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From meat to bamboo: The role of the hypertrophied zygomaticomandibularis muscle in the giant panda ( Ailuropoda melanoleuca )
Author(s) -
Heller Aaron,
Stock Stuart,
Wright Barth
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.lb704
Subject(s) - ailuropoda melanoleuca , biting , mandible (arthropod mouthpart) , bamboo , bite force quotient , mastication , anatomy , biology , skull , orthodontics , medicine , zoology , ecology , genus
The giant panda ( Ailuropoda melanoleuca ) has evolved craniodental adapations for producing and withstanding high and repetitive bite forces incurred during bamboo feeding. One such adaptation are hypertrophied zygomaticomandibularis muscles (ZMs), which allow the giant panda to laterally shift the mandible and effectively comminute bamboo. We examined changes in biomechanical efficiency and bite force during chewing and biting in the giant panda using finite element analysis (FEA). A FE model was created of the giant panda cranium and mandible. We compared biting (greater ZM force on the loading side) and chewing (greater ZM force on the balancing side) muscle loads, with all other model conditions held constant. We found that the mandible is more efficient (able to generate higher bite forces at lower strains) when chewing than when biting at various bite points, but incurs higher peak von Mises stress when chewing. The opposite is true for the cranium, which is more efficient when biting than chewing. The ultimate shape of the adult cranium and upper face is influenced by the morphogenesis of various systems including the sensory organs and the brain, which may constrain the upper jaw. The mandible is under fewer constraints and has perhaps evolved to counteract the limitations in cranial efficiency when chewing bamboo.