Sea urchin
Sea urchins or urchins () are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to . Their tests (hard shells) are round and spiny, typically from across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, and triggerfish.
Hemicentrotus
This sea urchin has a thick test and a large number of tiny, fine, sharp spines. The tubercles are small and closely packed, arranged in slightly zig-zag horizontal rows, with four to eight tubercles on each inter-ambulacral plate and three on each ambulacral plate. The pores are arranged in diagonal lines of four, with the rows being separated by small tubercles. The colour of this sea urchin is pale greenish-olive above and brownish-green below.