A parasitic barnacle called Sacculina injects itself into a crab, grows a root system through its host’s body, and chemically rewires the crab’s brain to care for the parasite’s eggs as if they were its own, even castrating male crabs so they behave like females tending a brood.

Sacculina carcini enters a shore crab as a droplet of cells, grows rootlets through the host's body, castrates and feminises males, and hijacks the crab into raising the parasite's eggs as if they were its own brood. The post A parasitic barnacle called Sacculina injects itself into a crab, grows a root system through its host’s body, and chemically rewires the crab’s brain to care for the…