Fertilization and development of eggs of the sea urchin Lytechinus variegatus maintained on an extruded feed

Sea urchin eggs are used extensively as models for studies in developmental and molecular biology. Developing aquaculture techniques and facilities for sea urchins would facilitate their use for this purpose and for production of young sea urchins for stock enhancement. A basic requirement for the aquaculture of sea urchins is the availability of a feed chat predictably produces eggs of a consistent, high quality. We tested an extruded feed with Lytechinus variegatus for this purpose. Lytechinus variegatus (mean horizontal diameter 55 mm, 75 g wet weight) were collected in April 1998. Nine individuals were maintained in each of four aquaria with closed, recirculating filtered sea water. They were fed approximately 1 g extruded feed/individual per week. All feed was consumed. The mean weight of the sea urchins changed little with this feeding regime. The sea urchins spawned spontaneously on a monthly basis during water changes. Four females in February and one in March were spawned by injection with potassium chloride. Fertilization was 99-100% successful in each case. Egg diameters from these spawnings and a spontaneous spawning in April ranged from 102 +/- 6 to 128 +/- 1 mu m. Gastrulation occurred in <20 h and metamorphosis after 22 to 37 d. Newly metamorphosed juveniles ranged in size from 435 +/- 38 to 473 +/- 56 mu m. Egg size, larval size, the chronology of embryonic and larval development, and size of newly metamorphosed juveniles are similar to those obtained from held individuals reported in the literature. These results indicate that a predictable production of high quality eggs by sea urchins under controlled conditions in the laboratory with a prepared feed is feasible.