5 Parasites That Plague Other Parasites

Can you be a host and a parasite at the same time? The answer is a stomach-turning “yes.” Like grotesque Matryoska dolls, naturalists sometimes find parasites within parasites.

1. "ANTI-ZOMBIE FUNGUS" FUNGUS 

Brain-controlling parasites sound like the villains of a cheap sci-fi movie. But make no mistake: They’re all too real.  Just ask an ant.

Members of the Ophiocordyceps fungal genus have evolved to attack a specific type of ant. In order to grow properly, these fungi need a patch of earth that meets several very specific conditions (perfect temperature, humidity, distance from the ground, etc.). But it needs transportation to get there.

When the right Ophiocordyceps encounters the right host, things get weird fast. Fungal spores infect the ant's brain, and literally control its mind. It drives the ant to prime Ophiocordyceps real estate, where the ant bites down onto a leaf and dies. After the ant expires, thread-like filaments spread through its body. These soon breach the exoskeleton and, before long, new Ophiocordyceps spores rupture the ant’s head, ready to repeat this cycle of mayhem.

A third player in this Jacobean drama was revealed in 2012. A team led by Penn State biologist David Hughes discovered a second fungus—one which saves countless ants from mental enslavement. This currently nameless organism turns the tables and makes a host out of Ophiocordyceps itself. “The hyperparasitic fungus effectively castrates the zombie-ant fungus so it cannot spread its spores,” Hughes says.

2. DOUBLE-PORED DOG TAPEWORM (DIPLYDIUM CANIUM)

Man’s best friend is a four-legged flea magnet. Multiple species target canines, with the aptly named dog flea (Ctenocephalides canis) being the most widespread. It also can infect the skin of felines and—occasionally—humans. 

Apart from being annoying, the flea can be a Trojan horse for a far more dangerous parasite. Larval fleas frequently eat the eggs of double-pored dog tapeworms. These hatch into cysticercoids (tapeworm larvae), which bide their time inside the flea’s intestines while the arthropod grows up. Should a dog, cat, or human accidentally swallow an infected flea, the cysticercoid will break out and develop into a mature, full-length tapeworm. Upon becoming sexually active, this segmented creature releases eggs that the host later poops out. Fleas then gobble them up, and the cycle repeats itself.

3. ASAPHES CALIFORNICUS WASP

Any parasitic organism that invades another one is called a “hyperparasite.” And then we have A. californicus, which counts as a “hyper-hyperparasite.” Pea aphids (Acyrthosiphon pisum) are red and green sap-suckers that can be found throughout much of Europe and North America. Commonly regarded as pests, the bugs are vulnerable to Aphidius smithi: a wasp whose larvae live inside them and mooch off the aphids’ food supply.

Life isn’t exactly a cakewalk for these freeloaders, however. Aphidius smithi larvae can themselves become infected by the larvae of another wasp: Alloxysta victrix. Those, in turn, will sometimes harbor A. californicus larvae. So, to recap, a single aphid might well have a parasite that has a parasite that has a parasite. Isn’t nature delightful?

4. DACTYLARIA THAUMASIA FUNGUS

As the old cliché goes, the enemy of your enemy is your friend … sometimes. Farmers the world over dread an outbreak of the cereal cyst nematode (Heterodera avenae). Under the right conditions, it’ll colonize wheat, oats, barley, and other profitable crops. Once inside, the nematode has a nasty habit of knotting up roots, which may ultimately kill the host. Economically, the consequences are often dire: In 1988, this organism single-handedly caused wheat productivity in Pakistan to drop by an estimated 15 to 20 percent.

Yet in our war against the menace, we’ve found an unlikely ally. Dactylaria thaumasia is a parasitic fungi that severely weakens nemotodes, putting a check on their destructive talents. Hence, as a precautionary measure, many crop-growers now plant the fungus directly into their soil.  

5. WOLBACHIA BACTERIA

This is another set of cascading parasitic relationships. From the onset, this bacterium stacks the deck in its favor. Wolbachia is a genus of microscopic marauders that plagues female wasps, which inject their larvae into young botflies (themselves parasitic). The bacteria arrest the wasp’s ability to produce male offspring. By making sure that wasp populations are kept disproportionately female-heavy, Wolbachia is able to maximize the number of larvae it can infect.

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How Bats Protect Rare Books at This Portuguese Library
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Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

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Honey Bees Can Understand the Concept of Zero
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The concept of zero—less than one, nothing, nada—is deceptively complex. The first placeholder zero dates back to around 300 BCE, and the notion didn’t make its way to Western Europe until the 12th century. It takes children until preschool to wrap their brains around the concept. But scientists in Australia recently discovered a new animal capable of understanding zero: the honey bee. According to Vox, a new study finds that the insects can be taught the concept of nothing.

A few other animals can understand zero, according to current research. Dolphins, parrots, and monkeys can all understand the difference between something and nothing, but honey bees are the first insects proven to be able to do it.

The new study, published in the journal Science, finds that honey bees can rank quantities based on “greater than” and “less than,” and can understand that nothing is less than one.

Left: A photo of a bee choosing between images with black dots on them. Right: an illustration of a bee choosing the image with fewer dots
© Scarlett Howard & Aurore Avarguès-Weber

The researchers trained bees to identify images in the lab that showed the fewest number of elements (in this case, dots). If they chose the image with the fewest circles from a set, they received sweetened water, whereas if they chose another image, they received bitter quinine.

Once the insects got that concept down, the researchers introduced another challenge: The bees had to choose between a blank image and one with dots on it. More than 60 percent of the time, the insects were successfully able to extrapolate that if they needed to choose the fewest dots between an image with a few dots and an image with no dots at all, no dots was the correct answer. They could grasp the concept that nothing can still be a numerical quantity.

It’s not entirely surprising that bees are capable of such feats of intelligence. We already know that they can count, teach each other skills, communicate via the “waggle dance,” and think abstractly. This is just more evidence that bees are strikingly intelligent creatures, despite the fact that their insect brains look nothing like our own.

Considering how far apart bees and primates are on the evolutionary tree, and how different their brains are from ours—they have fewer than 1 million neurons, while we have about 86 billion—this finding raises a lot of new questions about the neural basis of understanding numbers, and will no doubt lead to further research on how the brain processes concepts like zero.

[h/t Vox]

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