How a Scientist's Blunder Let Loose Stomach-Bursting Parasites on a Remote Island

A mistake by an ecologist led to the release on a remote island in Finland of a Russian doll set of stomach-bursting parasites.
Ilkka Hanski, an ecologist, introduced Glanville Fritillary butterflies (Melitaea Cinxia) to Sottunga, in order to see how they would survive in harsh environments.

He didn't know that there would be a trio of nested parasites along with them, two parasites living in another parasite and some butterflies.

The stomach-bursting parasites were borne from the Glanville fritillary butterflies. (Arterra/Getty Images

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These parasites, Hyposoter and Hyposoter hyposoter horticola's larvae, feed on the Glanville caterpillars. They are then injected from the inside. The larvae spin a cocoon around their host to reproduce.

H. horticola is home to two more parasite species. The second parasitic wasp, Mesochorus cf., is called a "hyperparasitoid". stigmaticus. Wolbachia pipientis is the third species, which makes H.horticola more vulnerable to M. stamius.

H. horticola kills caterpillars if all three stowaways have been aboard the host caterpillar. The hyperparasite burrows in 10 days, eating the bacteria-ridden flesh of first wasp parasite, then the carcass of caterpillar.

All four species are still alive 30 years after they were introduced.

Researchers published a new study July 7th in the journal Molecular Biology. They analyzed H. horticola's genetics and its bacterium to discover how these parasites managed this amazing feat.

Anne Duplouy was the principal author of the study. She stated that the fragile foothold of the butterflies on the island and the many instances of them near-elimination are "a classic story of loss of biodiversity".

After hatching, the parasitic wasp larvae consume the tobacco hornworm caterpillar. (Jim Lane/Getty Images).

According to Duplouy, an evolutionary biologist at Lund University, Sweden, Glanville butterflies only eat two types of meadow plants as caterpillars. This leaves the species vulnerable for sudden changes in their environment.

She said that if these meadows become too overgrown, then "bushes and trees will take over, and the host plants will go extinct under tree cover."

Glanville caterpillars can also be affected by extreme climatic events like drought. This can cause them to wake up too early from their diapause, a state of suspended animation that some embryos of animals enter to survive in harsh environments.

Duplouy explained to Live Science that if the drought happens in the fall, when the caterpillars awake from their diapause they will starve. The population will plummet because their host plants are unable to grow under severe drought conditions.

Despite many near-extinction events, the butterflies survived. This is due to their remarkable genetic diversity, which is due to the diversity of the individuals who were introduced to the island.

Parasites are just as resilient as their butterfly hosts. Duplouy cites two reasons why they are surviving. Firstly, Sottunga may have a butterfly population that is isolated from other species on the archipelago. However, its wasp parasites remain.

M. stigmaticus and H. horticola are both superior butterflies flyers, with H. horticola being able to surf in strong winds. According to their surveys, gusts can even transport individual H. horticola wasps north of Sottunga to previously unknown islands.

H. horticola is a wasp that has an extremely efficient reproductive strategy.

"The butterfly will lay its eggs in 50-200 egg clutches. Duplouy stated that research shows that wasps can find all of these butterfly egg nests in the field.

"One female parasitoid will travel around the field to check on the development of the butterflies eggs every day. The parasitoid will lay its eggs in the intact butterfly eggshell when the larvae are ready to hatch. It is probable that the wasp will also continue to exist as long as there is a butterfly.

The hyperparasitoid M. stamticus wasps aren't as efficient flyers than their H. horticola hosts and are therefore less widely distributed on the islands around Sottunga. They have turned to inbreeding for survival.

Researchers believe that the accidental introduction of parasites is a fascinating case study. However, it also serves as a warning to other endangered species and their species before any attempts to restore them to a new environment.

Parasitoid wasps are used as pest control in agriculture. However, they are well-known by humans. A more obscure species could have caused havoc in the new environment.

Duplouy stated that despite the remarkable survival of the butterflies, and their parasitoids so many years ago, population crashes due to sudden droughts are likely to get worse as climate change intensifies its effects.

"We are concerned for the Sottunga population, for the butterfly's parasitoids and for their habitat. She said that drought events are more frequent in recent years and that land-based population crashes have become more severe.

"The south Sottunga population, in Fgl has gone extinct a few years ago. Sottunga has only been a small population for many decades now. We fear that we may see the end of it soon. It would be a shame for it to go after so many years of perseverance.

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Live Science originally published this article. You can read the original article here.