Matthew Close is currently affiliated with Department of Biology, Box 6931, Radford University, Radford, VA 24142.
Special Issue Article
A Model of the Anterior Esophagus in Snakes, with Functional and Developmental Implications
Article first published online: 31 JAN 2014
Copyright © 2014 Wiley Periodicals, Inc.
The Anatomical Record
Special Issue: New Advances In Morphology and Evolution of Living and Extinct Squamates
Volume 297, Issue 3, pages 586–598, March 2014
How to Cite
Cundall, D., Tuttman, C. and Close, M. (2014), A Model of the Anterior Esophagus in Snakes, with Functional and Developmental Implications. Anat Rec, 297: 586–598. doi: 10.1002/ar.22860
- Issue published online: 19 FEB 2014
- Article first published online: 31 JAN 2014
- Manuscript Accepted: 24 AUG 2013
- Manuscript Revised: 23 AUG 2013
- National Science Foundation (USA). Grant Number: DEB-7903862
- Lehigh University Faculty Research Grants
- gut evolution;
- snake feeding;
The gross anatomy of the mouth of snakes has always been interpreted as an evolutionary response to feeding demands. In most alethinophidian species, their anatomy allows limited functional independence of right and left sides and the roof and floor of the mouth as well as wide separation of the tips of the mandibles. However, locations of the tongue and glottis in snakes suggest extraordinary rearrangement of pharyngeal structures characteristic of all vertebrates. Serial histological sections through the heads of a number of colubroid species show muscularis mucosal smooth muscle fibers appearing in the paratracheal gutter of the lower jaw at varying levels between the eye and ear regions. Incomplete muscularis externa elements appear beneath the paratracheal gutter more caudally but typically at otic levels. Both muscle layers encompass more of the gut wall at more posterior levels, encircling the gut at the level of the atlas or axis. The pattern in snakes suggests developmental dissociation of dorsal and ventral splanchnic derivatives and extensive topological rearrangements of some ventral pharyngeal arch derivatives typical of most tetrapods. When snakes swallow large prey, the effective oral cavity becomes extremely short ventrally. The palatomaxillary arches function as ratchets packing the prey almost directly into the esophagus. Our findings raise questions about germ layer origins and regulation of differentiation of gut regions and derivatives in snakes and suggest that significant aspects of the evolution of lepidosaurs may be difficult to recover from bones or molecular sequence data alone. Anat Rec, 297:586–598, 2014. © 2014 Wiley Periodicals, Inc.