A worldwide community photographing and learning about wildlife
Diadema paucispinum, Echinothrix diadema & Echinothrix calamaris
Black with white pointy spikes. Poisonous. Found in the ocean.
Ocean are found on reef flats and shallow reef slopes, where they are often wedged into crevices in the coral framework. Well-protected from nearly all reef predators, their calcite limestone skeleton, or test, bears two kinds of moveable spines, some up to six inches long.
Both the longer, primary spines (which are hollow) and the smaller, secondary spines are brittle and break off after puncturing the skin. The smaller spines bear toxin-producing tissue, and contact with them causes burning pain in the wound. Light-sensitive nerves in the urchins' skin detect the shadows of potential predators and the spines can be coordinated and directed toward the threat. The spines are attached to the skeleton by skin and muscle tissue and do not easily detach. Even light contact with the spines may result in puncture wounds from the spines, but the urchins cannot shoot their spines.
Echinometra mathaei or rock-boring urchin. This species non-venomous and not hazardous to touch gently. About the size of a golf ball, as its name suggests, it bores into reef and rock forming visible grooves.