LARVAL DEVELOPMENT, SETTLEMENT, AND EARLY POST-SETTLEMENT BEHAVIOR OF THE TROPICAL SEA STAR OREASTER RETICULATUS

The Caribbean sea star Oreaster reticulatus (Linnaeus, 1758) free-spawns large, negatively buoyant eggs. At average current velocities in natural habitats, these eggs could disperse at least 20 m before sinking to the bottom, which increases the probability of fertilization in this sparsely-distributed species. The planktotrophic larvae complete development within 23 d at 23 degrees C. In laboratory experiments, larvae settled mainly on the undersides of pebbles encrusted with coralline algae in both light and dark treatments, indicating a preference for cryptic microhabitats. Competent larvae spent approximately half their time exploring the substratum by moving in straight or circular paths at an average speed of 1.14 cm min(-1), stopping periodically to probe the surface and attach with a preoral or brachiolar arm. Once attached, larvae rotated around the adhesive disk for 20-180 s, sequentially attaching and detaching one or two brachiolar arms. Final attachment and metamorphosis occurred within 24 hrs of settlement, and based on speed and duration of movement, displacement distance could be up to 7 m for a searching larva under no flow. Recently metamorphosed juveniles moved at an average speed of 0.074 cm min(-1) oil glass, sand and coralline-encrusted pebbles, sequentially attaching and detaching tube feet in the direction of travel. Overturned juveniles were capable of righting themselves in 16-28 s. Post-settlement movement could enable settlers to locate cryptic microhabitats, particularly in seagrass beds, and thereby reduce the probability of being overturned or consumed.