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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]
Crowned sea urchins are nocturnal, foraging within a few meters of their shelters, to which they return at dawn. [4] [7] They are mostly carnivorous, feeding on sponges, tunicates, bryozoans, and algae. [8] Crowned sea urchins are gonochoric, which is to say that there are two sexes, and each individual is either male or female. Spawning takes ...
In 1983, for example, the mass mortality of the tropical sea urchin Diadema antillarum in the Caribbean caused a change from a coral-dominated reef system to an alga-dominated one. [103] Sea urchins are among the main herbivores on reefs and there is usually a fine balance between the urchins and the kelp and other algae on which they graze.
They are therefore related to sea cucumbers, sea urchins, and sand dollars. There are at least 1,900 different species of starfish, and they do not all look the same.
Sea otters are a classic example of a keystone species; their presence affects the ecosystem more profoundly than their size and numbers would suggest. They keep the population of certain benthic (sea floor) herbivores, particularly sea urchins, in check. Sea urchins graze on the lower stems of kelp, causing the
Echinodermata, including sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, crinoids, and sea daisies; Echiura, also known as spoon worms; Gnathostomulids, slender to thread-like worms, with a transparent body that inhabit sand and mud beneath shallow coastal waters;
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.
Mespilia globulus, the globular sea urchin, sphere sea urchin, or tuxedo urchin (trade name), is a sea urchin occurring in tropical shallow reef habitats. [1] The specific name refers to a small ball or spherule, describing its overall shape/morphology. [1] It is the only species in the genus Mespilia. [2]