Both authors contributed equally to this paper.
Horned lizards (Phrynosoma) incapacitate dangerous ant prey with mucus
Article first published online: 20 JUN 2008
Copyright © 2008 Wiley-Liss, Inc., A Wiley Company
Journal of Experimental Zoology Part A: Ecological Genetics and Physiology
Volume 309A, Issue 8, pages 447–459, October 2008
How to Cite
Sherbrooke, W. C. and Schwenk, K. (2008), Horned lizards (Phrynosoma) incapacitate dangerous ant prey with mucus. J. Exp. Zool., 309A: 447–459. doi: 10.1002/jez.472
- Issue published online: 30 AUG 2008
- Article first published online: 20 JUN 2008
- Manuscript Accepted: 13 MAY 2008
- Manuscript Revised: 6 MAY 2008
- Manuscript Received: 9 AUG 2007
- National Science Foundation. Grant Number: NSF IBN-9601173
- University of Connecticut Research Foundation
Horned lizards (Iguanidae, Phrynosomatinae, Phrynosoma) are morphologically specialized reptiles characterized by squat, tank-like bodies, short limbs, blunt snouts, spines and cranial horns, among other traits. They are unusual among lizards in the degree to which they specialize on a diet of ants, but exceptional in the number of pugnacious, highly venomous, stinging ants they consume, especially harvester ants (genus Pogonomyrmex). Like other iguanian lizards, they capture insect prey on the tongue, but unlike other lizards, they neither bite nor chew dangerous prey before swallowing. Instead, they employ a unique kinematic pattern in which prey capture, transport and swallowing are combined into a single feeding stage, apparently leaving the mouth, pharynx, esophagus and stomach vulnerable to bites and stings. Nevertheless, horned lizards consume dozens of harvester ants without harm. We show that their derived feeding kinematics are associated with unique, mucus-secreting pharyngeal papillae that apparently serve to immobilize and incapacitate dangerous ants as they are swallowed by compacting them and binding them in mucus strands. Radially branched esophageal folds provide additional mucus-secreting surfaces the ants pass through as they are swallowed. Ants extracted from fresh-killed horned lizard stomachs are curled ventrally into balls and bound in mucus. We conclude that the pharyngeal papillae, in association with a unique form of hyolingual prey transport and swallowing, are horned lizard adaptations related to a diet of dangerous prey. Harvester ant defensive weapons, along with horned lizard adaptations against such weapons, suggest a long-term, predator–prey, co-evolutionary arms race between Phrynosoma and Pogonomyrmex. J. Exp. Zool. 309A:447–459, 2008. © 2008 Wiley-Liss, Inc.