You didn’t see this on ‘Spongebob’: Cannibal sea star babies

by Joseph McClain, William & Mary 

Karina Brocco French explains that sea stars are like butterflies: They go through metamorphosis.

“They start out as adults on the sea floor, and they look like what you expect a starfish to look like,” she said. “And they spawn, and then those little embryos end up flying through the water, if you will, during a larval stage where they look like weird little spaceships.”

The weird little spaceship stage lasts around a month, Brocco French said, before they metamorphose into juveniles, settling onto the sea floor. Jon Allen said the juveniles are essentially pinhead-sized, star-shaped versions of their parents.

To grow, the juveniles must eat, and Brocco French and Allen discovered that what the young sea stars eat often turns out to be each other. Cannibalism is widespread in nature, but their discovery marks a heretofore unknown example of cannibalism in marine invertebrates fresh out of metamorphosis.

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