Evidence for a Substance Responsible for the Spacing Pattern of Aggregation and Fruiting in the Cellular Slime Molds

Abstract

ABSTRACT In the cellular slime molds, after the individual amoebae have finished their growth and depleted their food supply, they aggregate into centers. Each center ultimately produces a small fruiting body (a spore mass supported by a slender stalk) that rises into the air. In a previous study (Bonner & Dodd, 1962a) it was shown that the size of the aggregation territories remained constant for any one species under a given set of environmental conditions even though the density of the amoebae in the culture dish might vary considerably. From this it was suggested that one of the possible hypotheses might be that a center-inhibiting substance is diffusing outward from the first formed centers and its effectiveness is independent of the number of cells within a territory. In another study (Bonner & Dodd, 1962b) evidence was brought forth to support the notion that as the fruiting body rises into the air it orients with respect to the environment by producing a gas to which it is sensitive and it orients away from regions of high concentration. In the discussion of this second paper we made the point that the adaptive significance of these two phenomena are one and the same; they both tend to space the fruiting bodies, first by keeping the centers separate during aggregation, and then by keeping the sorocarps separate as they rise into the air. Together they produce optimum conditions for effective spore dispersal.