Leaf-cutting ants and an­cient drugs

Sunday Independent (Ireland) - - Viewpoints - 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 pro- duc­ing 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

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