Many benthic marine invertebrates, including polar species, produce larvae that must survive a period in the plankton before setting into benthic adult populations. Understanding the factors that influence larval survival therefore is crucial for understanding recruitment and the maintenance of adult populations. This study will clarify one of the most important of these factors: nutrition. Larvae may be nourish by particulate food, dissolved organic material, and/or yolk provided by the parent. The relative role of these sources for different types of larvae is poorly understood. This project will examine comparable larvae (asteroid and echinoid; feeding and nonfeeding) in two contrasting environments; Monterey Bay, California, where primary production and phytoplankton production are high during most of the year; and McMurdo Sound, antarctica, where phytoplankton production and biomass are markedly seasonal and extremely low during most of the year. The study will have important bearing on the understanding of how different nutritional environments affect larval growth, survival and subsequent availability of recruitment into adult populations and influence the evolution of larval nutritional modes.