89.1 Friday, Jan. 6 Extensible tissues and their contribution to macrostomy in snakes CLOSE, M T*; CUNDALL, D L; Lehigh University; Lehigh University firstname.lastname@example.org
Snakes swallow by passing whole prey between their mandibles. In three species of macrostomatan snakes we examined, the intermandibular soft tissues stretch five to eight times their resting distance during feeding and manual manipulations produced greater separation. Histological comparisons of unstretched and stretched lower jaws reveal some inextensible elements, including the mandibles, tongue, trachea, and epidermis. Lower jaw extensibility relies solely on the ability of the epithelia surrounding the region and the soft tissues around and between inextensible structures to stretch. The effects of stretch on epithelia primarily consist of unfolding of mucosa and interscale epidermis. The dermis matches scale patterns, its deepest elastic layer spanning the entire lower jaw, and its most superficial inelastic layers limited to scale regions. Elastin networks extend superficially into scales and major interscale folds, and remain anchored to these regions during extension. Nerves and vessels run longitudinally in loose connective tissue deep to the dermis. Muscles extending from the mandibles to the midline stretch, and appear to serve in producing the major folds of the rest condition, but their behavior and structure are complex and will be dealt with elsewhere. Our results suggest that collagen and keratin provide structural support and limit extension whereas elastin networks provide recovery and refolding following extension.