Stage-specific predation upon embryos and larvae of the Pacific sand dollar, Dendraster excentricus, by 11 species of common zooplanktonic predators

A series of laboratory feeding experiments determined rates of predation by 11 species of common zooplanktonic predators upon embryonic and larval stages of the Pacific Sand Dollar, Dendraster excentricus (Eschscholtz). Rate of predation by the predator species was not constant upon the prey stages, and four patterns of predation emerged: (1) Three crustacean and two hydromedusa species consumed embryo through gastrula or prism stages, but few pluteus larvae; (2) An amphipod and a chaetognath species ate motile pre-pluteus stages, but not unhatched embryos or plutei; (3) Two fish species ate unhatched embryos, prism and pluteus larvae, but ate few blastulae or gastrulae; (4) Two ctenophore species ate few or no prey during experiments. The observed patterns of predation were presumably caused by behavioral and morphological changes that occur during embryonic and larval development of the prey, and vary between groups of predators that use different feeding mechanisms. The nine invertebrate predator species consumed few, if any plutei, while the two fish species ate plutei in substantial numbers. It is suggested that field rates of predation upon plutei are lower than those upon pre-pluteus stages where invertebrate predators predominate. Conversely, where planktivorous fish are common, plutei may be consumed at high rates.