In the Last of Us, the most gruesome live-action adaptation of a video game about people being turned into fungus since 1993’s Super Mario Bros, a mutated species of Cordyceps destroys society by converting humans into mindless, sporulating mushroom people.

Cordyceps, a fungus that most commonly parasitizes ants, is real. It really does hijack its host’s nervous system, alter its behavior, and turn it into a spore-producing zombie. The outcome is strangely beautiful.

Though the current darling of gritty, realistic, science-based zombie fiction, Cordyceps is such a lightweight in the world of brain-breaking parasites that tech bros brew it into their adaptogenic coffee.

If you want to meet a truly unsettling zombie-making parasite, allow me to introduce you to Sacculina.

Sacculina is a genus of barnacle that parasitizes crabs. While most parasitic barnacles are perfectly happy growing on the carapace of a crab, Sacculina takes this partnership to the extreme.

Female Sacculina larvae drift through the ocean, until they encounter a crab. The larva then settles on the crab and searches for a joint in the crab’s carapace. Once it finds a gap in the arthropod’s armor, it transforms into a kentrogon, a specialized phase of the barnacle life cycle that possess a stylet–an organic syringe-like structure–which allows Sacculina to inject itself into the crab, and not much else. At this point, the hard shell attached to the crab’s carapace falls off and the barnacle continues to grown within its host.

It gets so much weirder from here.

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