The blue spiny starfish
Coscinasterias tenuispina is a starfish in the family Asteriidae. It is sometimes called the blue spiny starfish or the white starfish. It occurs in shallow waters in the Atlantic Ocean and the Mediterranean Sea. Coscinasterias tenuispina has from 6 to 12 arms (usually 7), often of varying lengths, and grows to 20 cm. in diameter. It is a creamy, slightly bluish colour, variously blotched with brown, and is rough textured with short spines. la stella marina variabile
The range of Coscinasterias tenuispina includes the Mediterranean Sea, France, Spain and Portugal, the Azores and other Atlantic Islands, Bermuda, Cuba and the American coast between North Carolina and Santos, Brazil. It is found on the lower shore and down to a depth of about 50 m.
A number of divergent populations of the starfish in the Atlantic and Mediterranean are believed to be deserving of being recognized as sub-species. The female population of the starfish in the Mediterranean is larger than that of the males. Coscinasterias tenuispina is a predator and an omnivore. The starfish is found on hard bottoms and under stones and seaweed where it mainly feeds on other echinoderms and on bivalve molluscs. la stella marina variabile
Echinoderms possess a unique water vascular system. This is a network of fluid-filled canals derived from the coelom (body cavity) that function in gas exchange, feeding, sensory reception and locomotion. This system varies between different classes of echinoderm but typically opens to the exterior through a sieve-like madreporite on the aboral (upper) surface of the animal. The madreporite is linked to a slender duct, the stone canal, which extends to a ring canal that encircles the mouth or oesophagus. From this, radial canals extend along the arms of asteroids and adjoin the test in the ambulacral areas of echinoids. Short lateral canals branch off the radial canals, each one ending in an ampulla. Part of the ampulla can protrude through a pore (or a pair of pores in sea urchins) to the exterior and is known as a podium or tube feet. The water vascular system assists with the distribution of nutrients throughout the animal’s body and is most obviously expressed in the tube feet which can be extended or contracted by the redistribution of fluid between the foot and the internal sac. Even starfish, like all marine organisms, if they are removed from the water are destined to die.