REGENERATION OF COMPLETE HYDRA FROM ISOLATED EPIDERMAL EXPLANTS

¹ Developmental Biology Center, Department of Biology, Case Western Reserve University, Cleveland, Ohio 44106

1. A method of separating cell layers in Hydra by perfusion is presented. Under optimum conditions about 50% of perfused animals show separation of epidermis from gastrodermis. With this technique it is possible to secure large pieces and even whole cylinders of living epidermis or gastrodermis free from contamination by the other cell layer.

2. Isolated explants of epidermis were tested for regeneration in H. fusca, H. oligactis, and H. pseudoligactis. Each species showed some regenerative ability, and complete minature hydras were obtained in H. oligactis and H. pseudoligactis. Other work (Haynes and Burnett, 1963; Normandin, 1960) has shown that isolated gastrodermis can regenerate complete hydras in H. viridis and H. oligactis. Thus the present work, showing that isolated epidermis can also regenerate complete polyps, makes Hydra the first animal in which it has been demonstrated that each layer alone can give rise to the other during regeneration.