Abatus cordatus | |
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External (above) and internal (below) views of test | |
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Scientific classification ![]() | |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Class: | Echinoidea |
Order: | Spatangoida |
Family: | Schizasteridae |
Genus: | Abatus |
Species: | A. cordatus |
Binomial name | |
Abatus cordatus (Verrill, 1876) | |
Synonyms [1] | |
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Abatus cordatus is a species of sea urchin in the family Schizasteridae. It is native to shallow seas surrounding certain island groups in the southern Indian Ocean. The body is protected by a hard test or shell which is covered with spines. The female broods its young in deep pockets on the upper surface, retaining the young in place with specialised spines. American zoologist Addison Emery Verrill first scientifically described A. cordatus in 1876. [2]
The test of this species is oval and bilaterally symmetrical, up to 5 cm (2 in) long. The oral (under) surface is relatively flat but the aboral (upper) surface is domed, the colour being some shade of yellowish or greenish-brown. The test is thin and fragile, and is entirely covered with spines of various lengths in different parts. The anterior ambulacrum forms a shallow depression and the other four ambulacra form a star-shaped furrow across the surface of the test; this is shallow in males, but much deeper in females, forming pockets in which the young are incubated. The pockets are protected by specialized spines. On the oral surface the spines are short and used for locomotion, while the surrounding spines are used for digging. [3]
Abatus cordatus is endemic to certain subantarctic island groups in the southern Indian Ocean. It is known from the Kerguelen Islands, and the Heard Island and McDonald Islands. It occurs buried in soft muddy or sandy sediment, usually at depths down to about 2 m (7 ft), but has been found at depths as great as 560 m (1,800 ft). [3]
This sea urchin is a detritivore and feeds on organic matter in the sediment. It is gonochoric, individuals being either male or female. The eggs are large and yolky, and when they have emerged from the female's gonopore, they fall into the adjacent pockets; here they undergo direct development, being brooded for about nine months, with a few dozen young in each pocket. [3] By this time they have developed into juveniles about 2 mm (0.1 in) in diameter with mouths and spines. They then crawl away from their mother. This is the first time that direct development has been observed among sea urchins. It is not clear precisely when the eggs are fertilised, but it has been discovered that the juveniles do not necessarily all share the same father. [3] [4]
Because of the absence of a larval stage, most juveniles do not disperse more than a few metres from their parent. They have no known predators, and under favourable conditions can be very numerous, with up to 200 per square metre having been recorded. Their lack of ability to disperse may make them sensitive to alterations in their habitat such as changes in seawater temperatures. [3]
Sea 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 hard shells (tests) are round and spiny, usually 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, triggerfish, and humans.
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.
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.
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).
Abatus elongatus is a species of sea urchin of the family Schizasteridae. Their armour is covered with spines. It came from the genus Abatus and lives in the sea. Abatus elongatus was first scientifically described in 1836 by Koehler.
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.
Cidaris blakei is a species of sea urchins of the family Cidaridae. Its armour is covered with spines of three types, one unique type being extended and fan-like, making it easily recognized. Alexander Agassiz first described it scientifically in 1878. It is present on the seabed in deep waters in the Gulf of Mexico and the Bahamas.
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.
Abatus is a genus of sea urchins belonging to the family Schizasteridae.
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