3. Planarian Flatworms
Planarian flatworms are masters of regeneration. If cut into pieces, each fragment can regrow into a complete worm, thanks to their plentiful pluripotent stem cells. These remarkable cells give planarians the ability to continually renew their tissues, potentially allowing for indefinite survival under the right circumstances.
As Live Science notes, their astonishing regenerative abilities make planarian flatworms a prime subject for studying the secrets of longevity and biological immortality.