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Feeding patterns of Chelus fimbriatus (Pleurodira: Chelidae)

Patrick Lemell^1,*, Christoph Lemell², Peter Snelderwaard³, Michaela Gumpenberger⁴, Robert Wochesländer¹ and Josef Weisgram¹

¹ Department of Comparative Anatomy and Morphology, Institute of Zoology, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria
² Institute for Theoretical Physics, TU-Vienna, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria
³ Department of Evolutionary Morphology, Institute of Evolutionary and Ecological Sciences, University Leiden, Kaiserstraat 63, NL-2311GP Leiden, The Netherlands
⁴ Clinic of Radiology, University of Veterinary Medicine, Vienna, Veterinärplatz 1, A-1210 Vienna, Austria

View larger version (13K): [in a new window]   Fig. 1. Schematic representation of a high-speed video frame of Chelus fimbriatus during prey capture. Dots mark the points digitized from recordings (for details see Materials and methods); grey dots mark lead markers for X-ray film. cbI, cornu branchiale I; cbII, cornu branchiale II.

View larger version (63K): [in a new window]   Fig. 2. Computer tomographic photographs of the skull of Chelus fimbriatus. (A) Lateral view; (B) ventral view. The arrow in B indicates the lower jaw, which is too thin to be reconstructed correctly. Note the enlarged ventral area of the hyoid apparatus (hyapp); cbI, cornu branchiale I; cbII, cornu branchiale II.

View larger version (27K): [in a new window]   Fig. 3. (A) Dorsal view of skull of Chelus fimbriatus. The arrows indicate the directions of forces produced during contraction of the jaw adductor muscles, the shaded areas indicate the extent of the muscles and the thickness of the arrows reflects the relative forces of the muscles; the resulting forces produced by the muscles shown on each side are indicated next to the skull. amextmed, pars medialis of external adductor; amextprof, pars profunda of external adductor; amextsup, pars superficialis of external adductor; ampost, posterior adductor; pt, pterygoid muscle (internal adductor). (B) Lateral view of the skull. The courses of the major visceral muscles connected to the hyoid are shown by arrows. The resulting forces produced during contraction of the muscles are shown at the bottom. bm, branchiomandibular muscle; chy, coracohyoid muscle; ghyI and ghyII, geniohyoid muscles I and II.

View larger version (154K): [in a new window]   Fig. 4. X-ray photograph of Chelus fimbriatus showing the characteristic neck position before a strike. - represent the angles between segments of neck vertebrae; C1-C8, cervical vertebrae; cbI, cornu branchiale I; cbII, cornu branchiale II; sk, skull; thvI, first thoracal vertebra. Scale bar, 1 cm.

View larger version (139K): [in a new window]   Fig. 5. Six single frames of a high-speed video recording (500 frames s-1) showing a Chelus fimbriatus capturing a fish. Each frame shows a side view (upper) and a ventral view (lower) recorded via a 45° mirror below the tank. The real time (s:ms) is specified above the NAC-generated time code. Grid size is 1 cmx1 cm.

View larger version (120K): [in a new window]   Fig. 6. Ten single frames of a high-speed X-ray film sequence (150 frames s-1) showing a lateral view of Chelus fimbriatus capturing a fish. The real time (s:ms) is specified in the top right corner of each frame. The prey item appears dark because of the X-ray contrast medium; the positions of lead markers on the turtle's skull can be seen clearly.

View larger version (133K): [in a new window]   Fig. 7. Eight single frames of a high-speed X-ray film sequence (150 frames s-1) showing a lateral view of Chelus fimbriatus during intraoral transport before swallowing. The real time (s:ms) is specified in the top right corner of each frame. The prey item appears dark because of the X-ray contrast medium; the positions of lead markers on the turtle's skull can be seen clearly.

View larger version (14K): [in a new window]   Fig. 8. (A) Distances covered between each frame (s) for predator and prey. (B) Ram-suction index (RSI) calculated for each frame of one representative feeding sequence of Chelus fimbriatus. Dpred and Dprey are the net distance moved by the predator and the prey, respectively.