TRANSLOCATIVE FUNCTIONS OF THE ENIGMATIC ORGANS OF STARFISH—THE AXIAL ORGAN, HEMAL VESSELS, TIEDEMANN'S BODIES, AND RECTAL CAECA: AN AUTORADIOGRAPHIC STUDY

¹ Department of Biology, Eckerd College, Box 12560, St. Petersburg, Florida 33733

Starfish (Echinaster graminicolus) were fed C¹⁴-labeled clams or liquid glucoseamino acid medium, and subsequently examined as autoradiographic sections. Ingested tracer was first incorporated into the cardiac stomach and lower-middle digestive gland. By 8 to 12 hours, increasing amounts were located throughout the axial organ, aboral hemal ring, radial hemal strand, and mesenteric hemal vessel. Subsequently (22 to 48 hours), label progressed into the genital hemal connectives and the gonads, as well as the connective tissue-hemal plexus of the tube feet. C1early, hemal tissues, together with associated perihemal spaces, play major roles in the translocation of nutritive materials to the gonads and parts of the tube feet. These nutritive materials, however, may not come directly from the digestive system, which only has poorly developed hemal connections, but from coelomic sources.

Also noted was a gradual build-up of labeled material in the rectal caeca, suggesting that these organs remove nutrients from circulating digestive fluid before its evacuation through the anus or mouth. In animals fed liquid medium, tracer rapidly appeared in all parts of the water vascular system. showing that inflow of sea water does occur through the madreporite. Intense, rapid uptake by the Tiedemann's bodies revealed that they must filter a portion of this inflow, possibly producing coelomic fluid for body turgor and stomach inflation.