Meeting Abstract

P1.95  Tuesday, Jan. 4  Function of the epaxial musculature in the desert lizard, Dipsosaurus dorsalis MORITZ, S.*; ARNOLD, D.; SCHOLLE, H-C.; SCHILLING, N.; Friedrich-Schiller-Universität Jena; Friedrich-Schiller-Universität Jena; Friedrich-Schiller-Universität Jena; Friedrich-Schiller-Universität Jena sabine.moritz@uni-jena.de

Although the trunk and its associated musculature plays an important role during locomotion in all tetrapods, studies on the locomotor apparatus in lizards are biased towards legs and only very few data on the axial musculature exist. Former studies suggested that the epaxial musculature stabilizes the vertebral column against long axis torsion as well as against sagittal and lateral displacements. Furthermore, a contribution to lateral bending has been discussed. We tested these hypotheses in a small, generalized lizard, Dipsosaurus dorsalis, using electromyography combined with high speed cineradiography. Chronically implanted silicone-matrix-electrodes were used to measure muscle activation in the mm. transversospinalis, longissimus et iliocostalis at different vertebral levels. The forces acting on the vertebral column were manipulated by adding masses to the limbs. During locomotion all three epaxial muscles exhibit an unilateral, uniphasic activation pattern beginning in the second half of the ipsilateral hind limb stance and extending throughout ipsilateral hind limb swing. The timing is appropriate to counteract lateral bending to the ipsilateral and initiate lateral bending to the contralateral side. The manipulation experiments indicate a contribution of the epaxial musculature to stabilization against long axis rotation. However, no evidence for a stabilization against sagittal forces could be found.