Spiders can regrow any one of their eight legs if they happen to lose one. A spider may also amputate its legs as a defense strategy. In order to regrow a leg, they have to shed the skin of their hard outer shell called an exoskeleton. This is also known as molting. They will molt many times throughout their lives until they are fully grown. It’s during this molting that they can regrow a missing leg! The new leg will usually be a bit smaller than the other seven. It can take two or three molts until the regenerated limb matches the original in appearance. Spiders also have the ability to grow new pedipalps, mouthparts, silk spinners, and more.
If the fish’s caudal fin gets bitten off or cut, the zebrafish can grow a new tail in about two to four weeks. Adult zebrafish are able to regenerate different organs, including all fins, the spinal cord, retina, the heart, and the kidney. Because zebrafish are such experts at regeneration, researchers have been using them as a model for complex tissue regeneration.
Planarians, a class of flatworms that are so flat that they need neither lungs nor a heart to take in and distribute oxygen in their bodies. Planaria also have amazing abilities to regrow itself. When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual. They can also reproduce asexually and just make more copies of themselves. And these animals can also regrow their heads.
But what’s shockingly weird about this animal is, in one study published in the Journal of Experimental Biology, researchers found that worms with regrown heads had the same memories as before. How? Well, the researchers aren’t so sure but they think that maybe their memories get stored in other cells in the body and then get imprinted into the new brain when it grows.
Hydractinia, is tiny, transparent, and stays fixed to one spot. Commonly called “snail fur” because it grows on the shells of snails and crabs, this tiny animal can regrow its entire head if it gets bitten off by a hungry predator. When the head of Hydractinia is cut off, stem cells in the animal’s mid-body section migrate to the end where the head used to be and multiply there. These stem cells then create a bud known as a blastema that develops into a new, fully functional head within two days.
Axolotl also is known as the Mexican walking fish. This creature is known for its remarkable regeneration capabilities and scientists all over the world have a great interest in its regeneration superpowers. Axolotl can regenerate not just its tail but also limbs, skin, and almost any other body part. It has the “superpower” of regenerating its limbs, spinal cord, heart, and even its brain.