48-Million-Year Fossil of Zombie Ants Unearthed

100818105730-large A 48-million-year-old fossilized leaf has revealed the oldest known evidence of a spooky predator – parasites taking control of their hosts to turn them into zombies. The macabre discovery was made by a research team led by Dr David P Hughes, from the University of Exeter, who specializes in parasites that can take over the minds of their hosts.

Scientists have been trying to track down when and where such parasites evolved. "There are various techniques, called a molecular clock approach, which we can use to estimate where and when they developed and fossils are an important source of information to calibrate such clocks," says Hughes."This leaf shows clear signs of one well documented form of zombie-parasite, a fungus which infects ants and then manipulates their behaviour."

The fungus, called Ophiocordyceps unilateralis, causes ants to leave their colonies and head for a leaf which provides the ideal conditions for the host to reproduce, where the ant goes into a 'death grip'- biting down very hard on the major vein of a leaf so that when the ant dies, its body stays put so the fungus has time to grow and release its spores to infect other ants.

After studying leaf fossils from the Messel Pit, a site on the eastern side of the Rhine Rift Valley in Hesse, Germany, Hughes and team found clear evidence of the death grip bite in a 48-million-year-old leaf specimen.

"The evidence we found mirrors very closely the type of leaf scars that we find today, showing that the parasite has been working in the same way for a very long time," says Hughes. "This is, as far as we know, the oldest evidence of parasites manipulating the behaviour of their hosts and it shows this parasitic association with ants is relatively ancient and not a recent development.

"Hopefully we can now find more fossilised evidence of parasitic manipulation. This will help us shed further light on the origins of this association so we can get a better idea of how it has evolved and spread."

Casey Kazan via the University of Exeter.

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