Budding and strobilation inAurelia (Scyphozoa, Cnidaria): Functional requirement and spatial patterns of nucleic acid synthesis.

Strobilation and polypoid budding occur at different locations in the scyphistoma (polyp). Initiation and completion of both forms of budding are inhibited by hydroxyurea (HU), which blocks 95% of DNA synthesis within 12 h. Gradients of thymidine incorporation into both cell layers of the body column precede and accompany strobilation, and an epidermal gradient precedes polypoid budding. In both, the highest labelling index is in the zone in which initiation will occur. Polypoid buds show high variation in labelling index, which is therefore not significantly different from body column labelling. Initiation and some elongation of polyp buds occurs in a small percentage of animals in HU, indicating that cell recruitment is important for these processes. Strobilation appears to be more highly dependent on localized nucleic acid synthesis than polypoid budding.