Behavioral manipulation of the shore crab, Hemigrapsus sanguineus by the rhizocephalan barnacle, Sacculina polygenea

Manipulation of the host's behavior by the rhizocephalan parasite, Sacculina polygenea, was observed in an aquarium with a video camera. The brachyuran host, Hemigrapsus sanguineus, cleaned the surface of the parasite's externa with its chelipeds. When the parasite released nauplii, the host assisted the parasite by adopting the stereotypic larval release behavior of female crabs. While releasing the nauplii, the host remained stationary on a rock, occasionally flexing its abdomen with a waving action. After releasing nauplii several times, the externa became smaller and withered, and the host removed it with its chelipeds and ate it. This behavior was displayed by both sexes of the host.