COUPLING INTERNAL AND EXTERNAL MECHANICS TO PREDICT SWIMMING BEHAVIOR- A GENERAL-APPROACH

The biological world is full of systems whose component parts interact in a coupled non-linear fashion. As a result, studying any component of the system in isolation may nor be representative of its natural be havior due to the coupling, and predicting the behavior of the entire system as a function of variation in any one parameter maybe quite dif ficult due to the non-linear nature of the interactions. Swimming with whole body undulations is just such a system. The component parts of the swimming-system (muscle, skeleton, soft-tissue, and the surroundin g fluid), are mechanically and physiologically coupled in a strongly n on-linear manner. Therefore, to predict the outcome of the entire syst em, i.e., swimming behavior, or to understand the role any one compone nt plays as a determinant of the outcome, a mechanistic approach encom passing the form of the component's interactions is required. This app roach is essential for developing scaling arguments, or discussing the consequences of morphological and physiological variation on behavior al and evolutionary ''performance.'' Below I outline an example of thi s method: a simplistic model of the mechanical interactions between th e swimming-system components of a leech. The model is based on irt vit ro characterizations of these components and first principle descripti ons of their interactions. Serving the model's governing equations gen erates swimming behavior in the model organism. in addition, the model can predict the behavior of the swimming-system's component parts, al lowing calculations of swimming performance and parameter variation no t possible with other approaches.