The Fascinating World of Attine Ants

Nicholas Wade examines leaf-cutter ants and their amazing agriculture

A  Leaf-cutting ants and their fungus ‘farm’ are a marvel of nature and perhaps the best-known example of symbiosis -- the mutual dependence of two species. Ants cultivate a mushroom-like fungus in ‘farms’. Both the ants and their so-called ‘agriculture’ have been extensively studied over the years, but recent research has uncovered intriguing new findings.

Ants invented agriculture 50 million years before people did, and the leaf-cutters, members of the large attine ant family, practise the most sophisticated example of it. They grow their fungus in underground chambers that can reach the size of a football. A single leaf-cutter nest may contain a thousand such chambers, embedded in an underground metropolis up to 18 feet deep, and support a society of more than a million ants.

B  These ant communities are the dominant plant-eaters of the Neotropics, the region comprising South and Central America, Mexico and the Caribbean. Biologists believe 15 percent of the leaf production of tropical forests disappears down the nests of leaf-cutter ants. In the nest, the leaves are shredded and added to the fungus, which digests the leaves and is in turn eaten by the ants. The attine ants’ achievement is remarkable because it allows them to consume, courtesy of their mushroom’s digestive powers, the harvest of tropical forests whose leaves are laden with poisonous chemicals.

C  There are more than 200 known species of the attine ant tribe, divided into 12 groups, or genera. The leaf-cutters use fresh vegetation; the other groups, known as the lower attines because their nests are smaller and their techniques more primitive, feed their gardens with similar leaves that have fallen on the ground and insect waste on the forest floor. Lower attine ants are all a similar size. However, leaf-cutter worker ants come in made-to-fit sizes -- large ants to saw off leaves, medium ones to shred them, and miniature workers to seed them with fungus and clean off alien growths.

D  In 1994, biologists from the United States Department of Agriculture analysed the DNA of ant fungi. They found that the leaf-cutters’ fungus was descended from a single pure strain, propagated for at least 23 million years. However, the fungi grown by lower attine ants fell into four different groups, as if the ants had domesticated wild fungi at least four times in evolutionary history. What could be driving these two patterns of fungus gardening -- the pure clone cultivation of the leaf-cutters and the multiple varieties of the lower attines?

E  The answer has been suggested by Cameron Currie of the University of Toronto. The pure strain of fungus grown by the leaf-cutters, it seemed to him, resembled the single crops grown by humans to the exclusion of all others, such as potato growing. These ‘monocultures’, which lack the genetic diversity to respond to changing environmental threats, are particularly vulnerable to parasites -- organisms that live and feed on their host, often causing harm. Currie felt there had to be a parasite in the ant-fungus system. But a century of ant research had provided no evidence for his idea. Textbooks describe how leaf-cutter ants scrupulously weed their gardens of all foreign organisms. "People kept telling me the ants keep their gardens free of parasites," said Currie. Nevertheless, after three years of sifting through attine ant gardens, Currie discovered several alien organisms, particularly a family of parasitic moulds called ‘Escovopsis’.

F  Escovopsis is a deadly disease that can devastate a fungus garden in a couple of days. It blooms like a white cloud which envelops the whole garden. Other ants won’t go near it, and the ants associated with the garden just starve to death. Evidently, the ants usually manage to keep Escovopsis and other parasites under control. Nevertheless, with any lapse in control Escovopsis will quickly burst forth. Although new leaf-cutter gardens start off free of Escovopsis, within two years some 60 percent become infected.

G  The discovery of Escovopsis’s role brings a new level of understanding to the evolution of the attine ants. In the last decade, evolutionary biologists have been increasingly aware of the role of parasites as driving forces in evolution. With Currie’s work, there is now a possible reason for the different varieties of fungus in the lower attine mushroom gardens -- to stay one step ahead of the relentless Escovopsis. Interestingly, the leaf-cutters had, in general, fewer alien moulds in their gardens than the lower attines, yet more Escovopsis infections. Clearly, the price they pay for cultivating a pure variety of fungus is a higher risk from Escovopsis.

H  So how do attine ants keep this parasite under control? People have known for a hundred years that ants have a whitish growth on their body surface. It was thought to be wax but, after examining it under a microscope, Currie discovered a specialised patch on the ants’ bodies that harbours a particular kind of bacterium, one well known to the pharmaceutical industry and the source of half the antibiotics used in medicine. This bacterium is a potent poisoner of Escovopsis, inhibiting its growth and suppressing spore formation.

Astoundingly, the leaf-cutter ants are accomplishing feats beyond the power of humans: they are growing a monocultural crop year after year without disaster, and they are using an antibiotic apparently so wisely that, unlike people, they are not provoking antibiotic resistance in the target disease-producing organism.

Translating: a key to international understanding?

A.  The term ‘translation’ is used for all cases where the meaning of expressions in one language (the ‘source’ language) is turned into the meaning in another (the target language), whether the medium is spoken, written, or signed. In specific professional contexts, however, a distinction is drawn between work with the spoken or signed language (interpreting), and work with the written language (translating), although certain tasks blur this distinction.

B.  It is sometimes said that there is no task more complex than translation -- a claim that can be readily believed when all the variables involved are taken into account. Translators not only need to know their source language well; they must also have a thorough understanding in the field of knowledge covered by the source text, and of any social, cultural, or emotional connotations that need to be specified in the target language if the intended effect is to be conveyed. The same special awareness needs to be present for the target language, so that points of special phrasing, contemporary fashions in expression, local expectations, and so on, can all be taken into account. On the whole, translators work into their mother tongue (or language of habitual use), to ensure a result that sounds as natural as possible -- though some translators have argued that, for certain types of text (e.g., scientific material) where translation accuracy is more crucial than naturalness, it makes more sense for the translators to be more fluent in the source language.

C.  The aim of translation is to provide semantic equivalence between source and target language. This is what makes translation different from other linguistic activities, such as adapting, precis writing, and abstracting. However, there are many problems hidden within this apparently simple statement, all to do with what standards of ‘equivalence’ should be expected and accepted.

D.  Exact equivalence is of course impossible: no translator could provide a translation that was a perfect parallel to the source text, in such respects as rhythm, puns and cultural allusions. Such a parallel is not even possible when paraphrasing within a single language: there is always some loss of information.

E.  On the other hand, there are many kinds of inexact equivalence, any of which can be successful at a certain level of practical functioning. It therefore follows that there is no such thing as a best translation. The success of translation depends on the purpose for which it was made, which in turn reflects the needs of the people for whom it was made. A rough and-ready translation of a letter can suffice to inform a firm of the nature of an enquiry. A translation of a scientific article requires careful attention to meaning but little attention to stylistic features. The provision of a dubbed film script will warrant scrupulous care over the synchronisation of lip movements, often at the expense of content. Literary work requires a sensitive consideration of form as well as content, and may prompt several translations, each of which emphasises a different aspect of the original. It is easy to see that what might be ‘best’ for one set of circumstances may be entirely unsuitable for another.

F.  Several different kinds of translation have been proposed to allow for this range of possibilities. A pragmatic translation emphasises accuracy and knowledge of the subject, required for instruction manuals and much scientific research. In an aesthetic translation, important for literary material, the focus is on preserving the emotional as well as the cognitive content of the work, and on maintaining some level of stylistic equivalence. Ethnographic or sociolinguistic translations aim to pay full attention to the cultural backgrounds of the authors and the recipients, and take into account differences between source and target language, and the ways of life in which they are embedded. And there are various kinds of linguistic translation, where the aim is to convey the structural flavour of the original text, often in quite a literal manner, emphasising such features as archaisms, dialecticisms, and levels of formality. Most translations, of course, are mixtures of these theoretical types, reflecting the complex reality of language in use.

G.  At another level, in a word-for-word translation each word in the source language is translated by a word in the target language. The result often makes no sense, especially when idiomatic constructions are used. In a literal translation the linguistic structure of the source text is followed, but is normalised according to the rules of the target language. In a free translation the linguistic structure of the source language is ignored, and an equivalent is found based on the meaning it conveys.

H.  Translators aim to produce a text that is as faithful to the original as circumstances require or permit, and yet that reads as if it were written originally in the target language. They aim to be "invisible people" -- transferring content without drawing attention to the considerable artistic and technical skills involved in the process. The complexity of the task is apparent, but its importance is often underestimated, and its practitioners’ social status and legal rights undervalued. Some countries view translation as a menial, clerical task, and pay their translators accordingly, while others regard it as a major intellectual discipline in its own right. The question of status is currently much debated, particularly in Europe, where demand for translators is rocketing, especially in relation to the European Union.