Novel shaker bottle cultivation method for the long spined sea urchin (Diadema antillarum; Philippi, 1845) results in high larval survival and settlement rates

The long spined sea urchin Diadema antillarum was an abundant grazer on Caribbean coral reefs, until 1983–1984, when densities were reduced by ∼98% during a region wide die-off. Since then, there has been very little natural recovery of the species and interest is growing in applying aquaculture as a tool for population enhancement. In this study we optimized a new shaker bottle cultivation method for D. antillarum. The method was tested in a series of experiments by culturing D. antillarum from egg to juvenile in the Netherlands as well as the USA. Larvae were cultured in standard 1-L glass reagent bottles, suspended by gentle constant movement on an orbital shaking table and fed with either the microalgae Rhodomonas lens or Rhodomonas salina. Effects on larval growth and survival were evaluated for different microalgal feeding concentrations, larval densities, and culture temperatures. Larval density and growth were measured twice a week over a period of up to 56 days. Larvae grew significantly faster on a higher feeding concentration up to 90,000 Rhodomonas sp. cells mL⁻¹, twice weekly, compared to 30,000 and 60,000 cells mL⁻¹. A density of 1 larvae mL⁻¹ resulted in the highest body size and survival compared to densities of 2 or 4 larvae mL⁻¹. Overall survival from larva to settled juvenile urchin increased from 8 to 10% settlement to 32–33% when the initial density was lowered further from 1.2 to 0.4 larvae mL⁻¹. Growth, survival, competency and settlement did not differ between larval cultures kept at 25 °C or 28 °C. We believe that this novel method for culturing D. antillarum larvae, once scaled-up and validated to pilot scale, could provide juveniles for restocking of urchin-depleted reefs that suffer from algae overgrowth.