Sea Urchin

Common Sea Urchin
http://www.reefed.edu.au/home/explorer/animals/marine_invertebrates/echinoderms/sea_urchins

Sea Urchins are a major group of the echinoderms and the one in which spines are best developed. Sea Urchins have tube feet between their spines and the feet are attached to the animal's water vascular system. The tube feet operate on hydraulic principles and allow the urchin to move about, although rather slowly.


Sea urchins are globe-shaped with no arms. They have a compact skeleton with closely fitted plates, moveable spines with a ball and socket joint. Sea urchins also have powerful scraping jaws known as 'Aristotle's lantern'.
The sea urchin is nocturnal, hiding in crevasses during the day and emerging at night to feed. Sea urchins can be found in both warm and cold water.
Sea urchins are not currently endangered, but like most Reef animals, they are susceptible to changes in water temperature and pollution