51.5 Saturday, Jan. 5 Differential use of nitric oxide to regulate metamorphosis is related to larval selectivity: an eco-devo test using the sea slug Alderia willowi, a species with a settlement dimorphism. BISHOP, C.D.*; KRUG, P.J.; St. Francis-Xavier Univ. Nova Scotia; Cal. State Univ. L.A. firstname.lastname@example.org
Settlement and metamorphosis among marine larvae is often environmentally mediated. Larvae competent to initiate this transformation display intra- and interspecific variation in habitat selectivity as a function of time in the competent state, and consequently, variation in the overall timing of settlement and metamorphosis. Theoretical work has modeled the kind of behavior that should maximize recruitment to the adult population. However, this approach does not inform the nature and dynamic behavior of the endogenous regulatory mechanisms that must operate downstream of environmental cues. In turn, research focused upon elucidating such mechanisms has documented variation in their function among taxa, yet suffers from the lack of a conceptual framework for interpreting that variation. The sea slug Alderia willowi produces non-selective and selective larvae in the same clutch. These two larval types approximate ecologically generalist and specialist larvae, thereby allowing comparative tests of the function of signaling systems while removing phylogenetic effects. By pharmacologically manipulating nitric oxide/cyclic GMP (NO/cGMP), serotonin and dopamine signaling systems in both classes of larvae, we show that among these three systems, NO signaling differs uniquely and categorically in its influence upon the “decision” of a larva to initiate the irreversible events of metamorphosis. We propose a model in which the degree of influence NO exerts on metamorphic “decisions” relates to larval selectivity.