Return of the brain-controlling zombie-ant parasitic fungi

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 René 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.