First published online May 8, 2007
Journal of Experimental Biology 210, 1834-1845 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001495
Effects of temperature on tuning of the auditory pathway in the cicada Tettigetta josei (Hemiptera, Tibicinidae)
P. J. Fonseca* and
T. Correia
Departamento de Biologia Animal e Centro de Biologia Ambiental,
Faculdade de Ciências da Universidade de Lisboa, Bloco C2, Campo Grande,
1749-016 Lisboa, Portugal
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Fig. 1. Set-up used to control the body temperature of the cicada during
intracellular recordings of auditory interneurons and recordings of the
auditory nerve activity. The temperature of the animal holder was modified
with a Peltier element and controlled via two thermocouples. The
sensor in the holder kept its temperature within values compatible with the
living tissues (10–40°C) while the second thermocouple measured and
was used to control the temperature of the cicada body. The flowing water is
needed to add to or remove heat from the Peltier element.
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Fig. 2. Examples of electrophysiological responses of the auditory interneurons.
The types varied from a phasic response (A) with a single action potential, to
a phasic-tonic (B) and a more tonic response (C). The examples are from three
cells recorded 20 dB above threshold at 6 kHz and at 24°C.
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Fig. 3. Examples of four morphological types of auditory interneurons (see
Table 1) (tj19-1, tj67-1,
tj67-2, tj71-2) with two sensitivity maxima that revealed a shift in the
characteristic frequency in the range 3–8 kHz. A fifth cell type
(tj52-1) with a different morphology was only partially stained and therefore
is not shown. The cells were stained with Lucifer Yellow.
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Fig. 4. Effects of body temperature on tuning, sensitivity, latency and response
strength of auditory interneurons of the cicada T. josei. (A,B)
Tuning curves of two interneurons exhibiting shifts in their tuning and
sensitivity with body temperatures ranging from 16°C to 28°C. Maximum
effects are observed at temperatures from 16–18°C to 24°C in the
frequency range 3 to 8 kHz. At higher frequencies the characteristic frequency
remains constant, but some effect on sensitivity is still present. (C)
Sensitivity at the characteristic frequency of 20 recordings, of the 29 cells
listed in Table 1, which
exhibited an increased sensitivity with temperature. The lines connect the
sensitivities of each interneuron. (D) Dependence of latency on temperature,
obtained from 29 recordings of interneurons. Latencies were measured 20 dB
above threshold at the characteristic frequency and decreased with increasing
temperature. (E) Dependence of the number of action potentials on the
temperature in 29 recordings. At each temperature the number of action
potentials is an average of five stimulus presentations at the characteristic
frequency and 20 dB above threshold.
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Fig. 5. Intracellular recording of an auditory interneuron showing the variation in
latency and strength of the response with temperature. The sound stimulus at 6
kHz was delivered 20 dB above threshold at each temperature.
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Fig. 6. Effects of body temperature on tuning, sensitivity and latency evaluated
from recordings of the auditory nerve of the cicada T. josei. (A)
Averaged and (B) example tuning curves measured at different temperatures
ranging from 16°C to 28°C. There is a strong effect in the
characteristic frequency and sensitivity in the range 3–8 kHz, but not
at higher frequencies. Error bars indicate the standard deviation. (C)
Sensitivity at the characteristic frequency measured in the 10 cicadas, from
19 recordings (see Table 2),
which exhibited increased sensitivity with temperature. The lines connect the
sensitivities evaluated from each auditory nerve recording. (D) Dependence of
latency on temperature measured in 19 cicadas. Latencies were measured 20 dB
above threshold and decreased with increasing temperature.
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Fig. 7. The typical effect of body temperature, in one of three males measured, on
the vibrations of the tympanal apodeme measured by laser Doppler vibrometry
(LDV). There is no clear effect on the vibration velocity (presented in
arbitrary units) and the phase angle, especially in the frequency range
3–8 kHz, where a strong effect of body temperature on auditory tuning
and sensitivity was measured in the nervous system. The diagram on the right
is of a the tympanum, tympanal apodeme and auditory organ, indicating the
point where the laser beam was focused.
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Fig. 8. Effects of 200 mmol l–1 tetraethylammonium (TEA) on tuning
and sensitivity evaluated from recordings of the auditory nerve of the cicada
T. josei. (A) Averaged and (B) example tuning curves measured before
and after drug application, and the effect of repeatedly washing with insect
saline. TEA resulted in a downward shift of the characteristic frequency and a
reduced sensitivity. Sensitivity and tuning were reestablished after
repeatedly washing the preparation with insect saline for up to 2 h 30 min.
Error bars in A indicate the standard deviation. Recordings were made at
ambient temperature of 24–28°C.
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© The Company of Biologists Ltd 2007
