For fans of “The Last of Us,” the terrifying concept of a parasitic fungus turning hosts into mindless creatures is chillingly familiar. While the HBO series and video game dramatize this scenario, the real-life inspiration—a group of fungi known as Cordyceps and its relatives like Ophiocordyceps—is just as fascinating, albeit on a much smaller scale. Now, a remarkable discovery in ancient amber reveals that these “zombie” fungi were terrorizing insects as far back as the age of dinosaurs.
Ancient Discovery Unearthed in Cretaceous Amber
An international team of researchers has announced the discovery of two previously unknown species of parasitic fungi preserved in 99-million-year-old amber fossils. These incredibly rare specimens, dating back to the Cretaceous period, offer a unique window into the deep evolutionary past of these complex host-parasite relationships.
The discovery, led by Yuhui Zhuang of China’s Yunnan University, centers on two insects – a fly and an ant pupa – trapped in amber from northern Myanmar. These fossils represent some of the oldest known records of fungi infecting animals. The findings were published in the prestigious journal Proceedings of the Royal Society B.
Key Fossils: A fossilized fly and an ant pupa.
Age: Approximately 99 million years old (Cretaceous Period).
Location: Amber from northern Myanmar.
Significance: Among the oldest records of animal-pathogenic fungi.
The researchers used advanced techniques, including optical microscopes and micro-computed tomography (a 3D X-ray imaging method), to meticulously examine the intricate details of the fossilized fungi and their insect hosts. The amber specimens themselves were procured before 2017, predating the recent conflicts in Myanmar, ensuring their ethical acquisition.
Unusual Infections: Glimpses of Ancient Parasitism
The detailed analysis revealed that both newly discovered fungi belong to the genus Ophiocordyceps, known today for species often called “zombie-ant fungus.” These modern fungi are infamous for their ability to manipulate an insect host’s behavior, driving it to a location optimal for fungal spore dispersal before erupting from its body.
However, the ancient infections showed surprising variations compared to modern Ophiocordyceps:
The fossilized fly, infected with the fungus now named Paleoophiocordyceps ironomyiae, was captured at a late stage, with the fungal fruiting body emerging from its head. Yet, unlike the smooth, swollen tips typical of many modern species, this ancient fungus’s fruiting body was unexpanded and textured.
Even more unusual was the ant pupa, infected with Paleoophiocordyceps gerontoformicae. The fungus did not emerge from the head, but instead erupted from the metapleural gland – a part of the ant that secretes antimicrobial compounds. This emergence point has never been observed in any known living Ophiocordyceps species.
These distinct morphological traits confirmed that researchers were indeed looking at two species previously unknown to science.
Tracing the Evolutionary Roots of Zombie Fungi
By comparing the structures of these ancient fungi to modern Ophiocordyceps species and using DNA data from living relatives, the team constructed a phylogenetic tree – a map of the genus’s evolutionary history. This analysis provided valuable insights into when these newfound species diverged and the overall timeline of Ophiocordyceps evolution.
The study suggests that the Ophiocordyceps genus originated surprisingly early, during the beginning of the Cretaceous period. The first known hosts were likely beetles. Over millions of years, by the mid-Cretaceous, the fungi diversified to infect a wider variety of insects, including butterflies, moths, bees, and ants. Researchers hypothesize that a boom in the diversity and abundance of insect species during this era likely fueled the rapid emergence of new Ophiocordyceps species.
Understanding the evolutionary journey of parasitic fungi has historically been challenging due to the scarcity of ancient specimens. As Edmund Jarzembowski, a co-author from London’s Natural History Museum, noted, “It’s fascinating to see some of the strangeness of the natural world that we see today was also present at the height of the age of the dinosaurs.”
These extraordinary amber fossils provide a rare and crucial glimpse into the ancient origins and early diversification of these highly specialized and adaptable fungal pathogens, showing that complex parasitic relationships have been a part of Earth’s ecosystems for vast stretches of time.
