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First published online December 16, 2008
Journal of Experimental Biology 212, 116-125 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.023929
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Kinematics of benthic suction feeding in Callichthyidae and Mochokidae, with functional implications for the evolution of food scraping in catfishes

Sam Van Wassenbergh1,*, Tim Lieben1, Anthony Herrel2, Frank Huysentruyt3, Tom Geerinckx3, Dominique Adriaens3 and Peter Aerts1,4

1 Department of Biology, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium
2 Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
3 Evolutionary Morphology of Vertebrates, Ghent University, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium
4 Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, B-9000 Gent, Belgium


Figure 1
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  		Fig. 1. Simplified phylogeny of catfishes (Siluriformes) based on molecular data (Sullivan et al., 2006Go), indicating the two lineages where scraping has evolved independently: Loricarioidei and Mochokidae. Triangles in the tree indicate a taxonomically large group.

 

Figure 2
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  		Fig. 2. Morphospace of cranial width versus cranial height at the level of the opercular slits, with each point representing a single species. All heads were isometrically scaled to a length of 72 mm. Non-loricarioid, non-mochokid suction feeders are shown [data from Van Wassenbergh et al. (Van Wassenbergh et al., 2006aGo)] in contrast to (A) scraping and non-scraping Loricarioidei or (B) Mochokidae. Note that closest relatives of the relatively broad-headed scraping Loricarioidei have a relatively high and narrow head with respect to other suction feeding catfish (A). The same trend, although less pronounced, can be observed within the Mochokidae (B).

 

Figure 3
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  		Fig. 3. Illustration of the frame of reference moving with the neurocranium, and the landmarks digitized for the kinematical analysis. These landmarks are: (1) the center of the eye, (2) the rostral base of the dorsal fin, (3) the tip of the lower jaw, (4) the tip of the hyoid and (5) the tip of the cleithrum. Scale bar, 10 mm.

 

Figure 4
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  		Fig. 4. Reconstruction of the starting volumes of the buccal cavities of Clarias (A), Corydoras (B) and Synodontis (C) from lateral view (top drawings) and dorsal view (bottom drawings) based on the ellipse method (Drost and Van den Boogaart, 1986Go) applied to X-ray images. Although the degree of lateral flattening is less pronounced at the level of the buccal cavity compared with the external head shape (because of the relatively high neurocranium in Corydoras and Synodontis compared with Clarias), a strong correlation (R2=0.983) exists between external shape and buccal cavity shape among these three species.

 

Figure 5
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  		Fig. 5. Example of a prey capture sequence in Corydoras splendens in lateral view (left column) and ventral view (right column). Scale bar, 10 mm.

 

Figure 6
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  		Fig. 6. Mean kinematical profiles of lower jaw depression, hyoid depression, cleithrum depression and neurocranium pitch angle in Clarias gariepinus [black; data from Van Wassenbergh et al. (Van Wassenbergh et al., 2005Go)], Corydoras splendens (red) and Synodontis multipunctatus (green). Shaded areas indicate standard errors (N=13 sequences per species; two individuals of C. gariepinus and S. multipunctatus, four individuals of C. splendens). Note that the difference in speed (longer prey-capture time for Clarias gariepinus) is due to body size differences (head length Clarias=80±13 mm).

 

Figure 7
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  		Fig. 7. Increase in the volume of the bucco-pharyngeal cavity during suction feeding calculated using ellipse models (see also Fig. 4 for start volumes). The 100% relative time (x-axis) corresponds to one frame after maximal volume. All models were scaled to a head length of 25 mm. TOT, total volume increase (ventral and lateral expansion; solid line); VEN, the volume increase due to only ventral expansion (dashed line); and LAT, the volume increase due to only lateral expansion (dotted line). Shaded areas indicate standard errors.

 

Figure 8
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  		Fig. 8. Correlations between the average aspect ratio of the cross-sections of the buccal cavity (height/width) and (A) the volume increase due to ventral expansion, and (B) the relative contribution of lateral expansion to the total volume increase during suction feeding in the three species studied [ordered with increasing buccal height to width ratio, or from dorsoventrally (DV) flattened to more laterally (LAT) flattened: Clarias gariepinus (gray), Synodontis multipunctatus (green) and Corydoras splendens (red)]. Boxes represent s.e.m., whiskers represent s.d.

 

Figure 9
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  		Fig. 9. Ancestral state reconstruction of head shape (A) and mouth position (B) in catfish assuming squared-change parsimony based on the Bayesian phylogeny of Sullivan et al. and Lundberg et al. (Sullivan et al., 2006Go; Lundberg et al., 2007Go). This reconstruction suggests that the ancestral state is a dorsoventrally flattened head, with evolution of a lateral flattened head only occurring within the Corydoras, Synodontis and Schilbe lineages (A). Mouth position is a phylogenetically highly variable trait, for which the ancestral state for catfishes can be either a terminal or subterminal mouth (B). These data suggest that a ventral mouth evolved in the suckermouth lineages (Astroblepus, Loricaria and Atopochilus) and Trichomycteridae (Ochmacanthus).

 

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© The Company of Biologists Ltd 2009