Pestilent secrets of a Trojan female

Neil Gemmell.

"They look fine, they behave normally but they are the proverbial Greeks bearing gifts," says Neil Gemmell.

The Otago scientist is talking about the clever heart of a new project using "Trojan females", quirks of nature uncovered by cutting-edge science but put to work in their own setting.

The aim is to make a real dent in the country's costly pest and predator problems.

Using advances in genetic science, Professor Gemmell and a small research team are testing whether it is possible to make an evolutionary loophole work to the advantage of pest control.

The strategy relies on naturally occurring mutations in part of a cell known as mitochondria. These provide power to cells - Professor Gemmell calls them "batteries" - and contain their own DNA. Studies have found that these genetic mutations can cause infertility in males, but pass harmlessly between females.

In essence, female offspring remain unaffected by variations in the DNA whereas male offspring lose the ability to reproduce.

The Dunedin researcher says: "It's an evolutionary cul-de-sac where males are held to ransom by this female inherited molecule."

Hence the Trojan female technique: "We coined the term to elicit the idea that there was something intrinsically hidden within them but probably wasn't going to do you any good," says Professor Gemmell, director of the Centre for Reproduction and Genomics at Otago University. (The more familiar Trojan Horse story is part of Greek mythology around the Trojan War in 1200BC. Greek soldiers hid inside a large wooden horse gifted to the city of Troy, emerging at night to open the city gates and allow Greek soldiers to overpower unprepared Trojan defenders.)

The 21st century idea works in theory and satisfies computer and mathematical models. Professor Gemmell says the next stage is achieving what the scientists call "proof of concept" - making the theoretical idea real.

Research, supported by a $1 million Smart Ideas grant from a biological industries fund run by the Ministry of Business, Innovation and Employment, will for the next few months focus on fruit flies. One of Professor Gemmell's colleagues in Australia has found mutations in fruit fly mitochondria that seemed to make males infertile but left females untouched.

The scientists want to use the flies with the fertility problems as their study focus, in secure laboratory conditions. They will use genetic sequencing to find out if females bred from the compromised flies carry the mutation and whether their male offspring are infertile. While this work is under way, a second line of research will study mice bred in Germany, where the same mutations may exist.

The new technology, argues Professor Gemmell, ticks the troubling boxes that surround pest control, and has some upsides. Only target species are affected, so collateral damage is avoided. What's more, a pest animal population can provide a source of females carrying the mutation to spread to other areas.

Professor Gemmell said: "These animals aren't harmed in any way, they're not physically deformed. They don't actually suffer, they just don't produce young. Across the globe there's a general move towards humane approaches to the eradication of pests and this fits with that trend."

No genetic modification was involved, which meant the non-lethal project would not become the target of opponents of GM. However, the project team includes a social scientist whose job is to monitor public perceptions about the application of the new science to pest control. Their role is to ensure that if it proceeds then it manages to avoid any ethical minefields.

Landcare Research scientist Dan Tompkins, part of the project team, says the Trojan approach would probably work best in tandem with conventional controls such as 1080, the poison used to kill possums.

Professor Gemmell puts the odds that the research will deliver the goods against pests that matter - ferrets, stoats, rabbits, possums, rats and grubs that destroy pasture - at better than 50:50. If it's not the silver bullet it will at least be an important part of the arsenal.

Poison or trap? Online hunt for new ideas

How do we clear New Zealand of pests and predators?

Dump poison on them? Trap, shoot or unleash a biological control? Or even let them be, based on a view that these mainly introduced, destructive invaders have as much right to be here.

These ideas are emerging on discussion threads in an online project by Landcare Research and managed by an information systems expert in California.

Landcare scientist Dr Bruce Warburton said the crowdsourcing approach recognised that scientists and pest control agencies were not the only places to find ideas to rid New Zealand of unwanted insects and animals.

"I think we accept that scientists might have knowledge about their topic but they might also be blinkered to other methods. By going online we can reach out and try and find novel ideas among the broader public."

Dr Warburton said the Predator-free New Zealand Challenge did not signal that the country's costly battle against pests was a failure. It recognised that indigenous species were declining due to continuous predation, and showed that where intensive pest control had been implemented native species had recovered.

Technology had changed where novel approaches - such as the trojan female technique - could be part of the new arsenal of pest control.

Information gathered during the 10 days will be reviewed by Landcare staff and Professor Ann Majchrzak of the Marshall School of Business at the University of Southern California in Los Angeles. The institution specialises in analysing material collected from online collaborations.

Federated Farmers and Forest and Bird have welcomed the challenge. Kevin Hackwell of Forest and Bird said unexpected ideas could surface which, together with traditional methods of controlling pests, could throw a lifeline to threatened species. Battling pests was slow and expensive. Any new technology which extended limited budgets could make a difference for the survival of unique New Zealand fauna.

Federated Farmers vice-president Dr William Rolleston said the country spent a lot just staying on top of pests and new tools to eradicate them were valuable.