Protula tubularia is a sedentary Mediterranean polychaete also present on the two sides of the Atlantic and in other seas. The vermiform body is protected by a solid calcareous tube, up to 1 cm broad, which the animal builds around, after having chosen for fixing itself a ridge where the currents rich in plankton pass. From the tube in which it moves, which is the house chosen for life, two elegant gill crowns come out …