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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]
Tripneustes gratilla, the collector urchin, is a species of sea urchin. Collector urchins are found at depths of 2 to 30 metres (7 to 100 ft) in the waters of the Indo-Pacific, Hawaii, the Red Sea, and The Bahamas. They can reach 10 to 15 centimetres (4 to 6 in) in size.
Sea urchins tend to be important members of their ecosystems by grazing on other organisms and stabilizing populations. In addition to this, sea urchins play a large role in different economies globally as the urchin themselves and their roe are sold for consumption. [1] The same is true for the species within the genus Echinus. [2]
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.
The subclass Euechinoidea includes almost all living species of sea urchin, with fossil forms going back as far as the Triassic. [1] [2] Taxonomy.
These sea urchins have a disc-like body, more or less bulging, structured by a flexible test, which is nearly unique among sea urchins. Most species can grow quite big and live in deep seas, though some genera contain shallow species (especially Asthenosoma). [1] The test is composed of thin and weakly calcified plates, not always continuous.
The purple sea urchin, along with sea otters and abalones, is a prominent member of the kelp forest community. [18] The purple sea urchin also plays a key role in the disappearance of kelp forests that is currently occurring due to climate change; [19] when urchins completely eliminate kelp from an area, an urchin barren results.
In Norway, small quantities are fished by hand by freedivers and SCUBA-divers. The fishery is not regulated, and the green sea urchin is considered a pest in the Norwegian waters, eating up the kelp forest. [14] It is not common to find the green sea urchin south of Hitra, and the urchin population is moving northward as water temperatures ...