| Asterina gibbosa | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Asteroidea |
| Order: | Valvatida |
| Family: | Asterinidae |
| Genus: | Asterina |
| Species: | A. gibbosa |
| Binomial name | |
| Asterina gibbosa | |
| Synonyms | |
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Asterina gibbosa, commonly known as the starlet cushion star, is a species of starfish in the family Asterinidae. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea.
Asterina gibbosa is a pentagonal starfish with short blunt arms and an inflated appearance. The aboral (upper) surface is clothed in groups of short, blunt spines. This starfish grows to a diameter of about 5 centimetres (2.0 in) and may be brown, green or orange. It is sometimes blotched with colour and individuals from deeper sea locations tend to be paler in colour. It can be distinguished from the closely related Asterina phylactica by the fact that it has two small spines on each of the plates surrounding its mouth, A. phylactica having no spines on these plates and having a plain olive-green aboral surface with a brown central star. [2] A. gibbosa, at 5 centimetres (2.0 in) is considerably bigger than A. phylactica which seldom exceeds 15 mm (0.6 in). At one time the two were believed to be the same species but it was realised in 1979 that besides the differences in appearance, the two occupied different ecological niches and had different reproductive strategies. [3]
Asterina gibbosa is mainly nocturnal, spending the day underneath boulders, overhangs or in caves, or hidden away under algae in rock pools. It is an opportunistic scavenger but the bulk of its diet comes from the film of bacteria and diatoms that exist on the surface of rocks. It feeds by everting its stomach (turning it inside out) against the surface of the rock and secreting enzymes which digest the film. Other foods found in its stomach included decaying toothed wrack ( Fucus serratus ), periwinkle faeces and bits of dead molluscs such as mussels ( Mytilus edulis ), oysters ( Ostrea edulis ) and periwinkles ( Littorina littorea ), but 95% of the stomachs contained no large particles indicating the importance in its diet of microscopic organisms. [3]
Asterina gibbosa is a protandric hermaphrodite. This means that it is born a male and later changes sex and becomes a female. Researchers found that at Plymouth, United Kingdom, the sex change happens when it has an arm length somewhere between 9 and 16 millimetres (0.35 and 0.63 in). Other researchers at Naples, Italy found that Mediterranean populations did not have such a clearcut change of sex. In the first year cohort, with arms averaging 11 millimetres (0.43 in), about 80% were male. In the second year batch, with arms averaging 17 millimetres (0.67 in), about 30% were male. By the third year, with 25 millimetres (0.98 in) arms, males were very scarce, but in even larger individuals of unknown age, about 15% were male. [4] Asterina gibbosa may live for six years or more. [5]
The eggs of Asterina gibbosa are laid in a mass and glued to the substrate by their jelly-like coating. Each developing embryo feeds on its egg yolk and hatches directly into a brachiolaria larva, without the intervening mobile planktonic phase of most starfish larvae. The larva has a pair of asymmetric arms which gradually lengthen, and an adhesive disc with which it cements itself to the seabed. It then undergoes metamorphosis, its arms are reabsorbed and tube feet develop and take on the role of anchoring it to the seabed. Later the mouth of the juvenile starfish develops and it is able to start feeding. [6]
Asterina gibbosa is found in the northeastern Atlantic Ocean and the Mediterranean Sea. Its range extends from England, Scotland, Ireland and the southern North Sea southwards to the Mediterranean Sea, Morocco, Tunisia, the Azores, Cape Verde Islands, the Canary Islands and Madeira. It is found from the lower shore down to a depth of about 125 metres (410 ft) in pools, on rocks, under boulders and overhangs. [1]
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 7,600 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.
A brachiolaria is the second stage of larval development in many starfishes. It follows the bipinnaria. Brachiolaria have bilateral symmetry, unlike the adult starfish, which have a pentaradial symmetry. Starfish of the order Paxillosida have no brachiolaria stage, with the bipinnaria developing directly into an adult.
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.
The common starfish, common sea star or sugar starfish is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens are known. The common starfish is usually orange or brownish in color, and sometimes violet; specimens found in deeper waters are pale. The common starfish is found on rocky and gravelly substrates where it feeds on mollusks and other benthic invertebrates.
Culcita schmideliana, commonly known as the spiny cushion star, is a species of pin-cushion star. It has a variety of base colors and often patches of a different color. It is pentagonal in shape and lives in the tropical Indo-Pacific. This species is rarely kept by hobby aquarists.
Asterina phylactica is a species of sea star. It can be found in geographically widespread sites around the British Isles and in the Mediterranean Sea. It has five arms, is about 1.5 cm across and is of a green colour with central brown markings. The species was formally described in 1979 and is very similar to Asterina gibbosa.
Oreaster reticulatus, commonly known as the red cushion sea star or the West Indian sea star, is a species of marine invertebrate, a starfish in the family Oreasteridae. It is found in shallow water in the western Atlantic Ocean and the Caribbean Sea.
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.
Astropecten jonstoni is a sea star of the family Astropectinidae.
Astropecten spinulosus is a sea star of the family Astropectinidae.
Acanthaster brevispinus, the short-spined crown-of-thorns starfish, is one of the two members of the starfish genus Acanthaster, along with the much better-known A. planci, the common crown-of-thorns starfish.
Archaster typicus is a species of starfish in the family Archasteridae. It is commonly known as the sand star or the sand sifting star but these names are also applied to starfish in the genus Astropecten. It is found in shallow waters in the Indo-Pacific region.
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.
Luidia senegalensis, the nine-armed sea star, is a tropical species of starfish in the family Luidiidae found in the western Atlantic Ocean.
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.
Pteraster tesselatus, the slime star or cushion star, is a species of starfish in the family Pterasteridae found in the North Pacific.
Neoferdina cumingi, also known as Cuming's sea star, is a species of starfish in the family Goniasteridae. It is native to the tropical Indo-Pacific region.
Asterina pancerii, commonly known as the seagrass asterina, is a species of starfish in the family Asterinidae. It is native to shallow parts of the Mediterranean Sea where it is usually found in seagrass meadows.
Porania pulvillus, also called the red cushion star or red cushion starfish, is a species of sea star in the family Poraniidae. The specific name pulvillus means "little cushion."
