crown-of-thorns starfish

crown-of-thorns starfish

Crown-of-thorns starfish

(credit: A. Giddings—Bruce Coleman Inc.)

Reddish and heavy-spined starfish (Acanthaster planci) that has 12–19 arms and is often 18 in. (45 cm) across. It feeds on the polyps of coral. Beginning c. 1963, its population on Australia's Great Barrier Reef exploded. Destruction of coral reefs and islands was feared, and intensive efforts were made to kill it off. Since then other outbreaks have been recorded throughout the southern Pacific. The cause of the outbreaks is unknown, but several factors have been proposed, such as the decimation of the starfish's chief predator, the Pacific triton (a marine snail), by shell collectors. Other factors, including the runoff of nutrient-rich soil into reef waters as a result of shorefront development, have also been implicated. Population fluctuations could also be a feature of the starfish's natural ecology, and human influence may alter these cycles.