NUTRIENT TRANSPORT IN STARFISH. I. PROPERTIES OF THE COELOMIC FLUID

Abstract

Serial analyses of organic substances in cell-free coelomic fluid of the starfish, Asterias forbesi, could not reveal significant differences between fed and fasted specimens. The mean value of total N was 63.5 [mu]g per ml, but large fluctuations occurred in all the specimens. Free ammonia was present fairly constantly with a mean value of 12.8 [mu]g N per ml. Protein represented about 25% of the total N in 2 analyses. Reducing sugar occurred in extremely low and moderately constant concentrations (mean value, 69 [mu]g per ml). When starfish were fed C -labeled algal protein hydro-lysate, glucose, and palmitic acid, these substances were stored in the digestive glands and reached other tissues only very slowly. Except possibly for palmitic acid, these nutrients appeared consistently in the coelomic fluid in all times following feeding. Small amounts of C -labeled algal protein hydrolysate, glycine, and glucose injected into the coelom were readily absorbed by the body tissues, especially digestive glands and to a much lesser extent, coelomocytes. These studies implicate the coelomic fluid as the most important medium of transport and suggest that transport is accomplished as part of a continual flux of substances between the coelomic fluid and the various body tissues.