A kinematic analysis of mesokinesis in the Nile monitor (Varanus niloticus).
Previous investigations attempting to document cranial kinetic movements in lizards have resulted in ambiguous and contradictory results. Mesokinesis during feeding in the Nile monitor (Varanus niloticus) was investigated using a new technique. Slotted mounts were attached to the frontal and parietal segments in three adult Nile monitors (0.8-1.7 kg). Extensions which exaggerate the relative movements of the bones were attached to these mounts. All phases of feeding behavior on mice were filmed (n = 9) at 50 frames/s. Before the strike and concomitant with jaw opening the muzzle slightly dorsiflexes (2-4 degrees). During the strike both jaws adduct simultaneously with the upper jaw ventroflexing past the rest position. During subjugation and inertial feeding the skull remains ventroflexed. Only after the prey passes into the esophagus do the cranial elements return to their rest position. The pattern of mesokinetic movements is consistent with several functional hypotheses. A mechanical analysis of the cranial skeleton predicts that mesokinetic movement of the upper jaw can be independent of lower jaw movement. Linear regression of upper jaw movement against lower jaw position and movement shows mesokinesis to be largely independent of lower jaw movement, as predicted by the model.
Condon
K
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Department of Anatomy, University of Illinois, Chicago 60612.
D000818:Animals; D004435:Eating; D005247:Feeding Behavior; D007596:Joints / Q000502:physiology; D007698:Kinesis; D008116:Lizards / Q000502:physiology*; D008953:Models, Anatomic; D009949:Orientation; D012886:Skull / Q000502:physiology*