All animals, including humans, are able to heal wounds but most animals can't regenerate limbs and organs. Some marine animals have the ability to regenerate body parts. Scientists study these animals that can in hopes of learning more about how bodies heal their own wounds and hope that perhaps in the future people will have the ability to regenerate their own body parts.
Starfish and Brittle-stars
Starfish have an amazing ability to regenerate lost or amputated body parts. They can regrow body parts even if as much as half of their body is missing. Some types of starfish can regrow a whole body from a single arm. The brittle-star also has the ability to regenerate body parts. Experiments revealed that if the radial nerve is severed when the limb is amputated no regeneration occurs.
Sea Cucumbers, Catfish and Tadpoles
Sea cucumbers use the same molecular method for both wound healing and regeneration of body parts. Sea cucumbers regenerate body parts quickly. Special cells known as morula cells move into the injured area and the repair is complete in just a couple of weeks. Catfish can easily regrow their barbels which resemble cat whiskers. Tadpoles can regenerate their tails but it is not known why frogs can't do the same with lost limbs.
Crustaceans such as lobsters and crabs can regenerate their legs and claws. The new appendages stay in a protective cuticle until the animal molts. Because crustaceans molt throughout their lives they always have the ability to regrow limbs. If they lose a limb before it's time to molt, the new limb begins to grow but does not fully develop until a few weeks before molting. Hormones trigger the continued growth of the limb when it's time.
Zebra Fish and Other Fish
Zebra fish have the ability to regrow their tails. Most fish can regenerate scales and gills. Bony fish can regenerate fins but gelatinous fish can't. Fins won't regrow if the nerve supply is cut. All regeneration depends on stimuli such as the nervous system or the spinal cord. Some scientists believe that there is not an adequate nerve supply in animals that don't regenerate body parts. The phenomenon has not been fully explained yet.
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