Meeting Abstract

P3.58  Jan. 6  Testing the Adaptive Value of Vertebrate Tail Stiffness, I: Robotic Simulation IRVING, K*; ENGEL, V; COMBIE, K; MCARTHUR, G; DOORLY, N; BANTILAN, K; ROOT, R; LIEW, C., Koob T., Long J.; Vassar College; Lafayette College, Mount Desert Island Biological Lab, Vassar College kiirving@vassar.edu

A long-standing hypothesis is that vertebrae evolved as a locomotor adaptation, stiffening the body axis and enhancing swimming performance in early vertebrates. While supported by biomechanical data, this hypothesis has not been tested using an evolutionary approach. We built autonomous robots as proxies of early vertebrates competing in a forage navigation task. Modeled after free-swimming larvae of sea squirts (Chordata, Urochordata), three robotic tadpoles (�Tadros�) were each equipped with a propulsive tail bearing a biomimetic notochord of variable spring stiffness, allowing them to search for, orient to, and orbit in two dimensions around a light source. Driven by selection for relative success in the navigation task and random genetic processes, the population of Tadros evolved. After ten generations, increased tail stiffness predicted enhanced navigational behavior, but stiffness alone was insufficient to explain the evolutionary patterns of Tadros. To examine alternative and more complex evolutionary scenarios, we are building new Tadros with a startle response to avoid robotic predators as they forage. Supported by the National Science Foundation grants BCS-0320764 and DBI-0442269.