| Seven-armed starfish | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Paxillosida |
| Family: | Luidiidae |
| Genus: | Luidia |
| Species: | L. ciliaris |
| Binomial name | |
| Luidia ciliaris | |
| Synonyms [1] | |
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Luidia ciliaris, the seven-armed sea star, is a species of sea star (starfish) in the family Luidiidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea. [1]
L. ciliaris is an orangeish-brown colour and has seven long arms radiating from a small disk. It is a large but fragile sea star, growing to 40 cm (16 in) across, and easily losing its arms (which afterwards regenerate). The arms have parallel sides and taper only near the tip. They have a conspicuous fringe of white spines along the margins. The upper surface is clothed in paxillae, spines shaped like a pillar with a flat top bearing tiny spinules. Also, many-lobed, nipple-like papillae are seen. No marginal plates are on the upper side of the arms, but those on the lower side bear pedicellariae with two valves. The tube feet are long and numerous. They do not have suction pads, but have two sets of terminal bulbs. The gonads are arranged in two rows along the length of the arms. A mouth is at the centre of the underside, with an oesophagus and a cardiac stomach, but no intestine, pyloric stomach, or anus. [2] [3]
L. ciliaris occurs on the seabed in the eastern Atlantic Ocean from Norway and the Faroe Islands southwards to Cape Verde and the Azores and in the Mediterranean Sea. It is found in the neritic zone at depths down to 400 m (1,300 ft), mainly on soft sediments into which it sometimes burrows, but sometimes on rock. [1] [3]
L. ciliaris is a predator and scavenger and feeds predominantly on other echinoderms. A study in the Irish Sea found that the brittle stars, Ophiothrix fragilis and Ophiura albida , and the sea urchin, Psammechinus miliaris , formed the chief items of prey. The brittle star Ophiocomina nigra was also consumed, but in lesser quantities because it had more efficient escape strategies. [4]
The seven-armed sea star moves rapidly in comparison with other sea stars. It hoists itself up on the tips of its arms, in which position it can "walk", [5] before launching itself at its prey. The ring of plates around its mouth are extensible or can even be ruptured to enable it to ingest food items much bigger than the normal size of its mouth. In this way, it can pounce on a brittle star 25 cm (9.8 in) in diameter and completely engulf it. Undigested remains are ejected through the mouth. [5]
L. ciliaris breeds in early summer. Each female releases millions of eggs into the water column, which stimulates the release of sperm by the males. About 4 days after fertilisation, the zygotes develop into bipinnarial larvae, which form part of the plankton. After several moults, the seven arms can be seen developing in what is called the "rudiment", which is connected to a stalk with several bands of cilia. The larvae reach a length of 35 mm (1.4 in) in 3 to 4 months. [6] It does not become a brachiolarial larva as is the case in most sea star taxa. Instead, it settles on the sea bed and metamorphosis takes place. Functional tube feet appear in the juvenile before the larval tissue is fully reabsorbed. [5] [7]
An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and 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 group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
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 live 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.
Brittle stars, serpent stars, or ophiuroids are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.
Luidia sarsii is a species of starfish. Sand colored with a velvety texture, the species expresses pentamerism or pentaradial symmetry as adults. The five gently tapering arms have conspicuous bands of long white marginal spines in groups of three. Luidia sarsi grow to approximately 20 cm across and are found in deeper water (20 m+) from Norway to the Mediterranean but in deep colder water in the south. They are usually found on muddy sediment and are most active at night, burying themselves under the sand during the day. Luidia sarsii larva develop from a fertilized egg and are unique in a number of respects. The larva of the species attains an unusual size and a juvenile starfish develops inside the larva. During metamorphosis the juvenile migrates to the outside and detaches from the swimming larval bipinnaria stage. The larva continues to live separately for several months.
Ophiothrix fragilis is a species of brittle star in the order Ophiurida. It is found around the coasts of western Europe and is known in Britain as the common brittle star. It is also found along the coast of South Africa where it is known as the hairy brittle star.
Sphaerechinus granularis is a species of sea urchin in the family Toxopneustidae, commonly known as the violet sea urchin, or sometimes the purple sea urchin. Its range includes the Mediterranean Sea and eastern Atlantic Ocean.
Luidia is a genus of starfish in the family Luidiidae in which it is the only genus. Species of the family have a cosmopolitan distribution.
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida. It occurs in the north-eastern Atlantic Ocean, the North Sea, and the Mediterranean Sea.
Luidia clathrata is a tropical species of starfish in the family Luidiidae. It is variously known as the slender-armed starfish, the gray sea star, or the lined sea star. It is found in the western Atlantic Ocean.
Luidia magnifica, the magnificent star, is a species of starfish in the family Luidiidae. It is found in the Pacific Ocean.
Luidia superba is a tropical species of starfish in the family Luidiidae. A single specimen was found off the Pacific coast of Colombia in 1888; the species has since been found in the Galapagos Islands. It is endemic to this area and has not been recorded elsewhere.
Luidia senegalensis, the nine-armed sea star, is a tropical species of starfish in the family Luidiidae found in the western Atlantic Ocean.
Luidia foliolata, the sand star, is a species of starfish in the family Luidiidae found in the northeastern Pacific Ocean on sandy and muddy seabeds at depths to about 600 m (2,000 ft).
Ophiura albida is a species of brittle star in the order Ophiurida. It is typically found on the seabed in the north eastern Atlantic Ocean and in the Mediterranean Sea and is sometimes known as the serpent's table brittle star.
The spiny sand seastar is a species of starfish in the family Luidiidae. It is found in shallow parts of the China Sea and in the vicinity of the Korean archipelago. The tissues of this starfish have been found to contain several secondary metabolites with medicinal potential.
Patiria pectinifera, the blue bat star, is a species of starfish in the family Asterinidae. It is found in the northern Pacific Ocean along the coasts of Japan, China and Russia. It is used as a model organism in developmental biology.
Luidia maculata is a species of starfish in the family Luidiidae in the order Paxillosida. It is native to the Indo-Pacific region. It is commonly known as the eight-armed sea star because, although the number of arms varies from five to nine, eight arms seems to be the most common.
Luidia magellanica is a species of starfish in the family Luidiidae. It is found in the southeastern Pacific Ocean on the coast of South America.
Luidia savignyi is a species of starfish belonging to the family Luidiidae. The species is found in the tropical and subtropical Indo-Pacific region. It is a large starfish and preys on other echinoderms.