Functional morphology of the cranio‐cervical integument and constrictor musculature in Alligator mississippiensis

The skin, superficial fascia, and constrictor muscles of alligators form a tri‐layered envelope of the neck. These structurally correlated layers determine the stretchability of the intermandibular, gular and cervical regions. The skin stretches only at the interscale skin, whose width is related to the size of the scales. The stretchability of the superficial fascia is determined by the organization of its fibers. In the stretchable intermandibular region, wide, longitudinal folds of interscale skin separate small scales laterally, and narrow interscale skin separates mid‐sized scales medially; the superficial fascia fibers are loosely organized. In the less stretchable gular region, wide interscale skin separates mid‐sized scales laterally, and narrow interscale skin separates larger scales medially; the superficial fascia splits into three laminae with crosswise oblique fibers. In the least stretchable cervical region, wide interscale skin separates mid‐sized scales laterally, and narrow interscale skin separates large scales medially; the superficial fascia fibers are mostly circumferential. During inertial feeding, food is propelled into the pharynx and stretches the intermandibular region, while the less stretchable skin and fascia of the rest of the neck assist the tri‐layered constrictor muscles in pushing the prey caudally and in repositioning the stretched tissues. Grant Funding Source : LSU Foundation