Asterina gibbosa
| Asterina gibbosa | ||||||||||||
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Asterina gibbosa |
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| Scientific name | ||||||||||||
| Asterina gibbosa | ||||||||||||
| ( Pennant , 1777) |
Asterina gibbosa is a rather small starfish from the family Asterinidae in the order of the valve stars (Valvatida), whichis native tothe eastern North Atlantic and the Mediterranean . It feeds mainly on bacteria, diatoms and carrion.
features
Asterina gibbosa has the shape of a somewhat "inflated" pentagon with short blunt arms and reaches a diameter of about 5 cm. The brown, green or orange-colored, sometimes slightly spotted skin on the top is provided with groups of short, blunt spines. While specimens in Exmouth in Devon (England) are more dark gray-green and in Start Point in Devon are spotted, individuals from Angle ( Pembrokeshire ) in Wales have a dark olive green color. At greater depths, starfish of this species are rather pale in color. Asterina gibbosa differs from the closely related Asterina phylactica , only up to about 15 mm in size , which has only been regarded as a separate species since 1979 , in that it has two small thorns on each side of the calcareous plate around the mouth, but no star-shaped brown ones Drawing in the middle.
Reproduction
In contrast to most other starfish - also in the Asterinidae family - Asterina gibbosa is a hermaphrodite , whereby one animal is first male and then female (protandric hermaphrodite as opposed to the simultaneous hermaphrodite Asterina phylactica ). In Plymouth ( England ) the sex change in an arm length of 9 mm and 16 mm takes place. In studies in the Mediterranean near Naples ( Italy ), however, no clear body size for the time of sex change could be determined. In the first year of life with an average arm length of 11 mm, about 80% were male, in the second year of life with an average of 17 mm long arms it was about 30% and in the third year of life with arms about 25 mm in length there were only a few males, but there were themselves in larger specimens of unknown age, about 15% males. Asterina gibbosa can live to be six years or older.
The eggs of Asterina gibbosa are laid in a cohesive mass covered with jelly and attached to the rocky subsoil. Unlike Asterina phylactica , they are not hatched. In contrast to the free-swimming plankton larvae of most starfish, the embryos feed on egg yolks and hatch directly as Brachiolaria larvae with two asymmetrical arms and an adhesive disc, with the help of which the larva soon attaches itself and undergoes a metamorphosis into a small starfish , whereby first five arms and the suction feet , then the new mouth opening are formed.
Distribution and occurrence
Asterina gibbosa is distributed in the north-east Atlantic from Scotland , Ireland and the southern North Sea to Morocco , around the Azores , Cape Verde Islands , Canary Islands and Madeira, and in the Mediterranean to Tunisia . It can be found in tide pools, on rocks, under stones and ledges to a depth of 125 m.
Lifestyle and diet
Asterina gibbosa is predominantly nocturnal and hides during the day under stones, ledges, in caves or under algae. It feeds mainly on bacteria and diatoms that live on the surface of rocks. For this purpose, the stomach is everted and the microorganisms are digested extraintestinally . In addition, it is detritus, fecal and scavengers : In her stomach rotting were Fucus serratus ( Fucus serratus ), Strandschneckenkot and scraps of dead mussels ( Mytilus edulis ), oyster ( Ostrea edulis ) and beach snails ( Littorina littorea found), but contained 95% of the stomach contents no larger pieces. She has also been seen eating the remains of dead mussels. While older studies and, as a result, popular scientific literature also state that the starfish feeds predatory on annelids, mollusks and brittle stars or on sponges and sea squirts, there was no evidence in more recent studies on the coast of Wales and south-west England that Asterina gibbosa preyed on live animals while it was observed eating microorganisms in large numbers.
literature
- Hubert Ludwig (1882): History of the development of the Asterina gibbosa . Journal of Scientific Zoology 37, pp. 1-98.
- Robin G. Crump, Roland H. Emson (1983): The natural history, life history and ecology of the two British species of Asterina . Field Studies 5 (5), pp. 867-882.
- Robin G. Crump, Roland H. Emson (1978): Some aspects of the population dynamics of Asterina gibbosa (Asteroidea) . Journal of the Marine Biological Association of the United Kingdom 58, 451-466.
- Robert Delavault (1961): La croissance d'Asterina gibbosa elevée en captivité . Bulletin du Laboratoire maritime de Dinard, 47, 3-7.
- S. Vasserot (1961): Caractère hautement spécialisé du régime alimentaire chez les asterides Echinaster sepositus et Henricia sanguinolenta, prédateurs de spongaires . Bull. Soc. Zool. France 86: 796-809
Web links
- Morvan Barnes: Asterina gibbosa - A cushion star . Marine Life Information Network, Biology and Sensitivity Key Information Sub-programs. Marine Biological Association of the United Kingdom, Plymouth 2009.
- Robin G. Crump: Cushion stars . Field Studies Council, 2008.
Individual evidence
- ^ Skewes, Marie: Asterina gibbosa . Marine Life Information Network. 2008. Retrieved November 13, 2015.
- ↑ a b Robin G. Crump, Roland H. Emson: The natural history, life history and ecology of the two British species of Asterina . In: Field Studies . 5, No. 5, 1983, pp. 867-882.
- ↑ Guido Bacci: On two sexual races of Asterina gibbosa (Penn.) . In: Experientia . 7, No. 1, 1951, pp. 31-33. doi : 10.1007 / BF02165480 .
- ^ Robin Crump: Cushion stars . In: The Seashore . Field Studies Council. 2008. Retrieved November 13, 2015.
- ^ Hubert Ludwig (1882).
- ↑ Delphine Haesaerts, Michel Jangoux, Patrick Flammang: Adaptations to benthic development: functional morphology of the attachment complex of the brachiolaria larva in the sea star Asterina gibbosa . In: Biological Bulletin . 211, No. 2, 2006, pp. 172-182. doi : 10.2307 / 4134591 .
- ↑ Christopher L. Mah: Asterina gibbosa (Pennant, 1777) . In: Christopher L. Mah: World Asteroidea database. World Register of Marine Species , 2008.
- ↑ Ralph Buchsbaum: Lower animals . Droemer Knaur, Munich 1960. p. 323.