A COUPLE of years ago I wrote about a fuzzy-haired Czech professor with a head full of brains who had discovered a virus that could get into a human mind and make its owner reckless, writes Damien Enright

An essential part of its normal lifecycle was in rats, which it made reckless so that they would be an easy prey for cats. Inside a cat, it could initiate the first stage of its development. So it reproduced itself, rat to cat, cat to rat, saecula saeculorum. That it sometimes ended up in a human was not part of the plan.

Unfortunately, having lodged in a human brain, it could steer the host into acts of fatal recklessness, such as running across a highway populated by fast-moving vehicles. This was something the professor, Dr Flegr, often did as a young man, and it was the memory of that insane behaviour that caused him to investigate it when he became a biologist at Charles University in Prague.

There, he discovered the virus Toxoplasma gondii (Toxo for short). I said in my article that perhaps criminals should be brain scanned to see if their minds were possessed by the “reckless virus”, and possibly plead exonerating cause for their behaviour. A surprising 30% to 40% of humans do carry it, but it remains largely inactive in most.

Recently, I read of another fascinating and bizarre case of one species invading another and controlling its behaviour. This time, it is a fungus controlling an insect, zombiefying it, if such a word exists.

Papa Doc Duvalier who once ruled Haiti was believed to have the power to turn his subjects into zombies if they displeased him. Having turned them into “the living dead”, he would then have them work as automatons in his gold, copper or diamond mines.

Or, he could hand them over to the Ton Ton Macoute, his secret police, who would then make the dead dead, equally exploitable in that the family business included selling Haitian cadavers and body parts to foreign medical schools. Thousands of Haitians were murdered for this purpose, and hundreds of thousands fled the island.

After Daddy Doc became dead himself, his son, Baby Doc, aided by his sister, Michelle, held power for a further 15 horrendous years. Jimmy Carter, as US president, managed to exert some restraint, but then Ronald Reagan again cosied up to them because they were (of course) staunchly anti-communist. However, Baby Doc didn’t have the alleged zombiefying powers that helped his father rule by fear, and he was deposed by popular revolution in 1986.

The aforementioned fungus, Ophiocordyceps unilateralis, popularly known as “the zombie ant fungus”, is a tropical mushroom that invades the body of Camponotus leonardi, a species of ant, and uses it as a vehicle for its self-perpetuation.

The way it invades the living ant is sinister, and what follows is bizarre, as other members of the ant colony attempt to save themselves from being similarly zombified.

The fungus releases microscopic spores that free-float in the air. One attaches itself to an ant and releases enzymes that eat through the insect’s external skeleton — the ‘shell’ that supports and protects the body — and takes over its central nervous system. The ant becomes a zombie, with no mind of its own. It is living but it is a machine, an automaton entirely in the fungus’s control.

So powerful is that control that it can entirely negate the ant’s instinctual behaviour and send it wandering away from its colony to search for conditions precisely favourable to the fungus: humidity 94% to 95%, temperature 20C to 30C. Having located this microclimate, the ant is steered to climb to the top leaves of a plant tall high enough to catch air movements, and locking onto the leaf with its powerful mandibles, to hang there, suspended, until it dies.

Finally, with the ant dead, the fungus releases its spores over the jungle floor to infect new ants.

However, the ants fight back. So vulnerable is the species to the fungus that it has learned to quarantine colony members exhibiting the first symptoms of zombiehood. If it did not, the fungus would take over, and kill, the entire colony. It is surely extraordinary that primitive vegetables and insects has evolved sequential, cause-and-effect strategies.

To end on a local note, I see that weeks ago, writing from La Gomera, I said that bluebells would shortly be carpeting the forest floor at home. I was premature. Bluebells are still unusually thin on the ground, as are ramsons. Blackthorn is flowering, and primroses are having a good year. Yesterday, I saw my first tortoiseshell butterfly slowly wakening after its winter-long hibernation.


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