September 21, 2013
Apocalypse Now: Legend Of the Zombie Ant
Zombies. One of the most feared monsters, and the easiest to make jokes of, do in fact exist. Sure, we picture zombies as brain washed former pupils who enjoy long unhurried walks, consistently dining out with other zombies and even the intermittent struggle with door handles. Brain washed by the pathogen that infected the nearly indestructible dispatch, zombies pretty much have one behavior to fulfill – to feed. The story is not nearly as romantic for a specific species of ant that is consumed by an exceedingly refined parasitic fungi that takes control of the insects’ mind.
As hard as it must be to feel sympathy for the ant, as they tend to be a nuisance – especially fire ants in Texas – but after watching a clip on the absolutely vicious domination, you can’t help but feel a little uneasy, and somewhat sympathetic.
“Once a disciplined member of a rigidly structured society, the affected any stumbles out of its colony like the town drunkard, guided by a pathogen that has pickled its brain with a cocktail of chemicals.” Notates Matt Simon of Wired.
How does this phenomenon happen you ask? It may not be diving into a gruesome attack on the cranium of its prey, but the fungus proves effective and precise ways to hunt and latch on to its prey spreading the disease. The ant heads to the exact location where the fungus has astonishingly decided to place itself in the habitat. Scientists studying the unfortunate ant species noticed a strange promptness in their travel patterns to the fungus and back. You would think after so much catastrophic casualties, the colony would move elsewhere or avoid the area.
The ants “are manipulated to bite onto very specific locations on the underside of a leaf, the main vein of a leaf, leaves orientated north, northwest, roughly 25 cm off the ground,” said David Hughes, a behavioral ecologist at Penn State. “And all of this happens with a remarkable precision around solar noon, making this one of the most complex examples of parasite manipulation of host behavior.”
As I said earlier, the sophisticated fungus chooses its position. Hughes experimented with this idea by moving the ants out of these humid spots to drier, hotter areas where the fungus failed to grow.
Once the ant has bit into the intoxicating leaf’s vein, it stumbles off dazed and confused, tripping and contracting in uncomfortable ways until it perishes. A stalk begins to protrude through the back of its head like a growing tree. The stalk can take up to three weeks to reach its desired height before dropping its captivating spores down onto the ant’s community attaching to their exoskeletons.
Here is where the zombie ant begins to get its name. Unaware the spores have attached themselves, the ants will continue about their work within the colony. “In order to get through [the exoskeleton], the fungus builds up a pressure,” Hughes explained. “We know from studies of fungal parasites of plants, particularly rice, they can buildup a pressure inside their spore equivalent to the pressure in the wheel of a 747. So they have a massive buildup of pressure, and when that’s at a sufficient level then they blow a hole through the wall and blow all the genetic material into the ant.”
Sounds like a horrifying way to go. The ants though, redeem themselves somewhat from the spread of the fungus by noticing the zombie-like traits of the infected. The colony will then rise against the ant and throw them out. This strange host takeover doesn’t stop there though. In fact, it’s only the beginning. Scientists have found that this remarkable relationship has been happening for at least 48 million years according to fossil records of bite-scarred leaves.
“The fungus needs to transmit,” said Hughes, “and it cannot do that inside the next, because in order for any societies to work, they have necessarily evolved a prophylactic immune system, which is reliant upon behavioral defense. So they have something called social immunity. They simply stop diseases spreading inside their nest by finding the diseased individuals and moving them out.”
These psychoactive tendencies are really drawing an interest to scientists all over the world. Hughes is trying a different angle of the study by hoping to extract what kinds of chemicals the fungi are actually using in order to achieve mind-control and how it actually controls the vessel implanted in.
“We’re discovering that over half of life on Earth is parasitic,” Hughes said. “It’s the most common mode of existence in the history of life on Earth. But only a tiny minority of parasites do mind-control. And why is that? What is the push in order to control the behavior of your host?”
Perhaps it’s just another attempt at world domination.
Image Credit: Thinkstock.com