| תקציר: | Hydra regeneration from a tissue fragment provides a unique experimental setup, allowing us to develop a physics framework for animal morphogenesis. We demonstrated before that by tuning an external electric field, we can drive morphogenesis in whole-body Hydra regeneration, back- and-forth, around a critical point. Our control of morphogenesis allows us to identify and characterize the primary morphological transition in the regeneration process — from a spherical structure to an elongated cylindrical shape, the final body form of a mature Hydra. We conceptualize morphogenesis as a self-organization process governed by a "morphological potential" and demonstrate that spatial fluctuations of the calcium distribution in the Hydra’s tissue drive this transition. The morphological transition shows characteristics of a first or second order-like phase transition, depending on inherited positional information from the donor animal. In the former case, a periodically modulated electric field leads to a new induced phase of the regenerating tissue, showing stochastic morphological swings, back and forth, between a nearly spherical structure and an elongated cylindrical shape with dynamics characteristic of a stochastic resonance; the tissue’s response to the perturbation exhibits a resonance-like behavior as a function of the noise level. Our findings offer a novel physical framework for morphogenesis distinct from Turing-like reaction diffusion mechanisms. |