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Fig. 5. Illustration of the steps carried out in modelling the buccal volume
increase, as a series of 21 elliptical cylinders in C. apus. (A) The
height and width of the buccal cavity were measured at several positions using
X-ray images of the (compressed) catfish head filled with radio-opaque fluid.
(B) These measurements were used to construct the elliptical cylinder model
for buccal volume, which is assumed to occur inside the catfish's head prior
to the start of suction feeding. (C) Next, simultaneous lateral and ventral
high-speed videos were recorded of catfish capturing pieces of fish. (D)
Finally, by assuming that the thickness of the head tissues bordering the
buccal cavity does not change in time (see arrows), the increases in the radii
of each elliptical cylinder during suction could be calculated. Note that the
part of the hypertrophied jaw adductors extending laterally at the level of
the eyes is not included in the external head boundaries a seen from a ventral
view (see lower drawings in B and D).
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