THE ANIMAL FILES

Common starfish

Asterias rubens

A small opening can turn into a meal.

The common starfish uses tube feet for movement and feeding.[1]

Follow the evidence ↓
Common starfish
Image: Hans Hillewaert · Commons · CC BY-SA 4.0
Feet along the arms
Tube feet serve movement and feeding[1]
Digestion through a gap
A stomach fold enters opened shells[1]
A floating beginning
Larvae drift before settling[1]

Feet along the arms

The common starfish usually has five arms, broad at the base and tapering towards slightly upturned tips. Rows of small tube feet run along the underside of each arm and serve movement and feeding.[1]

Digestion through a gap

When feeding on a mussel, the starfish attaches tube feet to the two valves and pulls them slightly apart. A fold of stomach enters the opening and releases enzymes to begin digestion. Once the tissues become liquid, the stomach is withdrawn with the food inside.[1]

A floating beginning

Eggs and sperm are released into the water, and larvae drift before settling and transforming into juveniles on the bottom.[1]

A COMMON MIX-UP

Must it swallow an entire closed mussel to eat?

No. It pulls the valves slightly apart and inserts part of its stomach through the gap.[1]

TRY A LITTLE REASONING

Why can a tiny shell opening still matter to this predator?

Reveal the explanation

It provides access for the stomach fold. The relevant step is not fitting the whole prey into the mouth but reaching the soft tissues inside the shell.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Common starfish (cited revision)
  2. NCBI Taxonomy — Asterias rubens

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