Humans aren't very good at regeneration — we can do it for skin, bone, and liver, but that's about it.
Flatworms, zebrafish, cockroaches, and salamanders can regenerate entire limbs. Yet even these abilities are unimpressive compared to those of Hydractinia symbiolongicarpus, aka a "squishy sea creature."
Only Simpler Animals Regenerate
Hydractinia, along with jellyfish, sea anemones, hydra, and corals, are among 11,000 or so species in phylum Cnidaria, from the Greek cnidos for "stinging nettle." The tiny animals have soft bodies, circular symmetry, and sting. The hydractinia are among the most ancient of the Cnidaria. We last shared an ancestor with these animals more than 600 million years ago. They live in saltwater and are small and tube-shaped, clinging to hermit crabs.
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