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Can a jellyfish turn back into an earlier life stage?

Most life cycles seem to move in one direction. The tiny jellyfish Turritopsis dohrnii can sometimes reverse part of its development, returning from a swimming medusa to an earlier polyp stage. That remarkable ability explains its “immortal” nickname, but restarting development is different from being impossible to kill.

3–7 min

Questions you could explore

  • What changes during the reversal, and what makes the resulting animal the same individual?

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