AN AUTORADIOGRAPHIC STUDY OF THE TRANSLOCATION AND UTILIZATION OF AMINO ACIDS BY STARFISH

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

1. Specimens of the starfish, Echinaster echinophorus, were injected in the disc region with small quantities of C¹⁴-labeled amino acid mixture. After periods ranging from 1 hour to 75 days they were sacrificed and histological sections of their arms prepared as stripping film autoradiographs.

2. By 1 hour after the injection bound radioactive material was detected in most tissues in the proximity of the coelomic cavity, and while translocations from these areas were noted, most of the labeled material remained in these areas even after 75 days.

3. By 24 hours large quantities of radioactivity were found spasmodically in the hemal septum and traced dispersing outward into the connective tissue layer of the tube feet and the suckers. It is believed that this material was transported from the pen-visceral coelom via the perihemal canals and fixed as an insoluble mucopolysaccharide by the cells of the hemal septum.

4. By 5 days significant dispersion of radioactive material through all regions of the body wall was evident. Strong retention of the radioactive material was found in the subepidermal layer, the large demal glands, osteocytes, and in the connective tissue layers adjacent to the somatic peritoneum.

5. As no sign of movement of radioactivity into the epidermis was seen in any of the sections, it is concluded that a previously theorized diffusion barrier beneath this layer must exist, and that epidermal cells obtain most of their nutrition from external sources.

6. Judging by their distribution in the various sections, it seems possible that the amoebocytes play a minor, purely secondary role in the dispersion of nutritive substances throughout the body.