Ancient Fungal Parasite of Ants Found Preserved in Baltic Amber
In a paper published this month in the journal Fungal Biology, a duo of paleontologists from the United States and France described a new genus and species of ancient parasitic fungus found in a piece of 50-million-year-old amber from Europe’s Baltic region.
The newly-described species, named Allocordyceps baltica, is the oldest known fossil fungus of an ant.
“It’s a mushroom growing out of a carpenter ant (tribe Camponotini),” said Professor George Poinar Jr., a researcher in the Department of Integrative Biology at Oregon State University.
“Ants are hosts to a number of intriguing parasites, some of which modify the insects’ behavior to benefit the parasites’ development and dispersion.”
“Carpenter ants seem especially susceptible to fungal pathogens of the genus Ophiocordyceps, including one species that compels infected ants to bite into various erect plant parts just before they die.”
Doing so puts the ants in a favorable position for allowing fungal spores to be released from cup-shaped ascomata — the fungi’s fruiting body — protruding from the ants’ head and neck. Carpenter ants usually make their nests in trees, rotting logs and stumps.
Allocordyceps baltica belongs to the fungi order Hypocreales and shares certain features with Ophiocordyceps, but also displays several developmental stages not previously reported.
“We can see a large, orange, cup-shaped ascoma with developing perithecia — flask-shaped structures that let the spores out — emerging from rectum of the ant,” Professor Poinar said.
“The vegetative part of the fungus is coming out of the abdomen and the base of the neck.”
“We see freestanding fungal bodies also bearing what look like perithecia, and in addition we see what look like the sacs where spores develop.”
“All of the stages, those attached to the ant and the freestanding ones, are of the same species.”
Allocordyceps baltica could not be placed in the Ophiocordyceps genus because ascomata in those fungi usually come out the neck or head of an ant and not the rectum.
“There is no doubt that Allocordyceps baltica represents a fungal infection of a carpenter ant,” Professor Poinar said.
“This is the first fossil record of a member of the Hypocreales order emerging from the body of an ant.”
“And as the earliest fossil record of fungal parasitism of ants, it can be used in future studies as a reference point regarding the origin of the fungus-ant association.”
George Poinar & Yves-MarieMaltier. Allocordyceps baltica gen. et sp. nov. (Hypocreales: Clavicipitaceae), an ancient fungal parasite of an ant in Baltic amber. Fungal Biology, published online June 5, 2021; doi: 10.1016/j.funbio.2021.06.002