Meeting Abstract

36.2  Thursday, Jan. 5  Mechanism underlying developmental plasticity in echinoid larval form ADAMS, D.K.*; SEWELL, M.A.; NOWAKOWSKI, N.M.; ANGERER, L.M.; National Institutes of Health, Bethesda, MD; University of Auckland, NZ; American University, Washington, DC; National Institutes of Health, Bethesda, MD

A mechanistic understanding of developmental plasticity is a key component to determining how phenotypic plasticity alters ecological and evolutionary processes. A clear example of developmental plasticity occurs in prefeeding sea urchin larvae, in which arm length varies when food densities change. As we show here, increases in the size of this feeding structure improve food acquisition rates. Although this plasticity has been thought to have been selected to improve resource acquisition, here we show that the mechanism regulating it works in the opposite direction. We demonstrate that sensation of food activates dopamine signaling through a type-D2 receptor, which reduces the size of the feeding structure and subsequent feeding. These results indicate that the developmental program combined with maternal provisioning predetermines the maximum feeding rate, independent of the environment. The food-dependent reduction in feeding structure size also decreases the expenditure of maternal lipids, providing a potential energy store to buffer future challenges or to invest in development towards the juvenile form. Thus, selective pressures on maternal inputs and/or the developmental program for increased feeding capacity must balance those operating on the food-induced dopamine-signaling mechanism for conserving lipids that hasten development. The use of dopamine in developmental plasticity in sea urchin larvae may have been co-opted from the use of food-induced dopamine signaling in behavioral responses of diverse organisms from worms to humans. Preliminary results surveying Echinoidea suggest that the putative co-option was an innovation of the regular urchins (Echinacea).