Neuroscience and medical science rely heavily on the concept that similar behaviors in different kinds of animals are produced by shared mechanisms in the brains of those animals. For example, behavioral testing in rodents is used to predict the efficacy of drugs on human behavior. It is imperative that we understand the extent to which similarity in behavior predicts similarity in neural mechanism. This project uses electrophysiology combined with computational simulations and molecular biology to examine this important question in the readily accessible nervous systems of nudibranch sea slugs. These animals have relatively simple nervous systems with individual nerve cells (neurons) that are individually identifiable not just from animal to animal within a species, but also across species. Furthermore, there is a tremendous diversity of these species that perform one of two types of swimming behaviors. These studies examine the extent to which neurons and neural circuits differ in species that behave similarly. The project also examines a fundamental question of whether the configuration of a neural circuit is a unique solution to producing a particular type of behavior or whether there are many ways for the behavior to come about. Finally, the project examines whether similar neurochemical signals are used in species that produce similar behavior. Information about the neurons and neural circuits is being shared in an online repository called www.NeuronBank.org. The broader impact of the project also involves further developing the molluscan neuroscience gateway (www.squishybrain.org) for sharing research about these animals. This work is important because of what it will reveal about how behavior is produced in different species.