Sunday, March 13, 2011

Ophiocordyceps unilateralis And Zombie Ants

Image by: Erich G. Vallery

Earlier this month, scientists David P Hughes, Simon L. Elliot , and Harry C. Evans, published an article in the online journal Plos one describing their discovery of four new species of Ophiocordyceps unilateralis, or the "Zombifying" fungus, as many of us have now come to know it.

is just one of literally hundreds of endoparasitic species of fungus belonging to the the genus Cordyceps, which can be found throughout the world, but are particularly abundant in humid areas like tropical forests. These endoparasites thrive by infecting a host animal, or in some cases other fungi, which they then begin to grow inside of and ultimately kill in order to complete their own life cycles. But what makes Ophiocordyceps unique amongst other cordyceps, is its ability to control the behavior of it's chosen host, in this case various species of ants.

Infection with these parasitic organisms begins with the host coming into contact with it's spores, which then gain access to the animals inner body cavity. As to the exact method of entry, I was unable to find a definitive answer, so I suspect it depends on the particular species of fungi you're dealing with. But what ever the method, once inside the spores continue to grow, extending fungal filaments called mycelia throughout the ants body and into it's brain.

Though the exact nature of how the plant manages to manipulate the animals behavior is unknown, it's at this point that the fungus manages to take control, driving it's host down from the canopy where the colony lives and onto the underside of leaves sprouting from the northwest side of plants growing on the forest floor where the colony forages. Once the Ant has reached this very specif destination, it is then compelled in the final moments of it's life to clamp its jaws down on the central vein of the leaf, where it will remained anchored even after it's death. This final resting place is purposely located in an ideal position to allow the fungi to continue to grow, ultimately erupting through the ants head and producing a spore pod, which eventually releases it's spores onto the forest floor below, allowing the cycle to begin once again.


Image credit: Erich G. Vallery
Source:, PLos, also posted on: Compendium oF Strange

Finally, a nice little clip from the "Planet Earth" Documentary via BBC Worldwide with a brief description of Cordyceps and some really amazing images of various insects infected by the fungus.

Posted by Youtube user:BBCWorldwide

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