STUDIES OF THE METABOLISM OF PHOSPHORUS IN THE DEVELOPMENT OF THE SEA URCHIN, STRONGYLOCENTROTUS PURPURATUS

¹ Department of Zoology and the Friday Harbor Laboratories, University of Washington, Seattle 5, Washington

1. The quantity of phosphorus in the barium-soluble, alcohol-soluble fraction of the acid-soluble phosphate compounds of the embryos of the sea urchin, Strongylocentrotus purpuratus (Stimpson), was measured until the formation of the early pluteus stage. In two experiments the phosphorus in the fraction decreased by 18.5% and 40.7% in reaching the late prism stage (72 hours).

2. During this period, the total phosphorus of the embryos increased an average of 14.4%.

3. The rate of penetration of radioactive phosphorus from sea water into the embryos during these experiments increased very greatly during cleavage and blastulation, reached a maximum at the onset of gastrulation, and decreased subsequently to a middle level at the prism stage.

4. The rate of uptake of radioactive phosphorus into the barium-soluble, alcohol-soluble fraction was extremely low in unfertilized eggs and in fertilized eggs before the first cleavage, amounting to 0.7% to 1.4% of the total uptake.

5. The rate of uptake of radioactive phosphorus into this fraction in cleaving eggs and embryos mirrored that of the total phosphorus, and the percentage of the labeled phosphorus in the fraction was relatively constant at all stages, averaging 6.5% of the total.

6. Chromatographic examination of the fraction has indicated the existence of at least three components.

7. It is concluded that there are several components in the fraction, at least one of which is a stored material that is steadily metabolized during development, and one or more others synthesized at a rate that is governed largely by the supply of available phosphate.

8. Synthetic radioactive propanediol phosphate added to a perchloric acid homogenate of eggs separated to the extent of 97% into the barium- and alcohol- insoluble, rather than the barium-soluble, alcohol-soluble fraction. It is concluded from this, in contrast to previous reports, that the latter fraction does not contain propanediol phosphate and that no evidence remains for the existence of this ester in sea urchin eggs.