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First published online March 31, 2005
Journal of Experimental Biology 208, 1421-1433 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01552

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Prey-capture in Pomacanthus semicirculatus (Teleostei, Pomacanthidae): functional implications of intramandibular joints in marine angelfishes

Nicolai Konow^* and David R. Bellwood

Centre for Coral Reef Biodiversity, Department of Marine Biology, James Cook University, Townsville, Queensland 4811, Australia

View larger version (53K): [in a new window]   Fig. 1. High-speed image frames from a 200 frames s–1 recording illustrating the feeding event in a Pomacanthus semicirculatus specimen (245 mm SL) feeding on sponge attached to a clip. Reference grid squares are 2 cm2, and time in ms from bite (TB) in bottom left corner of frames: (A) protrusion onset; (B) maximum protrusion; (C) bite; (D) feeding event complete. Arrows with numerals (in B) refer to manipulations used on dissections (see text). Black and white dots indicate 15 landmarks on skull topography, prey and origin reference digitised in feeding sequences. Linear measurements (in A): RTOT, total ram; RB, body ram; G, gape distance; P, premaxilla excursion; D, dentary excursion. Black distance marker indicates origin-reference used to compensate for bite-related and unnoticed prey movements in analyses. Angular measurements (in B–D): C, cranial elevation; O, opercular rotation; H, suspensorial rotation; S, pectoral girdle rotation; I, intramandibular rotation; M, maxillary rotation; L, lower jaw depression.

View larger version (25K): [in a new window]   Fig. 4. Mean kinematics profiles for three Pomacanthus semicirculatus (five bites per individual, all bites pooled ± S.E.M.), illustrating timing of onset, magnitude and duration of angular displacement (in degrees) in: (A) hyomandibular; (B) mandibular; (C) opercular and (D) intramandibular mechanisms. Note the alignment of kinematics profiles around time of bite (TB).

View larger version (35K): [in a new window]   Fig. 5. Mean kinematics profiles for three Pomacanthus semicirculatus [five bites per individual, all bites pooled, vertical axis shows ratio of head length (HL) ± S.E.M.], illustrating timing of onset, magnitude and duration of linear displacement of: (A) the premaxilla (square) and the mandible (triangle); and (B) body-ram (open circle) and total-ram (closed circle).

View larger version (24K): [in a new window]   Fig. 3. Schematic figure of the skull kinematics of Pomacanthus semicirculatus, illustrating the three significant phases of a grab-and-tearing feeding event. (A) Jaw apparatus prior to protrusion onset, (B) protruded, and (C) protruded-closed state (upon jaw retraction, C returns to A after the recovery phase, in preparation for the next feeding event). Colour coding: grey, neurocranium, red, oral jaws, yellow, maxilla, blue, suspensorium, green, opercular series and articular. Arrows indicate displacement, mediated by tendons and ligaments. Open circles indicate rotation and filled circles indicate passive linkage. Cones represent inferred contraction of a muscle group, with myology labelling as in Fig. 2. HPAX: hypaxialis musculature.

View larger version (53K): [in a new window]   Fig. 2. Illustration of the Pomacanthus semicirculatus skull (left lateral view) based on clear-stained preparations. (A) Feeding apparatus when relaxed. (B) Suspensorium and operculum rotated, and jaws protruded. (C) Detail of protruded-closed oral jaws. Osteology labelling: an, angular; art, articular; d, dentary; hyom, hyomandibular; ihy, interhyal; iop, interoperculum; mpt, metapterygoid; mx, maxilla; op, operculum; pal, palatine; pmx, premaxilla; pop, preoperculum; ptr, ectopterygoid; q, quadrate; sop, suboperculum; supcl, supracleitrum; sym, symplectic; urohy, urohyal; lc, lachrymal; points of flexion are indicated in A between hyomandibular with nc, neurocranium (filled circle) and between the palatopterygoid complex of the suspensorium with the lateral ethmoid (open circle). Open circle in C: IMJ, intramandibular joint. Myology labelling: A1 (10% grey); A2 (50% grey, and medial to A1 and A3); A3 (30% grey), adductor mandibulae segments. LOP: levator operculi, DOP: dilator operculi, LAP: levator arcus palatini, AAP: adductor arcus palatini. Ligament labelling (all in 75% grey): EF, naso–premaxilla elastic fibres; DLPM, dorsal premaxilla–maxilla ligament; LIM, interopercular–mandibular ligament; LIS, interopercular–subopercular ligament; ILPM, inner premaxilla–maxillary ligament; LPM, palatine–maxillary ligament; LRDM, articular–dentary–maxillary ligament; VLPM, ventral premaxilla–maxilla ligament. Scale bars, 10 mm.

View larger version (14K): [in a new window]   Fig. 6. Camera lucida drawings of the feeding apparatus in four biting coral reef teleosts with intramandibular joints marked by open circles. Proximal (articular) and distal (dentary) components of the joints are marked by solid black bars (see text for explanation). (A,B) joints rotated, (C,D) joints relaxed. (A) Pomacanthus (f. Pomacanthidae); (B) Ctenochaetus, (f. Acanthuridae); (C) Scarus, (f. Scaridae); (D) Escenius, (f. Blennidae). Scale bars, 10 mm, except D, 0.1 mm.Labelling follows Fig. 2.