title: Fast and Powerful: Biomechanics and Bite Forces of the Mandibles in the American Cockroach Periplaneta americana.
abstract: Knowing the functionality and capabilities of masticatory apparatuses is essential for the ecological classification of jawed organisms. Nevertheless insects, especially with their outstanding high species number providing an overwhelming morphological diversity, are notoriously underexplored with respect to maximum bite forces and their dependency on the mandible opening angles. Aiming for a general understanding of insect biting, we examined the generalist feeding cockroach Periplaneta americana, characterized by its primitive chewing mouth parts. We measured active isometric bite forces and passive forces caused by joint resistance over the entire mandibular range with a custom-built 2D force transducer. The opening angle of the mandibles was quantified by using a video system. With respect to the effective mechanical advantage of the mandibles and the cross-section areas, we calculated the forces exerted by the mandible closer muscles and the corresponding muscle stress values. Comparisons with the scarce data available revealed close similarities of the cockroaches' mandible closer stress values (58 N/cm2) to that of smaller specialist carnivorous ground beetles, but strikingly higher values than in larger stag beetles. In contrast to available datasets our results imply the activity of faster and slower muscle fibres, with the latter becoming active only when the animals chew on tough material which requires repetitive, hard biting. Under such circumstances the coactivity of fast and slow fibres provides a force boost which is not available during short-term activities, since long latencies prevent a specific effective employment of the slow fibres in this case.
authors.affiliation: Dept. of Zoology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Weihmann
authors.affiliation: Science of Motion, Friedrich Schiller University Jena, Jena, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Reinhardt
authors.affiliation: Entomology Group, Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Jena, Germany.
authors.forename: Kevin
authors.initials: K
authors.lastname: Weißing
authors.affiliation: Institute of Sport and Motion Science, University of Stuttgart, Stuttgart, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Siebert
authors.affiliation: Entomology Group, Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität Jena, Jena, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Wipfler
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001732:Bite Force; D020342:Finite Element Analysis; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology*; D008409:Mastication / Q000502:physiology; D008954:Models, Biological; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D010526:Periplaneta / Q000033:anatomy & histology / Q000502:physiology*; D014743:Videotape Recording