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.
Scientists have discovered four new species of fungi that target carpenter ants and manipulate their brains.
The modus operandi of the Cordyceps fungi is reminiscent of the famous chest-bursting scene in Ridley Scott's 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.
A dead ant infected with a parasitic Cordyceps fungus
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. (Exactly how the chemicals work is unknown; they may interfere with the host's geomagnetic sense.) 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, many hundreds 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.
