CONTENT - International Society of Zoological Sciences

S15 ICZ2008 - Abstracts
Temporal and amplitude parameters affecting mate choice
selectivity in Nezara viridula (L.) (Heteroptera: Pentatomidae).
Maarten de Groot, Andrej Čokl and Meta Virant-Doberlet
Department of Entomology, National Institute of Biology, Večna pot
111, Ljubljana, Slovenia
While on the same plant, males and females of the southern green
stink bug Nezara viridula use species and sex specific vibrational
signals transmitted through the substrate for recognition and
localization of conspecifics. We investigated the selectivity of the
behavioural responses of males to natural and altered female
calling song (FCS) in one- and two-side play-back experiments on
bean plants. We tested the influence of two temporal parameters
(signal and interval duration) and signal amplitude on triggering of
recognition (male calling) and searching. For all altered FCSs,
significantly more males were calling than searching. The results
show that the signal and interval duration were positively
correlated with the male calling and searching. In general, in twoside
playback experiments with natural and altered FCSs of equal
amplitude, more males responded with calling and searching
behaviour than in one-side stimulation experiments. In this
situation only signals with shorter than normal interval induced less
response, while duration of the signal had no effect on male
responsiveness. In two-side playback experiments with signals of
different amplitudes, more males were searching when stimulated
bilaterally by natural FCS. Fewer males were calling and searching
when altered FCSs were played back simultaneously. Results
indicate that males’ behavioural responses decreased in line with
the decrease of natural FCS amplitude. In conclusion, males are
able to discriminate between natural and altered FCS when played
simultaneously. Furthermore, the structural and intensity
differences of the FCS are important factors which underlie the
complex mate searching behaviour of N. viridula males.
Phenotypic plasticity and flexibility in the crowing behaviour
of a vocal non-learner species: the domestic Japanese quail
(Coturnix c. japonica)
Sébastien Derégnaucourt and Manfred Gahr
Max Planck Institute for Ornithology, Postfach 1564, D82305
Starnberg (Seewiesen), Germany
Previous studies have shown that species-specific behaviours
gradually emerge, via incomplete patterns, to the final complete
adult form. A classical example in the acoustic domain is birdsong,
a learned behaviour. In contrast to birdsong development, little is
known about ontogenetic changes of the vocalizations of vocal
non-learners species. This was the purpose of our study, using the
crowing behaviour of the domestic Japanese quail (Coturnix c.
japonica) as an example. Young males were maintained in social
isolation from the age of 3 weeks to 4 months, and their complete
crowing activity was continuously recorded. We observed
developmental changes in crow structure, both at the temporal and
at the spectral levels. Speed and trajectories of these
developmental changes did exhibit an unexpected high interindividual
variability. These ontogenetic changes present some
similarity to that of song in songbirds, both in general
developmental changes in vocalization structure and in plasticity of
form development. We also observed some daily changes in the
temporal pattern of the crow: crows emitted at night were longer
than crows emitted during the day. Such vocal changes were also
observed when quails were transferred from a regular light-dark
cycle to constant light: crows emitted in constant light were shorter
than crows emitted in a normal light-dark cycle. These results
suggest that, like in songbirds, melatonin, which is produced in
darkness, might affect the temporal pattern of birds’ vocalizations.
Studies on vocal non-learners could shed light on the specificity
and evolution of vocal learning.
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Mechanisms of avian songs and calls
Ole Næsbye Larsen
Institute of Biology, University of Southern Denmark, DK-5230
Odense M, Denmark
The avian vocal organ, the syrinx, is a specialized structure
located rather inaccessibly in an air sac close to the heart where
the trachea bifurcates into the two primary bronchi. The syrinx of
different avian taxa varies so much in position and morphology that
it has been used for taxonomy. It consists of a skeletal framework,
flexible membranes or soft tissue masses, labia, stretched
between elements of this framework, and the syringeal muscles.
Until a decade ago most of our knowledge about syringeal
mechanics was based on such indirect evidence as
electromyography, emitted sound, and anatomy. The use of thin,
flexible endoscopes has made direct observation of the syrinx
possible in situ. The effects of direct muscle stimulation on the
syringeal aperture have identified adductor and abductor muscles,
confirming results from electromyographic studies. Endoscopic
observations have revealed the dynamics of syringeal
reconfiguration during phonation, which in most bird species
investigated results in simultaneous movement of soft tissue
masses (the medial and lateral labia in songbirds and lateral
tympaniform membranes in non-songbirds) into the bronchial
lumen where they collide. High-speed video-filming during sound
production has revealed that sound pulses coincide with short
duration formation of slots between the soft tissue masses forming
a pneumatic valve, which suggests that the avian sound
generating mechanism is a similar to that in the human larynx.
Lately studies have revealed surprising properties of the syringeal
muscles and physical models of the syrinx have given us new
insight into the workings of this fascinating organ.
Testosterone early treatment affects production of song
learning in male zebra finches
Albertine Leitão and Manfred Gahr
Max Planck Institute for Ornithology, Eberhard-Gwinner-Str. 82319
Seewiesen, Germany
Songbirds as well as humans exhibit vocal learning. In male zebra
finches the sensory and motor phases overlap. Juveniles start to
sing and memorize the father’s song from 25 post-hatching days
(PHD) and they have to be exposed at least ten days with the
tutor’s song to be able to produce an accurate copy of the tutor,
when adult ca. 90PHD. Song learning and production are
controlled by a discrete neural circuit, which undergoes profound
developmental changes during the time when song is learned.
First singing starts when synaptic connections between two song
control areas, HVC and RA, are established, sometime after
PHD25. To understand how testosterone influences different
stages of behavioural and neural development, we implanted
juvenile males at PHD16 with testosterone (T) or placebo (P)
pellets. We removed the tutor at PHD25 and monitored
continuously their vocalizations until adulthood. We compared
song development in T and P groups with birds implanted with
placebo but that were kept exposed to the tutor’s song until PHD35
(C, control) and with juveniles implanted with testosterone that
were raised in acoustic isolation (no tutor). We found that
administration of T induces a shift in the onset of song production:
birds implanted with T started to sing at 19PHD, instead of 25 for C
and P groups. Moreover, while not exposed to the tutor’s song at
the ‘critical’ period T birds were nonetheless able to learn the
tutor’s song as C birds did. P birds produced a song similar to
isolate birds. We discuss these behavioural changes with our
findings in the organisation of the neural vocal system.