Meeting Abstract
Late stage marine larvae and many other plankton develop complex morphologies with features such as arms or other extensions, skeletons, and cilia or muscles that play important roles in orientation, speed and other elements of swimming performance. Equally interesting, and perhaps more basal in evolutionary history, are blastulae, gastrulae and other organisms with minimalist, spheroidal morphologies that swim, are subject to performance requirements, but lack elaborations traditionally associated with swimming. How do these “simple” organisms swim, and how are their morphologies constrained by the need to do so? Cell divisions that produce blastulae or gastrulae with uneven distributions of tissue have preferred orientations that are stable in still water and provide righting moments in turbulence. Theory predicts that if these stages have locomotory structures that are radially distributed around the axis determined by the offset centers of mass and buoyancy, they will swim in a direction parallel to this axis until the intensity of water motion overcomes their shape-dependent orientation abilities. We explored this prediction and inference by surveying the initial swimming stages of marine invertebrate taxa and with computational simulations which model shape, centers of mass and buoyancy and various arrangements of locomotory cilia.
