How do different organisms regenerate?
Organisms regenerate in different ways. Plants and some sea creatures, such as jellyfish, can replace missing parts by extensively remodeling their remaining tissues.
Some animals such as lobsters, catfish, and lizards replace missing parts by first growing a
blastema. The blastema cells rapidly divide to form the skin, scales, muscle, bone, or cartilage needed for creating the lost limb, fin, or tail.
In other animals, including humans, organs such as the liver undergo what’s called
compensatory hypertrophy. When part of the liver is removed or destroyed, the remaining portion grows to the original size and allows the liver to function as it did before. Our kidneys, pancreas, thyroid, adrenal glands, and lungs compensate for organ loss in a similar, but more limited, way.
Research organisms that are particularly useful for studying regeneration include the blue-and-white-striped zebrafish and the planarian, a type of flatworm. The zebrafish can replace a damaged or lost fin; and can also repair significant damage to its heart, pancreas, retina, brain, and even spinal cord.