GROWTH OF JUVENILE RED-SEA URCHINS (STRONGYLOCENTROTUS-FRANCISCANUS) FED ZOSTERA-MARINA OR NEREOCYSTIS-LUETKEANA

Juvenile red sea urchins, 10- to 30-mm test diameter (TD) were fed Ner eocystis luetkeana or Zostera marina or starved for 90 days in aquaria to determine their rate of growth in TD and jaw length (JL). Juvenile urchins grew faster, measured as TD and JL, when fed Nereocystis comp ared with Zostera, with little or no growth when starved. Ratios of JL /TD in starved urchins were similar to those of wild urchins and were higher than fed urchins. Ratios were lower in urchins fed Nereocystis compared with Zostera, reflecting a faster growth of TD from the forme r feed. The results indicated that Zostera did not support somatic gro wth as well as Nereocystis for juvenile red sea urchins.