Body Snatchers: Four of Nature’s Freakiest Parasites
Zombies, vampires and mind-controlling body snatchers aren’t just fantastical creatures from horror movies. In nature, a fungus can control the mind of a fruit fly, a hairworm can hijack a cricket’s brain and body, tiny vampire-like mites feast on honeybees, and a tiny parasite can sabotage a monarch butterfly’s metamorphosis.
TRANSCRIPT
Zombies, mind control, vampires. The Invasion of the Body Snatchers isn’t as far fetched as you might think. In fact, it’s happening all around us – right now.
Like horsehair worms that enter the body of a cricket and then take over its mind.
Or diabolical varroa mites that live off the bodies of honeybees and their offspring.
And tiny parasites that hide on a Monarch caterpillar’s favorite food, and attack it from inside – as it grows.
First up, see how this killer fungus turns a fruit fly into a zombie that will do its bidding.
We like to think we’re in control – that our minds are our own.
But that’s not true for this fruit fly.
Its brain has been hijacked by another organism and it’s not going to end well.
It all starts when the fly is innocently walking around, sipping on overripe fruit.
It picks up an invisible fungus spore, which bores under its skin.
For a few days, everything seems normal.
But inside, the fungus is growing, feeding on the fly’s fat, and infiltrating its mind.
At dusk on the fourth or fifth day, the fly gets a little erratic, wandering around.
It climbs to a high place. Scientists call this behavior “summiting.”
Then it starts twitching. The fungus is in control.
The fly sticks out its mouthpart and spits out a tiny drop of sticky liquid.
That glues the fly down, sealing its fate.
A few minutes later, its wings shoot up. And it dies.
Now that the fungus has forced the fly into this death pose – wings out of the way – nothing can stop it. It emerges.
Tiny spore launchers burst out of the fly’s skin. Hundreds of spores shoot out at high speed, catching a breeze if the fly climbed high enough.
They’re the next generation of killer fungus. It continues for hours, spores flying out.
These flies are in the wrong place at the wrong time. And if spores land on a wing, which they can’t bore into, they shoot out a secondary spore to increase their chances of spreading.
So how does a fungus take control of a brain?
At Harvard, Carolyn Elya is trying to understand that.
She thinks the fungus secretes chemicals to manipulate the fly’s neurons, maybe stimulating the ones that make flies climb.
But don’t worry: The fungus can’t hurt humans.
Scientists have tried to harness its power for our benefit, to kill flies in our kitchens and farms.
They haven’t had any luck though. The deadly spores are actually pretty fragile and short-lived.
It turns out, this lethal puppet master does only what it needs to for its *own* survival.
How’s your appetite for more mind control? These hairworms get inside the body – and brain – of a cricket.
The day starts normally enough. You give your pet some food and water.
But later in your pet’s water dish, you find this.
A hairworm.
It didn’t get here on its own.
It came out of a little cricket.
Don’t believe me? OK.
These hairworms are gnarly parasites. They actually control a cricket’s mind to get to their home: the water.
The hairworm’s journey starts innocently enough in a river, as an egg – one of many in this long string.
The eggs grow into squiggly larvae, which get eaten by a mayfly larva that also lives in the river.
And inside the mayfly is exactly where the hairworm needs to be.
The hairworm uses this pointy part to burrow into the mayfly’s flesh.
Then it curls up and waits.
Because, really, it’s not after a mayfly.
It’s after a cricket.
So it sits tight, while the mayfly larva turns into an adult and heads to dry land where it just might get eaten by a cricket – that has no idea what it’s in for.
Inside the cricket, the hairworm goes at it, eating all the cricket’s stored-up fat, for about a month.
The cricket loses its chirp, but the hairworm doesn’t kill the cricket because the worm needs a lift back to the water.
Crickets usually avoid bodies of water. They’re not great swimmers.
So the worm takes over, boosting chemicals in the cricket’s brain, which make the cricket walk around mindlessly until it happens to reach water.
Scientists in France watched this infected cricket make a beeline for the pool.
The hairworm makes a break for it.
Still going.
Ugh, that’s just – ugh.
But don’t worry. They don’t target humans.
Ready for more?
This one at the University of New Mexico has a whole lot of hairworms inside it.
They don’t waste any time, curling around each other to mate even before they’re fully outside the cricket.
But it’s more than a gruesome spectacle of nature.
Learning about these hairworms could help scientists understand parasites like toxoplasma that make us very sick.
As for the crickets, don’t feel bad.
If they don’t drown, most of them survive their ordeal.
At least that’s what scientists have seen in the lab.
They go back to being crickets and hopefully stay on dry land.
And that’s not all. Vampiric mites are hungry for honeybee organs, and could destroy a whole colony. Unless the bees eat them first.
Here’s a go-to recipe for beekeepers. It’s called a “sugar shake.”
Take a half-cup of bees. That’s about 300.
Put them in a jar and cover them with a mesh lid.
Add two tablespoons confectioners’ sugar.
Shake for 30 seconds. We’re going for a nice, even coat.
Empty the sugar onto a tray. And there you have it: frosted varroa mites, aka Varroa destructor. They’re a honeybee’s worst enemy.
The fine-powdered sugar made them lose the grip they had on their hosts.
A minute ago, the mites were on the bees in the hive.
It’s as if you were carrying around a tick the size of a dinner plate.
Every year, up to half the managed honeybee hives in the United States die from hazards like pesticide exposure, lack of flowers to forage on year-round, and varroa mites.
To feed, a varroa mite nestles between the bees’ protective plates.
It digs in with its gnarly mouth, the gnathosoma. The mite sinks it into a crucial organ called the fat body. It’s a layer of tissue that lines the abdomen.
Sort of like the human liver, the fat body helps the bee break down harmful stuff, including pesticides. And it maintains the bee’s immune system. So, when varroa mites attack the fat body, they seriously weaken the bee.
The mites can also transmit a virus that causes a bee to be born with deformed wings, no good for flying.
Let’s go back to the “sugar shake.” Beekeepers use them to monitor the varroa mites in their hives.
As few as three mites per half-cup of bees could kill a hive within the year. That’s because varroa mites are great at sneaking into hives, hiding, and reproducing like mad.
The first mite gets into a hive by hitching a ride on a bee from another colony. Maybe the bee’s own colony wasn’t doing well and it was looking for a new home.
The mite sniffs around for a bee larva and sneaks in right before the bees cover the cell with wax.
The defenseless larva is now trapped with its enemy, which begins to feed.
As the larva grows into a pupa, the mite, called a foundress, starts her family. Take a look underneath this bee pupa.
The mite’s firstborn is always a son. The rest are daughters. They’re hard to tell apart when they’re young.
When the siblings come of age inside the cell, they’ll meet up on this pile of mite poop – maybe they’re guided by the scent. And they’ll mate with each other.
Sometimes two foundresses make it into a cell. Then their offspring get to mate with someone they’re not related to.
The mites live off the bee pupa, but they don’t kill it.
When the bee is all grown up, it chews its way out of the cell.
The mite slips onto its next victim.
So, why don’t the bees just pick those mites off themselves?
Well, we didn’t start seeing varroa mites in the U.S. until the 1980s. They evolved on eastern honeybees, in Asia. That’s why the western honeybees in the Americas and Europe aren’t yet good at defending against them.
When beekeepers find mites in a sugar shake, they treat a hive with pesticide strips that kill the mites. But mites are becoming resistant.
So, researchers are selectively breeding honeybees to fight back.
The U.S. Department of Agriculture and private companies are breeding bees that can sniff out varroa mites. When the bees find some, they uncap the cells and interrupt reproduction. The bees then, um, “recycle” the unlucky pupa. Yep, they’re eating it.
At Purdue and Central State universities, scientists breed honeybees known as “mite-biters.”
After collecting sperm from a male bee, they inseminate a queen.
Both the queen and the male come from colonies that are particularly good at killing mites by chewing off their legs.
It’s a grisly end for these tormentors and – just maybe – a fair shake for the honeybees.
Finally, monarch butterfly metamorphosis is a splendid thing – unless it gets hijacked by a parasite.
It’s a magical moment in the life of a monarch butterfly — and a vulnerable one.
Its metamorphosis complete — it breaks free from its chrysalis and pumps fluid from its abdomen into its spectacular new wings.
But for some it’s a struggle.
An old enemy, a parasite called Ophryocystis elektroscirrha, known as OE, is making it harder for monarchs to undergo this crucial transformation.
The infection causes sticky sores on the abdomen, trapping the butterfly inside its own chrysalis.
And by trying to help monarchs, we humans might be making it worse.
Each summer, monarchs make their homes in milkweed patches all over North America.
When infected females lay their eggs on the plant, they unknowingly drop microscopic OE spores onto the eggs and surrounding leaves.
A few days later the next generation begins.
The caterpillar goes to work, munching on the empty shell of its old egg.
Then it’s on to the milkweed.
With each bite, the caterpillar downs more and more of these microscopic, football-shaped spores.
Inside the caterpillar’s gut, the spores break open, releasing wormy-looking parasites that burrow out of the gut and into the caterpillars flesh.
When the caterpillar transforms into a chrysalis …
The parasite starts multiplying rapidly, stealing nutrients and taking up space where the monarch would normally grow skin and scales.
When it’s time to emerge, the weakened butterfly fights to free itself from the sticky chrysalis – attracting predators and exhausting itself.
Some never escape.
Others do, but with wings that are all crumpled and deformed, never fully extending.
Or just bent and uneven, making it harder to fly.
Researchers at Emory University in Atlanta take samples of monarch scales to hunt for OE under the microscope.
See all those tiny black specs wedged in between the monarch’s scales?
Those are OE spores.
Unfortunately, this one’s infected.
But OE has been around a long time.
So what’s making it such a big problem now?
Well, monarchs have lost much of their summertime milkweed habitat to agriculture and development.
Every stage of their life cycle is connected to this family of unassuming plants.
At the end of summer the local milkweed dies off and the monarchs head south for the winter.
When the plant dies back, it takes the OE down with it.
That’s good.
But, in an effort to help monarchs, some of us plant tropical milkweed in our gardens, with its showy yellow and red flowers.
Tropical milkweed sticks around a lot later into the year than native milkweeds.
That means more time for OE to build up on its leaves.
And because the tropical kind doesn’t die back with the rest of the milkweed, some monarchs don’t get the signal to start migrating.
They just hang out on the infested plants, missing their chance to hook up with all the other butterflies that spend their winters partying down south.
What’s worse, they spread OE to healthy butterflies that pass through on their migration.
So, if you wanna help the monarchs – do ’em a solid!
Cut back your tropical milkweed in the fall.
And the next time you plant milkweed make sure it’s a native kind.
With all the problems that monarchs face, this is one small thing we can do to help.