ENERGY-METABOLISM AND AMINO-ACID-TRANSPORT DURING EARLY DEVELOPMENT OF ANTARCTIC AND TEMPERATE ECHINODERMS

The rates of oxygen consumption by embryos of antarctic echinoderms (A codontaster hodgsoni, Odontaster validus, Psilaster charcoti, and Ster echinus neumayeri) were compared to the biomass (ash-free dry organic weight) of the egg of each species. These species could survive for mo nths to years (range: 10 months to 5 years) by relying solely on the r eserves present in the egg. However, certain species did not use any o f the egg's reserves during early development. Embryonic stages of O. validus (a species with planktotrophic larvae) did not decrease in lip id, protein, or total biomass during the first 35 days of development. During the first 42 days of development, embryos of A. hodgsoni (a sp ecies with lecithotrophic development) used protein as an energy sourc e, For both species lipid composed 40 to 50% of egg biomass, but was n ot used as an energy reserve. Larvae of O. validus have a high-affinit y transport system for amino acids dissolved in seawater (K-t, = 1.3 m u M for alanine). The rate of alanine transport from a low concentrati on (50 nM) could supply 32% of the larva's metabolic needs. This is a 10-fold higher input to metabolism than was determined (3% at 50 nM) f or larvae of a temperate asteroid, Asterina miniata. Larvae of antarct ic echinoderms live in an environment where the food supply is low for most of the year. Relative to their metabolic rates, antarctic larvae have larger energy stores and planktotrophic larvae have higher nutri ent transport capacities when compared to larvae from temperate region s. These physiological differences allow antarctic larvae to survive f or long periods without particulate food.