Effects of variation in egg energy and exogenous food on larval development in congeneric sea urchins

Abstract

Planktotrophic larvae of marine invertebrates develop and grow by utilizing a combination of endogenous materials contained in the egg and exogenous food consumed during development. In general, larger eggs contain more reserves for morphogenesis and metabolism than smaller eggs. Interspecific comparisons among planktotrophic echinoderms have generally found that increased maternal provisioning decreases the length of development in the plankton, leading to the widely held idea that large eggs are likely to be selectively favored in low-food or high-mortality environments. Despite long interest in these patterns, however, few studies have examined how exogenous and endogenous supplies interactively affect larval development in phylogenetically controlled and environmentally relevant contexts. We investigated the direct and interactive effects of both endogenous egg materials and exogenous food supply on larval performance of 3 closely related tropical sea urchin species (Echinometra spp.). We found that egg size was positively correlated with egg energy among these 3 species, and that larvae of species with larger (and more energy-rich) eggs developed more rapidly than those from smaller (and lower-energy) eggs. Likewise, across species, larvae fed higher rations grew more rapidly than those fed less. Length of development was most strongly affected by food level in the species with the smallest eggs. Compared to the lowest food treatment, satiating levels shortened development by 9, 7, and 4 d for E. vanbrunti, E. lucunter, and E. viridis, respectively (listed in order of increasing egg energy). Our study supports the hypothesis that the growth and development of larvae are more strongly affected by exogenous food availability when they develop from lower-energy eggs than when larvae develop from energy-rich eggs. © Inter-Research 2013.