| Labidiaster annulatus | |
|---|---|
 | |
| Museum specimen | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Forcipulatida |
| Family: | Heliasteridae |
| Genus: | Labidiaster |
| Species: | L. annulatus |
| Binomial name | |
| Labidiaster annulatus Sladen, 1889 [1] | |
Labidiaster annulatus, the Antarctic sun starfish or wolftrap starfish is a species of starfish in the family Heliasteridae. It is found in the cold waters around Antarctica and has a large number of slender, flexible rays.
Labidiaster annulatus has a wide central disc and 40 to 45 long narrow rays and can reach a diameter of 60 centimetres (24 in). [2] The disc is slightly inflated and is raised above the base of the rays. The madreporite is large and near the edge of the disc. The aboral or upper surface is covered in a meshed network of small slightly overlapping plates. These are covered by a membrane with numerous raised projections called papulae, some small spines and a few large triangular pedicellariae, wrench-like organs that can grasp objects. The rays are crowded together where they join the disc and their aboral surface is similarly clad in overlapping scales in a quadrangular mesh pattern. There are also short spines and many papulae and a number of small pedicellariae. At intervals down each ray there are transverse bands armed with numerous large pedicellariae. The oral or lower surface of the disc has a central mouth surrounded by further scales. The ambulacral grooves are wide and run down the centre of the oral side of each ray. There are widely separated narrow scales on either side of the grooves with two spines on each, one overlapping the groove and the other projecting from the side of the ray. There are rows of tube feet on either side of the groove, each foot having a button-like suction pad at the tip. [3]
Labidiaster annulatus is found around the Antarctic Peninsula, South Georgia and the South Sandwich Islands. The depth range is from the intertidal zone down to 554 metres (1,818 ft) but this starfish most commonly occurs between 30 and 400 metres (98 and 1,312 ft). It lives on the seabed and is found on sand, mud and gravel and among rocks. [4]
Labidiaster annulatus is an opportunistic predator and scavenger. It moves about on the seabed using various combinations of rays. It often climbs to an elevated position on top of a rock or a large sponge. Here it holds on with some of its rays while it extends others like fishing rods. [4] The rays are long and flexible and writhe about in search of prey. Invertebrates or even small fish that come in contact with the extended rays are grasped by the pedicellariae which snap shut. Other rays then curl around the struggling prey. It is manipulated to the underside of the rays where it is passed along by the tube feet to the mouth. This is extensible and can ingest large items. The prey continues to struggle while it is being transported and may escape. Analysis of stomach contents showed that krill and amphipods were the most frequent diet items. Sediment was also often present and may have contained microflora such as of foraminiferans. A portion of a fish measuring 6 centimetres (2.4 in) was found in one individual but it was unclear whether it had been caught alive or had been scavenged. Other dietary items were varied and included smaller starfish of this species and brittle stars such as Ophionotus victoriae . [4]
Little is known of the reproduction of Labidiaster annulatus, but the larvae pass through at least one bipinnaria and one brachiolaria stage as has been demonstrated by DNA analysis. The larvae are planktonic and spend many months drifting with the currents before settling on the seabed and undergoing metamorphosis into juveniles. [5]
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish occur on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
The Echinasteridae are a family of starfish in the monotypic order Spinulosida. The family includes eight genera and about 133 species found on the seabed in various habitats around the world.
Ceramaster patagonicus, the cookie star, is a species of sea star. It is bright orange or yellow in colour. Its arms are short and it has no spines. It is a deep water species and lives on rocky sea beds. Its diet includes sponges.
Astropecten irregularis is a sea star of the family Astropectinidae. Common names include Sand sea star.
Leptasterias hexactis is a species of starfish in the family Asteriidae, commonly known as the six-rayed star. It is found in the intertidal zone of the western seaboard of the United States. It is a predator and is unusual among starfish in that it broods its eggs and young.
Asterias forbesi, commonly known as Forbes sea star, is a species of starfish in the family Asteriidae. It is found in shallow waters in the northwest Atlantic Ocean and the Caribbean Sea.
Evasterias troschelii is a species of starfish in the family Asteriidae. Its common names include the mottled star, false ochre sea star and Troschel's true star. It is found in Kamchatka and the north western coast of North America.
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.
Stylasterias is a genus of starfish in the family Asteriidae. Stylasterias forreri, the velcro star, is the only species in the genus. It is found on the Pacific coast of Canada and the United States.
Orthasterias is a genus of sea stars in the family Asteriidae. Orthasterias koehleri, the rainbow star or red-banded sea star, is the only species in the genus. It is found in the North Pacific Ocean.
Pteraster tesselatus, the slime star or cushion star, is a species of starfish in the family Pterasteridae found in the North Pacific.
Leptasterias tenera is a species of starfish in the family Asteriidae. It is found on the eastern coast of North America.
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines are the only parts of the animal likely to be fossilized after an echinoderm dies.
Cryptasterina pentagona is a species of starfish in the family Asterinidae. It is found in shallow waters in north eastern Australia. Its life cycle includes the release of large-yolked eggs and the development of planktonic larvae which is in contrast to the very similar Cryptasterina hystera which is viviparous. The two appear to have diverged from a common ancestral line only a few thousand years ago.
The Brisingidae are a family of starfish found only in the deep sea. They inhabit both the Atlantic and Pacific Oceans at abyssal depths, and also occur in the Southern Ocean and around Antarctica at slightly shallower depths.
Poraniidae is a family of starfishes in the order Valvatida.
Astropecten duplicatus, the two-spined sea star, is a starfish in the family Astropectinidae. It is found in the eastern Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.
The Freyellidae are a family of deep-sea-dwelling starfish. It is one of two families in the order Brisingida. The majority of species in this family are found in Antarctic waters and near Australia. Other species have been found near New Zealand and the United States.
Paranepanthia is a genus of starfish of the family Asterinidae. Members of the genus have five rays and are found in the waters around Australia, Indonesia and Antarctic New Zealand.
Freyella elegans is a species of deep-water starfish in the family Freyellidae in the order Brisingida, living at abyssal depths in the northwestern Atlantic Ocean.