The mesoglea of Hydra. 3. Fiber system changes in morphogenesis.

Examination of isolated mesogleas of Hydra pseudoligactis demonstrates that the organization of the collagen-elastin-like fiber system is dependent on the morphogenic state of the animal. There is a fiber system change associated with each of the three morphogenic capabilities of the animal: budding regeneration, and body column growth. Non-budding animals maintain a complete oral-aboral fiber system throughout the body column. Hydra in the early stages of budding exhibit an organized fiber system in the peduncle only. Hydra maintained as continuously budding do not reorganize the mesogleal fiber pattern. The molecular or macromolecular changes in the fiber system are not, as yet, known. Fiber system changes experimentally induced by feeding or hypostome excision appear the same as the breakdown associated with budding but differ in their extent through the animal. The observed changes are related to the different morphogenic capabilities of Hydra through a theory of cell migration and cell adhesion.