Mushrooms turn ants into zombies to control ants, to kill ants around the nest

(aahoc.tv) - A parasitic fungus that has to kill hosts as ants, outside the nest of ants to be able to reproduce and infect fungal diseases, manipulate the ants its victims die in the The neighborhood of the nest to ensure continuous supply of potential hosts , according to researchers at Penn State and colleagues at the Vicosa Federal University of Brazil.

Previous research has shown that the fungus Ophiocordyceps camponoti-rufipedis is known as the " antsome fungus" (zombie ant fungus) , controlling the behavior of worker ants of wood-chisel ants - Camponotus rufipes - to die and corpses attached to the leaves under the canopy of the tropical forest, the study's lead author, Dr. Raquel Loret, a research entomologist at Penn State College of Agricultural Sciences, notes.

'After climbing the tree and biting the leaf veins or leaf edges on the underside of the leaves, the fungal ants die, still sticking to the leaf after death, this is where they will become a platform. mushroom development ' , Loreto said.

Mushrooms grow on a stalk, called a substrate (stroma) , protruding from the ant's body. On the stroma, a large circular structure called ascoma (spore pocket) is produced on the substrate. The fungal spores grow inside the sporangia and fall to the forest floor below, where they can infect ants out of the nest looking for food.

The reproductive activity of this fungus must take place outside the ants partly because of the social immunity of ants, which is the act of ant colonies taken to avoid spreading the disease, co-author of the study. , assistant to professor of entomology and biology at Penn State, David Hughes said.

'Previous studies conducted in the laboratory show that social immunity is an important property of insect society, especially against ants,' Hughes said. 'This is the first time we have seen evidence of ants in the wild in nature'.

The researchers examined social immunity by placing 28 ants killed by fungi into two ant colonies - 14 ants into a living ant nest and 14 ants into the nest without ants. They found that the fungus was not fully developed in any of these 28 bodies. In a living ant nest, 9 out of 14 fungal infections have disappeared, perhaps spared by ants in an effort to prevent the disease from spreading.

"Very good ants cleanse their nests to prevent disease ," Hughes said. 'But we also found that this parasitic fungus did not grow to the proper stage to spread within the nest whether or not it was there . This happens because of space and because the climate in the ants does not allow the fungus to complete its development. '

Next, the researchers began recording the prevalence of ants in the study area at the research station Mata do Paraíso, in southern Brazil. After marking and searching for 22 cross sections covering 16,988 square miles, they discovered 17 ant colonies with fungal infections attached to the leaves above the nest, indicating a prevalence of fungi at 100% scale. ant populations.

In more detail, in a 12-month survey of four of these groups, scientists assessed the parasitic pressure by mapping the exact locations of ants dying from fungi. and search around trails near the ant nest.

'We have limited the survey around the ant area because this is the area where ants have to go through and return to the nest , ' Loreto said. 'To better understand how ants find their way we have drawn a 3D map of the trails formed by ants, and this allows us to determine the location of new potential host ants. , that could be ants on the way to find food ".

By measuring the position of worker ants and redrawing these positions related to ants, researchers have shown that fungal ants have died on the ant's 'threshold' .

'What the basic destructive fungi create is a sniper path that ants (the mushroom's future host) must pass ,' Mr Hughes said. ' The parasitic fungi don't need to. mechanisms must be developed to overcome the social immunity that ants have in the ants, and this helps to ensure a constant amount of sensitive hosts. '

Although the ant nesting rate is high and the long-term survival of the fungus over time, the researchers did not observe which ants were wiped out, showing the function of parasitic fungi as a condition. prolonged but acceptable for ants.

'We think this parasitic fungus can be described as a' chronic disease ', which in humans can be controlled but cannot be cured , ' Loreto concluded.