Morphogenetic influences of buds on pattern formation in Hydra

In hydra buds are thought normally to inhibit head regeneration or the formation of additional buds in the close vicinity. However we have recently demonstrated the possibility of buds developing in close vicinity of a regenerating head under experimental conditions. To further clarify this aspect of hydra development, influences of buds on head regeneration and on additional bud development were studied in Hydra attenuata. Regeneration capacity of the distal part (lacking the peduncle) and the proximal part (lacking the gastric and head zone of hydra with or without a bud. Another group of chimeras was prepared in the same way, but lacking a head. The presence of a bud in the proximal part of a regenerate generally delayed head regeneration. Significant bud induction and tentacle stimulation was Seen in chimeras each having a head and possessing a bud in both the distal and proximal parts. A slight increase in bud forming capacity was also seen in all the chimeras studied. Significantly increased numbers (14-15) of tentacles were regenerated in chimera lacking a head, except in the group with a bud only at the distal half. These results indicate that increased tissue mass generally augments bud forming capacity. However the presence of two original buds in a chimera with a head has certain synergistic effects on bud promotion. Furthermore, dynamic changes associated with head regeneration seem to be easily influenced by increased animal mass and the presence of buds to yield supernumerary tentacles in hydra. These findings indicate the positive influence of buds on head regeneration and on bud development in hydra in addition to the conventionally known negative effect on the above processes.