Barnacles means crust in Old Norse. Barnacles has a few centimeters wide cone-shaped house of lime. The groove gets stuck on for example stone, ship bottoms or crabs and mussels. The entrance hole in the housing can be closed by four movable lime plates. In this way, the animal can keep the water inside the house, thereby avoiding drying out. It has the shape of a small volcano and is up to 1.5 cm in height and width. Barnacles is a crustacean whose larvae get stuck and build a lime shell around it, like corals. The entrance hole is at the top. Here, the pipe stretches out its moving arms and captures plankton. The tube is hermaphroditic,  it has both male and female genitals. However, it cannot fertilize itself, and fertilization occurs by the fact, that Barnacles protrudes his up to 7.5 cm long penis into a close-knit species trap and delivers his sperm. The barnacle lives at the same place all his life and can be 4 years.

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Barnacles have always been a major problem for shipping, as the coatings reduce the speed of the ships. The cages must be scraped by the ship’s bottom and screws one or more times a year.