Abstract
Ascidian larvae use a simple set of locomotor behaviors during dispersal and settlement. The swimming performance and the ability of an ascidian larva to orient within its environment depend on the biomechanics of its rudimentary locomotor morphology. The undulatory motion of the tail generates fluid forces that propel the body with a rate and direction determined by body mass and its spatial distribution. Differences in morphology and behavior among species influence these dynamics and create differences in swimming performance. Furthermore, the ability of a larva to orient within its environment depends on its ability to coordinate the motion of its body with respect to perceived sensory cues. Research on the swimming of ascidian larvae demonstrates the biomechanical basis of tactic orientation and interspecific differences in performance in a large and diverse group of animals.