Life cycle of slime moulds. Animation of the stages of the life cycle of Acrasiomycota slime moulds. As shown, the spores develop into free-living, soil-inhabiting amoeba cells, each with a single haploid nucleus. During their feeding stage, these cells divide repeatedly, producing independent uninucleate daughter cells rather than a multinucleate plasmodium. As the local food supply diminishes, the behaviour of the amoeba suddenly changes. Two quite different cycles (one sexual and the other asexual) are possible, depending on environmental conditions. Most often the amoebae enter the asexual cycle: they cease feeding and begin to aggregate at central collecting points where they clump together to form a slug-like pseudoplasmodium. The individual haploid cells retain their separate identities within the pseudoplasmodium, and they do not fuse. The pseudoplasmodium may move around as a unit for a while, but eventually it becomes sedentary and in the culmination of the asexual phase forms a stalked fruiting body in which new spores are produced. For this animation without labels, see K004/2707. |