A disc of up to twenty-one arms under a coat of five-centimeter spines, sitting on a coral head that is turning white beneath it. Forty centimeters (16 in) across at its largest, and the most destructive animal on this reef.
It eats by turning itself inside out. The stomach is pushed out through the mouth, spread over the coral like a cloth, and the polyps are digested where they sit; the star moves on and leaves bare white skeleton behind. A single adult clears something like its own area of living coral every day. At normal densities that is part of how a reef renews itself. In an outbreak - and outbreaks happen - it strips whole reefs.
The arithmetic behind an outbreak is the problem. One female releases tens of millions of eggs in a season, and the larvae do well when the water is rich in nutrients, which is what runoff from land provides. Kill one by cutting it up and the pieces regenerate; the only reliable field method is a single injection of bile salts or vinegar per animal.
The spines are venomous, brittle, and break off in the wound, where they keep releasing toxin - the tissue carries saponins, the same soap-like poison sea cucumbers use. Stings hurt for hours and swell for days, and a fragment left inside is a matter for a doctor. Its most effective natural predator is a snail: the Triton's Trumpet, which is why taking those shells has consequences nobody sees for years.
- flat disc with 12 to 21 arms, far more than any other sea star here
- covered in long sharp spines, up to 5 cm
- color from gray-green to purple and orange-red
- sits on a coral head with a white feeding scar spreading under it
- diameter up to 40 cm
