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Why Do Starfish Lose Their Arms?

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Robin Burden Profile
Robin Burden answered
Starfish arms (more commonly referred to as 'rays') can drop off for a number of reasons.

The most common cause is a form of self-defense called autotomy (which comes from the Greek words for self-severing).

Certain species of starfish can even reproduce by dividing asexually, although this is less common.

Why do starfish lose their arms? A starfish has the ability to sever its own arm in order to escape a predator. In most cases, a ray will become detached to help a starfish escape the clutches of a bigger fish (starfish are preyed on by manta rays and sharks).

The limbs of a starfish are detachable, thanks to a special kind of tissue that softens in reaction to nervous signals sent by the starfish's ring of nerve cells (they don't have a brain). This is why a starfish might also 'accidentally' lose an arm if it becomes frightened, irritated or nervous.

Whilst a starfish is recovering from the loss of limb, it is at a very high risk of infection. This is why the defense mechanism is considered an option of last resort.

You might also be fascinated to learn that an entire starfish can regenerate from a severed limb, and that some species actually reproduce asexually by dividing into several separate starfish.
Anonymous Profile
Anonymous answered
Starfish will lose arms as a result of stress. Even with a long acclimatization period, starfish will still drop arms as a result of the stress of transportation.

This behavior is an attempt to better its chances at survival. If the arms look healthy and you don't see them decay, they may develop into full starfish.

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