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),
741-751.
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
depth.
Kind regards
Sonja
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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