UPTAKE AND RELEASE OF FREE AMINO ACIDS BY STARFISHES

¹ Department of Biology, Florida Presbyterian College, St. Petersburg, Florida 33733

1. Net uptake and release of dissolved free amino acids was measured in experiments with 10 species of Puget Sound starfishes, utilizing gas liquid chromatography.

2. When specimens were placed in filtered sea water with 0.5 mM/l L-alanine, most of the amino acid was removed within a 6 hour period, and no more than trace quantities of other amino acids appeared in the media.

3. When specimens were placed in filtered sea water with 0.5 mM/l concentrations of 12 amino acids, there was considerable net uptake of all the amino acids except glycine, which in two cases with Pteraster was further released into the media.

4. In a similar experiment in which glycine and L-methionine were omitted from the mixture, there was significant net release of glycine but not l-methionine, simultaneously with considerable uptake of the majority of the other 10 amino acids in most cases.

5. When the uptake mechanism for neutral amino acids was partially inhibited by including 1.0 mM/l L-alanine in the media, a fairly large efflux of glycine and occasionally a much lesser amount of l-serine and other amino acids was detected. The amino acids released by the various species appeared to correlate with those maintained free in their tissues.

6. The results of the study support the concept that starfish can receive net benefit from dissolved nutrients in their environments. They further indicate that the transport system for taking up amino acids is also significant in the retention of those amino acids already in the metabolic pools.