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Tom Phillips
Tom Phillips

8 Parasites that Create Zombie Animals

Tom Phillips
Tom Phillips

Five years ago, I wrote The Invasion of the Zombie Animals and 7 More Zombie Animals. Those two lists covered the best-known cases of parasitic creatures that take over the minds and bodies of other animals for their own selfish ends. But there are many more such parasites that do exactly the same thing. They give us nightmares and feature films, but life is even worse for their victims.

1. Zombie Fish Has a Hot Flash


Photograph by Solveig Schjorring.

The bird tapeworm Schistocephalus solidus uses three hosts in its life cycle. Its eggs are laid in a bird’s digestive system. When the eggs reach the water in bird droppings, they hatch into larvae, which are eaten by copepods, a type of crustacean. The copepods are eaten by stickleback fish. This is where the tapeworm wants to grow large. Through some chemical mechanism, the tapeworm changes the fish’s behavior. The fish no longer stays with its school, but swims to the warmer water preferred by a growing tapeworm. Leaving the other fish also make the stickleback more likely to be eaten by a seabird, which is where a mature tapeworm wants to be in order to lay its eggs. And the cycle can start all over again.

2. Zombie Honeybees Head Toward the Light


Photograph by Core A, Runckel C, Ivers J, Quock C, Siapno T, et al.

Apocephalus borealis is a fly that lays its eggs in bumblebees, but has been observed to use honeybees as a host more recently. This makes it a suspect in the widespread Colony Collapse Disorder. The fly lays its eggs in the bee’s body, and the infected bee stops working and abandons the colony. Its behavior becomes more like a moth in that it tends to move toward lights, throwing off its navigation. However, while a moth flies around a light, infected honeybees will stagger and fall down. The bee eventually dies when the fly larvae burst out from behind its head.

3. Zombie Caterpillars “Plant” Themselves


Photograph by L. Shyamal.

Ophiocordyceps sinensis is a parasitic fungus that is actually classified as an endangered species. It lives in soil, but eventually reproduces with the help of a ghost moth caterpillar. The infected caterpillar will “plant” itself in soil, with its head pointing toward the surface. The fungus grows over winter, digesting the caterpillar from the inside. In the spring, a fruiting body will burst through the caterpillar’s head and “sprout” above the soil. Often the “stalk” of fungus will be bigger than the caterpillar itself.

The fungus grows only in Tibet and the Himalayas, where the dead infected worms are collected and sold for medicinal use under the name yartsa gunbu. It’s not easy to harvest, but a pound of it can bring $50,000. Overharvesting led to the endangered classification

4. Zombie Spiders Become Tailors


Photographs by Stanislav Korenko and Stano Pekár.

Czech scientists Stanislav Korenko and Stano Pekár describe the effects of a parasitic wasp, Zatypota percontatoria, on the spider Neottiura bimaculata. The tiny wasp will inject an egg into the abdomen of the spider. The egg hatches and feeds on the spider. The zombie mind-control only occurs when the larva is almost mature: that's when the spider stops its normal web-spinning pattern (B in the above picture) and begins spinning a different kind of web (A) -one that is a perfect place for a wasp cocoon, with a platform to keep it off the ground and a hood to shield it from the weather. When the “customized” web is ready, the larva bursts from the spider, killing it, and spins its own cocoon in the web (C and D).

Another species of spider affected this way is Anelosimus octavius, which is a “tangle web spider.” It produces a rather unstylish web until infected by a wasp of the genus Zatypota. Then it is directed to build an elaborate tent for the parasitic wasp’s cocoons. See the affected webs here.

Yet a third pairing of spiders and wasp parasites was covered in the second list in this series.

5. Zombie Crickets Shoot Blanks


Photograph by Flickr user Tom Phillips.

The virus IIV-6/CrIV is a sexually-transmitted disease that affects crickets. But this virus has a trick up its sleeve- it affects the behavior of crickets for its own ends. A cricket infected with IIV-6/CrIV will become more sexually active than a non-infected cricket, which facilitates the spread of the virus from one host to another. The crickets, however, become sterile, both male and female, which means they will continue to mate until they die. The virus does not make the crickets feel sick, though, because that would be counterproductive to sexual activity. If an STD could be thought of as sentient, this one would be a genius.

6. The Zombie Drug-addict Ant Slaves


Photograph by Alexander L. Wild.

The Central American acacia tree and the ant Pseudomyrmex ferrugineus live in a symbiotic relationship. The tree provides sweet nectar for the ants, and the ants protect the tree from weeds and animals. But we now know that the relationship is rather one-sided, as the tree not only causes the ants to become addicted to its nectar, but also damages the ants to make them unable to digest any other food! Martin Heil of Cinvestav Unidad Irapuato in Mexico studied the ants, and found that they are born with the ability to digest a variety of sugars, but then lose their invertase, an enzyme that breaks down sugars. The disabled ants can then only survive on the partially-digested sugar of acacia nectar.

Heil has now shown that the tree itself is responsible. Writing in the Ecology Letters journal, he reports that acacia nectar contains chitinase enzymes that completely block invertase.

Shortly after the workers emerge from their pupae as adults, they take their first sip of nectar and their invertase becomes irreversibly disabled.

That's kind of like a nefarious baby food company that offers to pay for your rotten teeth to be pulled instead of repaired. Like I've always said, never trust a tree bearing gifts.

7. Brainless Zombie Ants Carry On and Bury Themselves


Photograph by S.D. Porter, USDA-ARS.

Pseudacteon litoralis is a parasitic fly that victimizes fire ants in South America. The female fly lays an egg in the ant’s body with an ovipositor that resembles a hypodermic needle. The egg hatches inside the ant, and then the larva works its way to the ant’s brain, which it eats. The rest of the colony doesn’t even notice that the infected ant no longer has a brain, because the fly larva causes the ant to keep on working and behaving as always! That is, until the larva matures into a pupa. Then it causes the ant to go off by itself and snuggle down in a bed of forest litter, very un-antlike, for the climax of the story. That’s when the mature fly pops off the ant’s empty head and emerges from the dead body to fly off and reproduce.

8. The Meta Parasite


Photograph by Andy Potter.

Just because a wasp is a parasite that feeds off other insects doesn’t mean it has no natural predators. They can become victims themselves! Parasites that feed on other parasites are called “hyperparasitoids.” Ed Yong says, “It’s like a cross between the films Alien and Inception.” This story involves not only a caterpillar and two (or more) parasites, but also a cabbage that communicates.

When a cabbage begins to be eaten by a caterpillar, it emits a chemical signal, like an alarm. The scent of the chemical summons the parasitic wasps Cotesia rubecula and/or Cotesia glomerata, which infect the caterpillar with their eggs. This benefits the cabbage in the long run by controlling the cabbage-eating caterpillars. But the chemical also attracts the wasp Lysibia nana, which lays its egg in the Cotesia grub that is already feeding off the still-living caterpillar! Now, the L. nana wasp can tell which Cotesia species is inside the caterpillar, because the grub changes the chemical composition of its host’s saliva, and L. nana can smell the difference. It prefers a caterpillar infected with C. glomerata. One hypothesis is that C. rubecula has evolved to alter the caterpillar’s saliva more subtly for the purpose of hiding from the the hyperparasitoid L. nana.

But of course, the L. nana wasp is vulnerable to yet other meta-parasites. None are safe.

See also: The Invasion of the Zombie Animals and 7 More Zombie Animals.

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Animals
Why Tiny 'Hedgehog Highways' Are Popping Up Around London
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Hedgehogs as pets have gained popularity in recent years, but in many parts of the world, they're still wild animals. That includes London, where close to a million of the creatures roam streets, parks, and gardens, seeking out wood and vegetation to take refuge in. Now, Atlas Obscura reports that animal activists are transforming the city into a more hospitable environment for hedgehogs.

Barnes Hedgehogs, a group founded by Michel Birkenwald in the London neighborhood of Barnes four years ago, is responsible for drilling tiny "hedgehog highways" through walls around London. The passages are just wide enough for the animals to climb through, making it easier for them to travel from one green space to the next.

London's wild hedgehog population has seen a sharp decline in recent decades. Though it's hard to pin down accurate numbers for the elusive animals, surveys have shown that the British population has dwindled by tens of millions since the 1950s. This is due to factors like human development and habitat destruction by farmers who aren't fond of the unattractive shrubs, hedges, and dead wood that hedgehogs use as their homes.

When such environments are left to grow, they can still be hard for hedgehogs to access. Carving hedgehog highways through the stone partitions and wooden fences bordering parks and gardens is one way Barnes Hedgehogs is making life in the big city a little easier for its most prickly residents.

[h/t Atlas Obscura]

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Penn Vet Working Dog Center
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Stones, Bones, and Wrecks
New Program Trains Dogs to Sniff Out Art Smugglers
Penn Vet Working Dog Center
Penn Vet Working Dog Center

Soon, the dogs you see sniffing out contraband at airports may not be searching for drugs or smuggled Spanish ham. They might be looking for stolen treasures.

K-9 Artifact Finders, a new collaboration between New Hampshire-based cultural heritage law firm Red Arch and the University of Pennsylvania, is training dogs to root out stolen antiquities looted from archaeological sites and museums. The dogs would be stopping them at borders before the items can be sold elsewhere on the black market.

The illegal antiquities trade nets more than $3 billion per year around the world, and trafficking hits countries dealing with ongoing conflict, like Syria and Iraq today, particularly hard. By one estimate, around half a million artifacts were stolen from museums and archaeological sites throughout Iraq between 2003 and 2005 alone. (Famously, the craft-supply chain Hobby Lobby was fined $3 million in 2017 for buying thousands of ancient artifacts looted from Iraq.) In Syria, the Islamic State has been known to loot and sell ancient artifacts including statues, jewelry, and art to fund its operations.

But the problem spans across the world. Between 2007 and 2016, U.S. Customs and Border Control discovered more than 7800 cultural artifacts in the U.S. looted from 30 different countries.

A yellow Lab sniffs a metal cage designed to train dogs on scent detection.
Penn Vet Working Dog Center

K-9 Artifact Finders is the brainchild of Rick St. Hilaire, the executive director of Red Arch. His non-profit firm researches cultural heritage property law and preservation policy, including studying archaeological site looting and antiquities trafficking. Back in 2015, St. Hilaire was reading an article about a working dog trained to sniff out electronics that was able to find USB drives, SD cards, and other data storage devices. He wondered, if dogs could be trained to identify the scents of inorganic materials that make up electronics, could they be trained to sniff out ancient pottery?

To find out, St. Hilaire tells Mental Floss, he contacted the Penn Vet Working Dog Center, a research and training center for detection dogs. In December 2017, Red Arch, the Working Dog Center, and the Penn Museum (which is providing the artifacts to train the dogs) launched K-9 Artifact Finders, and in late January 2018, the five dogs selected for the project began their training, starting with learning the distinct smell of ancient pottery.

“Our theory is, it is a porous material that’s going to have a lot more odor than, say, a metal,” says Cindy Otto, the executive director of the Penn Vet Working Dog Center and the project’s principal investigator.

As you might imagine, museum curators may not be keen on exposing fragile ancient materials to four Labrador retrievers and a German shepherd, and the Working Dog Center didn’t want to take any risks with the Penn Museum’s priceless artifacts. So instead of letting the dogs have free rein to sniff the materials themselves, the project is using cotton balls. The researchers seal the artifacts (broken shards of Syrian pottery) in airtight bags with a cotton ball for 72 hours, then ask the dogs to find the cotton balls in the lab. They’re being trained to disregard the smell of the cotton ball itself, the smell of the bag it was stored in, and ideally, the smell of modern-day pottery, eventually being able to zero in on the smell that distinguishes ancient pottery specifically.

A dog looks out over the metal "pinhweel" training mechanism.
Penn Vet Working Dog Center

“The dogs are responding well,” Otto tells Mental Floss, explaining that the training program is at the stage of "exposing them to the odor and having them recognize it.”

The dogs involved in the project were chosen for their calm-but-curious demeanors and sensitive noses (one also works as a drug-detection dog when she’s not training on pottery). They had to be motivated enough to want to hunt down the cotton balls, but not aggressive or easily distracted.

Right now, the dogs train three days a week, and will continue to work on their pottery-detection skills for the first stage of the project, which the researchers expect will last for the next nine months. Depending on how the first phase of the training goes, the researchers hope to be able to then take the dogs out into the field to see if they can find the odor of ancient pottery in real-life situations, like in suitcases, rather than in a laboratory setting. Eventually, they also hope to train the dogs on other types of objects, and perhaps even pinpoint the chemical signatures that make artifacts smell distinct.

Pottery-sniffing dogs won’t be showing up at airport customs or on shipping docks soon, but one day, they could be as common as drug-sniffing canines. If dogs can detect low blood sugar or find a tiny USB drive hidden in a house, surely they can figure out if you’re smuggling a sculpture made thousands of years ago in your suitcase.

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