cAMP plays a primary role; it is secreted in periodic waves by aggregation centres to mediate the aggregation of starving cells. (32) Later, organizing tips become the sources of cAMP waves (Fig. 1) , which direct the movement of cells in multicellular structures. (33) Secreted cAMP also triggers the differentiation of the prespore cells. (34, 35) In turn, the prespore cells secrete a chlorinated polyketide, DIF, that induces regulated redifferentiation of prespore cells into prestalk cells. (14) Ammonia, which is produced by protein degradation in the starving cells, represses terminal spore and stalk cell maturation during slug migration, (36, 37) and is implicated in cell sorting, slug phototaxis and fruiting body phototropism. (38, 39) Two secreted peptides, conditioned medium factor (CMF) and prestarvation factor (PSF) induce the growth to development transition. (40) Other peptides, the spore differentiation factors (SDFs), trigger the maturation of spores. (13) There is no information on the conservation of the peptide signals in other social amoeba species. Ammonia is always produced by starving amoebas, and at least some of its roles are therefore likely to be conserved. DIF was identified in another group 4 species, D. mucoroides, which also has the DIF-degrading enzyme, DIF dechlorinase. D. minutum and P. violaceum, which reside in group 3 and between groups 3 and 4, respectively, synthesize chlorinated factors that induce stalk cell differentiation in D. discoideum. However, they do not have DIF dechlorinase, indicating that the DIF signaling pathway is at best partially conserved. (41, 42) More information is available on the conservation of cAMP signalling. All tested group 4 species use cAMP to aggregate, but no species outside group 4. However, early biochemical work showed that species that use other attractants to aggregate, nevertheless display cAMP binding sites and cAMP phosphodiesterase on their cell surface after aggregation. (43, 44) The group 3 species, D. minutum, aggregates by continuous release of folic acid, but shows cAMP waves emerging from the tip region after aggregates have formed. (43, 45) This suggested that the role of the tip as a pacemaker of cAMP waves is deeply conserved in the social amoebas.