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Chewing or not? Intraoral food processing in a salamandrid newt
Author(s) -
Egon Heiss,
Daniel Schwarz,
Nicolai Konow
Publication year - 2019
Publication title -
journal of experimental biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.367
H-Index - 185
eISSN - 1477-9145
pISSN - 0022-0949
DOI - 10.1242/jeb.189886
Subject(s) - amniote , tetrapod (structure) , biology , tongue , anatomy , dentition , mastication , mandible (arthropod mouthpart) , vertebrate , zoology , paleontology , medicine , biochemistry , pathology , gene , genus
Food processing refers to any form of food mechanical breakdown prior to swallowing. Variations of this behaviour are found within all major gnathostome groups. Chewing is by far the most commonly used intraoral processing mechanism and involves rhythmic mandibular jaw and hyobranchial (tongue) movements. Chewing occurs in chondrichthyans (sharks and rays), actinopterygians (ray-finned fishes), dipnoi (lungfishes) as well as amniotes and involves similarities in the patterns of muscle activity and movement of the feeding apparatus. It has been suggested that amniote chewing, which involves the interaction of movements of the mandibular jaw and the muscular tongue, has evolved as part of the tetrapod land invasion. However, little is known about food processing mechanisms in lissamphibians, which might have retained many ancestral tetrapod features. Here, we identify a processing mechanism in the salamandrid newt, Triturus carnifex, which after prey capture displays cyclic head bobbing in concert with rhythmic jaw and tongue movements. We use high-speed fluoroscopy, anatomical reconstructions and analyses of stomach content to show that newts, although not using their mandibular jaws, deploy a derived processing mechanism where prey items are rasped rhythmically against the dentition on the mouth-roof, driven by a loop-motion of the tongue. We then compare patterns and coordination of jaw and tongue movements across gnathostomes to conclude that food processing in this newt species shares traits with processing mechanisms in fish as well as amniotes. This discovery casts salamanders as promising models for reconstructing the evolution of intraoral processing mechanisms at the fish-tetrapod split.