Friday 20 September 2019

Country Matters: Leaf-cutting ants and ancient drugs

ANT AT WORK: Leaf-cutter ant
ANT AT WORK: Leaf-cutter ant

Joe Kennedy

Newly discovered words are fascinating. Last week I came upon 'faience', used by the American poet AE Stallings to describe the sky's autumnal brilliance, a feeling of snatching "a last sweetness" out of the year's turning.

('Faience', according to my battered copy of the Oxford Dictionary for Writers and Editors [INM, circa 1988], is "glazed pottery, a unique image".) She had seen, off a Greek island, the sudden blue darting of a kingfisher, which sent her on a search over pristine water.

I don't quite have that in southern Portugal. Far from kingfisher sightings, I must make do with ants and their activities near my feet, and a scientific discovery.

For leaf-cutter ants have been found to have been producing antibiotics for millions of years. These fungi-raising underground farmers had to align themselves with bacteria to fend off crop parasites in order to survive.

Microbial ecologist Cameron Currie and his colleagues at the University of Wisconsin have found evidence of a prehistoric link between ants and antimicrobial bacteria. Clues were revealed from two 20-million-year-old ants trapped in amber found in the Dominican Republic.

Dr Currie, in a study published in the journal Proceedings of the National Academy of Sciences of the US, likened these particular ants to "walking pharmaceutical factories". They had pre-dated man in growing crops and also by tens of millions of years in associating with microbes to produce antibiotics.

Along a cliff path that had been scoured by rain I contemplated the medical muscle of ants as they trekked continuously in regular lines, like conveyor belts, to and from several small openings in the ground. One stream was carrying minute pieces of leaf into the largest hole, while emerging colleagues, having deposited their loads, were setting off on an endless cycle. A night's rain did not deter them.

The following day, apart from some terrain changes, work continued as before, the endless stream of labour slaves harvesting from battered bush vegetation.

These ants must work non-stop to keep their underground gardens in production. They live on the fungi growing in their formicaries, nurtured by leaf shreds chopped up by others down below. Stalk cutters and gardeners all have their tasks; if a toxic leaf is found, they stop collecting from that source and move to another.

The ants travel out about 200m and place guards along the routes to watch for other ant raiders that might steal their bounty. There is constant vigilance. Other groups try to take over colonies and enslave those they capture. Within the formicaries, queens, who can live for up to 15 years, preside over vast numbers of from 100,000-500,000 workers. The world's largest colony was found in Switzerland with 300m ants in 1,200 colonies crossing 60km of tracks in the Jura Mountains.

Ants have been found to make the supreme sacrifice in aiding each other: a recently discovered species in Asia can explode their bodies when attacked, killing themselves to protect their colleagues beneath the ground.

Joe Kennedy was reporting from Portugal

Sunday Independent

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