A Model forDictyosteliumSlug Movement

Dictyosteliumslug movement results from the coordinated movement of its 105constituent cells. We have shown experimentally that cells in the tip of the slug show a rotational cell movement while the cells in the back of the slug move periodically forward (Siegert & Weijer, 1992). We have put forward the hypothesis that cell movement in slugs is controlled by chemotaxis to scroll waves generated in the tip which convert to twisted scroll or planar waves in the back of the slug (Bretschneideret al., 1995). The coordinated movement of all individual cells in response to these waves could then result in forward movement of the slug. We now test this hypothesis by extending our model for mound formation (Bretschneideret al., 1997) to include two cell types with different signalling and movement properties. All cells are able to relay cAMP and move chemotactically in response to cAMP gradients. Cells interact by adhesion, pressure and friction with neighbouring cells and the extracellular matrix. The model can generate stable scroll waves propagating from the tip to the back of a slug which coordinate forward cell movement and result in slug migration. We use the model to investigate the influence of cell type specific differences in excitability, adhesion and cell interactions on slug motion.