What is the name of the starfish that preys on corals and can cause large-scale reef damage?

The starfish that preys on corals and can cause large-scale reef damage is the crown-of-thorns starfish. Its scientific name is Acanthaster planci, and it feeds mainly on the living tissue of hard, reef-building corals.

Rather than biting coral, the starfish attaches itself to a colony and everts its stomach over the coral surface. Digestive enzymes liquefy the living tissue, leaving behind a conspicuous white scar on the exposed skeleton. A large individual can consume several square meters of living coral in a year.

The animal’s name comes from the numerous sharp, thorn-like spines covering its upper surface. These spines can injure predators and people, and its tissues contain irritating saponins. At ordinary population levels, crown-of-thorns starfish are a natural part of reef ecosystems. During outbreaks, however, their feeding can outpace coral growth and remove extensive areas of living coral.

The parrotfish is a common mix-up: it also grazes on reef organisms, but it is a fish, not the coral-eating starfish described here.