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First published online December 2, 2005
Journal of Experimental Biology 208, 4757-4768 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01938

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Functional morphology of feeding in the scale-eating specialist Catoprion mento

Jeff Janovetz

Department of Biology, Sweet Briar College, Sweet Briar, VA 24595, USA

View larger version (130K): [in a new window]   Fig. 1. Landmarks of 11 points digitized on each frame for calculation of the 12 kinematic variables used to describe prey capture behavior. For a description of the points, see text.

View larger version (151K): [in a new window]   Fig. 2. Representative sequence of Catoprion mento scale feeding on a goldfish. (A) Time zero marks the start of jaw opening; (B) 52 ms later, gape angle exceeds 90° well before contact is made with the prey; (C) 76 ms, maximum gape angle; (D) 136 ms, maximum opercular expansion as the teeth rasp the flank of the fish; (E) 164 ms, jaw closing and ingestion of scales during the bite; (F) 260 ms, post-strike, cranial elements have returned to resting position. Note the loose scales in the water column removed during the strike. Note also the integrated use of body and tail undulations throughout the strike to power the ramming attack.

View larger version (22K): [in a new window]   Fig. 3. Plots of mean kinematic values (± S.E.M.) for 25 scale-feeding strikes from five Catoprion mento individuals. All variables for all strikes were standardized by time of maximum gape angle. The broken line marks the time of prey contact, while the solid line marks the time of maximum gape angle in each plot. Note the plateau stage of stability at near-maximum displacement for cranial elevation and opercular rotation.

View larger version (134K): [in a new window]   Fig. 4. Representative sequence of Catoprion mento capturing a live fish. (A) Time zero marks the start of jaw opening; note the fast-start behavior of the prey; (B) 36 ms later, gape angle widens but most of the distance between Catoprion and the fish has been closed by movement of the predator; (C) 52 ms, at maximum gape, most of the fish is within the buccal cavity; (D) 60 ms, maximum hyoid depression; (E) 64 ms, maximum opercular expansion; (F) 116 ms, post-strike, cranial elements have returned to resting position.

View larger version (173K): [in a new window]   Fig. 5. Representative sequence of Catoprion mento capturing a loose scale. (A) Time zero marks the start of jaw opening. The circle identifies the scale prey, which is also visible in B and C. (B) 40 ms later, gape angle widens but most of the distance between Catoprion and the scale has been closed by movement of the predator. Note the smaller distance moved by Catoprion compared with during strikes on fish; (C) 52 ms, continued lower jaw rotation at a slower rate than fish strikes; (D) 64 ms, maximum gape; (E) 92 ms, maximum opercular expansion; (F) 112 ms, slow return of cranial elements to resting position.

View larger version (22K): [in a new window]   Fig. 6. Plots of mean kinematic values (± S.E.M.) for 25 strikes on live fish from five Catoprion mento individuals. All variables for all strikes were standardized by time of maximum gape angle, marked by the vertical line in each plot. Note the bell shape of all kinematic plots and the anterior-to-posterior sequence of cranial movements.

View larger version (21K): [in a new window]   Fig. 7. Plots of mean kinematic values (± S.E.M.) for 25 strikes on loose scales from five Catoprion mento individuals. All variables for all strikes were standardized by time of maximum gape angle, marked by the vertical line in each plot. Note the lower displacements and longer durations of cranial movements compared with fish strikes.

View larger version (24K): [in a new window]   Fig. 8. Histograms comparing mean values (± S.E.M.) for kinematic displacement variables for each prey. The key for all graphs is as given in the gape angle plot. Vertical lines connect prey whose means are not significantly different according to a Bonferroni-corrected value of P<0.05; separate lines indicate that means are significantly different.

View larger version (25K): [in a new window]   Fig. 9. Histograms comparing mean values (± S.E.M.) for kinematic timing variables for each prey. The key for all graphs is as given in the gape angle plot. All pair-wise comparisons are statistically different according to a Bonferroni-corrected value of P<0.05.

View larger version (22K): [in a new window]   Fig. 10. Principal components analysis of all 75 strikes by Catoprion mento on three prey. Each symbol represents one feeding sequence; F, live fish; L, loose scales; S, scale feeding. Boundary lines surrounding each prey category are subjectively drawn. Factor loadings for all kinematic variables are listed in Table 3.

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