Bacteria-free sea urchin larvae: selective uptake of neutral amino acids from seawater.

Bacteria-free suspensions of larvae of Strongylocentrotus purpuratus (Stimpson) were prepared without the use of antibiotics. Net rates of removal of 18 amino acids, each supplied at 125 nanomoles per liter, and the appearance of ammonia were measured by high-performance liquid chromatography. Taurine and acidic and basic amino acids were not taken up. Removal of neutral amino acids from the medium occurred at rates adequate to contribute to the carbon and nitrogen balance of the larvae at ecologically relevant substrate concentrations.