GEORGE, S. B.*; FOX, C. A.; Georgia Southern University: Ingestion rates on natural and artificial particles by pacific echinoderm larvae

Ingestion rates of the seastars Dermasterias imbricata (larval size:1201-1492µm), Pisaster ochraceus (1613-1799µm), and Evasterias troschelii (1356-1624µm), the sea urchin, Strongylocentrotus purpuratus (348-807µm) and the sand dollar Dendraster excentricus (534-731µm) were investigated in the laboratory using three natural algal diets Isochrysis galbana(small), Dunaliella tertiolecta (medium) and Rhodomonas sp. (large) and an artificial diet composed of large (in 2004) and small (in 2005) particles. The efficiency to capture particles varied between years, with species, larval size and stage of larval development. In both years, ingestion rates by all five species were highest on the large alga Rhodomonas sp. Ingestion rates were similar among seastars, with higher ingestion rates on the larger particles (Rhodomonas sp. and D. tertiolecta) and lower ingestion rates on the smaller particles (I. galbana and the artificial diet). Ingestion rates varied with larval age for the two forcipulate seastar larvae E. troschelii and P. ochraceus. The efficiency to capture small particles was highest for younger forcipulate larvae. The efficiency to capture particles of various sizes reached a maximum between the 20^th and 25^th day then dropped between the 29^th and 38^th day after fertilization for these forcipulate seastars. Despite their small size, D. excentricus larvae were highly efficient at ingesting both small and large particles. S. purpuratus larvae were the least efficient at ingesting the small I. galbana and artificial particles. A combination of factors including changes in the density of cilia per length of ciliated band, and variation in water current velocity along different sections of the ciliated band during larval development might partly explain variation in ingestion rates among species.