Further evidence for the sorting out of cells in the differentiation of the cellular slime mold Dictyostelium discoideum

The observation of Takeuchi's that the denser cells of Dictyostelium discoideum tend to sort out towards the anterior end of the migrating slug (and the lighter cells towards the posterior end) has been confirmed using spore size as a method of identifying cells populations. A fraction of the anterior and posterior ends of a slug are isolated and allowed to fruit; their spores are then measured. The same is done for preaggregation cells which have been separated into heavy and light fractions, using Takeuchi's technique of centrifugation of the cells in a dextrin solution equal to the mean specific gravity of the cells. Invariably, in three experiments with different strains of D. discoideum, the spores derived from dense cells corresponded perfectly with spores derived from the anterior cells of the slug, and a similar correspondence was found between spores derived from light cells and posterior slug cells. Contrary to a previous view (Bonner, 1959), cell size did not always correlate with position; in one strain the anterior cells were larger, in the other two they were smaller.