SELECTION FOR SPIRAL WAVES IN THE SOCIAL AMEBAS DICTYOSTELIUM

Starving Dictyostelium amoebae emit pulses of the chemoattractant cAMP that are relayed from cell to cell as circular and spiral waves. We h ave recently modeled spiral wave formation in Dictyostelium. Our model suggests that a secreted protein inhibitor of an extracellular cAMP p hosphodiesterase selects for spirals. Herein we test the essential fea tures of this prediction by comparing wave propagation in wild type an d inhibitor mutants. We find that mutants rarely form spirals. The ter ritory size of mutant strains is approximately 50 times smaller than w ild type, and the mature fruiting bodies are smaller but otherwise nor mal. These results identify a mechanism for selecting one wave symmetr y over another in an excitable system and suggest that the phosphodies terase inhibitor may be under selection because it helps regulate terr itory size.