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First published online December 14, 2006
Journal of Experimental Biology 210, 27-36 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02619

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No trade-off between biting and suction feeding performance in clariid catfishes

Sam Van Wassenbergh^1,*, Anthony Herrel¹, Dominique Adriaens² and Peter Aerts^1,3

¹ Department of Biology, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium
² Evolutionary Morphology of Vertebrates, Ghent University, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
³ Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, B-9000 Gent, Belgium

View larger version (98K): [in this window] [in a new window]   Fig. 1. Side view of the head of Gymnallabes typus that clearly shows the bulging, hypertrophied jaw adductor muscles.

View larger version (31K): [in this window] [in a new window]   Fig. 2. Partial phylogeny of Clariidae based on the consensus tree of several analyses on ribosomal DNA sequences presented elsewhere (Jansen et al., 2006) indicating the species studied (Clarias gariepinus, Gymnallabes typus and Channallabes apus). Illustrations of the external head morphology (left drawings) showing the closed skull roofs of C. gariepinus, Clarias buthupogon and the outgroup sister species of Clariidae Heteropneustes fossilis, as opposed to the hypertrophied jaw adductors in G. typus and C. apus that fill a large part of the head behind the eyes. This jaw adductor hypertrophy has evolved four times independently in Clariidae, of which only two lineages are illustrated here. The jaw adductors imposed on osteological drawings of the head (right drawings) for the three species studied clearly illustrate the jaw muscle hypertrophy in G. typus and C. apus compared to the relatively slender jaw muscles of C. gariepinus, which are partly covered by neurocranial bones. The graphs give the maximal bite force (perpendicular to the lower jaw) at the anteriormost teeth (black bars) and posteriormost teeth (grey bars) of animals with a cranial length scaled to 39 mm and at a gape angle of 10° as calculated by Herrel et al. (Herrel et al., 2002).

View larger version (57K): [in this window] [in a new window]   Fig. 3. Selected X-ray video frames for Clarias gariepinus (cranial length 70.2 mm) capturing a spherical piece of shrimp meat (into which a radio-opaque marker was inserted) presented loosely on the top of a needle. White circles highlight the prey. The fish-bound frame of reference is shown in the top frame.

View larger version (14K): [in this window] [in a new window]   Fig. 4. Comparison of the average magnitude of rotation (light grey) and average peak velocity of hyoid depression (dark grey) for three C. gariepinus individuals (1-3) capturing three different prey (illustrated above) during X-ray video recording [kinematic data from Van Wassenbergh et al. (Van Wassenbergh et al., 2005)]. The graph shows that suction effort on the relatively small, spherical prey attached on the tip of a needle (left) is not reduced compared to suction feeding sequences on firmly attached prey (shrimp; middle) or large, voluminous prey pieces (fish; right). Values are means ± s.d.; N=10, 5 and 5 for the three prey, respectively (for each individual).

View larger version (26K): [in this window] [in a new window]   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).

View larger version (101K): [in this window] [in a new window]   Fig. 6. Lateral (Ai-Ci) and ventral view (Aii-Cii) prey trajectories (blue curves and circles) and the corresponding plots of prey velocities versus prey position (graphs) for an individual of each species with the highest suction performance (A: C. gariepinus, B: G. typus and C: C. apus). Prey velocities and positions are in the fish-bound frame of reference. Colour codes and positive directions of the velocities are explained on the left side of the graphs.

View larger version (5K): [in this window] [in a new window]   Fig. 7. Logarithmic plot of peak prey velocities as a function of cranial length (individual maxima of unfiltered data; filled black symbols) and the scaling relationship (least-squares regression with 95% confidence limits) of peak flow velocities (white circles) (from Van Wassenbergh et al., 2006b). C. gariepinus is represented by circles, G. typus by the triangle and C. apus by squares. No significant interspecific differences between C. gariepinus and C. apus were found for the residuals of peak prey velocities with respect to the scaling relationship (ANOVA, P=0.41).

View larger version (15K): [in this window] [in a new window]   Fig. 8. Increase in the volume of the bucco-pharyngeal cavity during suction feeding calculated using ellipse models (see also Fig. 5). The 100% relative time (x-axis) corresponds to one frame after maximal volume. All models are scaled to a length of 25 mm. In addition to the total volume increase (ventral and lateral expansion), also the volume increase due to only ventral expansion is shown (legend above graphs). Shaded areas indicate standard errors. The arrows indicate the volume increase due to lateral expansion.