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How Does a Starfish Regenerate?

Starfish possess the ability to regrow lost arms, or even partial bodies, after they are injured. They do this to heal injuries and in reproduction. If you cut a starfish into five segments, each containing one original arm and a segment of its central disc, five new starfish will grow.

Regenerative Process
- A deviation during the regenerative phase produces additional, asymmetrical limb formations.
  
  Starfish regenerate via a three-phase process. First, the repair phase heals the exposed wound. After the repair phase, the regenerative phase begins. During this phase the starfish body generates new cells and initiates the start of new growth. Finally, during the advanced regenerative phase, major cell proliferation begins. Neurally derived growth factors determine the mechanisms responsible for pattern formation during the final phase. If anything interferes or causes deviation from this pattern while the starfish is regenerating, the final result may be deformed.
Self Cloning
- Replacing lost limbs isn't the only way in which a starfish regenerates. Starfish are also able to reproduce asexually by tearing apart their own bodies. Each of the severed body segments has the potential to grow a new animal that is genetically identical to others from the same animal. Starfish also use this trait to clone themselves after an attack or injury separates their bodies into segments, as was once common when oyster fishermen used to cut starfish up before throwing them back. The fishermen thought they were killing the starfish, but were actually boosting their populations.
Central Disc
- In most cases, a starfish cannot clone itself unless the intended clone contains part of the central disc. The central disc is, as its name implies, the center of the starfish's body. The typical pattern of five arms radiates symmetrically out from the central disc. A severed arm with some segment of the central disc will create a clone, but one severed at a distance from the disc will not. Although, on occasion, a severed arm will regrow some additional arm tissue.
Regeneration Without the Central Disc
- Dried remains of Linckia diplax show their long, thick limbs.
  
  Although cloning without the central disc is highly atypical, researchers have observed it in the species Linckia diplax. The long, thick severed arms of this species may sometimes grow a tiny new central disc with four small arms, all of which then grow to full size. Scientists are uncertain whether this ability is present only in intentionally discarded limbs, as occur in asexual reproduction, or if a limb severed during an injury may also grow a complete new clone.

Animals & Science