P2.29 Thursday, Jan. 5 Evolution of food-induced developmental plasticity in echinoids ADAMS, D.K.*; NOWAKOWSKI, N.M.; ANGERER, L.A.; National Institutes of Health, Bethesda, MD; American University, Washington, DC; National Institutes of Health, Bethesda, MD email@example.com
Recent work in the model echinoid, Stronglyocentrotus purpuratus, has shown that phenotypic plasticity during the pre-feeding larval stage is mediated by a food-induced dopamine signal that alters the developmental program. Elucidation of part of the mechanism allows us to probe Echinoidea to determine when developmental phenotypic plasticity arose in larval urchins, with the long-term goal of uncovering the evolutionary and mechanistic steps by which an environmental signal becomes integrated into the developmental program. Within the regular urchins, a derived and basal species showed a developmental response to food mediated by dopamine. Another regular urchin, Lytechinus variegatus, did not demonstrate a phenotypic response to food, but did alter arm length in response to dopamine signaling and developed putative dopaminergic neurons in an appropriate temporal and spatial pattern. Thus, while the developmental response to food may have been lost in some regular urchins, the underlying molecular mechanism remained intact supporting the conservation of developmental plasticity within this clade. In a sister clade, larvae of multiple sand dollars lacked both the developmental response to food as well as a response to dopamine and delayed development of dopaminergic neurons until after the prefeeding period. Initial examination of the pencil urchin, which is basal to both the regular urchins and the sand dollars, also revealed no response to food and dopamine, but putative dopaminergic neurons did develop in a temporal and spatial pattern similar to that of the regular urchins. Thus, our preliminary results suggest that the developmental response to algae was an innovation of the regular urchins (Echinacea) that built upon neurobiology already present in basal echinoids.