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...

worms.jpgThe screwworm isn't really a worm at all; it's a type of fly. But if living under a false name were the worst of the screwworm's misdeeds, you can be sure it wouldn't appear in this story. No, this parasite's rap sheet is about to get much, much more disturbing. To find its host, an adult female screwworm seeks out exposed flesh on an animal (usually some sort of livestock, but an injured soldier or a human baby isn't out of the question) in search of a place to lay her eggs. She prefers wounds, but may also settle on using the eyes, nostrils, or anus of her victim to construct a nursery. Next, the 200-or-so eggs hatch, and the larvae start burrowing into their host's flesh. Once they're situated in their cozy little meat tunnels, the infant flies continue to feed and grow. The bigger they get, the more they have to eat. Eventually, this creates a whole lot of festering and oozing on the host, which attracts more flies, which lay more eggs, which do more feeding and burrowing. It's a brutal onslaught, and a swift one. Screwworm larvae are reportedly capable of consuming an entire sheep or dog from the inside out in five to seven days.

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

Sacculinacarciniweb.jpgIf 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

lf2.jpgFilarial worms are the nasty little suckers you can thank for lymphatic filariasis, which, according to the Pacific Program to Eliminate Lymphatic Filariasis, is the second-leading cause of permanent and long-term disability in the world. (Mental illness is No. 1.) Filarial worms are round, thread-like parasites that travel from human to human via that harbinger of disease transmission, the mosquito. How do they make the leap of host? In an interesting (if scary) example of parasite ingenuity, filarial worm embryos living underneath the skin can sense the onset of night, which is their cue to head upward to the skin's surface in order to increase their chances of being picked up by a passing 'skeeter. Should they get sucked up, they grow into larvae within the mosquito's muscle fibers and then get themselves injected into new hosts. Once they've returned to a human home, they open up a franchise in the family business—Wreaking Havoc. Filaria often lodge in the body's lymphatic system, where they can inflict any number of torturous symptoms, not the least of which involves carting your genitals off to the elephantiasis clinic in a wheelbarrow.

5. Guinea Worms: Exposing Parts Nobody Wants to See

guinea-worm.jpgWhere there are guinea worms, there is Guinea Worm Disease—and that's usually in Africa. When a human consumes water contaminated with guinea worms, the little buggers infiltrate their host's intestinal walls and commence mating. After conception, the males die off, and the females hang around for about a year, growing and eating. Eventually, these slender ladies get bored and decide they need to lay some eggs. To do so, they make their way down the body to the lower extremities, where they bore a small hole through the skin. The resulting lesion begins to fester and burn, which usually leads the host to plunge his or her foot into a soothing bucket of water. (Of course, in areas where an entire village shares a single water source, this helps spread the infection.) Unfortunately for the sufferer, the water doesn't solve the problem of having a three-foot female worm dangling its genitalia out of your foot. And to complicate matters, if you yank on that sucker, it'll break apart and could cause a fatal infection. So how do you rid yourself of the not-so-little hitchhiker? You go see a doctor, who—over the course of three or four weeks—will kindly wind the worm around a stick, inch by agonizing inch. Not the most pleasant method, but certainly a proven one. This cure for a guinea worm infection has been around so long, some believe it's where we get the snakes-around-a-staff symbol for medicine.

6. Leucochloridium paradoxum: Parasite for Sore Eyes

mimicry_2.jpgPrepare to be dazzled. This parasite's got a life cycle more mind-bending and chilling than an M. Night Shyamalan film. Leucochloridium paradoxum are a type of fluke (a.k.a., parasitic flatworm) that prey on birds—a fascinating turn of events considering they begin their lives as eggs in bird droppings. Thus, the problem facing baby Leucochloridium paradoxum is, "How do I get myself back into one of those feathery things?" Taking a page from Greek history, the infant flatworms rely on Trojan trickery. First, they hang out in the droppings until a snail happens along and eats the bird dung. Then they initiate their devious plan of action by taking up residence in the snail's eyestalks. (Sure, it sounds slimy and gross to us, but after a childhood spent living in bird feces, it's a step up.) As they mature, the flukes become visible through the snail's translucent skin. And that's when things really get interesting. To a bird, this fluke-filled eyestalk looks like a caterpillar. So the bird devours the stalk and ends up with a bellyful of Leucochloridium paradoxum that will, of course, lay eggs and begin the cycle again. Meanwhile, the snail shakes its head, shops for an eye patch, and vows never to eat feces again.

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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.

This article was pulled from an earlier edition of mental_floss. Make our editors happy and subscribe today.

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.
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There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

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