First published online August 17, 2006
Journal of Experimental Biology 209, 3281-3287 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02383
The pressures of suction feeding: the relation between buccal pressure and induced fluid speed in centrarchid fishes
Timothy E. Higham1,*,
Steven W. Day2 and
Peter C. Wainwright1
1 Section of Evolution and Ecology, University of California, One Shields
Avenue, Davis, CA 95616, USA
2 Department of Mechanical Engineering, Rochester Institute of Technology,
76 Lomb Memorial Drive, Rochester, NY 14623-5604, USA
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Fig. 1. Representative sequences of gape (black circles), fluid speed (green
squares), and pressure (red triangles) for bluegill sunfish (A) and largemouth
bass (B). Note that the magnitudes of subambient pressure and fluid speed are
both greater in bluegill sunfish than largemouth bass.
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Fig. 2. A log-log plot of time to peak gape (TTPG, ms) versus
peak buccal pressure (kPa) for largemouth bass (black circles) and bluegill
sunfish (red triangles). For this plot, the absolute value of pressure was
used. Note that as the duration of time to peak gape gets longer, the
magnitude of pressure decreases. The relationship between these variables is
much stronger for bluegill (r2=0.95) than for bass
(r2=0.29).
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Fig. 3. The relative timing of peak pressure and peak fluid speed with respect to
20% of peak gape (dotted vertical line on the left) and 95% of peak gape
(dotted vertical line on the right) for largemouth bass (black squares) and
bluegill sunfish (red circles). Each value is scaled to the duration of time
to peak gape where 0 is 20% and 1 is 95% of peak gape. Note that peak fluid
speed follows peak gape in both largemouth bass and bluegill sunfish. The
timing of peak pressure is earlier, relative to 95% of peak gape, in bass
(0.51) than in bluegill (0.76).
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Fig. 4. Measured values of peak fluid speed (cm s-1) and peak buccal
pressure (kPa) for largemouth bass (black upward triangles) and bluegill
sunfish (red squares), and the fluid speeds predicted from the model
(Muller et al., 1982 ) for
largemouth bass (black downward triangles) and bluegill sunfish (red circles).
As in previous plots, the absolute value of buccal pressure is shown. The
lines designated as `model' are based on values of peak fluid speed calculated
using the model (Muller et al.,
1982) for the pressures that we measured. This was done separately
for each species. See text for additional explanations. The slopes of the
linear regressions fit to the model output (0.51) are higher than the slopes
of the empirical data for largemouth bass (0.36) and bluegill sunfish (0.38),
and the values for fluid speed predicted by the model are well above the
measured values. Note that pressure explains more of the variation in fluid
speed for bluegill (r2=0.79; P<0.001) than
bass (r2=0.56; P<0.001). (A) Fluid speeds
where we measured them are shown, at a distance equal to  peak gape
away from the mouth aperture; (B) fluid speeds at the mouth aperture. In order
to transform the measured values of fluid speed to values at the mouth
aperture, we multiplied the bass values by 4.6
(Higham et al., 2006) and the
bluegill values by 3.6 (Day et al.,
2005), based on empirical relationships of the drop in fluid speed
with distance from the mouth aperture. Note that the two species exhibit
different relationships between pressure and fluid speed for fluid speeds
measured at the mouth aperture, whereas the two species are similar for fluid
speeds measured at peak gape away from the mouth.
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© The Company of Biologists Ltd 2006
