Variable spiny starfish
The Variable spiny starfish (Coscinasterias tenuispina) is called this because instead of the classic five arms it usually has seven. It is therefore an exception regarding the classic five-ray symmetry of echinoderms. Furthermore, as can be seen in this specimen, three of the seven arms are very small and are therefore slowly growing back.
It often happens that some starfish lose one of their 5, 7, or 9 arms due to a predator. The peculiarity of this species is that it is able to regenerate them and almost always a new starfish is born from the severed arm, equal to the original. The variable spiny starfish represents one of the few cases of cloning in nature, that is, if an arm is torn off from a starfish, it is regenerated and the torn arm can regenerate the missing parts, giving rise to a new starfish with the same DNA as the original one.
The Variable starfish (Coscinasterias tenuispina Lamarck, 1816) is an echinoderm of the Asteriidae family, common in the Mediterranean Sea.
Irregular shape with arms in variable numbers, from 6 to 12 (usually 7), with a diameter of up to 20-25 centimetres. The body is characterized by spines, varying in color from white, grey, brown, red and sometimes blue.
Common in the Mediterranean Sea and the eastern Atlantic Ocean, on rocky seabeds rich in algae or on Posidonia oceanica up to 100 metres.
It can be confused with Marthasterias glacialis.