound and that at sternite 4 was maximal at 4 kHz for the right loud IN pulse and showed a peak at this frequency for both loud and soft IN and OUT pulses. The 4 kHz components of all pulses, and particularly that of the right loud IN pulse, which has the loudest 4 kHz component, excited sympathetic sound radiation from the abdominal sternite region. Measured at the tympanal opercula, both loud IN pulses produced peaks at 7-8 kHz of similar power. The transfer functions between the Tymbal sound and that at the tympanal opercula showed peaks of power at this frequency range for both loud and soft IN and OUT pulses, suggesting that this component excites sympathetic radiation via the tympana. Components of the sound pulses produced by one Tymbal are also transmitted via the contralateral Tymbal. The pulses transmitted during both loud IN pulses had ragged envelopes, but the soft IN pulses and all OUT pulses were transmitted as clean coherent pulses with slow build-up and slow decay, suggesting that the ipsilateral Tymbal excited a sympathetic resonance in the contralateral one. The Tymbals of T. gastrica have two unusual features. At the dorsal end of rib 2, there is a horizontal bar that extends anteriorly over rib 3 and posteriorly over rib 1 to the dorsal end of the Tymbal plate. This bar appears to couple the three ribs so that they buckle in unison. The resilin sheet at the ventral ends of ribs 1, 2 and 3 was significantly wider, dorso-ventrally, in the right Tymbal than in the left in eight insects that were measured (mean right-to-left ratio, 1.37). The asymmetry between the right and left loud IN pulses correlates with the morphological asymmetry of the Tymbals. The complexities of the song in T. gastrica appear to result from the preferential excitation of sound radiation from the abdomen surface or via the tympana by components of the distinct pulses produced by the asymmetrical Tymbals and from the Tymbals themselves. Moribund or fatigued insects were successively unable to produce the right loud pulse and then the left loud pulse. The complex song may in this way act as an honest signal of male fitness.
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PHASIC ACTION OF THE TENSOR MUSCLE MODULATES THE CALLING SONG IN CICADAS
The Journal of Experimental Biology, 1996Co-Authors: Paulo J. Fonseca, R. M. HennigAbstract:The effect of tensor muscle contraction on sound production by the Tymbal was investigated in three species of cicadas (Tettigetta josei, Tettigetta argentata and Tympanistalna gastrica). All species showed a strict time correlation between the activity of the Tymbal motoneurone and the discharge of motor units in the tensor nerve during the calling song. Lesion of the tensor nerve abolished the amplitude modulation of the calling song, but this modulation was restored by electrical stimulation of the tensor nerve or by mechanically pushing the tensor sclerite. Electrical stimulation of the tensor nerve at frequencies higher than 3040 Hz changed the sound amplitude. In Tett. josei and Tett. argentata there was a gradual increase in sound amplitude with increasing frequency of tensor nerve stimulation, while in Tymp. gastrica there was a sudden reduction in sound amplitude at stimulation frequencies higher than 30 Hz. This contrasting effect in Tymp. gastrica was due to a bistable Tymbal frame. Changes in sound pulse amplitude were positively correlated with changes in the time lag measured from Tymbal motoneurone stimulation to the sound pulse. The tensor muscle acted phasically because electrical stimulation of the tensor nerve during a time window (010 ms) before electrical stimulation of the Tymbal motoneurone was most effective in eliciting amplitude modulations. In all species, the tensor muscle action visibly changed the shape of the Tymbal. Despite the opposite effects of the tensor muscle on sound pulse amplitude observed between Tettigetta and Tympanistalna species, the tensor muscle of both acts by modulating the shape of the Tymbal, which changes the force required for the Tymbal muscle to buckle the Tymbal.
Bennet-clark - One of the best experts on this subject based on the ideXlab platform.
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Transduction of mechanical energy into sound energy in the cicada cyclochila australasiae
The Journal of experimental biology, 1999Co-Authors: Bennet-clark, DawsAbstract:The anatomy of the paired Tymbal muscles of Cyclochila australasiae was described. Force-distance relationships of the sound-producing in-out cycle of Tymbal movement were measured. The largest forces were measured when the push occurred at the apodeme pit on the Tymbal plate at angles similar to the angles of internal pull of the Tymbal muscle. Initially, inward movement was opposed by the elasticity of the Tymbal, which stored energy. At a mean force of 0. 38 N after a mean inward strain of 368 microm, the Tymbal ribs buckled, the mean energy release being 45.1 microJ. The energy release occurred over 2-10 ms in three or four sound-producing steps as successive Tymbal ribs buckled inwards. After the ribs had buckled, the force decreased to a mean value of 0.17 N. The force returned to zero during the outward movement, during which the Tymbal ribs buckled outwards. The mean energy dissipated in the outward movement was 32.8 microJ. During contraction, the Tymbal muscle produced mean values for the peak active force of 0.31 N over 295 microm, which gave mean values for the area of the work loops of 47.0 microJ. The calling song of C. australasiae had a mean pulse rate of 234 Hz (117 Hz for each side of the insect). The peak power to mean power ratio for the songs was 8.51:1 (+9.30 dB). Measurements of the sound field around tethered insects and of the peak power to mean power ratio of the songs gave values for the mean power of the song of 3.15-7 mW; these correspond to an energy per song pulse of 13.5-30 microJ. Previously reported mean values are 3. 15 mW for protest song and 5.1 mW for calling song. The efficiency of transduction of mechanical energy into sound energy is between 18 and 46 %.
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The role of the Tymbal in cicada sound production
The Journal of experimental biology, 1995Co-Authors: Young, Bennet-clarkAbstract:1. The Tymbal of Cyclochila australasiae consists of a biconvex membrane bearing alternating long and short ribs anteriorly and an irregularly shaped Tymbal plate posteriorly. These sclerotised regions are coupled together by the surrounding highly flexible cuticle, which contains resilin. Dorsally, there is a thick pad of resilin, which functions as a spring, returning the Tymbal to the out position and maintaining the stress on the long ribs. 2. Contraction of the Tymbal muscle causes the Tymbal plate to swing inwards, acting as a lever so that the surface of the Tymbal moves through more than twice the distance of muscle shortening. This produces an inward movement and twisting of the dorsal ends of the long ribs, which then buckle in sequence, with each rib undergoing a sudden deformation from a convex to a V-shaped profile. Buckling takes place at the rib's weakest point, which is the narrow, highly sclerotised mid-region. 3. Inward buckling of the Tymbal generates a loud click with a dominant frequency around 4 kHz. Resonances close to 4 kHz can be demonstrated in a buckled-in Tymbal when driven by internal sound or by vibration at the Tymbal plate. These resonances occur in sealed cicadas and those in which the abdominal air sac has been opened at both its anterior and posterior ends, which shows that the resonances are not due to the air sac; the Tymbal itself is a resonant system. The maximum amplitude of Tymbal vibration occurs at the V-shaped dimples in the centre of the long ribs. 4. When the Tymbal plus abdominal air sac system is driven by vibration at the Tymbal plate, the Q3dB of the sound radiated through the tympana is about 12.5, which is approximately the sum of those of the Tymbal (Q=9.3) and of the air sac (Q=3.4) resonators. When the Tymbal is not loaded by the air sac, i.e. in the sealed cicada and open cicada preparations, the Q3dB of its resonance is higher, between 13 and 20. 5. The click produced as the Tymbal pops out is over 20 dB quieter than the in-click and has a dominant frequency around 6 kHz. When driven in the resting position, resonances are found close to 6 kHz but there is only a weak general vibration of the ribs and Tymbal plate. When the Tymbal is pushed in gradually, the resonant frequency changes from about 5.5 kHz to about 4.3 kHz as the Tymbal buckles inwards. The left and right Tymbals of the same insect may differ slightly in their acoustic properties. 6. As the Tymbal buckles inwards, it displaces a volume of approximately 6 µl into the abdominal air sac volume of about 2 ml. The resulting sound pressure inside the air sac attains peak values of 155159 dB SPL; the root mean square values are 141144 dB SPL. The mean peak value just outside the tympana is 148.5 dB SPL. 7. Overall, the present work supports and extends our earlier model of cicada sound production: the Tymbal click provides a coherent resonant source that drives the abdominal resonator, from which sound is radiated via the tympana. At the same time, the system provides the pressure transformation between muscle power and sound power that is desirable for efficient sound radiation.
J. H. Fullard - One of the best experts on this subject based on the ideXlab platform.
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The adaptive function of tiger moth clicks against echolocating bats: an experimental and synthetic approach
Journal of Experimental Biology, 2005Co-Authors: John M. Ratcliffe, J. H. FullardAbstract:We studied the efficiency and effects of the multiple sensory cues of tiger moths on echolocating bats. We used the northern long-eared bat, Myotis septentrionalis , a purported moth specialist that takes surface-bound prey (gleaning) and airborne prey (aerial hawking), and the dogbane tiger moth, Cycnia tenera , an eared species unpalatable to bats that possesses conspicuous colouration and sound-producing organs (Tymbals). This is the first study to investigate the interaction of tiger moths and wild-caught bats under conditions mimicking those found in nature and to demand the use of both aerial hawking and gleaning strategies by bats. Further, it is the first to report spectrograms of the sounds produced by tiger moths while under aerial attack by echolocating bats. During both aerial hawking and gleaning trials, all muted C. tenera and perched intact C. tenera were attacked by M. septentrionalis , indicating that M. septentrionalis did not discriminate C. tenera from palatable moths based on potential echoic and/or non-auditory cues. Intact C. tenera were attacked significantly less often than muted C. tenera during aerial hawking attacks: Tymbal clicks were therefore an effective deterrent in an aerial hawking context. During gleaning attacks, intact and muted C. tenera were always attacked and suffered similar mortality rates, suggesting that while handling prey this bat uses primarily chemical signals. Our results also show that C. tenera temporally matches the onset of click production to the `approach phase' echolocation calls produced by aerial hawking attacking bats and that clicks themselves influence the echolocation behaviour of attacking bats. In the context of past research, these findings support the hypotheses that the clicks of arctiid moths are both an active defence (through echolocation disruption) and a reliable indicator of chemical defence against aerial-hawking bats. We suggest these signals are specialized for an aerial context.
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The Closed-Loop Nature of the Tymbal Response in the Dogbane Tiger Moth, Cycnia tenera (Lepidoptera, Arctiidae)
Brain behavior and evolution, 1996Co-Authors: Mark A. Northcott, J. H. FullardAbstract:The dogbane tiger moth, Cycnia tenera, emits ultrasonic sounds by rhythmically buckling a pair of Tymbals when stimulated by pulsed sounds resembling bat echolocation. We monitored the central pattern generator governing this response by recording the motor output of the Tymbal branch of the metathoracic leg nerve. The rhythm of the Tymbal motor pattern can be altered midway (500 m/sec from its initiation) by changing the period and, to a lesser degree, the intensity of the stimulus. The Tymbal response of C. tenera is therefore closed-looped to stimulus pulse period and intensity. Our results suggest that C. tenera relies less on the changes in an attacking bat's echolocation intensity when responding with this behaviour because this acoustic parameter may be a more unreliable indicator of the proximity of the bat than its echolocation call period.
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The neuroethology of sound production in tiger moths (Lepidoptera, Arctiidae)
Journal of Comparative Physiology A, 1995Co-Authors: J. W. Dawson, J. H. FullardAbstract:When stimulated either acoustically or tactually, certain species of arctiid moths rhythmically emit trains of clicks from metathoracic Tymbals. The purpose of the experiments presented here was to determine the location within the central nervous system (CNS) of the proposed Tymbal central pattern generator (CPG) in Cycnia tenera . Motor neuron impulses that underlie Tymbal activation were recorded extracellularly from the Tymbal nerve while moths were subjected to selective severing of the suboesophageal, prothoracic, pterothoracic and abdominal ganglia connectives. Motor output evoked by either acoustic or tactile stimulation originates from a common CPG because Tymbal nerve spikes in both cases are similar in amplitude, waveform and rhythmicity. Our results showed: (1) removal of the CNS posterior of the second abdominal neuromere had no effect, (2) removal of the head decreased the responsiveness of the animal to acoustic stimulation and, (3) severing the connectives between the prothoracic and pterothoracic ganglia abolished responses to acoustic stimuli and diminished responses to tactile stimuli. We conclude that although the minimal circuitry sufficient for activating the Tymbals resides in the pterothoracic ganglion, the prothoracic and cephalic ganglia are required for the normal, and in particular, auditory-evoked operation of the Tymbal CPG.
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The neuroethology of sound production in tiger moths (Lepidoptera, Arctiidae)
Journal of Comparative Physiology A, 1992Co-Authors: J. H. FullardAbstract:1. Certain species of tiger moths emit clicks when stimulated by bat-like sounds. These clicks are generated by modified thoracic episterna (Tymbals) (Fig. 1) and constitute a rhythmic behaviour activated by simple sensory input. 2. Tymbal periods are indirectly related to stimulus intensity and periods (Fig. 3). Moths initiate sounds with the Tymbal opposite to the stimulated ear and once a sequence commences it continues in an undisrupted fashion. 3. The Tymbal is innervated by a pleural branch (IIIN2a) of the metathoracic leg nerve, a similar anatomy to that in the unmodified episterna of silent moths (Fig. 5). Backfills of the IIIN2a in Cycnia tenera reveal sensory fibres and a cluster of 5–9 motor neurons with densely overlying dendritic fields (Fig. 6). 4. Extracellular recordings of the IIIN2a reveal a large impulse preceding each Tymbal sound (Fig. 7). I suggest that this impulse results from the synchronous firing of 2–3 motor neurons and is the motor output of the Tymbal central pattern generator (CPG). The spikes alternate (Figs. 9, 10) and are bilaterally co-related (Fig. 11) but with an phase asymmetry of 2–3 ms (Fig. 12). 5. Normal motor output continues in the absence of Tymbal sounds (Fig. 13) and when all nerve-Tymbal connections are severed (Fig. 14, Table 1) therefore this CPG operates independent of sensory feedback. A model is proposed for the Tymbal circuitry based upon the present data and the auditory organization of related noctuid moths (Fig. 15). I propose that the Tymbal response in modern arctiids evolved from either flight or walking CPGs and that preadaptive circuitry ancestral to Tymbal movements still exists in modern silent Lepidoptera.
