Sea Urchins

Sea urchin / Diadema savignyi / Family Diadematidae

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.

Physiology

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'.

Habitat

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.

Feeding

Urchins are grazers, using their multi-toothed powerful scraping jaws to scrape algae off the surfaces of rocks. They also eat both plants and animals.

Predators

Predators of Sea Urchins include octopus and triggerfish, which bite off the spines enabling the fish to crack open the body of the urchin.

Threats

Sea urchins are not currently endangered, but like most Reef animals, they are susceptible to changes in water temperature and pollution.