Evolution of muscle activity patterns driving motions of the jaw and hyoid during chewing in gnathostomes

Nicolai Konow, Anthony Herrel, Callum F. Ross, Susan H. Williams, Rebecca Z. German, Christopher P J Sanford, Chris Gintof

Research output: Contribution to journalArticlepeer-review

Abstract

Although chewing has been suggested to be a basal gnathostome trait retained in most major vertebrate lineages, it has not been studied broadly and comparatively across vertebrates. To redress this imbalance, we recorded EMG from muscles powering anteroposterior movement of the hyoid, and dorsoventral movement of the mandibular jaw during chewing. We compared muscle activity patterns (MAP) during chewing in jawed vertebrate taxa belonging to unrelated groups of basal bony fishes and artiodactyl mammals. Our aim was to outline the evolution of coordination in MAP. Comparisons of activity in muscles of the jaw and hyoid that power chewing in closely related artiodactyls using cross-correlation analyses identified reorganizations of jaw and hyoid MAP between herbivores and omnivores. EMG data from basal bony fishes revealed a tighter coordination of jaw and hyoid MAP during chewing than seen in artiodactyls. Across this broad phylogenetic range, there have been major structural reorganizations, including a reduction of the bony hyoid suspension, which is robust in fishes, to the acquisition in a mammalian ancestor of a muscle sling suspending the hyoid. These changes appear to be reflected in a shift in chewing MAP that occurred in an unidentified anamniote stem-lineage. This shift matches observations that, when compared with fishes, the pattern of hyoid motion in tetrapods is reversed and also time-shifted relative to the pattern of jaw movement.

Original languageEnglish (US)
Pages (from-to)235-246
Number of pages12
JournalIntegrative and Comparative Biology
Volume51
Issue number2
DOIs
StatePublished - Aug 2011

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Plant Science

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