The Martasteria or Spiny Starfish, Marthasterias glacialis, is an echinoderm of the Asteriidae family common in the Mediterranean Sea. Also called a Tank star, due to the characteristic plates bristling with thorns that distinguish it from other starfish, it has a regular shape with five arms. The body is characterized by spines of variable color: white, gray, brown, red, blue. It appears to be the largest species in the Mediterranean, capable of reaching even 85 centimeters in diameter.