Crown-of-thorns sea star

Much larger than the sea urchin it resembles, the crown-of-thorns sea star is a predator of the coral reef. Growing to over a foot in length, this isn't your typical starfish. With more than 20 arms and an intimidating exterior, the crown-of-thorns starfish should be approached with caution. Its sharp spines have been known to sting humans.

A canivore, this sea star's main diet consists of coral polyps, which it digests by secreting an acidic ooze as it latches onto the coral's surface. In a single year, a crown-of-thorns starfish can eat dozens of square feet of coral! This can cause a decline in the coral cover, but for the most part, the sea star is just doing its part in maintaining the ecological balance in the tropical sea.