Regeneration in hydrozoa distal vs. proximal transformation in hydractinia echinata
Mueller, W.A.; Plickert, G.; Berking, S.
Wilhelm Roux's Archives of Developmental Biology 195(8): 513-518
ISSN/ISBN: 0340-0794 Accession: 006282337
Polyps of mature colonies of Hydractinia echinata obey the "rule of distal transformation" by regenerating heads but not stolons. However, this rule is not valid for young polyps as these regenerate stolons from proximal cut ends. Also, small cell aggregates and even small fragments excised from full-grown polyps are capable of stolon formation. Aggregates produced from dissociated cells undergo either distal or proximal transformation depending on their size, speed of head regeneration in the donor used for dissociation and the positional derivation of the cells. The latent capability of stolon formation is released under conditions that cause loss of morphogens and depletion of their sources. However, internal regulative processes can also lead to gradual proximal transformation: regenerating segments of polyps sometimes from heads at both ends and the distal pattern is duplicated. Subsequently, all sets of proximal structures, including stolons, are intercalated. In contrast to distal transformation, proximal transformation is a process the velocity of which declines with the age and size of the cell community.