Cost of movement in the multicellular stage of the social amoebae Dictyostelium discoideum and D. purpureum

• Published in: Ethology, ecology & evolution ecology & evolution, 2011-01, Vol.23 (4), p.358-367
• Main Authors: Jack, C.N, Adu-Oppong, B, Powers, M, Queller, D.C, Strassmann, J.E
• Format: Article
• Language: English
• Subjects: Amoeba; Bacteria; Cells (biology); conflict; cooperation; Costs; Dictyostelium; Dictyostelium discoideum; Dictyostelium purpureum; Dispersal; Dispersion; Feeding; Fertility; Fruit bodies; fruiting bodies; Growth; microbes; migration; Migrations; prediction; Predictions; Slugs; sociality; Soil; Soil bacteria; Soil microorganisms; Specialization; Spores
• ISSN: 1828-7131; 0394-9370; 1828-7131
• DOI: 10.1080/03949370.2011.584907

One of the challenges of microbial life is that the best location for feeding and growth may not be the best location for dispersal. This is likely to be the case for the social amoebae Dictyostelium discoideum and Dictyostelium purpureum that feed on soil bacteria in the amoeba stage, but then group into a multicellular slug that moves towards light before forming a fruiting body. Here we examine this short-range social dispersal in the social amoebae, Dictyostelium discoideum and D. purpureum. We predicted D. purpureum would have higher migration costs and travel less far because it forms a dead stalk from living cells as it moves, while D. discoideum delays stalk formation until movement ceases. We found that D. purpureum migrated shorter distances than D. discoideum, in accord with our prediction. D. discoideum slugs moved an average of 2.46 ± 0.19 cm while D. purpureum slugs moved an average of 1.04 ± 0.06 cm. In both species, migration incurred a cost in reduced spore production, compared to experimental conditions where slugs did not migrate. D. discoideum under the no migration treatment produced 0.55± 0.05 spores per cell and under the migration treatment produced 0.25 ± 0.04 spores per cell. D. purpureum under the no migration treatment produced 1.01± 0.06 spores per cell and under the migration treatment produced 0.85 ± 0.06 spores per cell. We also found that D. discoideum produced fruiting bodies with fewer spores after migrating while D. purpureum did not. It appears that the evolutionary loss of stalked migration gives D. discoideum cells the advantage of delaying specialization and the ability to colonize more distant locations, but has significant costs due to migration distance, such as the fraction of cells that become fertile spores.