6 Horrifying Parasites

By Chris Connolly

These life-sucking go-getters have managed to carve out some of the most ingenious survival strategies in the world. By some estimates, parasites outnumber free-living species nearly four to one. So show some respect. After all, mooching isn't as easy as it looks.

1. Cymothoa exigua: Biting Your Tongue, So You Don't Have To

When fish mommies want to strike fear in the hearts of their misbehaving fish babies, we suspect they draw on the chilling animal savagery of the Cymothoa exigua. As a youngster, this nasty little parasitic crustacean begins a life of terror by fighting its way through the gills of its fish host of choice, the snapper. Once there, it attaches itself to the fish's tongue and begins feeding on the rich blood pumping through the artery underneath. As the parasite grows, it drinks more blood and eventually causes the tongue to atrophy and disintegrate. But does the Cymothoa mouth-squatter leave its fishy friend tongueless? Of course not. It does what any crafty parasite would do and replaces the old tongue with its own body. The fish is actually able to use the parasite just like a normal tongue, only it has to share all the food with its new friend. Yes, the whole foster-tongue thing seems like a pretty nice gesture on the part of ol' Cymothoa—until you remember there was nothing wrong with the fish's old tongue in the first place.

2. Screwworms: Causing Problems Right out of the Hatch

Plenty more (disgusting) creatures after the jump...

3. Sacculina carcini: Reasons You Shouldn't Pick up a Hitchhiker

If you ever have a choice between being possessed by the devil and being possessed by a Sacculina carcini, opt for the devil—no contest. A female sacculina begins life as a tiny free-floating slug in the sea, drifting around until she encounters a crab. When that fateful day arrives, she finds a chink in the crab's armor (usually an elbow or leg joint) and thrusts a kind of hollow dagger into its body. After that, she (how to put this?) "injects" herself into the crab, sluicing through the dagger and leaving behind a husk. Once inside, the jellylike sacculina starts to take over. She grows "roots" that extend to every part of the crab's body—wrapping around its eyestalks and deep into its legs and arms. The female feeds and grows until eventually she pops out the top of the crab, and from this knobby protrusion, she will steer the Good Ship Unlucky Crab for the rest of their commingled life. Packed full of parasite, the crab will forgo its own needs to serve those of its master. It won't molt, grow reproductive organs, or attempt to reproduce. It won't even regrow appendages, as healthy crabs can. Rather than waste the nutrients on itself, a host crab will hobble along and continue to look for food with which to feed its parasite master.

4. Filarial Worms: Proof You Need Thicker Skin

5. Guinea Worms: Exposing Parts Nobody Wants to See

6. Leucochloridium paradoxum: Parasite for Sore Eyes

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Ed. note: We thought the parasites were so horrifying that we decided to get the very talented Randy Riggs to film a B-horror movie around the subject. Here's the trailer for what he came up with.

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