Our recent research on the mechanisms regulating the metamorphic transition and settlement in the purple sea urchin Strongylocentrotus purpuratus has focused on the involvement of a variety of endocrine and neuroendocrine mechanisms in this process. Together with two other undergraduate students, my student Joshua Sutherby published a paper on the function of histamine as a regulator of metamorphic competence in the sea urchin in BMC Developmental Biology (Sutherby et al., 2012)as part of his honors thesis project. This paper provides functional and immunohistochemical (IHC) evidence that histamine (HA) is a modulator of metamorphic competence in the sea urchin. Another undergraduate student, Luke Hoekstra, investigated the distribution of histamine in the sea cucumber Leptosynapta clarki and found that this neurotransmitter is abundant in sensory neurons (Hoekstra et al., 2012). This work has raised several new and interesting questions on the function and evolution of histamine in echinoderm life histories which are further outlined in this proposal.