Abstracts - Deutsche Zoologische Gesellschaft

66 Morphology SymposiumO MO.3 (Su) - DEThe effect of vertical head movements on the locomotor economy of quadrupedalmammalsDavid M. Loscher, Carsten NiemitzInstitut für Biologie / Humanbiologie und Anthropologie, Freie Universität BerlinDuring locomotion in the walk, horses perform characteristic vertical movements of the head. Whilethis kinematic feature also appears in a variety of other large ungulates, it seems absent in smallsized and noncursorial mammals. To investigate function and distribution of this kinematic pattern,we analysed the motion of the head and thoracic spine of various species of ungulates, carnivoresand primates during locomotion in the walking gait. Within all carnivores and primates, we foundvertical movements of the head and thorax being in phase and similar in range. By contrast, mostungulates moved their head out of phase and with higher range than the thorax. When swingingvertically, the load that the head and part of the neck excert on the forelegs fluctuates during thegait cycle. A proper timing of these fluctuations with limb movements results in reduced loads onthe forelimbs during the phases of double support, when muscle work is required for redirecting thebody centre of mass. During the phases of single limb support, the load increases accordingly, butis carried with less effort, because of the passive movements of the supporting legs which act likeinverted pendulums. Therefore, some ungulates economise locomotion by carrying the load of headand neck (in horses around 10% of body weight) very efficiently. The fact that this technique wasnot observed in the carnivore and primate species, implies, that an effective use might be determinedby neck size.O MO.4 (Su) - DE3D architecture of muscle fascicles and its change during contractionHeiko StarkInstitut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universität JenaBiomechanical models describing muscle characteristics are very complex in their modelling anduse different techniques like forward kinematics, inverse kinematics, and finite element methods.None of them take all influential 3D features into account such as the fibre type distribution or thegeometrical arrangement of the muscle fascicles. In particular, the arrangement of the fascicles hasan influence on the force production of the muscle. The aim of this study was to reconstruct andcompare the 3D architecture of the fascicles of the m. soleus and the m. gastrocnemius medialis fixatedin relaxed and contracted states and to document possible internal inhomogeneities. For this, themuscles of the rat were shock-frozen and, from serial cross-sections, the muscle fibre bundles werereconstructed and evaluated as 3D polynomials using different techniques. The muscles showedlocally different pinnation angles and curvature distributions, which furthermore changed duringcontraction. The results specifically show that models often oversimplify muscle architecture. Thissimplification neglects local differences in the pinnation angles which have an effect on the muscle’scontraction properties. Therefore, a detailed, nature-orientated muscle model has to take local inhomogeneitiesinto account.