Prior posts have noted the wonderfully diverse world in which we live, and the interesting results that reflect the results of the evolution of biota. A new study shows that a fungus that attacks living ants apparently manipulates their behavior for its own benefit.
When the Ophiocordyceps unilateralis fungus strikes, an infected ant climbs to a leaf not far off the ground (often on the north-northwest side of a tree), bites into a leaf, and dies with jaws locked in place. Experiments now show that these low-hanging leaves give the fungus prime conditions for growing a spore-bearing spike out of the ant’s neck.
Researchers studied O. unilateralis’s effects on ants in a Thai forest. They found natural graveyards of dead ants, belonging to the species thought to be the fungus’s main host, clamped onto leaves not far above the ground, typically just some 25 centimeters up.
To test if this first meter above the forest floor has more fungus-friendly humidity than the zones of the tree five meters and higher, the researchers selected dead ants at an early stage of infection and moved some of the carcasses onto the forest floor and moved others high into the canopy. The fungus in ants that were relocated to the leaf litter quickly disappeared; some foragers presumably ate them, or rain just swept them away. The high canopy did not suit the fungus either; dissections of ant corpses from this locale revealed deformed fungal growth that did produce spores.
Reflecting a Goldilocks’s location, the leaves near the tree base proved to be “just right”. Forming the protruding body allows the fungus to reproduce.