Invading Barnacles

Preview a barnacle sits at the base of a crab's abdomen
(Ernst Haeckel)

 Sacculina is a species of barnacle that infects crabs and then manipulates their behavior to benefit itself—all to the detriment of the unsuspecting crab. They do so by growing a rootlike system throughout the crab’s entire body, which the parasite uses to feed on the crab. As the parasite develops, part of its body grows outside of the crab on its lower abdomen, right where a crab would carry its eggs. The parasitic barnacle then manipulates the crab by tricking it into treating the parasite like it would treat its own eggs – carefully caring for and nurturing the parasite by protecting it, grooming it, and flushing it with oxygenated water.