Regeneration in Medusa buds and Medusae of Hydrozoa

Abstract

Isolated medusa buds of Podocoryne carnea (Anthomedusa) can either develop autonomously to functional medusae or transform to stolons and polyps. Up to stage 8 the percentage of transformaiion can be idised 10 100% by repeated traumatization of the isolated buds. From stage 9 onwards, even traumatized buds always regenerate medusae and never transform to polyps. At stage 8 the bud is differentiated, lacking only the swelling of the outer mesoglea to become a normal medusa. A correlation between the swelling of this mesoglea and the decrease of the percentage of transformation to zero can be observed between stages 8 and 9. The presence of a swollen mesoglea is not the only factor in stabilizing medusa structures, since, despite removal of the mesoglea by the dissociation method, aggregates of dissociated buds of stages 7 and 8 always formed medusa structures and never transformed to stolons or polyps. Regeneration of the manubrium in adult Hydromedusae shows a graded distribution, being highest in the center of the umbrella and decreasing rapidly towards the circular canal. The extent of manubrium regeneration is not influenced by the amount of wound material or the components of the gastrovascular system.