Meeting Abstract

P3.39  Jan. 6  Modeling Muscle-skeleton Interaction in Early Vertebrates ARMAH, George*; CREED, Ross; CUI, Shiliang; QIAN, Jinjin; ROOT, Robert G.; Lafayette College; Lafayette College; Lafayette College; Lafayette College; Lafayette College robroot@lafayette.edu

We propose that the evolution of vertebrae results at least in part from improved performance of a fish during a fast start. In particular, the presence of vertebrae allows for increased energy storage and so more efficient energy usage during fast starts. Specifically, the muscular energy generated in stage 1 is stored in the axial skeleton in order to be available to increase acceleration in phase 2. This efficiency might offer a greater chance that the fish will escape its predator. To investigate the energetic hypothesis, we created a simple mechanical model examining the interaction between muscle and axial skeleton for a midbody segment of a transitional vertebrate. The complex 3-dimensional morphology described by Gemballa is simplified to a 2-dimensional model of deformation and force generation. The model accounts for length and contraction velocity due to muscle forces and interaction with the axial skeleton, using realistic active and passive muscle force generation under dynamic conditions of stimulation and deformation. Drawing on the classical Huxley model and recent refinements, the model allows variable active state intensity. The axial skeleton, with either a notochord or a vertebral column of ring centra, is modeled as a nonlinear visco-elastic rod with variable stiffness. Supported by the National Science Foundation grant DBI-0442269