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New Study on Parasitic Wasps Sounds Like the Plot of a Horror Movie

Wasps: now with parasitic viral sidekicks.
​Ladybird protecting multiple parasites like a total sucker. Image: coniferconifer.

The natural world is packed with delightfully grotesque behaviors, from sexual cannibalism to the mind control powers of T. gondii. But a newly discovered parasitic relationship, described in a study p​ublished today in the Proceedings of the Royal Society B, may genuinely have them all beat.

The study focuses on Dinocampus coccinellae, a parasiticwasp species that uses the lady beetle (aka ladybug or ladybird) as a makeshift incubator, bodyguard, and babysitter. The wasp implants its egg into the beetle's underbelly, leaving the larva to eat away at its host's own eggs, organs, and fat tissue.

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When the larva is ready to hatch, it tunnels out through the beetle's insides, and sets up shop in a cocoon underneath its host. This process paralyzes the beetle, and causes it to develop an e​erie twitch that scares off predators.

A video of the ladybird's disconcerting, defensive twitches. Credit: YouTube/mozygish.

About a week later, the wasp pupae emerges from the cocoon and abandons its zombified, disemboweled host, free to repeat the process on some other poor, unsuspecting lady beetle.

By itself, this scenario would be worthy of a Guillermo del Toro horror flick, but it actually gets much worse (or better, depending on which side you're rooting for). The study's authors, led by parasitologist ​Nolwenn Dheilly of Stony Brook University, wanted to know how the wasp larva managed to control the beetle's brain during the paralysis stage.

They discovered that there is a third parasite in play: an RNA virus that is introduced by the wasp when the egg is implanted. In this way, the wasp delivers a viral payload to take over the beetle's brain, in addition to housing its egg inside the host. It's a bizarre, collaborative arrangement that has never before been observed.

"Other species of parasitoid wasps are associated with viruses that participate in the host's immunosuppression, developmental arrest, and assist the developing larva," Dheilly told me over email. "However, this is the first observation of a parasite using a virus to manipulate the behavior of its host."

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"Actually this is the first evidence of any parasite-associated microorganism involved in behavior manipulation," she added.

In this way, the D. coccinellae paralysis virus (DcPV) is essentially a parasite within a parasite, uniquely adapted to support the wasp's brainwashing endeavors. As the larva feeds off of its host's tissues, the virus actively replicates and invades the beetle's nervous system, Dheilly told me.

"After about 20 days, the larva extracts itself from the lady beetle abdomen and ties a cocoon between its legs," she said. "The lady beetle is then paralyzed, most probably because of a virus-induced neurodegenerescence, and acts as a bodyguard that protects the pupae against predators such as crickets or jumping spiders."

"In the cocoon, the wasp will pupate into an adult wasp, and after a week it will fly away," she added. "The lady beetle recovers, and abandons the empty cocoon."

Yes, you read that right: about a quarte​r of the lady beetles subjected to this horrific experience end up walking away from it. Some even live through​ multiple parasitic invasions. These resilient beetles are able to bolster their immune systems enough to permanently kick the mind-controlling virus out of their brains.

"Jane, snap out of it!" Image: Charlie Barnes.

"In recovering lady beetles, the virus had been eliminated and we observed traces of neuron regeneration in the nervous tissue," said Dheilly.

The sheer weirdness of this exploitative partnership, combined with its utter novelty, implies that there is a lot more at play in parasitic relationships than previously assumed. Dheilly and her colleagues plan to build on their study—which is appropriately entitled "Who is​ the puppetmaster?"—by seeking out insect-virus tag teams in other species, as well as delving deeper into the mechanics of the D. coccinellae trio.

"We would like to break down the system and study the different interactions independently from each other: The virus and the wasp, the virus and the lady beetle, and the lady beetle and the wasp," she told me. "This will provide crucial information on the symbiotic interaction between the wasp and the virus, and also on the respective roles of the wasp and the virus in triggering the behavior manipulation."

It will be interesting to see what future studies into this behavior reveal. But until then, it's enough to digest this new platter of weirdness that nature has served up, and to hope that those poor, ravaged beetles have some kind of ladybird support group to console them.