Phenotypic plasticity as the foundation of lifelong development

Many animals retain the capacity to transform their form and function throughout life, yet developmental biology has predominantly focused on early stages. Non-bilaterian animals, in particular, offer opportunities to investigate the principles underlying lifelong development, including regeneration, asexual reproduction, morphological plasticity and reverse development. We examine these transformations through the lens of phenotypic plasticity, presenting a modular framework that highlights how environmental cues trigger developmental programs. This framework supports a conceptual shift from viewing development as a terminal process to one of dynamic navigation through stable yet responsive organismal states, positioning non-bilaterian metazoans as key models for understanding lifelong developmental competence.