Turritopsis dohrnii: The Living Embodiment of the Paradox of Theseus

The Ship of Theseus paradox is traditionally discussed as an artefact puzzle about repair, replacement, and reassembly. However, the hydrozoan Turritopsis dohrnii exhibits a strikingly analogous process in vivo: under stress, a mature medusa can reverse its life cycle, transforming into stolons and juvenile polyps from which medusae may later reappear. This paper models the organism’s life cycle as a labeled state-transition graph and treats biological continuity in terms of ancestral overlap among cellular lineages rather than strict token identity. Within this framework, the life-cycle reversal of Turritopsis dohrnii realizes a concrete instance of Theseus-like continuity while also clarifying where the analogy breaks down in biological branching processes.