Researchers combing the rainforests of Brazil have uncovered four new species of fungi that turn ants into zombies.
Although it is not the first time the fungi has been seen affecting ants, the discovery of four distinct species in close proximity highlights the level of biodiversity in the Amazon.
Their study appears online in the journal PLoS One.
The research, led by Assistant Professor David Hughes of the University of Pennsylvannia, identified and described the parasitic fungus Ophiocordyceps unliateralis living on four species of carpenter ant (Camponotini sp.) in the Zona da Mata region of Brazil.
Ants become infected when they come into contact with spores released by the fungus. Within a week the ant enters a zombie-like state.
“This so-called zombie or brain-manipulating fungus alters the behaviours of the ant host, causing it to die in an exposed position, typically clinging onto and biting the adaxial surface of shrub leaves,” the study authors write.
The fungus then grows out of the head of the ant, releasing spores into the air, which rain down onto unsuspecting ants and the forest floor.
In 2009, Hughes led a team of researchers studying zombie-ants in Indonesia. They found the infected ants consistently attached to leaves 25 centimetres above the ground in an environment with 95 per cent humidity – perfect conditions for the fungus to grow.
In the current study, Hughes and colleagues found each species of fungus was different in size and shape, and adapted to live only in one particular species.
Two of the species of fungus have also adapted to grow secondary spores, doubling their chances of finding a new host.
Limited impact on species
Dr Steve Shattuck, an entomologist with CSIRO Ecosystem Sciences, says there are records of the fungus existing in Australia, but its range is limited to tropical regions of Australia.
“It’s hard to find. Exactly how common it is, who knows? But obviously if it was too common it would kill all the ants and then go away,” he said.
He says while there are many examples of ants living in symbiotic relationships with other organisms such as bacteria and other types of fungi, none are as invasive as Ophiocordyceps.
And despite the fungus’ ability to destroy a whole colony of ants, Dr Shattuck says its potential for use in pest control is very limited.
“What the paper found was that the fungi were species specific,” he said. “So unless one of ants was your pest it doesn’t do you any good.”
It also means the possibility that the fungi will turn our 2000-odd species of Australian ant into a zombie army is highly remote.
“It would be very unlikely,” Dr Shattuck said. “If the fungi did get here it wouldn’t have anything to live on and would just die out in all likelihood.”
According to Professor Hughes’ website, his team plans to study the zombie-inducing fungus in Colombia, Guyana, Brazil, Peru, Malaysia, Papua New Guinea and Australia.