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New bioacoustic articles in J. Comp. Physiol. A

Subject: New bioacoustic articles in J. Comp. Physiol. A
From: Sonja Amoser <>
Date: Tue, 25 Sep 2012 11:03:20 +0200
M. Hartbauer, M. E. Siegert, I. Fertschai & H. Römer (2012): Acoustic signal 
perception in a noisy habitat: lessons from synchronising insects. J. Comp. 
Physiol. A 198 (6), 397-409.

Abstract: Acoustically communicating animals often have to cope with ambient 
noise that has the potential to interfere with the perception of conspecific 
signals. Here we use the synchronous display of mating signals in males of the 
tropical katydid Mecopoda elongata in order to assess the influence of 
nocturnal rainforest noise on signal perception. Loud background noise may 
disturb chorus synchrony either by masking the signals of males or by 
interaction of noisy events with the song oscillator. Phase-locked synchrony of 
males was studied under various signal-to-noise ratios (SNRs) using either 
native noise or the audio component of noise (<9 kHz). Synchronous entrainment 
was lost at a SNR of −3 dB when native noise was used, whereas with the audio 
component still 50 % of chirp periods matched the pacer period at a SNR of −7 
dB. Since the chirp period of solo singing males remained almost unaffected by 
noise, our results suggest that masking interference limits chorus synchrony by 
rendering conspecific signals ambiguous. Further, entrainment with periodic 
artificial signals indicates that synchrony is achieved by ignoring 
heterospecific signals and attending to a conspecific signal period. 
Additionally, the encoding of conspecific chirps was studied in an auditory 
neuron under the same background noise regimes.

Christopher Bergevin, Edward J. Walsh, JoAnn McGee & Christopher A. Shera 
(2012): Probing cochlear tuning and tonotopy in the tiger using otoacoustic 
emissions. J. Comp. Physiol. A 198 (8), 617 - 624.

Abstract: Otoacoustic emissions (sound emitted from the ear) allow cochlear 
function to be probed noninvasively. The emissions evoked by pure tones, known 
as stimulus-frequency emissions (SFOAEs), have been shown to provide reliable 
estimates of peripheral frequency tuning in a variety of mammalian and 
non-mammalian species. Here, we apply the same methodology to explore 
peripheral auditory function in the largest member of the cat family, the tiger 
(Panthera tigris). We measured SFOAEs in 9 unique ears of 5 anesthetized 
tigers. The tigers, housed at the Henry Doorly Zoo (Omaha, NE), were of both 
sexes and ranged in age from 3 to 10 years. SFOAE phase-gradient delays are 
significantly longer in tigers—by approximately a factor of two above 2 kHz and 
even more at lower frequencies—than in domestic cats (Felis catus), a species 
commonly used in auditory studies. Based on correlations between tuning and 
delay established in other species, our results imply that cochlear tuning in 
the tiger is significantly sharper than in domestic cat and appears comparable 
to that of humans. Furthermore, the SFOAE data indicate that tigers have a 
larger tonotopic mapping constant (mm/octave) than domestic cats. A larger 
mapping constant in tiger is consistent both with auditory brainstem response 
thresholds (that suggest a lower upper frequency limit of hearing for the tiger 
than domestic cat) and with measurements of basilar-membrane length (about 1.5 
times longer in the tiger than domestic cat).

Yuto Furusawa, Shizuko Hiryu, Kohta I. Kobayasi & Hiroshi Riquimaroux (2012): 
Convergence of reference frequencies by multiple CF–FM bats (Rhinolophus 
ferrumequinum nippon) during paired flights evaluated with onboard microphones. 
J. Comp. Physiol. A 198 (9), 683-693.

Abstract: The constant frequency component of the second harmonic (CF2) of 
echolocation sounds in Rhinolophus ferrumequinum nippon were measured using 
onboard telemetry microphones while the bats exhibited Doppler-shift 
compensation during flights with conspecifics. (1) The CF2 frequency of pulses 
emitted by individual bats at rest (F rest) showed a long-term gradual decline 
by 0.22 kHz on average over a period of 3 months. The mean neighboring F rest 
(interindividual differences in F rest between neighboring bats when the bats 
were arranged in ascending order according to F rest) ranged from 0.08 to 0.11 
kHz among 18 bats in a laboratory colony. (2) The standard deviation of 
observed echo CF2 (reference frequency) for bats during paired flights ranged 
from 50 to 90 Hz, which was not significantly different from that during single 
flights. This finding suggests that during paired flights, bats exhibit 
Doppler-shift compensation with the same accuracy as when they fly alone. (3) 
In 60 % (n = 29) of the cases, the difference in the reference frequency 
between two bats during paired flights significantly decreased compared to when 
the bats flew alone. However, only 15 % of the cases (n = 7) showed a 
significant increase during paired flights. The difference in frequency between 
two bats did not increase even when the reference frequencies of the 
individuals were not statistically different during single flights.

Johannes Schul, Anne M. Mayo & Jeffrey D. Triblehorn (2012): Auditory change 
detection by a single neuron in an insect. J. Comp. Physiol. A 198 (9), 695-704.

Abstract: The detection of novel signals in the auditory scene is an elementary 
task of any hearing system. In Neoconocephalus katydids, a primary auditory 
interneuron (TN-1) with broad spectral sensitivity, responded preferentially to 
rare deviant pulses (7 pulses/s repetition rate) embedded among common standard 
pulses (140 pulses/s repetition rate). Eliminating inhibitory input did not 
affect the detection of the deviant pulses. Detection thresholds for deviant 
pulses increased significantly with increasing amplitude of standard pulses. 
Responses to deviant pulses occurred when the carrier frequencies of deviant 
and standard were sufficiently different, both when the deviant had a higher or 
lower carrier frequency than the standard. Recordings from receptor neurons 
revealed that TN-1 responses to the deviant pulses did not depend on the 
population response strength of the receptors, but on the distribution of the 
receptor cell activity. TN-1 responses to the deviant pulse occurred only when 
the standard and deviant pulses were transmitted by different groups of 
receptor cells. TN-1 responses parallel stimulus specific adaptation (SSA) 
described in mammalian auditory system. The results support the hypothesis that 
the mechanisms underlying SSA and change-detection are located in the TN-1 
dendrite, rather than the receptor cells.

André A. Dagostin, Claudio V. Mello & Ricardo M. Leão (2012): Increased 
bursting glutamatergic neurotransmission in an auditory forebrain area of the 
zebra finch (Taenopygia guttata) induced by auditory stimulation. J. Comp. 
Physiol. A 198(9), 705-716.

Abstract: The caudomedial nidopallium (NCM) is a telencephalic area involved in 
auditory processing and memorization in songbirds, but the synaptic mechanisms 
associated with auditory processing in NCM are largely unknown. To identify 
potential changes in synaptic transmission induced by auditory stimulation in 
NCM, we used a slice preparation for path-clamp recordings of synaptic currents 
in the NCM of adult zebra finches (Taenopygia guttata) sacrificed after sound 
isolation followed by exposure to conspecific song or silence. Although 
post-synaptic GABAergic and glutamatergic currents in the NCM of control and 
song-exposed birds did not present any differences regarding their frequency, 
amplitude and duration after song exposure, we observed a higher probability of 
generation of bursting glutamatergic currents after blockade of GABAergic 
transmission in song-exposed birds as compared to controls. Both song-exposed 
males and females presented an increase in the probability of the expression of 
bursting glutamatergic currents, however bursting was more commonly seen in 
males where they appeared even without blocking GABAergic transmission. Our 
data show that song exposure changes the excitability of the glutamatergic 
neuronal network, increasing the probability of the generation of bursts of 
glutamatergic currents, but does not affect basic parameters of glutamatergic 
and GABAergic synaptic currents.

Shigeki Mantani, Shizuko Hiryu, Emyo Fujioka, Naohiro Matsuta, Hiroshi 
Riquimaroux & Yoshiaki Watanabe (2012): Echolocation behavior of the Japanese 
horseshoe bat in pursuit of fluttering prey. J. Comp. Physiol. A 198(10), 

Abstract: Echolocation sounds of Rhinolophus ferrumequinum nippon as they 
approached a fluttering moth (Goniocraspidum pryeri) were investigated using an 
on-board telemetry microphone (Telemike). In 40 % of the successful 
moth-capture flights, the moth exhibited distinctive evasive flight behavior, 
but the bat pursued the moth by following its flight path. When the distance to 
the moth was approximately 3–4 m, the bats increased the duration of the pulses 
to 65–95 ms, which is 2–3 times longer than those during landing flight (30–40 
ms). The mean of 5.8 long pulses were emitted before the final buzz phase of 
moth capture, without strengthening the sound pressure level. The mean duration 
of long pulses (79.9 ± 7.9 ms) corresponded to three times the fluttering 
period of G. pryeri (26.5 × 3 = 79.5 ms). These findings indicate that the bats 
adjust the pulse duration to increase the number of temporal repetitions of 
fluttering information rather than to produce more intense sonar sounds to 
receive fine insect echoes. The bats exhibited Doppler-shift compensation for 
echoes returning from large static objects ahead, but not for echoes from 
target moths, even though the bats were focused on capturing the moths. 
Furthermore, the echoes of the Telemike recordings from target moths showed 
spectral glints of approximately 1–1.5 kHz caused by the fluttering of the 
moths but not amplitude glints because of the highly acoustical attenuation of 
ultrasound in the air, suggesting that spectral information may be more robust 
than amplitude information in echoes during moth capturing flight.

Nicole Stange & Bernhard Ronacher (2012): Song characteristics and 
morphological traits in four populations of the grasshopper Chorthippus 
biguttulus L. J. Comp. Physiol. A 198 (10), 763-775.

Abstract: We investigated four populations of the grasshopper Chorthippus 
biguttulus with respect to differences in morphological traits and 
characteristics of their communication signals. A special focus was laid on 
possible correlations between morphological and song traits of males that could 
be used by females to infer quality cues of potential mates. We also tested 
whether females exhibit preferences for males of their own population. Specific 
song features (onset accentuation, offset, syllable period) of males—but not of 
females—differed between populations. We observed size differences both in 
males and females from different populations, but the size ranks of the two 
sexes were not always correlated. Environmental factors appear to have a strong 
influence on different size traits, compared to genetic origin. In all 
populations a specific song feature, the accentuation of syllable onsets, 
showed a similar correlation with a morphological trait, hind leg size, but its 
correlation with other size indicators sometimes differed in sign. Females did 
not prefer songs of males from their own population. The best predictor for 
song attractiveness was—unexpectedly—not the onset accentuation but the offset 

Kind regards

Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach

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