The crown-of-thorns sea star is an echinoderm, which means “spiny skin.” Hiding itself in crevices in the reef during the day, this starfish likes to crawl around on the reef in huge groups of 20-200 individuals. It can move around easily using its muscular tube feet, which it also uses to collect food. At the end of each of its arms it has an eyespot. It cannot see shapes or colors with its eyespots, but it can see changes between light and dark.