First published online March 8, 2005
Journal of Experimental Biology 208, 929-938 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01433
Fast-start muscle dynamics in the rainbow trout Oncorhynchus mykiss: phase relationship of white muscle shortening and body curvature
Jeremy A. Goldbogen1,*,
Robert E. Shadwick1,
Douglas S. Fudge2 and
John M. Gosline2
1 Marine Biology Research Division, Scripps Institution of Oceanography, La
Jolla, CA 92093-0204, USA
2 Department of Zoology, University of British Columbia, 6270 University
Boulevard, Vancouver, British Columbia V6T 1Z4, Canada
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Fig. 1. Sequential frames from high-speed videography (250 Hz) during induced
fast-starts. A representative example of a response under low strain (A) and a
response under high strain (B). Markers are visible on the back of the fish at
0.4L and 0.7L.
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Fig. 2. Midline kinematics in x–y coordinate space derived from the
digitized outlines of each video frame (250 Hz). Colored circles correspond to
each video frame shown in Fig.
1 for a response under low strain (A) and a response under high
strain (B), starting with dark red colors and progressing through the colors
of the rainbow to violet. Arrows denote orientation of the head as an
extension of the first two digitized segments.
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Fig. 3. Stage 1 angle (dark circles) and the average measured peak strain between
the anterior and posterior axial positions (gray circles) expressed as a
function of the minimum distance measured between the head and caudal peduncle
(an index of total body curvature, where smaller distances are interpreted as
greater overall curvatures) over the course of the escape response. The dashed
line (12.3% average strain) corresponds to the arbitrary division used to
separate high strain and low strain events.
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Fig. 4. Maximum curvature experienced along the length of the body during 20
fast-starts of six fish. Axial location runs from the tip of the head
(0.0L) to the tail (1.0L). Gray profiles denote individual
trials and the black profile shows the mean curvature. Note the local minimum
at approximately 0.4L.
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Fig. 5. Time series of measured strain (solid lines) from sonomicrometry and
predicted strain (open circles) from midline curvature for the anterior (blue)
and posterior (red) positions. Vertical dashed lines represent sequential
video frames shown in Fig. 1
for a weaker response (A) and a stronger response (B). Sonometric crystals are
located on the concave side of the bend for each response and, thus, show
muscle shortening.
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Fig. 6. White muscle strains measured by sonomicrometry at both axial locations
(0.4L and 0.7L) closely match strains estimated from body
curvature, but this trend deviates at higher strains. Peak (black circles),
initial and final (gray circles) strains were measured during induced
fast-starts. The solid line represents the linear regression through initial,
peak and final strains (r2=0.82, P<0.05). The
strain relationship of a homogeneous bending beam is expressed by the dashed
line.
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Fig. 7. The effect of high strain on the phase shifts between measured and
estimated strain during induced fast-starts for the anterior (0.4FL)
and posterior (0.7FL) locations. Stronger escapes (11 trials, four
individuals), which experience an average strain between the anterior and
posterior position greater than 12.3%, are represented by black open circles
and average phase shifts are represented by horizontal black bars. Weaker
escapes (nine trials, four individuals), less than 12.3% average strain, are
shown by gray-filled circles and average phase shifts are represented by
horizontal gray bars. High strain significantly increases the average phase
shift from 0.005±0.005 s to 0.021±0.009 s at 0.7L
(Mann-Whitney U-test, P<0.005).
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Fig. 8. Comparison between measured peak strain at the anterior (0.4FL)
and posterior (0.7FL) positions for each response. High strain events
(>12.3%) are shown by black circles, whereas low strain events (<12.3%)
are shown by gray circles. A linear regression of the data is shown for high
strain events (P<001, r2=0.84,
N=9).
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Fig. 9. Strain magnitude calculated from simple bending beam theory accurately
predicts axial strain measured by sonomicrometry (blue line;
P=0.0001; r2=0.9163; N=22). Blue circles
represent observations from steady swimming, fast-starts, and sprinting in
several species of fish (Coughlin et al.,
1996 ; Katz et al.,
1999; Wakeling and Johnston, 1999;
Ellerby and Altringham, 2001).
Tuna steady swimming, represented by red circles, are excluded from the
regression because of their specialized myotendinous architecture
(Shadwick et al., 1999;
Katz et al., 2001). Fast-start
data from this study are superimposed onto this figure: strains calculated at
the anterior position (squares) and the posterior position (triangles) are
shown for weaker responses (light blue) and stronger responses (dark blue and
red). Note that only the posterior location under high strain lies outside the
95% confidence interval that contains the one-to-one predictor (gray line).
Standard errors of the mean are only shown for the present study for brevity.
Figure adapted from Long et al.
(2002).
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Fig. 10. Muscle strain rate (gray line) minimum at 0.4L is coincident with
the rapid increase in head turning rate (black line). Muscle strain rate was
derived from the muscle strain profile shown by the dotted gray line.
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© The Company of Biologists Ltd 2005
