Return of the brain-controlling zombie-ant parasitic fungi

neurophilosophy — Thu, 03 Mar 2011 08:25:37 +0000

A dead ant infected with a parasitic Cordyceps fungus (David P. Hughes).

A team of entomologists working in the Brazilian rain forest has discovered four new species of parasitic Cordyceps fungi, which infect insects and manipulate the behaviour of their hosts in order to disperse their spores as widely as possible.

The modus operandi of Cordyceps is reminiscent of the famous chest-bursting scene in the movie Alien. Microscopic spores infiltrate the host via the spiracles - the holes in the exoskeleton through which insects breathe - and the fungus begins feeding on its non-vital organs.

When it is ready to release its spores, Cordyceps brainwashes its host: its filaments grow into the insect's brain, and release chemicals that cause it to climb a nearby plant and attach itself near the top by biting onto a leaf or stem. The host is then killed, and a mushroom containing spores sprouts from the top of its head.

Cordyceps fungi were first described in the nineteenth century by Louis RenÃ© Tulasne in the book Selecta Fungorum Carpologia, first published in 1865. This monumental three-volume work was filled with beautiful plates produced by his brother Charles, who came to be known as 'The Audubon of mycology' due to the outstanding quality of his work. The detail below shows an infected carpenter ant, which Tulasne mistakenly identified as a leaf-cutter, with the fruiting body of the mushroom which has sprouted from its head.

Since then, thousands of Cordyceps species have been identified, each specific to one, or sometimes two, host species. The four new species were discovered by David Hughes of Pennsylvania State University and his colleagues, in samples collected at two different sites in the State of Minas Gerais in south-eastern Brazil.

Each one infects a different species of carpenter ant, and they can be distinguished from one another by the size and shape of the spores they produce. All four produce mushrooms that sprout from the host's head, but two also produce smaller stalks that emerge from the feet and joints in the lower leg.

The researchers note that the sites at which the specimens were collected have become markedly drier and hotter in recent years, and attribute the climatic changes to global warming. Although ants can easily adapt to these changing conditions, Cordyceps cannot, and Hughes fears that one of the newly-discovered species may soon become extinct.

Related:

Brainwashed by a parasite

Evans, H., et al. (2011). Hidden Diversity Behind the Zombie-Ant Fungus Ophiocordyceps unilateralis: Four New Species Described from Carpenter Ants in Minas Gerais, Brazil. PLoS ONE 6 (3) DOI: 10.1371/journal.pone.0017024.

neurophilosophy Thu, 03/03/2011 - 03:25

This Week's Sci-Fi Worthy Parasite

cwilcox — Tue, 21 Apr 2009 02:00:00 +0000

This Week's Sci-Fi Worthy Parasite

Now that I've grossed most of you out with my last week's pick, I think I'll go ahead and make this week's pest a little easier to look at.

The image looks like a mustard plant with nice, yellow flowers. But alas! It is actually the product of this week's parasite, the rust fungus Puccinia monoica.

The fungus infects mustard plants and completely changes their 'behavior' to facilitate its own reproduction. Firstly, the fungus infects the plant as a whole, stealing nutrients and generally acting like a parasite. But Puccinia is a sexual fungus - to reproduce it must combine genes with another member of its species. Of course, it's hard to mate when you're stuck on a stationary plant. So the fungus has evolved a unique (and impressive) means of getting laid.

The first thing it does is emit hormones which cause the host to stop flowering. Then it makes the infected plant create pseudoflowers from clusters of leaves. The pseudoflowers look almost identical to natural flowers, even in untraviolet light. And as if looks alone weren't enough to get the job done, the fungus' fake flowers also emit a strong scent and are sticky with a sweet substance that attracts insects. That, in the end, is the goal of these amazing mimics. Bees and other pollinating insects feed on the pseudoflowers, and in the process, they pick up the sperm and eggs produced by the fungus much like pollen. These creatures then land on another fake flower, thus transferring the genetic material and allowing the fungus to reproduce as well as infect other plants.

It's actually quite remarkable how well the fungus has managed to imatate flowers and get itself spread. Imagine a parasite spreading through the human population by castrating us and convincingly reproducing the look of our sexual organs... Maybe like a Cymothea, but not for our tongues. *shudder* If that's not sci-fi freaky, I don't know what is.

cwilcox Mon, 04/20/2009 - 22:00

Parasitic Fungus

Return of the brain-controlling zombie-ant parasitic fungi

This Week's Sci-Fi Worthy Parasite