PRE-FEEDING EMBRYOS OF ANTARCTIC AND TEMPERATE ECHINODERMS USE DISSOLVED ORGANIC MATERIAL FOR GROWTH AND METABOLIC NEEDS

The energy reserves of eggs of marine invertebrates have been assumed to supply the metabolic needs of development until feeding on particle s commences. This view is challenged by recent laboratory studies whic h show that marine invertebrate embryos of some nonarthropodan phyla a re able to transport and use dissolved organic material (DOM, e.g. ami no acids and fatty acids) in seawater as a source of material (energy) for metabolic needs and growth. Here we present results of experiment s conducted in situ (in Antarctica and N. Pacific) and in the laborato ry, which show that embryos could, in some cases, meet the metabolic c osts of embryonic development and increase in organic weight (biomass) prior to being able to feed on particles. Increases in biomass of emb ryos of temperate species correlated with the timing of spring phytopl ankton blooms. In contrast, the biomass of embryos (of temperate speci es) reared during periods of low primary productivity decreased, or re mained constant. Phytoplankters exude DOM into seawater and these exud ates are shown here to enhance embryonic growth. In most cases, there was no net use of endogenous reserves during prefeeding development; g rowth and energy needs were apparently met through consumption of DOM in seawater. We suggest that DOM is an important food source for embry os of soft-bodied marine invertebrates in polar and temperate oceans.