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 5,000 metres. Their tests are round and spiny, typically from 3 to 10 cm 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.
The diadema urchin or blue-black urchin is a species of tropical sea urchin, member of the Diadematidae family.
Echinus esculentus, the European edible sea urchin or common sea urchin, is a species of marine invertebrate in the Echinidae family. It is found in coastal areas of western Europe down to a depth of 1,200 m (3,900 ft). It is considered "Near threatened" in the IUCN Red List of Threatened Species.
Meoma ventricosa, known by the common names cake urchin and red heart urchin, is a large species of sea urchin which lives in shallow waters in the Caribbean. It may reach a diameter of twenty centimeters and is covered in reddish-brown spines. It has both pentagonal radial symmetry and bilateral symmetry, giving it a sand-dollar appearance; however, two of its five sections are merged more closely than the others.
Astropyga radiata, the red urchin, fire urchin, false fire urchin or blue-spotted urchin, is a species of sea urchin in the family Diadematidae. It is a large species with long spines and is found in the tropical Indo-Pacific region. It was first described in 1778 by the German naturalist Nathaniel Gottfried Leske.
Lytechinus variegatus, commonly called the green sea urchin or the variegated sea urchin, is a species of sea urchin that can be found in the warm waters of the western Atlantic Ocean and Caribbean Sea.
Tripneustes ventricosus, commonly called the West Indian sea egg or white sea urchin, is a species of sea urchin. It is common in the Caribbean Sea, the Bahamas and Florida and may be found at depths of less than 10 metres (33 ft).
Spatangus purpureus, commonly known as the purple heart urchin, is a species of sea urchin in the family Spatangidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea, where it lives immersed in the sediment.
Abatus agassizii is a species of sea urchin of the family Schizasteridae. Their armour is covered with spines. It is in the genus Abatus and lives in the sea. Abatus agassizii was first scientifically described in 1889 by Georg Pfeffer.
Abatus cavernosus is a species of sea urchin of the family Schizasteridae. Their armour is covered with spines. It is in the genus Abatus and lives in the sea. Abatus cavernosus was first scientifically described in 1845 by Rodolfo Philippi. Females brood their young in a brood pouch through the gastrula stage until they are juveniles.
Abatus shackletoni is a species of sea urchin of the family Schizasteridae. Their armour is covered with spines. It is in the genus Abatus and lives in the sea. Abatus shackletoni was first scientifically described in 1911 by Koehler.
Aspidodiadema jacobyi is a small sea urchin in the family Aspidodiadematidae. It lives in tropical seas at great depths. Aspidodiadema jacobyi was first scientifically described in 1880 by Alexander Emanuel Agassiz, an American scientist.
Anasterias rupicola is a species of starfish in the family Asteriidae. It is found in shallow waters in the Southern Ocean and sub-Antarctic Indian Ocean.
Lytechinus williamsi, the jewel urchin, is a sea urchin in the family Toxopneustidae. It occurs on shallow reefs off the coasts of Panama, Belize, the Florida Keys and Jamaica.
Echinometra lucunter, the rock boring urchin, is a species of sea urchin in the family Echinometridae. It is found in very shallow parts of the western Atlantic Ocean and the Caribbean Sea.
Phormosoma placenta is a species of sea urchin in the order Echinothurioida. It is a deepwater species, seldom being found at depths less than 500 m (1,600 ft), and occurs on either side of the Atlantic Ocean on the continental slope.
Tetrapygus is a genus of sea urchins in the family Arbaciidae. It is a monotypic genus and the only species is Tetrapygus niger which was first described by the Chilean naturalist Juan Ignacio Molina in 1782. It is found in the southeastern Pacific Ocean on the coasts of South America.
Lytechinus pictus, commonly known as the painted urchin, is a sea urchin in the family Toxopneustidae. It occurs on shallow reefs in the tropical and subtropical eastern Pacific Ocean, off the coasts of California, Central America and South America as far south as Ecuador.
Goniocidaris umbraculum is a species of cidaroid sea urchin that inhabits the continental shelf off the southern coasts of New Zealand. It is plentiful on a seabed composed of seashell and bryozoan rubble at a depth of 95 m (310 ft) off Otago.
Echinocyamus pusillus, commonly known as the pea urchin or green urchin, is a species of sand dollar, a sea urchin in the family Fibulariidae, native to the northeastern Atlantic Ocean and the Mediterranean Sea. It buries itself in gravel or coarse sand at depths down to about 1,250 m (4,000 ft).
