Metabolic differences between "demersal" and "pelagic" development of the Antarctic sea urchin Sterechinus neumayeri

Early development of the Antarctic sea urchin Sterechinus neumayeri was exa mined under two different culture regimes: one to simulate development near -bottom ("demersal development") and the other to simulate the development of embryos in the water column ("pelagic development"). When embryos of bot h treatments reached the hatching blastula stage at 5 d post-fertilization (-1.5 degrees C), the blastulae that had undergone demersal development evi denced significant differences (by ANOVA or suitable non-parametric compari son) in the following: a thicker blastoderm layer (12%, P < 0.001), higher ash-free dry weights (19%, P < 0.01), lower mass-specific respiration rates (50%, P < 0.001), higher incorporation rates of S-35-methionine into prote in (23%, P < 0.003), and a differential pattern of protein synthesis. When embryos developed demersally, they remained in the jelly-coat material rele ased with the eggs at spawning. Quantitative isolation of this jelly-coat m aterial in S. neumayeri demonstrated that it contained a significant amount of organic matter, 115 ng ash-free dry mass per egg, equivalent to 17% of the egg's initial organic mass. Uptake of external nutrients during embryog enesis may be a significant component of the physiological energetics of th is polar invertebrate by allowing the utilization of jelly-coat material re leased by a female during spawning.