Meeting Abstract
The feeding larvae of marine invertebrates may often be food-limited in rates of growth and development, a result with important implications for larval ecology and evolution. The generality of this result is uncertain, however, as studies addressing larval food limitation are few, and conflicting results have been reported. We tested for food limitation in larvae of the sand dollar Dendraster excentricus in nearshore waters of southern California in six experiments from 2017-19. In each experiment we compared the form and development rates of larvae reared in natural seawater (NS) to those of larvae reared in natural seawater supplemented with Rhodomonas lens (NS+); as a control, we also reared larvae in natural seawater diluted 1:1 with filtered seawater (NS-). During our experiments, chlorophyll a levels in NS treatments were fairly high, ranging from 1.48-4.57 µg L-1. Despite this, compared to NS+ larvae, larvae reared in NS consistently had slightly higher postoral arm/midline body length ratios, indicative of a phenotypically plastic response to low food levels, and slightly greater time to 50% metamorphic competence, suggesting subtle food limitation. Larvae reared in NS- were very clearly food-limited: they always had much higher postoral arm/midline body length ratios and much greater time to 50% competence than did larvae in the other two treatments. Our results suggest that even in habitats with relatively high standing stocks of chlorophyll a, larvae may routinely experience food limitation.
