DIGESTION, STORAGE, AND TRANSLOCATION OF NUTRIENTS IN THE PURPLE SEA URCHIN (STRONGYLOCENTROTUS PURPURATUS)

¹ Department of Bacteriology, University of California, Berkeley 4, California

1. In the purple sea urchin the digestion and absorption of the C¹⁴-labelled constituents of the alga, Iridaea, occur mainly in the esophagus and adjacent festoons of the stomach.

2. The fauna and flora of the sea urchin gut do not appear to he involved in this digestive process.

3. The absorbed materials arc stored mainly in the wall of the gut.

4. During absorption there is a diffusion of labelled material into the plasma of the perivisceral fluid. A peak level is reached around the sixth hour after the start of feeding. Galactose accounts for 90% of this material and must have been liberated enzymatically from galactose-containing compounds such as galactosyiglycerol.

5. The peak level of activity is replaced by a prolonged interval in which the level of activity is reduced hut quite constant. The radioactivity is distributed over a variety of compounds including both amino acid and carbohydrates.

6. Translocation of nutrients is accomplished by the perivisceral fluid. No evidence for the participation of either the haemal or water vascular systems could be demonstrated.