Gerlinde Höbel and Johannes Schul (2007): Listening for males and bats:
spectral processing in the hearing organ of Neoconocephalus bivocatus
(Orthoptera: Tettigoniidae). J. Comp. Physiol. A 193(9), 917-925.
Abstract: Tettigoniids use hearing for mate finding and the avoidance of
predators (mainly bats). Using intracellular recordings, we studied the
response properties of auditory receptor cells of Neoconocephalus
bivocatus to different sound frequencies, with a special focus on the
frequency ranges representative of male calls and bat cries. We found
several response properties that may represent adaptations for hearing
in both contexts. Receptor cells with characteristic frequencies close
to the dominant frequency of the communication signal were more broadly
tuned, thus extending their range of high sensitivity. This increases
the number of cells responding to the dominant frequency of the male
call at low signal amplitudes, which should improve long distance call
localization. Many cells tuned to audio frequencies had intermediate
thresholds for ultrasound. As a consequence, a large number of receptors
should be recruited at intermediate amplitudes of bat cries. This
collective response of many receptors may function to emphasize predator
information in the sensory system, and correlates with the amplitude
range at which ultrasound elicits evasive behavior in tettigoniids. We
compare our results with spectral processing in crickets, and discuss
that both groups evolved different adaptations for the perceptual tasks
of mate and predator detection.
URL: http://www.springerlink.com/content/6q6757g362w77862/
For reprints please contact Johannes Schul (Email:
Vivek Nityananda, Jürgen Stradner, Rohini Balakrishnan and Heinrich
Römer (2007): Selective attention in a synchronising bushcricket:
physiology, behaviour and ecology. J. Comp. Physiol. A 193(9), 983-991.
Abstract: Synchronising bushcricket males achieve synchrony by delaying
their chirps in response to calling neighbours. In multi-male choruses,
males that delay chirps in response to all their neighbours would remain
silent most of the time and be unable to attract mates. This problem
could be overcome if the afferent auditory system exhibited selective
attention, and thus a male interacted only with a subset of neighbours.
We investigated whether individuals of the bushcricket genus Mecopoda
restricted their attention to louder chirps neurophysiologically,
behaviourally and through spacing. We found that louder leading chirps
were preferentially represented in the omega neuron but the
representation of softer following chirps was not completely abolished.
Following chirps that were 20 dB louder than leading chirps were better
represented than leading chirps. During acoustic interactions, males
synchronised with leading chirps even when the following chirps were 20
dB louder. Males did not restrict their attention to louder chirps
during interactions but were affected by all chirps above a particular
threshold. In the field, we found that males on average had only one or
two neighbours whose calls were above this threshold. Selective
attention is thus achieved in this bushcricket through spacing rather
than neurophysiological filtering of softer signals.
URL: http://www.springerlink.com/content/l82t38211w76n502/
For reprints please contact Vivek Nityananda (Corresponding author)
(Email:
Brigitte Gottsberger and Frieder Mayer (2007): Behavioral sterility of
hybrid males in acoustically communicating grasshoppers (Acrididae,
Gomphocerinae). J. Comp. Physiol. A 193(7), 703-714.
Abstract: The effectiveness of hybridization barriers determines whether
two species remain reproductively isolated when their populations come
into contact. We investigated acoustic mating signals and associated leg
movements responsible for song creation of hybrids between the
grasshopper species Chorthippus biguttulus and C. brunneus to study
whether and how songs of male hybrids contribute to reproductive
isolation between these sympatrically occurring species. Songs of F1,
F2, and backcross hybrids were intermediate between those of both
parental species in terms phrase number and duration. In contrast,
species-specific syllable structure within phrases was largely lost in
hybrids and was produced, if at all, in an irregular and imperfect
manner. These divergences in inheritance of different song parameters
are likely the result of incompatibility of neuronal networks that
control stridulatory leg movements in hybrids. It is highly probable
that songs of hybrid males are unattractive to females of either
parental species because they are intermediate in terms of phrase
duration and lack a clear syllable structure. Males of various hybrid
types (F1, F2, and backcrosses) are behaviorally sterile because their
songs fail to attract mates.
URL: http://www.springerlink.com/content/m7124756285vt787/
For reprints please contact Brigitte Gottsberger (Email:
Mark E. Hauber, Phillip Cassey, Sarah M. N. Woolley and Frederic E.
Theunissen (2007): Neurophysiological response selectivity for
conspecific songs over synthetic sounds in the auditory forebrain of
non-singing female songbirds. J. Comp. Physiol. A 193(7), 765-774.
Abstract: Female choice plays a critical role in the evolution of male
acoustic displays. Yet there is limited information on the
neurophysiological basis of female songbirds? auditory recognition
systems. To understand the neural mechanisms of how non-singing female
songbirds perceive behaviorally relevant vocalizations, we recorded
responses of single neurons to acoustic stimuli in two auditory
forebrain regions, the caudal lateral mesopallium (CLM) and Field L, in
anesthetized adult female zebra finches (Taeniopygia guttata). Using
various metrics of response selectivity, we found consistently higher
response strengths for unfamiliar conspecific songs compared to tone
pips and white noise in Field L but not in CLM. We also found that
neurons in the left auditory forebrain had lower response strengths to
synthetics sounds, leading to overall higher neural selectivity for song
in neurons of the left hemisphere. This laterality effect is consistent
with previously published behavioral data in zebra finches. Overall, our
results from Field L are in parallel and from CLM are in contrast with
the patterns of response selectivity reported for conspecific songs over
synthetic sounds in male zebra finches, suggesting some degree of sexual
dimorphism of auditory perception mechanisms in songbirds.
URL: http://www.springerlink.com/content/333625h74n354r97/
For reprints please contact Mark E. Hauber (Email:
Kind regards
Sonja
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University of Vienna, Dept. of Behavioural Biology
Sonja Amoser, PhD
Althanstrasse 14
1090 Vienna
Austria
tel: +43 (1) 4277 54467
fax: +43 (1) 4277 54506
mobile: +43 (664) 500 61 06
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