FRUITING BODY ARCHITECTURE, SPORE CAPSULE CONTENTS, SELFISHNESS, AND HETEROCYTOSIS IN THE CELLULAR SLIME-MOLD DICTYOSTELIUM-DISCOIDEUM

Two strains of Dictyostelium discoideum (NC-4H and HPS104), grown in mixed culture, on a low dextrose medium, exhibited evidence of behavior that was sensitive to patterns of relatedness. Differences in fruiting body architecture and spore capsule composition revealed that the strain NC-4H acted more selfishly than when grown in pure culture. This was indicated by the larger spore capsule diameter and a shorter stalk in the mixed culture. Counts of the morphologically distinguishable spores in the spore capsules showed that NC-4H predominated, leaving HPS104 to act altruistically and sacrifice itself to form the stalk. When grown on a high dextrose medium, the fruiting body architecture revealed longer stalks in the mixed culture but spore capsule diameters similar to those in the pure cultures. However spore counts of the mixed spore capsules showed that the strain NC-4H still predominated. Therefore, NC-4H acted selfishly under these growth conditions as well.