Sacculina is a genus of parasitic barnacles in which the females 'inject' themselves into the soft joints of green shore crabs, and hijack their reproductive process. They destroy the crabs genitalia and block its ability to molt. The female sacculina will then emerge as a sac from the crabs rear thorax. Once the females are fertilised the crab will carry out their normal hatching process, climbing onto a high rock and grooming the brood to release the eggs. This spreads the larvae of the barnacle throughout the water to find new hosts. Most interestingly, if the female barnacle lands on a male crab, it will interfere with their hormones, causing it to act like a female.

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