Energy Metabolism and Amino Acid Transport During Early Development of Antarctic and Temperate Echinoderms

The rates of oxygen consumption by embryos of antarctic echinoderms (Acodontaster hodgsoni, Odontaster validus, Psilaster charcoti, and Sterechinus neumayeri) were compared to the biomas (ash-free dry organic weight) of the egg of each species. These species could survive for months to years (range: 10 months to 5 years) by relying solely on the reserves present in the egg. However, certain species did not use any of the egg's reserves during early development. Embryonic stages of O. validus (a species with planktotrophic larvae) did not decrease in lipid, protein, or total biomass during the first 35 days of development. During the first 42 days of development, embryos of A. hodgsoni (a species with lecithotrophic development) used protein as an energy source. For both species lipid composed 40 to 50% of egg biomass, but was not used as an energy reserve. Larvae of O. validus have a high-affinity transport system for amino acids dissolved in seawater (K1 = 1.3 {mu}M for alanine). The rate of alanine transport from a low concentration (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) for larvae of a temperate asteroid, Asterina miniata. Larvae of antarctic 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 nutrient transport capacities when compared to larvae from temperate regions. These physiological differences allow antarctic larvae to survive for long periods without particulate food.