Common starfish
| Common starfish | ||||||||||||
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Common starfish ( Asterias rubens ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Asterias rubens | ||||||||||||
| Linnaeus , 1758 |
The common starfish ( Asterias rubens ) is a species from the order of the pincer stars (Forcipulatida). This species occurs in all European seas except the Mediterranean. It lives in the bank area to a depth of no more than 200 m and prefers lake water with a salt content of at least 0.8 percent.
description
The common starfish usually has five arms (four- or six-armed individuals are also rare) and can grow up to about 30 centimeters. On the underside there are suction discs in four rows at the end of each arm that it uses to move. The yellow to brown-violet color is characteristic.
The common starfish has a nervous system instead of a brain or heart . In addition, there is a lack of eyes with which he could recognize or identify objects. However, there are several simple light sensory cells on the tips of his arms in order to be able to perceive differences in brightness in the surroundings.
nutrition
Like most starfish, the common starfish feeds mainly on molluscs such as mussels (mostly mussels ), but also fish eggs. He sits down on the mussel, sucks himself in with his suction feet and pulls on the shell. However, the mussel closes when there is danger. This struggle can last for hours before the mussel opens its shell to let in fresh water to breathe. The starfish holds the mussel in this position and turns its stomach, which it can produce outward, into the interior of the mussel. Through digestive secretions, he digests the clam in its own shell, slurps the food in with his stomach, and withdraws. Therefore, it is a feared predator on mussel beds below the low water line.
There are almost no starfish on the mussel beds, which are in the tidal area, as they are eaten by seagulls such as the herring gull.
photos
(Rarely occurring) four- and six-armed individuals of the common starfish ( Asterias rubens )
Undersides of the above two
Five-armed individual ( Asterias rubens ) with a split arm (front and back)
Reproduction
Like most starfish, the common starfish is segregated. During the summer, the females produce a large number of eggs from which planktonic larvae form. In addition, asexual reproduction takes place via Fissiparie .
Web links
Individual evidence
- ↑ Common starfish. In: Animal Lexicon for Children; SWR children's network Oli's Wilde Welt. Accessed in 2014 .
- ↑ Kerstin Viering: On the bottom of the Baltic Sea. Article in the Berliner Zeitung , 13./14. August 2016, p. 4 of the magazine supplement .
- ↑ Westheide, Wilfried; Rieger, Reinhard (Hrsg.): Special zoology. Part 1: Protozoa and invertebrates. Munich, 2007