How a Sea Star Eats Through a Crack
An oyster’s shell is a strong defense, but it is not perfectly sealed. A sea star can take advantage of the tiny opening between the two halves. Rows of small, suction-cupped tube feet grip the shell, while muscles in the sea star’s arms keep pulling. The force is applied steadily rather than in a single crushing blow, gradually widening the gap enough for the next step.
A Stomach That Can Leave the Body
Sea stars have a two-part stomach. Once the shell opens a little, the sea star pushes its cardiac stomach out through its mouth, which is on the underside of its body. The stomach slips through the narrow gap and spreads over the oyster’s soft tissues.
Digestive enzymes break those tissues down outside the sea star’s body, turning them into material the stomach can absorb. The sea star then draws the stomach back in, carrying the partly digested meal with it. This is external digestion: digestion begins beyond the animal’s body, not inside a gut reached only after swallowing prey whole.
Why the Method Works
The oyster does not have to be shattered or pulled completely from its shell. The sea star needs only enough room to make contact with the edible tissue. Its tube feet provide the persistent grip needed to open the shell, and its flexible stomach makes a narrow entrance useful.
That combination lets a sea star feed on prey that is bulky and well protected. The shell remains mostly intact; the crucial change is simply that a small gap becomes large enough for a stomach to pass through.
