Thoughts on life, technology, and maybe some amusing stuff now and then
Termites: Nature's Russian Dolls
TERMITES: NATURE'S RUSSIAN DOLLS.
If ever you find yourself in one of the world's tropical savannas or forests, chances are that you will discover ancient cities. These huge societies are not dead civilisations of some long-lost human ancestor; indeed, they are still very much alive and have been around for far longer than humankind's existence. I am talking about termite mounds.
For such a small creature, termite mounds are truly remarkable constructions. Just their size beggars the mind, particularly when you bare in mind that for us to build on a relative scale would demand mile-high skyscrapers. Not only that, but some species of termite have earned the name 'compass termite' for always building their mounds so that they are orientated precisely north-south.
You would be forgiven for dismissing termites as quite unremarkable insects if ever you came across just a few of them. As Lewis Thomas pointed out, "two or three termites gathered together on a dish...may move about and touch each other nervously, but nothing happens". If, however, you were to keep adding more termites, eventually a critical mass would be reached and those tiny insects would begin to organise themselves into a workforce behaving for all the world as if it were executing some plan. Thomas again: "As though they had suddenly received a piece of extraordinary news, they organize in platoons and begin stacking up pellets to precisely the right height, then turning the arches to connect the columns, constructing the cathedral and its chambers in which the colony will live out its life".
I said that these termites act as if they are executing a plan, but don't take that to mean they are consciously working on erecting their magnificent home. No, each individual termite has no concept whatsoever of anything other than very simple micro-rules, which Richard Dawkins supposed might be something along the lines of "If you come upon a heap of mud with a certain pheromone on it, put another dollop of mud on top". Just as the cells in our body organised themselves into the various bones, muscles and organs that comprise a human being, following genetic instructions guided by environmental stimulus, so too do termites follow a chemical blueprint coded in their genes, and the termite mound, that mile-high city (relatively-speaking) is the end result of this emergent behaviour.
In many ways, it is apt to compare a colony of termites to a single body, which brings us to the reason why I call termites 'Russian dolls'. Really, the term 'individual termite' should never be used because these are social insects whose community is so well organised they are best not thought of as lots of cohabiting individuals but a single organism that happens to be comprised of a million or more mobile units. The termite mound is not just an impressively tall monolith of dried mud, it has many attributes of an organism, including an anatomy, physiology and even 'organs' that carry out vital functions such as regulating temperature. As Lewis Thomas said, "they are not the dense mass of individuals they appear to be; they are an organism, a thoughtful, meditative brain on a million legs".
So, termites are nature's Russian dolls because they live in societies so well-coordinated these colonies are often viewed as a single organism in its own right? Partly, yes, but there is more to this tale than just the fact that termites have pretty much forsaken individuality and thrive in the ultimate communist society in which the collective functions very much like an organism in its own right. To see how the Russian doll analogy goes much further than that, we need to look inside a termite and understand how it achieves another remarkable feat.
Termites are not just remarkable architects but also remarkable eaters. They are able to consume foodstuffs which most other animals find indigestible, particularly wood which contains cellulose, lignin and other materials which stomachs normally cannot cope with. The reason why termites are able to digest that which most animals' stomachs cannot cope with is because there is a colony living inside every single termite, just as each single termite is one unit in a colony of such insects.
The digestion of cellulose requires enzymes known as cellulases, and although most animals are incapable of producing this enzyme, some micro-organisms do have that ability. Inside the gut of every termite there lives a colony of just such a micro-organism. Known as 'mixotricha paradoxa', it is a protozoan, about half a millimetre in size. These protozoans digest wood chips that have been conveniently chopped up into manageable chunks by the termite whose stomach they live inside, and that termite lives off of the waste products resulting from this process.
As Dawkins said, "if the mound is a town of termites, each termite gut is a town of micro-organisms. We have here a two-level community".
However, we are still not done in opening up our Russian dolls to find another one hidden inside. To see why, we need to understand the reason why that protozoan has the name 'mixotricha paradoxa'. Translated into English, it means 'unexpected combination of hairs'. It earned that name because, when it was first examined in the 1930s by one J.L Sutherland, she noticed that mixotricha paradoxa is covered in tiny hairs. These are known as cilia, and they are common in animal cells. She also saw a few longer hairs at the front of the protozoan, and these longer whip-like structures are called flagella. It was seeing both cilia and flagella together in one organism that inspired the name 'mixotricha paradoxa' because experience had taught microbiologists that microorganism either have one or the other, but never both.
Further studies with an electron microscope (these studies were conducted by L. R Cleveland and A.V Grimstone) revealed that what looked to Sutherland like cilia were not cilia at all but bacteria. As Dawkins wrote, "each one of the thousands of tiny hairs is a single spirochaete- a bacterium whose entire body is a long, wiggling hair...They normally swim freely, but mixotricha's spirochaetes are stuck to its body wall, exactly as though they were cilia".
Sutherland mistook those spirochaetes for cilia because they appeared to have basal bodies. In fact, those are not basal bodies at all, but a completely different kind of bacteria. As Dawkins wrote, "little could she (Sutherland) know that both 'cilia' and 'basal bodies' were hitchhiking bacteria...we have here a triple-decker dependency".
So, if ever you find yourself in a tropical Savannah or forest, you will likely encounter an organism comprised of a million or more tightly coordinated termites; each termite is capable of digesting material most other animals wouldn't touch because it has a colony of microbes living inside its gut, and that microbe has a colony of bacteria living symbiotically with it. That is why I call the termite 'nature's Russian dolls".
REFERENCES
"The Ancestor's Tale" by Richard Dawkins
"The Extended Phenotype by Richard Dawkins"
"Seven Wonders" by Lewis Thomas



