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Termite mounds: Agricultural Greenhouses

by Bart Wursten

Termite_ZZZzzf  Gorongosa Park and Mountain-(c) Jeffrey BarbeepTermite mounds are in fact highly organized agricultural green houses where the termites actively grow special kinds of macrofungi.  A species of termite often has a specific relationship with one species of fungus so there is a whole family of macrofungi, called Termitomyces, which has evolved through these relationships.  Many of them are edible and the actual, often large mushrooms (the fruiting bodies of the fungus) are often collected and sold on the side of the road along Gorongosa National Park during the rainy season.

Termites harvest dead plant material largely to feed the young (nymphs) and the reproductive queen and "kings."  The problem is that they themselves are not able to digest the cellulose cell membranes of the dead plant material.  That is what they need the fungus for.  Underground, the nest consists of many levels where the half digested material is spread out.  The fungus grows there and lives on the indigestible parts, breaking this down further.  The eventual broken down "paste" is harvested and fed to the queen and the termite nymphs.  Therefore the fungus helps the termites, and the termites help and perpetuate the life cycle of the fungus; it is the perfect symbiosis in order to make the fungus thrive. 

The termites are able to regulate both temperature and humidity accurately inside the mound.  They do this by opening and closing hundreds of openings in the elaborate above ground structures we normally see.  These structures are in fact huge thermostats.  It has been demonstrated that the workers are able to keep the temperature inside the fungus-growing nurseries constant to within half a degree.  Humidity is kept constant by adding or removing moisture.  In the Central Kalahari, termites are known to have shafts going hundreds of feet deep into the ground with workers going up and down to add moist soil to increase humidity.

Termite_IMG_2388Building the towers, termites mix clay-like soils with a kind of saliva to harden.  That is why the mounds are so strong and can last dozens of years after the actual colony has died or moved.  The combination of the mineral-rich soils and saliva, plus the organic wastes from the fungus plantations and colony make termite mounds a very fertile place in an often otherwise infertile environment.  That is why you always see trees and shrubs growing on termite mounds.  In cases of large trees this is mostly not because the termites built it around the tree.  In fact the mound may be hundreds of years old and no longer inhabited by termites but the tree has grown from the richer soils.  Many species of shrubs and trees are closely affiliated with termite mounds.  Others that are normally restricted to riverine areas can be seen away from rivers but only in association with termite mounds.  This way termites are not only farmers but are also very important long-term landscapers.  In floodplain or swamp areas, like Gorongosa or the Okavango Delta in Botswana, termites, over tens of thousands of years, rearrange the flows of streams and form of islands.

A termite colony survives as long as there is a queen and a sustainable colony.  To counter the problems of over population and to spread the genes to other areas, another fascinating thing happens.  Usually at the start of the rains a certain percentage of the workers and soldiers transforms and becomes winged.  During this time they are also fertile females and males.  These winged termites are called alates and hundred of thousands fly out of the colony.  About 99.9 percent will end up as a feast for all the other insects, spiders, reptiles, frogs, birds, mammals, and even people that eat them.  The male and female alates are able to find each other through chemical signals and the very lucky, very few that are able to get underground in a suitable place, will be able to start a new colony.  They will produce some off spring to start a work force and eventually will transform into the next queen and king.

But what about the fungus? Where does that come from? Before each alate flies out of the old colony, some spores of the fungus are stored in a special cavity in the thorax, so they actually bring it along when they go.


This page contains a single entry from the blog posted on March 6, 2008 8:40 PM.

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