The morphological potential underlying Hydra morphogenesis

A remarkable hallmark of animal morphogenesis is the robust convergence of developmental processes into a stereotypic viable body plan. Hydra regeneration offers a unique experimental platform to study this phenomenon and allows us to develop a physics-based framework for this pattern formation process. Traditional models of morphogenesis emphasize biochemical patterning as a hierarchy of forward-driven processes. In this talk, I propose an expanded view, highlighting the synergistic interplay of mechanical, biochemical, and electrical dynamics as the foundation of morphogenetic robustness. Our experiments allowed us to identify and characterize the primary morphological transition during Hydra regeneration, where a tissue fragment undergoes a transformation from the incipient spherical structure to an elongated cylindrical shape — the final body form of a mature animal. Further insights come from external perturbations: applying an electric field induces stochastic morphological oscillations between spherical and cylindrical shapes. Moreover, application of a periodically modulated electric field results in morphology dynamics consistent with stochastic resonance, where the tissue’s response to perturbations peaks at an optimal noise level.

I will present a physical framework that conceptualizes morphogenesis as a self-organization process governed by a "morphological potential." This approach incorporates principles from fundamental physics, including noise-driven symmetry breaking and phase transitions, which have successfully explained pattern formation in non-living systems. Specifically, it will be demonstrated that the primary morphological transition is driven by spatial fluctuations of calcium (Ca²⁺) within the tissue, coupled with its local curvature. A field-theoretic model based on this insight, interprets the morphological transition as an activation over a barrier, akin to a first-order phase transition. These findings demonstrate the significant role of noise as an activator of morphogenesis, challenging conventional models and suggesting that morphogenesis is not merely biochemical but an emergent process shaped by multiple interacting physical forces. This perspective provides a fresh view of morphogenesis, offering a framework distinct from Turing-like mechanisms, emphasizing the morphological potential as a key organizing principle.