Anurans can only regenerate their limbs during embryonic development. He is unable to regenerate missing limbs or organs. However, the damaged system can only partially regenerate Astrid. Some sharks can regenerate scales and even skin following damage. In practice, stem cells are identified by whether they can regenerate tissue. Should players take damage, their health meter will gradually regenerate to its halfway point. Should player characters take damage, the character's health will gradually regenerate. She uses the blood acquired by the mosquitos to regenerate her limbs and become stronger. Flatworms have the ability to regenerate themselves from a single cell. A tarantula may also regenerate lost appendages gradually, with each succeeding molt. Ecosystems regenerate, withstand, and are forever adapting to fluctuating environments. This would also regenerate water and oxygen. Buried crowns can regenerate into healthy kudzu. The plant can regenerate from the roots. Homocysteine can be used to regenerate methionine or to form cysteine.