Rare Amber Fossils Capture ‘Zombie’ Fungus Infecting Insects During a Time When Dinosaurs Still Walked the Earth
An ant and fly from the Cretaceous period offer insights into the history of Ophiocordyceps, the fungal parasite made popular by HBO’s “The Last of Us”
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Scientists have discovered two new species of a prehistoric zombifying fungus in insect fossils preserved in amber. The 99-million-year-old specimens are some of the earliest to offer a look at how these parasites evolved alongside their hosts.
“Amber gives us this opportunity to visualize the ancient ecological relationships preserved in fossils,” says Yuhui Zhuang, a researcher at the Institute of Paleontology at Yunnan University in China and lead author of the new work, to Katie Hunt at CNN.
Zhuang stumbled upon the first fossil by accident, reports Sofia Caetano Avritzer for Science News. He was poking around in his lab’s basement when he spotted a fungus-infected ant pupa—the stage of insect development between larva and adult—preserved in amber. Zhuang and his team used optical microscopes and 3D imaging to study the fossil and spotted the fungi sprouting from the ant’s back. Then, they searched for similar fossils and uncovered a fungus-infected fly in amber.
The fungi both share similarities with the living genus Ophiocordyceps, which infects the brains of its hosts and controls their behavior. The researchers named the first species Paleoophiocordyceps gerontoformicae and the second Paleoophiocordyceps ironomyiae and described their findings in June in the journal Proceedings of the Royal Society B: Biological Sciences.
Need to know: Can the zombifying fungus infect humans?
Ophiocordyceps and similar fungi are highly specialized parasites that have evolved to infect certain insects only—so no, they can’t infect humans.
They’re two of the oldest ancestors of Ophiocordyceps known to researchers, which means the fungi were infecting insects as dinosaurs roamed the Earth. “We think [these fossils] are one of the most important evidences for the co-evolution between [insects] and Ophiocordyceps,” Zhuang adds to Science News.
Ophiocordyceps might be familiar to viewers of The Last of Us, a TV series and video game that takes place in a post-apocalyptic world ravaged by a fungal infection. The franchise’s creators were inspired by the real-life fungus and its mind-controlling effects on insects.
The way Ophiocordyceps infects its hosts is rather ghastly. The spores of the fungus penetrate the body of a creature like a fly, cicada, beetle or ant. Then, the fungus slowly takes control of the insect’s behavior. For instance, the fungus compels an ant to leave its colony and seek out a location that favors fungal growth. The ant will move to a point above ground and sink its jaws into a plant in what’s called a “death grip.” Then, once the fungus is done feeding on its host, it will explode out of the ant’s head or back and release its spores into a new set of victims.
Previous research suggests that ancestors of Ophiocordyceps originally evolved to infect beetles, and the new paper supports that idea, according to a statement from the Natural History Museum in London. But it also shows the pathogen changed to parasitize other species.
“The fossil evidence shows that the infectious fungi were already adapted to two different insect hosts 100 million years ago, an ant and a true fly,” explains Edmund Jarzembowski, a scientist at London’s Natural History Museum and study co-author, in the statement. “This suggests that the fungus made this jump to other insects as they diversified with the rise of flowering plants and new insect groups, especially moths and butterflies.”
The fossil of an infected fly is especially rare, as Conrad Labandeira, senior scientist and curator of fossil arthropods at the Smithsonian’s National Museum of Natural History who was not involved in the research, tells CNN. Today, Ophiocordyceps doesn’t often infect flies.
Parasite diversity played a key role in shaping our planet. Because their infections are lethal, it’s likely that Ophiocordyceps helped control populations of insects during the Cretaceous, as similar parasites do now.
“Even as we find a remarkable diversity of organisms entombed in amber, it’s important to remember that we really do only capture the smallest glimpse. For any given fossil ant or beetle, we can imagine all of the parasites, fungus and bacteria that such insects support,” adds Phil Barden, an evolutionary biologist at the New Jersey Institute of Technology who wasn’t involved in the new work, in an email to CNN.
Next, scientists will need to examine Cretaceous leaves for evidence of death grips to see if the prehistoric fungi had evolved to manipulate insects’ behavior during this time, says Jarzembowski in the statement.
