Morphology and behavior of the feeding apparatus in Cryptobranchus alleganiensis (Amphibia: Caudata)

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Abstract
Cine and high-speed videographic analyses of feeding in Cryptobranchus alleganiensis demonstrate that prey are captured by either inertial suction or a strike combined with suction. Movements of cephalic elements during capture are generally similar to those of other suction-feeding vertebrates but more variable than those of most aquatic salamanders. Following capture, prey frequently are manipulated and transported into and out of the buccal cavity across the teeth. Specific features of the skull, mandibles, hyoid apparatus, and cephalic musculature of Cryptobranchus correlate directly with behavior. Although the skull is massive, sutures of the anterior braincase permit limited torsion, the maxillae move on their attachments to the braincase, and left and right mandibles are separated by elastic connective tissues. These features provide flexibility and permit asynchronous and asymmetric movements of the mandibles. Equivalent asymmetry and asynchrony of hyobranchial movements are also correlated with specific structural arrangements that may be neither paedomorphic nor primitive. Its feeding mechanics suggest that Cryptobranchus represents a unique and highly derived condition among salamanders. Its ability to modulate movements of the left and right sides of its head argues strongly for the existence of bilaterally asynchronous motor patterns, and patterns of force generation, similar to but much faster than those employed in mammalian mastication.