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 fo r sea urchins would facilitate their use for this purpose and for productio n of young sea urchins for stock enhancement. A basic requirement for the a quaculture of sea urchins is the availability of a feed chat predictably pr oduces eggs of a consistent, high quality. We tested an extruded feed with Lytechinus variegatus for this purpose. Lytechinus variegatus (mean horizon tal diameter 55 mm, 75 g wet weight) were collected in April 1998. Nine ind ividuals were maintained in each of four aquaria with closed, recirculating filtered sea water. They were fed approximately 1 g extruded feed/individu al per week. All feed was consumed. The mean weight of the sea urchins chan ged little with this feeding regime. The sea urchins spawned spontaneously on a monthly basis during water changes. Four females in February and one i n March were spawned by injection with potassium chloride. Fertilization wa s 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. Gas trulation occurred in <20 h and metamorphosis after 22 to 37 d. Newly metam orphosed juveniles ranged in size from 435 +/- 38 to 473 +/- 56 mu m. Egg s ize, larval size, the chronology of embryonic and larval development, and s ize of newly metamorphosed juveniles are similar to those obtained from hel d individuals reported in the literature. These results indicate that a pre dictable production of high quality eggs by sea urchins under controlled co nditions in the laboratory with a prepared feed is feasible.