Common starfish

Common Starfish (Asterias rubens )

The common starfish (Asterias rubens ) is a species in the order of pliers stars ( Forcipulata ).

Particulars of

The common starfish usually has five arms ( rarely four or six -armed individuals before ). On the bottom are at the end of each arm suction discs in four rows. Characteristic is the yellow to brown-violet color.

The common starfish has no eyes with which he could recognize or identify objects. However, are located on its arm tips several photoreceptor cells to perceive differences in brightness in the environment.

Habitat

This species occurs in all European seas off except in the Mediterranean. He lives near the shore to depths of up to 200 m and preferably seawater with a salinity of at least 0.8 %.

Nutrition

Like most of the congregation starfish starfish feeds mainly on molluscs such as mussels (mainly mussels ), but also fish eggs. He sits down on the mussel and sucks firmly with its suckers and draws on the shell. However, the shell closes at risk. This fight can last for hours, until the mussels open their shells must be a gap to let in fresh water to breathe. The starfish keeps the mussel in this position and his stomach inside out, he can bring the outside into the inside of the mussel. By digestive secretions he digests the mussel in its own shell, the food slurps a with his stomach and withdraws. Therefore, he is a feared predator on mussel beds, which are below the low water line. On the mussel beds that are located in the tidal range, one finds almost no sea stars because they are eaten by the gulls as the herring gull.

Reproduction

Like most of the congregation starfish starfish is dioecious. During the summer, the females produce a large amount of eggs, from which are formed planktonic larvae.