Budding in Hydra attenuata: bud stages and fate map.

Ten bud stages are defined and their profiles illustrated. A fate map of the developing bud of Hydra attenuata was made using vital intracellular marking. Marks made at increasing distances from the young bud tip end up in increasingly more proximal regions of the bud. There is no major difference between the recruitment patterns of cells from above, below and lateral to the bud tip. The angular positions of cells on the parent is directly correlated with their final angular positions on the bud axis. Therefore, tissue is recruited in concentric rings around the young bud tip and is distorted directly outward into the bud column. At the youngest bud stages, the fate map of the bud extends about 180° around the parent. Tissue recruitment from the parent ends at the time that tentacle rudiments appear on the bud. Thus, tissue recruitment and hydranth morphogenesis are separate processes.