First published online April 8, 2004
Journal of Experimental Biology 207, 1643-1654 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00928
Sound generation in the searobin (Prionotus carolinus), a fish with alternate sonic muscle contraction
Martin A. Connaughton
Washington College, Department of Biology, 300 Washington Ave,
Chestertown, MD 21620, USA
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Fig. 1. (A) The position of the swimbladder (SB), sonic muscles (SM) and sonic
nerve (SN) in the northern searobin, Prionotus carolinus. (B) A view
of the dorsal surface of the swimbladder illustrating the intrinsic sonic
muscles and the sonic nerve innervating them.
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Fig. 2. The sonagram (A), waveform (B) and power spectrum (C) of a Prionotus
carolinus voluntary disturbance call recorded in air.
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Fig. 3. (A) Fundamental frequency (N=12) and (B) number of action
potentials that failed to produce an acoustic pulse from call onset
(N=10) regressed across holding tank temperature. Data were taken
from simultaneous acoustic and unilateral electromyogram recordings of
voluntary in-air disturbance calls.
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Fig. 4. Sound and (A) unilateral or (B) bilateral sonic muscle electromyogram (EMG)
traces from voluntary disturbance calls recorded in air. In the bilateral
trace, action potentials from the right sonic muscle deflect down, while those
from the left muscle deflect up. Muscle action potentials occur before
alternate sound pulses in the unilateral trace but before each sound in the
bilateral trace (dotted lines). Note the action potentials failing to produce
acoustic pulses early in both calls and the two attenuated sound pulses at the
end of each call that are not associated with any action potentials (double
arrows in both traces). Note also the sound pulse in the unilateral trace
denoted with a single arrow. This sound indicates that the contralateral
(off-trace) sonic muscle contracted last in this call.
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Fig. 5. Acoustic fundamental frequency (sound repetition rate) regressed across
unilateral action potential repetition rate. Values were generated from the
period of the respective waveforms, not from fast Fourier transformation
(N=10).
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Fig. 6. Acoustic (top panels) and bilateral sonic muscle electromyogram (EMG;
bottom panels) traces from a single evoked twitch and a voluntary call. The
single twitch was evoked by stimulating the sonic nerve at 50 Hz and generated
a two-part acoustic waveform. In the voluntary call, sound pulses from the
right (R) and left (L) sonic muscle twitches are noted. Descriptions and mean
durations of intervals A–H can be found in Tables
1,
2.
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Fig. 7. A diagram of sonic muscle electromyogram (EMG; 1–5) and acoustic
traces from a voluntary disturbance call with a breakdown of dual-waveform
sounds produced by each muscle twitch (vertical 1–5). Right and left EMG
traces are superimposed on the same trace all deflecting up and the acoustic
trace has been simplified to highlight the negative pressure peaks. Note that
the 2nd sound waveform (relaxation sound; see text) of a single twitch
coincides with the 1st waveform (contraction sound) of the next twitch of that
sonic muscle, not the contralateral muscle (compare traces 2 and 4, double
arrows, and traces 3 and 5, single arrows). Note also that the first two sound
pulses in the call are not reinforced in this manner. Finally, note that the
relaxation sounds of the final twitch of the right and left sonic muscles
account for the two attenuated sound pulses at the end of the call.
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Fig. 8. Mean (± S.D.; N=2–5) sound pressure level
of sounds evoked by stimulation of the sonic nerve at frequencies of
50–200 Hz. Sound pressure level was measured as the average pressure
(re: 20 µPa) over the duration of a 90 ms stimulus sweep.
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Fig. 9. Acoustic and electromyogram traces from calls evoked by 90 ms trains of
stimuli applied unilaterally to the sonic nerve. The sonic muscle is fast
enough that stimulation at 50 Hz resulted in a series of separate twitches in
which the entire two-part waveform of the produced sound can be seen. Action
potentials matched stimulation frequencies to 360 Hz (not shown) but responded
to alternate stimuli at 400 Hz.
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Fig. 10. (A) Sample distribution of sound pressure level (SPL) across stimulus rate
for sounds evoked bilaterally and unilaterally from the same fish (90 ms
sweeps at 100–150 Hz). (B) SPL difference between bilaterally and
unilaterally evoked calls (mean ± S.D.; N=4). SPL
was measured as the average pressure (re: 20 µPa) over the duration of a 90
ms stimulus sweep.
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© The Company of Biologists Ltd 2004
