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

Abstract

The red alga, Iridaea flaccidum labelled with C14O2 by photosynthetic assimilation was fed and tissues and fluid systems were sampled at intervals. Digestion and absorption of labelled constituents was accomplished in the esophagus and 1st festoons of the gut. Ninety per cent of the algal C14 was converted to animal C14. These same portions of the gut appear to be the sight of storage. Nutrients are translocated from the intestine by way of the perivisceral fluid. Neither the water vascular nor the haemal systems contribute to nutrient transport. The labelled materials were present in both the plasma and the coelomocytes. At the peak level attained 6 hours after the start of feeding the plasma contains the bulk of the labelled material. The level of labelled nutrients falls to a constant value that is maintained for several days. During this steady state condition the coelomocyte contain the bulk of the labelled materials.