Fungi species, such as Cordyceps unilateralis (Ophiocordyceps unilateralis), depend heavily on the ant species for survival. Cordyceps unilateralis ‘is a parasitoid fungus that infects ants, and alters their behavior in order to ensure the widespread distribution of its spores’. (Wikipedia, 2010) In an article ‘Parasite Causes Zombie Ants to Die in an Ideal Spot’ found on Science Daily, it states that Cordyceps unilateralis will scatter their reproductive spores on ants which pass by the fungus. Such spores will not kill the infected ant immediately, but will instead control the movement of the ant. The infected ant will move to an area which the fungus deems fit for reproduction to take place and the ant will die at the chosen spot. A few weeks after the ant’s death, the stroma, which is the fungus’s fruiting body, grows out of the ant’s head. After a week or two, the stroma will release spores onto the forest ground. Carpenter ants have been found out to be frequent victims as such processes due to the weak defence against such a reproductive mechanism. As a result of learning of such consequences, carpenter ants have learnt to build their nests far away from the places such fungi reside. A typical fungal breeding zone is dark, moist and near ground level. To avoid such breeding grounds, ants have learnt to build their nests high up in the tree canopy, far away from the fungal breeding grounds.
However, this is not the only interaction between the fungi species and ants. Another ant species worth mentioning is the leaf-cutter ants (Atta laevigata). This specific species of ants illustrate a very rare of example of animal agriculture. Leaf-cutter ants will collect leaves, however, they will not eat these leaves. Instead, these ants will grow and cultivate fungal gardens on them and eat the grown fungus. The ants will ‘cultivate their fungi to produce specialized ‘fruits’ that the ants will harvest and eat for food.’ (Science Daily, 2008) As a result of such behaviour, leaf-cutter ants actually help the cultivated fungus to reproduce. However, it is important to keep in mind that fungi do not depend entirely on ants in their reproduction as it has been observed that all fungus-farming ants cultivate similar funguses. Results have shown that ‘fungal genes have been recombining’, indicating that reproduction between funguses have been taking place. (Science Daily, 2006) The widespread of the funguses are also indicators against funguses’ total dependence on ants for reproduction. This wide geographical spread proves to be impossible for ants, and this is only possible through funguses’ airborne spores.
Through these 3 articles, the strong dependency between the ants and the funguses is evident. A slight difference will be that in the first case of carpenter ants, the fungus has the dominating power as it controls the infected ant’s movement. In the second case, both parties are active participants as both are involved in the reproduction process of the fungus.
References:
1) University of Chicago Press Journals (2009, August 13). Parasite Causes Zombie Ants To Die In An Ideal Spot. ScienceDaily. Retrieved April 4, 2010, from http://www.sciencedaily.com /releases/2009/08/090811161345.htm
2) Smithsonian (2008, March 25). Ants Are Experienced Fungus Farmers. ScienceDaily. Retrieved April 4, 2010, from http://www.sciencedaily.com /releases/2008/03/080324173459.htm
3) University of Texas at Austin (2006, June 28). Symbiotic Fungus Does Not Depend On Fungus-farming Ants For Reproduction, Researchers Say. ScienceDaily. Retrieved April 4, 2010, from http://www.sciencedaily.com /releases/2006/06/060628095216.htm
4) Cordyceps unilateralis (4 April 2010). Wikipedia, Retrieved 6 April 2010, from http://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis