Fungi farming by leaf cutting ants
(Atta cephalotes).
- The leaf-cutting ants are a division of the attine ants that engage in a symbiotic relationship with fungi. The ants literally garden lepiotaceae fungus in special areas of their nests and then feed on its hyphal tips (filaments). The ants are unable to digest the complex cellulose molecules found in leaves, and so use the fungus's ability to do so instead. By feeding the fungus on leaves, the ants make it convert cellulose into carbohydrates that they in turn can live off.
- The ants divide up the labour of caring for the fungus, with medium sized ants bringing bits of fresh leaves back to the nest, before smaller ants process the leaf matter, fertilising it with faeces and eliminating invading fungi with the chemicals in their secretions and by eating them. The ants have also modified the architecture of their nests to accommodate their fungus gardens. A system of lower passages is constructed in order to drain the chambers when it is wet and other tunnels help ensure that the temperature can also be controlled.
- The ants do not allow the fungus to mature and produce mushrooms. Therefore, in becoming a symbiont, the fungus has to rely solely upon the ants for its reproduction. The founding queen ant (the mated female) will bring spores from her original nest with her to start the fungus gardens in her new nest. By comparing the phylogenies of both the ant and the fungus, mycologists have discovered that more developed attines have clonally propagated the same basidiomyceteae family lineage for over 23 million years! The fungi has a guaranteed food supply and its survival is not threatened by competition as the ants remove any invading fungi.
- Thus, it can be seen how, in becoming symbionts, both the ant and the fungus have become interdependent and have adapted to benefit from their relationship.
Acknowledgements must be made to the following people and web sites (some of which are linked):
Milwaukee Public Museum (http://www.mpm.edu/collect/tirimbina/ants.html)
Scientific American. 1967. 217. pp.112-120. 'The Fungus Gardens of Insects'. LR & SWR Batra.
Lukas, Julian, Paul and Cadi.
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