BRYAN, Patrick J; Central Washington University: Energetic cost of development through metamorphosis for the seastar Mediaster aequalis

Rates of oxygen consumption were measured for embryos, larvae and juveniles of the seastar Mediaster aequalis for 76 days post-fertilization. The rate increased from 0.65 nmol O2 ind-1 h-1 at 6 h after fertilization to 2.8 nmol O2 ind-1 h-1 at day 35. Larvae became competent to metamorphose around day 35 post-fertilization and began to decrease their metabolic rate after this time. Metamorphosed juveniles consumed 0.74 nmol O2 ind-1 h-1. Eggs contained 138.6 �g lipid ind-1 and 12.1 �g protein ind-1. Lipid levels decreased in concentration throughout development while protein levels increased slightly. The lipid levels decreased by 88.5 �g from eggs to day 76 larvae, accounting for 3.5 J of energy. Total oxygen consumption to this point was 3.74 �mol O2 ind-1, accounting for 1.84 J. The energetic demand up to day 76 was completely met through the use of lipid reserves. Metamorphosed juveniles expended 0.5 J more than larvae at the same age. Tubes of the polychaete Phyllochaetopterus prolifica were able to induce metamorphosis in M. aequalis larvae and a non-polar extract of these tubes also triggered metamorphosis. Larvae that are delayed to metamorphose can sustain their metabolic rate with lipid reserves for a limited, yet undetermined, period.