Contrasting predation rates on planktotrophic and lecithotrophic propagules by marine benthic invertebrates

•Predation rates on propagules of various taxa by benthic invertebrates were studied.•Active filter feeders were generally more successful predators than suspension feeders.•Higher survival rates occurred in lecithotrophic than in planktotrophic propagules.•Size and age were weak predictors of survival within each developmental mode.•Predator-specific and stage-specific results were recorded.

When modeling life-history evolution of marine benthic invertebrates, it has been common to assume constant mortality rate of offspring during the pre-settlement phase and greater propagule vulnerability in the pelagic than in the benthic habitat. However, recent findings have challenged these assumptions, emphasizing the need for further empirical tests. Here we present the results of a multifactorial experimental investigation of predation rates on propagules of various taxa by benthic invertebrates. Planktotrophic and lecithotrophic propagules of echinoderms, cnidarians and annelids (i.e. sea cucumbers, sea stars, sea urchins, corals, sea anemones, jellyfishes, and polychaetes) were tested at various stages of development to examine the effects of ontogeny, size and behavior on predation rates by common filter feeders (mussels, tunicates) and suspension feeders (sea anemones). Overall, propagule survival was positively correlated with their size, although on closer inspection this was essentially due to the size difference between developmental modes (larger lecithotrophic propagules being less vulnerable). A slight inverse relationship between survival and age was detected in both lecithotrophic and planktotrophic propagules; however ingestion rates were not systematically higher on more advanced life stages within prey species due to predator-specific responses to ontogenetic changes. Filter feeders were generally more effective predators than suspension feeders. Tunicates expressed greater selectivity based on size and age of propagules than on their behavior, while the inverse occurred in the two other predators. A combination of factors, i.e. size, buoyancy and chemical defenses, presumably underlie overall higher survival rates in lecithotrophic than in planktotrophic propagules, supporting the hypothesis that the former but not the latter may have evolved due to increased epibenthic predation.