Table 1) Comparison of the tympanal ears of vertebrates and insects
number ofQ10dBfrequency range
auditory receptors
[kHz]
vertebrates:
fish 1,2
amphibians 3
reptiles 4
birds 4
mammals 5
insects:
moth 6
mantid 7
bushcrickets 8, 9, 10
crickets 11
grasshoppers 12, 13
fly 14, 15
cicadas 16, 17, 18
>50000.35
14 - 1500 0.3
50 - 2000 (12000)
5800 - 9600 2
2500 - 14000 2
2
20
20
50
30
30
600
-
4
<1
35 <1
601 - 2
701 - 2
80 (2000)
200 <1
2100 1
-1 (2)0,05
- 3 0,1 - 4
1 - 70,01
- 12 1 - 10
-2000,1- 200
-1
-5
10 -120
20 -100
0,1 - 80
0,1 - 60
~10,1- 50
1 -40
- 7 0,1 - 25
Table 1) Number of auditory receptors in the ear of vertebrates (hair cells) and
insects (scolopidial cells), Q10dB-values and frequency range within the auditory
pathway. Numbers indicate the range commonly observed between species in a
given group, numbers in brackets refer to exceptions rather than the rule.
Q10dB-values provide a measure of frequency tuning derived from a neuron’s
tuning curve at 10 dB above threshold of the characteristic frequency (CF i.e.
frequency at which a cell shows the lowest threshold), and is defined by: CF
divided by the bandwidth at 10 dB above threshold of CF. References for the
data are available from the authors.
References
1.
Fay, R.R. & Popper, A.N. (eds) Comparative hearing, fish and
amphibians. (Springer, Berlin Heidelberg New York 1998)
2.
Webster, D. B., Fay, R. R. & Popper, A. N. (eds) The evolutionary
biology of hearing. (Springer, Berlin Heidelberg New York,
1992)
3.
Llinas, R. & Precht, W. (eds) Frog neurobiology. (Springer, Berlin
Heidelberg New York, 1976)
4.
Manley, G.A. Peripheral hearing mechansims in reptiles and birds.
(Springer, Berlin Heidelberg New York, 1989)
5.
Fay, R.R. & Popper, A.N. (eds) Comparative hearing: mammals.
(Springer, Berlin Heidelberg New York, 1994)
6.
Fullard, J. H. The tuning of moth ears. Experientia 44, 423 - 428.
(1988)
7.
Yager, D.D. & Hoy, R. R. The cyclopean ear: a new sense for the
praing mantis. Science 231, 727 - 729 (1986)
8.
Rö mer, H. Tonotopic organization of the auditory neuropile in the
bushcricket Tettigonia viridissima. Nature 306, 60 - 62
(1983)
9.
Oldfield, B. P. Tonotopic organization of the insect auditory
pathway. TINS 11, 267 - 270 (1988)
10. Stumpner, A. Tonotopic organization of the hearing organ in a
bushcricket - physiological characterization and complete
staining of auditory receptor cells. Naturwissenschaften
83, 81 - 84 (1996)
11. Huber, F., Moore, T. E. & Loher, W. (eds) Cricket behavior and
neurobiology (Cornell University Prerss, Ithaca London,
1989)
12. Jacobs, K., Otte, B. & Lakes-Harlan, R Tympanal receptor cells of
Schistocerca gregaria: correlation of soma positions and
dendrite attachment sites, central projections and
physiologies. J. Exp. Zool 283, 270 - 285 (1999)
13. van Staaden, M. & Rö mer, H. Evolutionary transition from stretch to
hearing organs in ancient grasshoppers. Nature 394, 773 776 (1998)
14. Robert, D., Amoroso, J. & Hoy, R.R. The evolutionary convergence
of hearing in a parasitoid fly and its cricket host. Science
258, 1135 - 1137 (1992)
15. Stumpner, A. & Lakes Harlan, R. Auditory interneurons in a hearing
fly /Therobia leonidei, Ormiini, Tachinidae, Diptera). J.
Comp. Physiol. A 178, 227 - 233 (1996)
16. Michel, K. Das Tympanalorgan von Cicada orni L. (Cicadina,
Homoptera). Zoomorphologie 82, 63-78 (1975)
17. Doolan, J.M. & Young, D. The organization of the auditory organ of
the bladder cicada, Cystosoma saundersii. Phil. Trans. R.
Soc. Lond. B 291, 525-540 (1981).
18. Fonseca, P. J. Acoustic communication in cicadas (Homoptera,
cicadoidea): Sound production and sound reception.
Doctoral Thesis, University of Lisbon (1994)
Materials and methods
Animals and Electrophysiology: Experiments were performed mostly
on males of Tettigetta josei caught near Lisbon, Portugal. The
animal was waxed to a slender brass rod, ventral side up. The
thoracic nervous system was exposed by ventral dissection and
stabilized on a metal plate. The response of the auditory nerve was
monitored with silver hook electrodes (75 µ m). Micropipette
electrodes (resistance 30 - 50 MOhm with 2 M KAc) were filled with
Lucifer Yellow (Sigma cat nº L-0259, 5% in 0.5 M LiCl) for recording
and subsequent staining by hyperpolarizing current (1-5 nA, 2- 10
min). We identified 47 interneurons of which the recorded action
potentials were typically greater than 30 mV. To facilitate
penetration, the sheath of the ganglion at the intended recording site
was treated locally with collagenase (Sigma type I, cat nº C0130)
for 10 to 30 seconds. Temperatures inside the recording set up
were 24 ° C to 26 ° C.
Acoustic stimulation, calibration and recording: Acoustic sine stimuli
were generated computer controlled (Turbolab) and delivered via a
D/A board (Data Translation DT2821-F-8di) at 100 kHz (12 BIT
resolution). The signal passed two computer controlled attenuators;
one to compensate the frequency response of the loudspeaker, the
other for signal attenuation. Sine pulses lasted 25 ms (2 ms ramps)
and were broadcast via a loudspeaker (Dynaudio D28/2) placed 23
cm anteriorly in the longitudinal axis of the preparation. For each
frequency and intensity 5 stimuli were presented. Calibration of the
acoustic set up (lined with sound absorbing material) was achieved
by computing the frequency response and coherence functions
(average of 25 presentations; coherence values: ≥ 0.8; acoustic
calibration with a Brü el & Kjæ r 1/4" microphone, type 4135) at the
position later occupied by the preparation. Repeated calibration
procedures showed that the signal was not affected by small
deviations of the microphone which indicates that the sound field at
the preparation was rather uniform. Stimulus intensities refer to 20
µ P (SPL).
Spectrum of male song The songs of 8 individual males were
recorded (Brü el & Kjæ r microphone 1/4" type 4135; ca. 20 cm from
animal) and digitized online with the above computer board at 100
kHz. The frequency spectrum was computed from single loud song
pulses. For each individual 4 pulses were averaged.
Data analysis Electrophysiological recordings were digitized off line
at sampling rates of 10 kHz per channel (Data translation and
Turbolab see above). Further analysis was aided by Neurolab and
Fonseca et al.: materials and methods
custom written programs (Visual C). For computation of the
threshold curves of auditory nerve recordings and interneurones, first
intensity response curves were determined for each frequency from
30 dB to 90 dB SPL from averaged responses. For intracellular
recordings this was performed twice; first low pass filtered to
determine excitatory and inhibitory synaptic input, and second high
pass filtered for action potentials. In order to determine the
threshold for each frequency, first the mean of spontaneous activity
was computed for each recording from activity without acoustic
stimuli. The threshold criterium was set at 4 standard deviations
from the mean of spontaneous activity. From these intensity
response curves the threshold for each frequency was determined
which - due to the conservative criterium - provides cautious
measures of threshold for all recordings.
4