The newborn wasp larva forces the caterpillar to guard itself, from the body of which it has just “hatched”
No, this is not a horror movie. And not a voodoo cult. And not even banal hypnosis. Science fiction is also not drawn, because this is the data of biologists respected in the scientific community. So, maybe nature has come up with its own special type of biological weapon?
Many unusual facts are known about the strange behavior of animals attacked by parasites or simply deceived. For example, worms force grasshoppers to drown in water, and ants make them easy prey for birds, flies force crickets to stop trilling, and butterflies force ants to carry their offspring.
In very many cases, biologists have not yet been able to figure out how the parasite affects its host. Although it is more or less clear what happens if the parasite settles in his body. It changes various chemical reactions inside the host's organism, which naturally affects the behavior of the "attacked" one. Scientists suggest that even a person is subject to such an influence.
But how do the parasitic wasps of the genus Glyptapanteles manage to control caterpillars after they have left their body? Mystic? Hardly. There must be some scientific explanation.
However, everything in order. Scientists from the University of Amsterdam (Universiteit van Amsterdam - UvA) and the Brazilian Federal University of Visosa (Universidade Federal de Viçosa) have found that parasites are able to manipulate their host from a distance and thereby increase their chances of survival by almost two times.
The female wasp finds the moth caterpillar Thyrinteina leucocerae and lays about 80 eggs directly into the body of an unsuspecting victim.
Insect larvae develop inside the host, feeding on the fluid circulating in its body. Then they gnaw their way out, fix themselves on a nearby branch or leaf and create a cocoon around themselves.
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As a rule, in such situations, the owner dies immediately. But this, apparently, is not enough for wasps. And here the fun begins.
The still living caterpillar behaves as if the larvae still control its behavior. Instead of continuing its peaceful existence (going to eat, for example), the moth remains in place and arches over the cocoon, protecting it from outside encroachments.
In fact, the zombie caterpillar remains alive throughout the wasp pupation stage. Thyrinteina leucocerae dies almost simultaneously with the "hatching" of adult insects.
“We don't know exactly what is killing the former hosts of the parasites, but it certainly has something to do with the end of the pupal stage in wasps,” says one of the researchers, Dr. Arne Janssen.
To confirm the hypothesis of caterpillar manipulation by wasps, entomologists conducted the following experiment in laboratory conditions.
Scientists have allowed wasps to infect caterpillars with larvae. Then, when the “newborns” emerged from the bodies of the moths and formed cocoons, they separated part of the caterpillars and replaced them with healthy ones. And so that they would not "run away", they were fixed on the stem with caterpillar glue.
Then "on the scene" there was a bug, which hunts wasp cocoons in the wild. It turned out that 17 out of 19 infected moths, when a bug appeared, began to shake their heads in all directions and, in the end, shook the predator off the branch or put it to flight.
At the same time, uninfected individuals did not notice the scutellor, even if he climbed on them. See this
video.
To test whether this behavior affects the survival of wasp cocoons, biologists placed 400 infected caterpillars on guava and eucalyptus trees that grow on the campus of a Brazilian university. After about a day, the larvae were supposed to leave the bodies of the owners. Once the cocoons were fixed on nearby leaves and branches, the researchers removed half of the "guards."
As a result, the cocoons that were protected by zombie caterpillars were almost twice as many as those that were unattended. All numbers and graphs can be found in the article
published in the open access in PLoS ONE magazine.
It is now clear that the caterpillars are not getting any benefit from the wasps. But it is still unclear how the parasites manage to control the moths.
“We assume that several of the laid wasp eggs sacrifice themselves to help everyone else survive,” Janssen summarizes in a press release.
University of Amsterdam.
Dissection of dead caterpillars showed that one or two eggs remain in the body of the moths, which, apparently, control the hosts during the pupation period of the rest of the individuals.
It is said that even Darwin believed that the existence of such parasites as Glyptapanteles contradicted one of the central tenets of natural theology, which considers the study of nature as a way to demonstrate the good intentions of God. He could not convince himself that God could create insects that feed on the bodies of living caterpillars.
But how many more unusual things are hidden in the animal world! Perhaps, if biologists continue in the same spirit, then there will be enough for tens and even hundreds of chilling films.