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In the late 1980s, researchers Giorgio Bavestrello and Christian Sommer stumbled upon a remarkable jellyfish, later named Turritopsis dohrnii. Unlike most animals, this tiny creature can reverse its life cycle, transforming from an adult back into its juvenile polyp stage under stress. This process, called ontogeny reversal, challenged the long-held belief that life follows a one-way path from birth to death. Marine zoologist Stefano Piraino and colleagues confirmed the phenomenon in the early 1990s, showing that these so-called “immortal jellyfish” can repeat the cycle multiple times, avoiding death from old age.
Scientists have since investigated how T. dohrnii achieves this biological reset. Early studies revealed that certain tissues can undergo transdifferentiation, where specialized cells switch identities to form new ones. More recent research has focused on the jellyfish’s genome. In a study led by María Pascual-Torner and Carlos López-Otín, published in Proceedings of the National Academy of Sciences, the team compared T. dohrnii with a related species that lacks this ability. They found that the “immortal” jellyfish carries more copies of genes linked to DNA repair, telomere maintenance, and protection against oxidative stress—mechanisms that help maintain genomic stability and delay aging.
Further gene expression studies have highlighted the importance of the cyst stage, when the adult medusa collapses into a ball of tissue before regenerating as a polyp. During this stage, genes related to DNA repair, telomere protection, and stress resistance are highly active, while those linked to cell differentiation are suppressed. This mirrors processes seen in mammalian stem cells and reprogramming techniques pioneered by Shinya Yamanaka, suggesting that T. dohrnii may serve as a living model of in vivo rejuvenation.
While these jellyfish are not truly immortal—they can still be eaten or die from disease—their ability to sidestep aging has captivated scientists. By uncovering the genetic and molecular tricks that grant T. dohrnii its unique longevity, researchers hope to apply the lessons to human health. Insights into DNA repair, telomere maintenance, and stress resistance could eventually guide new approaches in regenerative medicine, anti-aging therapies, and even gene editing. For now, the immortal jellyfish remains a powerful reminder of how unexpected discoveries in marine biology can reshape our understanding of life itself.
