organism form aggregation stage BTO:0002007 BrendaTissueOBO During development of the cellular slime mold Dictyostelium discoideum, amoebae exhibit different types of cell-cell interactions. At the aggregation stage, certain cells begin to secrete cAMP and neighboring cells respond by undergoing chemotactic migration toward the source of CAMP. Meanwhile, cells acquire new antigenic determinants on the surface and become more cohesive. fungus form