Analysis of a foot regeneration deficient strain of Hydra oligactis.

A foot regeneration deficient strain of Hydra oligactis with altered size regulation was investigated. Analysis of the concentration of four morphogenetically active substances in Hydra oligactis showed that the foot regeneration deficiency was mainly due to a drastically reduced foot activator concentration. Foot activator was distributed as a very steep gradient in Hydra oligactis leading to a more severe impairment of foot regeneration the closer to the head cutting was done. The concentration of foot inhibitor was comparable, that of head activator slightly increased and that of head inhibitor reduced compared to Hydra vulgaris. Studies at the cellular level implied that the enlarged gastric region was due to an elevated level of inhibition hinting at a shift in the ratio between bound and free head inhibitor in this animal.