FUNCTIONAL CONSEQUENCES OF PHENOTYPIC PLASTICITY IN ECHINOID LARVAE

Phenotypic plasticity in feeding structures has been described for sev eral larvae of marine invertebrates, including four species of echinoi ds. In these echinoids, larvae grown with scarce food grow a longer ci liated band than larvae grown with abundant food. Such phenotypic plas ticity may be functionally significant if longer ciliated bands permit higher feeding rates when food is scarce. We replicate an earlier res ult showing that larvae of a sand dollar, Dendraster excentricus, grow longer ciliated bands in culture with scarce food. We show that these larvae can capture suspended food particles at the tips of longer arm s, and that longer ciliated bands result in higher maximum clearance r ates. The maximum clearance rate is enhanced by this phenotypic plasti city both early and late in larval life. However, longer ciliated band s did not completely compensate for reduced food supply: larvae grown with scarce food needed more time to complete larval development and m etamorphosed into smaller juvenile sand dollars relative to larvae gro wn with abundant food.