Meeting Abstract
Many marine invertebrate larvae must feed in the plankton in order to complete development. During this time, larval mortality is high due to factors such as predation and advection. Larvae that most rapidly obtain the energy needed to reach competence are most likely to survive to metamorphosis; thus larvae should maximize their feeding rates. Larval feeding rates are commonly measured in suspensions of edible particles, but natural plankton also contains particles so large that they can not be ingested (e.g., some dinoflagellates and diatoms). Hansen (1991, JEMBE 152:257-269) showed that feeding rates of copepodites and veligers are lower in the presence of large inedible particles at high concentrations (1,000-20,000•ml-1). We hypothesized that the presence of such particles reduces feeding rates of echinoderm larvae. Larvae of two asteroids (Astropecten armatus and Patiria miniata) and two echinoids (Dendraster excentricus and Lytechinus pictus) were permitted to feed briefly on 6 µm beads alone, or in combination with large inedible beads (asteroids, 100 µm; echinoids, 75 µm) at concentrations of 25, 50, 100 or 500•ml-1. We quantified ingestion rates of 6 µm beads and estimated clearance rates in each treatment. Clearance rates of all four species were ~50% lower in treatments including large inedible beads at 100 or 500•ml-1, consistent with our hypothesis. In the presence of large inedible particles, larvae may alter their swimming behavior, or engage in particle rejection behavior; both activities might reduce the amount of time larvae would otherwise spend feeding. Our results suggest that the feeding performance of larvae in nature may depend not only on the amount of available food, but also on the presence and abundance of potentially interfering non-food particles.
