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Sea urchins or urchins (/ ˈ ɜːr tʃ ɪ n z /) 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 (16,000 ft; 2,700 fathoms). [1]
Diadema antillarum, also known as the lime urchin, black sea urchin, or the long-spined sea urchin, [2] is a species of sea urchin in the family Diadematidae. This sea urchin is characterized by its exceptionally long black spines. It is the most abundant and important herbivore on the coral reefs of the western Atlantic and Caribbean basin.
Diadema setosum is a widely distributed species of sea urchin. Its range stretches throughout the Indo-Pacific basin including Malaysia, [6] longitudinally from the Red Sea and then eastward to the Australian coast. Latitudinally, the species can be found as far north as Japan and its range extends as far south as the southern tip of the ...
Fossil of Acrocidaris, an extinct sea urchin. Echinoid fossils are the fossilised remains of sea urchins, spiny marine invertebrates that live on the seabed.Humans have been interested in these fossils for millennia, have considered them lucky, have imbued them with magical powers and linked them to their deities.
Echinothrix diadema is a long spined urchin. With its spines, the typical diameter is 10–20 cm (3.9–7.9 in). [2] The internal organs are enclosed in the test, covered by a thin dermis and epidermis. [3] It is generally black or blue-black in colour, and always dark (the spines show a blue sheen in the light).
A mysterious sea urchin plague has spread across the world, causing the near extinction of the creature in some areas and threatening delicate coral reef ecosystems, a new study suggests.
They may be banded with lighter and darker shades in juveniles and the occasional individual sea urchin is completely white. [2] Diadema savignyi is similar in appearance to the closely related Diadema setosum with which it is sympatric, that is, the two species share a common range and frequently come into contact with each other. [3]
Back before the first sea urchin die-off, Levitan recalled seeing reefs in the U.S. Virgin Islands blanketed in the spiny creatures. Now, those reefs look much different — choked by algae ...