Crypt-keeper wasps can control the minds of 7 other species of wasp

By Michael Le Page

A recently discovered parasitic wasp appears to have extraordinary mind-controlling abilities – it can alter the behaviour of at least seven other species.

Many parasites manipulate the behaviour of their victims in extraordinary ways. For instance, sacculina barnacles invade crabs and make them care for barnacle larvae as if they were their own offspring. If the host crab is male, the parasite turns them female.

It was thought each species of parasite could manipulate the behaviour of only one host, or least only very closely related species. But the crypt-keeper wasp Euderus set is more versatile.

It parasitises other wasps called gall wasps. Gall wasps lay their eggs in plants, triggering abnormal growths – galls – inside which the wasp larvae feed and grow. Adult gall wasps chew their way out of the gall and fly off.

The crypt-keeper wasp seeks out oak galls and lays an egg inside them. The crypt-keeper larva then attacks the gall wasp larva. Infected gall wasps still start chewing their way out of the gall, but they stop chewing when the hole is still small and then remain where they are with their head blocking the exit and thus protecting the larva growing inside them – “keeping the crypt”.

How the crypt-keeper larva makes the gall wasp stop chewing at such a precise point is not clear. “I’d love to know how they do it,” says Anna Ward of the University of Iowa.

When the crypt-keeper larva turns into an adult wasp after a few days, it then chews through the head of the gall wasp to get out of the gall.

The crypt-keeper wasp, which was only described in 2017, was thought to parasitise just one species. But when Ward’s team collected 23,000 galls from 10 kinds of oak trees as part of a bigger study, they found at least 7 of the 100 species of gall wasp they collected were parasitised by the same crypt-keeper wasp. “What we found is that it is attacking different hosts that don’t seem to be closely related,” says Ward.

And there are likely many more extraordinary parasites out there. Ward thinks there are more species of parasitic wasps – most yet to be discovered – than there are species of beetle. So far 350,000 species of beetle have been described, the most of any group of animals. Parasitic wasps are small and hard to find, and hardly anyone looks for them, she says.

Journal reference: Biology Letters, DOI: 10.1098/rsbl.2019.0428

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Mind-controlling molecules (ampulexins) from wasp venom could someday help Parkinson’s patients

After being stung by a parasitic wasp, the American cockroach loses control of its behavior, becoming host to the wasp’s egg. Days later, the hatchling consumes the cockroach alive. While this is a gruesome process for the cockroach, scientists now report in ACS’ journal Biochemistry the discovery of a new family of peptides in the wasp’s venom that could be key to controlling roach minds, and might even help researchers develop better Parkinson’s disease treatments.

Scientists have long studied venoms, such as that of the wasp, seeking out novel and potent molecules to treat disease, among other applications. In the case of the enigmatic wasp Ampulex compressa, it uses its venom in a two-pronged approach against the cockroach, with an initial sting to the thorax to paralyze the front legs and a subsequent sting directly to the brain. This second sting causes the roach first to vigorously groom itself, then to fall into a state of lethargy, allowing the wasp to do whatever it wants. This immobile state resembles symptoms of Parkinson’s disease, and both may be related to dysfunction in the dopamine pathway. In this study, Michael E. Adams and colleagues wanted to identify the ingredients in wasp venom that dictate this behavior.

The researchers milked wasps for their venom and then analyzed the components using liquid chromatography and mass spectrometry. They identified a new family of alpha-helical peptides and named them ampulexins. To test their function, the team injected the most abundant venom peptide into cockroaches. Afterward, the bugs needed, on average, a 13-volt electric shock to the foot to get them moving, while an average of 9 volts sufficed prior to the injection, suggesting the peptides help the wasp immobilize its prey. Future work will focus on identifying cellular targets of ampulexins, and potentially generating a useful animal model for the study of Parkinson’s disease treatments.

The authors acknowledge funding from the United States-Israel Binational Science Foundation, the University of California, Riverside Office of Research and Economic Development and the University of California Agricultural Experiment Station.

How a Wasp Turns Cockroaches into Zombies

By Christie Wilcox

The jewel wasp depends on live cockroaches to provide crucial food for its newly hatched larvae.

To force cockroaches into submission and into a necessary torpor, the wasp has evolved a particular chemical mix that it injects into a roach’s brain to alter its behavior and metabolism.

Many other wasp species also use complex venoms to parasitize spiders, caterpillars and even wasp larvae—sometimes turning them into zombie larva defenders.

I don’t know if cockroaches dream, but i imagine that if they do, jewel wasps feature prominently in their nightmares. These small, solitary tropical wasps are of little concern to us humans; after all, they don’t manipulate our minds so that they can serve us up as willing, living meals to their newborns, as they do to unsuspecting cockroaches. It’s the stuff of horror movies, quite literally; the jewel wasp and similar species inspired the chest-bursting horrors in the Alien franchise. The story is simple, if grotesque: the female wasp controls the minds of the cockroaches she feeds to her offspring, taking away their sense of fear or will to escape their fate. But unlike what we see on the big screen, it’s not some incurable virus that turns a once healthy cockroach into a mindless zombie—it’s venom. Not just any venom, either: a specific venom that acts like a drug, targeting the cockroach’s brain.

Brains, at their core, are just neurons, whether we’re talking human brains or insect brains. There are potentially millions of venom compounds that can turn neurons on or off. So it should come as no surprise that some venoms target the carefully protected central nervous system, including our brains. Some leap their way over physiological hurdles, from remote injection locations around the body and past the blood-brain barrier, to enter their victims’ minds. Others are directly injected into the brain, as in the case of the jewel wasp and its zombie cockroach host.

Making of a zombie

Jewel wasps are a beautiful if terrifying example of how neurotoxic venoms can do much more than paralyze. The wasp, which is often just a fraction of the size of her victim, begins her attack from above, swooping down and grabbing the roach with her mouth as she aims her “stinger”—a modified egg-laying body part called an ovipositor—at the middle of the body, the thorax, in between the first pair of legs. The quick jab takes only a few seconds, and venom compounds work fast, paralyzing the cockroach temporarily so the wasp can aim her next sting with more accuracy. With her long stinger, she targets her mind-altering venom into two areas of the ganglia, the insect equivalent of a brain.

The wasp’s stinger is so well tuned to its victim that it can sense where it is inside the cockroach’s dome to inject venom directly into subsections of its brain. The stinger is capable of feeling around in the roach’s head, relying on mechanical and chemical cues to find its way past the ganglionic sheath (the insect’s version of a blood-brain barrier) and inject venom exactly where it needs to go. The two areas of the roach brain that she targets are very important to her; scientists have artificially clipped them from cockroaches to see how the wasp reacts, and when they are removed, the wasp tries to find them, taking a long time with her stinger embedded in search of the missing brain regions.

Then the mind control begins. First the victim grooms itself, of all things; as soon as the roach’s front legs recover from the transient paralysis induced by the sting to the body, it begins a fastidious grooming routine that takes about half an hour. Scientists have shown that this behavior is specific to the venom, as piercing the head, generally stressing the cockroach, or contact with the wasp without stinging activity did not elicit the same hygienic urge. This sudden need for cleanliness can also be induced by a flood of dopamine in the cockroach’s brain, so we think that the dopaminelike compound in the venom may be the cause of this germophobic behavior. Whether the grooming itself is a beneficial feature of the venom or a side effect is debated. Some believe that the behavior ensures a clean, fungus- and microbe-free meal for the vulnerable baby wasp; others think it may merely distract the cockroach for some time as the wasp prepares the cockroach’s tomb.

Dopamine is one of those intriguing chemicals found in the brains of a broad spectrum of animal life, from insects all the way to humans, and its effects are vital in all these species. In our heads, it’s a part of a mental “reward system”; floods of dopamine are triggered by pleasurable things. Because it makes us feel good, dopamine can be wonderful, but it is also linked to addictive behaviors and the “highs” we feel from illicit substances like cocaine. It’s impossible for us to know if a cockroach also feels a rush of insect euphoria when its brain floods with dopamine—but I prefer to think it does. (It just seems too gruesome for the animal to receive no joy from the terrible end it is about to meet.)

While the cockroach cleans, the wasp leaves her victim in search of a suitable location. She needs a dark burrow where she can leave her child and the zombie-roach offering, and it takes a little time to find and prepare the right place. When she returns about 30 minutes later, the venom’s effects have taken over—the cockroach has lost all will to flee. In principle, this state is temporary: if you separate an envenomated roach from its would-be assassin before the larva can hatch and feed and pupate, the zombification wears off within a week. Unfortunately for the envenomated cockroach, that’s simply too long. Before its brain has a chance to return to normal, the young wasp has already had its fill and killed its host.

The motor abilities of the roach remain intact, but the insect simply doesn’t seem inclined to use them. So the venom doesn’t numb the animal’s senses—it alters how its brain responds to them. Scientists have even shown that the stimuli that normally elicit evasive action, such as touching the roach’s wings or legs, still send signals to the animal’s brain; they just don’t evoke a behavioral response. That’s because the venom mutes certain neurons so they are less active and responsive, leading to the roach’s sudden lack of fear and willingness to be buried and eaten alive. This venom activity requires toxins that target GABA-gated chloride channels.

GABA, or γ-aminobutyric acid, is one of the most important neurotransmitters in insect—and human—brains. If neuron activity is a party, then GABA is a wet blanket; it dampens a neuron’s ability to be triggered through activation of chloride channels. When chloride channels open, they allow negative chloride ions to flow. Because these ions like to hang out with positive ions, if these channels are open when a sodium channel happens to open, chloride ions can cross the membrane at almost the same pace as sodium ions, making it harder for the sodium ions to start the domino cascade that is neuron signaling. Even though a neuron receives the “go” command, the action potential is stopped in its tracks. GABA isn’t a complete inhibitor, however—the chloride channels can’t wholly keep up with the sodium channels, so a strong stimulus can overcome the dampening effect. This dulling system is what the wasp co-opts to make the cockroach do her bidding. Her venom is packed with GABA and two other compounds that also activate the same chloride receptors, β-alanine and taurine. These also work to prevent the reuptake of GABA by neurons, prolonging the effect.

Although these venom compounds can cut the brain activity that would make her prey flee, what they can’t do is make their way to the right parts of the cockroach brain by themselves. That’s why the wasp has to inject them directly into the cockroach’s ganglia. Fortunately for her, in a convenient quirk of nature, the same venom that zombifies roach brains works like magic to produce the transient paralysis needed to line up the cranial injection. GABA, β-alanine and taurine also temporarily shut down motor neurons, so the wasp only needs one venom to complete two very different tasks.

With her prey calm and quiescent, the wasp can replenish her energy by breaking the roach’s antennae and drinking some sweet, nutritious insect blood. Then she leads her victim to its final resting place, using what remains of an antenna as an equestrian uses the reins on a bridle. Once inside her burrow, she attaches one egg to the cockroach’s leg, then seals her offspring and the roach in.

Fresh meals

As if the mind manipulation wasn’t bad enough, the wasp’s venom has one final trick. While the roach awaits its inevitable doom, the venom slows down the roach’s metabolism to ensure it lives long enough to be devoured still fresh. One way metabolism can be measured is by how much oxygen is used up over time, as all animals (including us) use oxygen in the process of creating energy from food or fat stores. Scientists have found that oxygen consumption by cockroaches that have been stung is much lower than that of their healthy roach friends. They thought this might be the result of the reduced movement of the complacent victims, but even when paralysis is induced by using drugs or severing neurons, the stung cockroaches live longer. The key to the prolonged survival seems to be hydration. How exactly the venom acts to keep a roach hydrated is not known, but it ensures that when the wasp larva hatches from its egg, its meal is ready to eat. And soon enough after that, a new wasp emerges from the burrow, leaving the roach carcass behind.

Jewel wasp venom is only one example of neurotoxic venom taken to the extreme. There are more than 130 species in the same wasp genus, including the newly described Ampulex dementor (named for the soul-sucking guards of the magical prison Azkaban in the Harry Potter series). Ampulex belongs to a very large and diverse group of wasps, numbering at least in the hundreds of thousands of species, which are known for some serious mental manipulation. All have a macabre life cycle: as adults, they feed like other wasps and bees, but as larvae, they must feed off other animals. They’re not quite independent, not quite parasites—they’re parasite-ish, or as scientists call them, parasitoids.

Cockroaches are not their only targets; there are parasitoid wasps that lay their eggs in spiders, caterpillars and ants. The temperate Northern Hemisphere wasp Agriotypus will dive underwater to attach her eggs to caddis fly larvae and can remain submerged for up to 15 minutes to accomplish her task. The brave Lasiochalcidia wasps of Europe and Africa throw themselves into the nightmarish jaws of an ant lion, pry them apart and insert their eggs into its throat. There are even wasps called hyperparasitoids that parasitize other wasps like themselves, such as Lysibia species of Europe and Asia, which will sniff out caterpillars parasitized by fellow parasitoid wasps in the genus Cotesia and lay eggs in the freshly pupated wasp larvae. In some cases, multiple wasp species parasitize one another, leading to a Russian doll of parasitic interactions.

And to ensure their safe passage from larva to adulthood, these wasps often gain more than just a meal from their hosts. One of them turns its caterpillar hosts into undead bodyguards that will defend pupating young wasps that just ate through its body. Another species’ larva forces its spider host to spin it a deformed but durable web to protect its cocoon just before killing the arachnid.

Whereas the wasps in this unusual family may have perfected the art of mind control, there are other venomous species whose toxins alter mental states. There are even species whose neurotoxic compounds get through our own blood-brain barrier, a feat that no wasp venom can yet achieve. But unlike cockroaches, we Homo sapiens have a strange affinity for substances that mess with our minds. Although the roaches run from those that would twist their brains, some people are willing to pay upward of $500 for a dose of venom to have a similar experience.