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We're inching closer to Halloween and it's getting spookier out there! This week let's learn about some animals that get zombified for various reasons. This is an icky episode, so you might not want to snack while you're listening. Thanks to Sylvan for the suggestion about the loxo and mud crabs!\n\nFurther reading:\n\nZombie Crabs!\n\nLadybird made into 'zombie' bodyguard by parasitic wasp\n\nA mud crab held by a dangerous wizard:\n\n\n\nA paralyzed ladybug sitting on a parasitic wasp cocoon:\n\n\n\nA cat and a rodent:\n\n\n\nShow transcript:\n\nWelcome to Strange Animals Podcast. I\u2019m your host, Kate Shaw.\n\nIt\u2019s another week closer to Halloween, so watch out for ghosts and goblins and zombie animals! Zombie animals?! Yes, that\u2019s this week\u2019s topic! Thanks to Sylvan for suggesting the loxo parasite, which we\u2019ll talk about first. Brace yourself, everyone, because it\u2019s about to get icky!\n\nBefore we learn about loxo, let\u2019s learn about the mud crab, for reasons that will shortly become clear. Mud crab is the term for a whole lot of small crabs that live in shallow water, mostly in the Atlantic or eastern Pacific Oceans but sometimes in lakes and other fresh water near the ocean, depending on the species. Most are less than an inch long, or under about 30 mm. The largest is called the black-fingered mud crab, which grows to as much as an inch and a half long, or 4 cm. Most mud crabs are scavengers, eating anything they come across, but the black-fingered mud crab will hunt hermit crabs, grabbing their little legs and yanking them right out of their shells. It also uses its strong claws to crack the shells of oysters.\n\nLoxothylacus panopaei is actually a type of barnacle. You know, the little arthropods that fasten themselves to ships and whales and things. But loxo, as it\u2019s called, doesn\u2019t look a bit like those barnacles except in its larval stages. After it hatches, it passes through two larval stages; during the first stage, it molts four times in only two days as it grows rapidly.\n\nThen, during the cyprid larval stage, the microscopic loxo searches for a place to live. The male remains free-swimming but the female cyprid larva is looking for a mud crab. She enters the crab\u2019s body through its gills and waits for it to molt its exoskeleton, during which time she metamorphoses into what\u2019s called a kentrogon, basically a larva with a pointy end. As soon as the crab molts its exoskeleton, the female loxo uses her pointy end, called a stylet, to stab a hole in the crab\u2019s unprotected body. Then she injects parasitic material that actually seems to be the important part of herself, which enters the crab\u2019s blood\u2014called hemolymph in arthropods like crabs. Like most invertebrates, crabs don\u2019t have blood vessels. The hemolymph circulates throughout the inside of the body, coming into direct contact with tissues and organs. This means that once the loxo has infiltrated the hemolymph, she has access to all parts of the crab\u2019s body.\n\nAt this stage, the loxo matures into something that isn\u2019t anything like a barnacle, but is an awful lot like something from a horror movie. She grows throughout the crab, forming rootlets that merge with the crab\u2019s body and changes them. Basically, the female loxo becomes part of her crab host. Eventually she controls its nervous system and molds it to her own needs. She even molds the body to her own needs, since if she\u2019s parasitized a male crab she has to widen its body cavity so it can hold her eggs.\n\nThe crab stops being able to reproduce and doesn\u2019t want to. It only wants to care for the eggs that the female loxo produces. She extrudes an egg sac so that it hangs beneath the crab\u2019s abdomen, where a male loxo can fertilize it when he swims by. The crab then treats the egg sac as if it contains its own eggs, protecting them and making sure they get plenty of oxygenated water. This is true even for male crabs, which ordinarily don\u2019t take part in protecting their own eggs.