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Echinoidea
Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of sea urchins are round and spiny, ranging in diameter from . Sea urchins move slowly, crawling with tube feet, and also propel themselves with their spines. Although algae are the primary diet, sea urchins also eat slow-moving (sessile) animals. Predators that eat sea urchins include a wide variety of fish, starfish, crabs, marine mammals. Sea urchins are also used as food especially in Japan. Adult sea urchins have fivefold symmetry, but their pluteus larvae feature bilateral (mirror) symmetry, indicating that the sea urchin belongs to the Bilateria group of animal phyla, which also comprises the chordates and the arthropods, the annelids and the molluscs, and are found in every ocean and in every climate, from the tropics to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinothurioida
The Echinothurioida are an order of sea urchins in the class Echinoidea. Echinothurioids are distinguished from other sea urchins by the combination of a flexible test and hollow spines. The membrane around the mouth contains only simple plates, in contrast to the more complex mouth parts of their close relatives, the Diadematoida. They are nearly all deepsea dwellers. Characteristics Echinothurioids have regular tests (shells) with 10 columns of plates. These plates are fused in groups of three with a central primary plate and a half plate on either side. The edge of each group of plates overlaps the next one in the manner of tiles on a roof and this means the test is flexible. These animals usually collapse to a disc shape when brought to the surface. The primary tubercles which articulate with the spines are each perforated by a hole and the spines are hollow. The primary spines are usually long and are used to support the test and in locomotion. In many species, the second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoderm
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian. The echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the biotic desert of the deep sea, as well as shallower oceans. Most echinoderms are able to reproduce asexually and regenerate tissue, organs, and limbs; in some cases, they can undergo complete regeneration from a single li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atelostomata
The Atelostomata are a type of sea urchins. They are distinguished from other sea urchins by their irregular shape and the absence of a feeding lantern. The group includes the well known heart urchins, as well as some less familiar and extinct forms. List of orders * order ''Holasteroida'' (Durham & Melville, 1957) * order ''Spatangoida The heart urchins or Spatangoida are an order of sea urchins. Their body is a somewhat elongated oval in form, and is distinguished by the mouth being placed towards one end of the animal, and the anus towards the other. As a result, heart urchi ...'' (L. Agassiz, 1840) References * * Echinoidea Animal superorders {{echinoidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinometra Viridis
''Echinometra viridis'', the reef urchin, is a species of sea urchin in the family Echinometridae. It is found on reefs in very shallow parts of the western Atlantic Ocean and the Caribbean Sea. Description The reef urchin has an elliptical reddish brown test (shell) covered with medium length spines. These are greenish in colour with paler bases and darker, often violet, tips. This urchin grows to a diameter of with the longest spines being . It looks very similar to the rock-boring urchin '' Echinometra lucunter'', but the dark tips and the greater length of the spines are distinctive. Distribution The reef urchin is found on reefs in the Caribbean Sea from southern Florida to Venezuela at depths down to about . It is not as common as the rock-boring urchin and seems to be absent from the West Indies to the east of the Virgin Islands. Biology The reef urchin conceals itself in crevices or under boulders. It emerges at night to feed by grazing on algae with its fiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassiduloida
Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only seven extant species remain. A 2019 phylogenetic systematics study by Souto et al. presented a revised classification of the cassiduloids, and hypothesised that the order probably originated in the Early Cretaceous. Description and characteristics Cassiduloids have a rounded or slightly oval appearance, and look somewhat similar to heart urchins, although they are actually more closely related to the sand dollars. They are distinguished from other sea urchins by the presence of smaller intervening areas between the main ambulacral areas on the oral surface. They have no lantern as adults, and the petaloids are poorly developed or absent. List of families and genera * family Cassidulidae (L. Agassiz and Desor, 1847) ** genus Cassidulus (Lamarck, 1801) ** genus Paralampas (Duncan & Sladen, 1882) ** genus Rhyncholampas (Agassiz, 1869) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phymosomatoida
The Phymosomatoida are an order of sea urchins, found in Europe, North America, North Africa and the Middle East. They are distinguished from other sea urchins by the presence of large fused plates on top of the feeding lantern. The test is usually sculpted to some degree, but, unlike their close relatives the Temnopleuroida, the tubercles are never perforated. The opening in the test through which the anus passes, known as the periproct The periproct is the final body segment in annelid worms. The anus is located on this segment. The term also refers to the small region surrounding the anus of the sea urchin. See also *Prostomium *Earthworm *Sea urchin Sea urchins () are s ..., is unusually large in sea urchins from this group. The apical disc, around the mouth, is only loosely attached to the rest of the test and is often missing in fossil species, giving the false impression that they also have a large oral opening. References * * Extant Early Jurassic first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perischoechinoidea
Perischoechinoidea is a subclass of primitive sea urchins that were abundant in the Palaeozoic seas. However, the great majority of species died out during the Mesozoic, as the more advanced euechinoid sea urchins became common. Today, only a single order, the Cidaroida, survives. Most fossil forms had multiple columns of ambulacral plates, rather than the two rows found in all living species of sea urchin. They also lacked a perignathic girdle around the mouth. Taxonomy The group is probably a paraphyletic assemblage of stem forms, united only by their lack of more advanced features, rather than a true taxonomic clade. Subclass Perischoechinoidea * Order Cidaroida Cidaroida is an order of primitive sea urchins, the only living order of the subclass Perischoechinoidea. All other orders of this subclass, which were even more primitive than the living forms, became extinct during the Mesozoic. Description ... * Order Bothriocidaroida † * Order Echinocystitoida † ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euechinoidea
The subclass Euechinoidea includes almost all living species of sea urchin, and fossil forms going back as far as the Triassic. Taxonomy List of orders according to World Register of Marine Species : * Infra-classis '' Acroechinoidea'' ** Order ''Aspidodiadematoida'' ** Order '' Diadematoida'' ** Order '' Micropygoida'' ** Order ''Pedinoida'' * Infra-classis ''Carinacea'' ** Super-order ''Calycina'' *** Order ''Phymosomatoida'' † *** Order ''Salenioida'' ** Super-order '' Echinacea'' *** Order ''Arbacioida'' *** Order ''Camarodonta'' *** Order ''Stomopneustoida'' * Order ''Echinothurioida'' * Infra-classis ''Irregularia'' ** Super-order ''Atelostomata'' *** Order ''Holasteroida'' *** Order ''Spatangoida'' ** Order ''Echinoneoida'' ** Order ''Holectypoida'' † ** Super-order ''Neognathostomata'' *** Order ''Cassiduloida'' *** Order ''Clypeasteroida'' *** Order '' Echinolampadoida'' *** Order '' Nucleolitidae'' † File:Spatangus purpureus rob.jpg , ''Spatangus purp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoida
Echinoida is an order of sea urchins in the class Echinoidea. They are distinguished from other sea urchins by simultaneously possessing both an un-sculpted test and a feeding lantern with large plates fused across the top of each pyramid. Taxonomy Order Echinoida * family Echinidae Gray, 1825 * family Echinometridae Gray, 1825 * family Parasaleniidae * family Strongylocentrotidae Gregory, 1900 Image:Paracentrotus lividus profil.JPG, ''Paracentrotus lividus'' ( Echinidae) Image:Echinometra lucunter.jpg, '' Echinometra lucunter'' (Echinometridae) Image:Urchinhand 300.jpg, ''Strongylocentrotus franciscanus'' ( Strongylocentrotidae) See also *''Colobocentrotus atratus'' - Shingle urchin *'' Echinus acutus'' - White sea urchin *'' Echinus esculentus'' - Common sea urchin *''Echinus tylodes'' *'' Evechinus chloroticus'' - New Zealand sea urchin *''Heterocentrotus mammillatus'' - Red pencil urchin *''Heterocentrotus trigonarius ''Heterocentrotus trigonarius'', commonly known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holectypoida
The Holectypoida are an order of sea urchins related to the sand dollar Sand dollars (also known as a sea cookie or snapper biscuit in New Zealand, or pansy shell in South Africa) are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are ...s. The order consists of just two living genera, but was once more diverse. Description and characteristics In appearance, the living holectypoids are similar to sand dollars, but with less flattened bodies and an oval outline. They also lack the petal-like patterns found on the bodies of sand dollars. Taxonomy According to World Register of Marine Species : * family Anorthopygidae Wagner & Durham, 1966b † * family Coenholectypidae Smith & Wright, 1999 † * family Discoididae Lambert, 1900 * family Holectypidae Lambert, 1900 † References * Gnathostomata (echinoid) Extant Early Jurassic first appearances {{echinoidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Test (biology)
In biology, a test is the hard shell of some spherical marine animals and protists, notably sea urchins and microorganisms such as testate foraminiferans, radiolarians, and testate amoebae. The term is also applied to the covering of scale insects. The related Latin term testa is used for the hard seed coat of plant seeds. Etymology The anatomical term "test" derives from the Latin ''testa'' (which means a rounded bowl, amphora or bottle). Structure The test is a skeletal structure, made of hard material such as calcium carbonate, silica, chitin or composite materials. As such, it allows the protection of the internal organs and the attachment of soft flesh. In sea urchins The test of sea urchins is made of calcium carbonate, strengthened by a framework of calcite monocrystals, in a characteristic "stereomic" structure. These two ingredients provide sea urchins with a great solidity and a moderate weight, as well as the capacity to regenerate the mesh from the cuti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathostomata (echinoid)
The Gnathostomata are a superorder of sea urchins, including the familiar sand dollar Sand dollars (also known as a sea cookie or snapper biscuit in New Zealand, or pansy shell in South Africa) are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are ...s. Gnathostomatans are irregular in shape, but unlike other irregular sea urchins, possess a feeding lantern. The mouth is located in the centre of the lower surface, as it is in most other sea urchins, but the anus is found to one side of the upper surface, rather than being central. The members of the group are adapted for burrowing in soft-bottomed marine environments. References * Echinoidea Extant Early Jurassic first appearances Animal superorders {{echinoidea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
