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First published online August 17, 2007
Journal of Experimental Biology 210, 3096-3106 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003210

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Kinematic analysis of an appetitive food-handling behavior: the functional morphology of Syrian hamster cheek pouches

Carolyn A. Buckley^*, Jill E. Schneider and David Cundall

Lehigh University, Bethlehem, PA 18015, USA

View larger version (134K): [in this window] [in a new window]   Fig. 1. Mirrored filming chamber containing four large food items (lab chow pellets cut to 2.5±0.5 g). Green arrow shows camera angle. Photo lamp (to decrease shadows) is a 100-W bulb approximately 4.5 m from the filming chamber. Another lamp (750 W) was set up about 1.5 m from the filming chamber.

View larger version (120K): [in this window] [in a new window]   Fig. 2. Dissections of hamster cheek pouch from M. auratus. (A) Bifurcation of retractor muscle posterior to caudal end of pouch (apex). (B) Transverse bisection of pouch wall showing longitudinal folds. (C) A longitudinal cut on the lateral wall reveals the morphology of the pouch lumen at the point of retractor insertion, where longitudinal folds end and apex pocket begins. (D) Full cheek pouch. All pictures are from hamsters given nembutol anesthesia (9 mg 100 g–1 body mass) then sacrificed with C02 asphyxiation, and fixed in 4% paraformaldehyde solution, except in D, where the animal received no anesthesia before CO2 in order to maintain the full pouch. Scale bars=1 cm.

View larger version (9K): [in this window] [in a new window]   Fig. 3. Mean lengths of jaw cycle phases and total jaw cycles in number of frames (filmed at 60 frames s–1). Gape phase was significantly longer during pouching of large food items than small. SC/SO phases were significantly shorter for pouching of small items than for mastication or pouching of large items. Total jaw cycle length was significantly different for mastication, pouching large food items and pouching small food items. *Bars grouped together are significantly different from each other (P<0.001). Lg, large items; Sm, small items.

View larger version (18K): [in this window] [in a new window]   Fig. 4. Kinematic profiles of relative gape distance over time for one male hamster during (A) mastication, (B) pouching large food items and (C) pouching small food items, measured in arbitrary scale units (a function of image size on the video display, to the nearest 0.5 unit) using points on the lower jaw and rostrum. Measurements end where views were obstructed (A,B) or where the pouching event ended (C). Shaded areas at maximum gape distance (B,C) illustrate `gape phase'. Note that `0' refers to the minimum gape distance for each set of measurements, and in B, does not indicate full occlusion.

View larger version (7K): [in this window] [in a new window]   Fig. 5. Mean number of frames (1 frame=1/60 s) required to completely pouch each of two pellets to a cheek pouch with a denervated (closed circles) or an intact (open squares) retractor muscle. (A) Interval A, from lateral shift of the pellet to mouth closed. (B) Interval B, from mouth closed to end of pouching event. (C) Complete event (Intervals A+B). *Values significantly different from each other (P<0.05) for second pellet, intact vs denervated retractor.