Far from harbouring toxic bacteria in their mouths as long believed, Komodo dragons produce venom from complex glands in their lower jaws, according to a team led by of the University of Melbourne, Australia.

The study also suggests that the largest venomous creature to have ever existed was a 5.5-metre-long ancestor of the Komodo – .

Man-eating monitor

Komodos, which live on three Indonesia islands, repeatedly slash at their prey until they are weak enough to eat. They can take down a 40-kilogram Rusa deer, and .

For decades, wildlife documentaries have promoted the idea that Komodo dragons owe their success as predators to toxic bacteria in their saliva – a claim bolstered by a 2002 study reporting .

However, magnetic resonance imaging of a preserved Komodo head by the Fry team from the Museum of Natural History at Humboldt University in Berlin revealed an alternative explanation: huge venom glands opening to ducts at the front of the jaw.

Shocking bite

The finding was confirmed when the team surgically removed the glands from a terminally ill Komodo at Singapore Zoo. Genetic and chemical analysis revealed a large array of venomous substances – including those that prevent blood clotting and widen blood vessels. These would cause blood pressure to plummet, potentially inducing shock, if injected into a mammal.

The team’s computer modelling of the Komodo bite suggests a relatively weak bite – a maximum bite force of 39 newtons, compared to 252 N for an Australian saltwater crocodile of the same size – but the powerful neck and razor-sharp teeth are ideal for a slashing attack.

“They slash and pull back, but it’s the venom that nails it. It lowers blood pressure, and stops blood clotting. Prey goes into shock and can’t even struggle,” says Fry. The venom could lead to the development of novel pharmaceuticals, he adds.

Missing the obvious

The existence of venom also fits with Fry’s own experiences observing a keeper at the Singapore Zoo who was bitten by a Komodo. “He was very frightened. He bled for three or four hours. That doesn’t happen with a bacterial infection; a normal wound would have close by then,” says Fry.

By comparing the ecology and skeletal structure of the Komodo, Megalania and the – a reptile closely related to both – the Fry team concluded that Megalania is the largest ever venomous creature.

The venom gland “is not a trivial structure, [but] a big bulge” on the lower jaw, says Fry, who compares previous ignorance of the Komodo dragon’s venomous capabilities as akin to “missing the teeth on great white sharks and saying they are plankton eaters”.

Journal reference:

How Mexico deploys its flu drugs may be key to determining the size of any pandemic that emerges from the current H1N1 outbreak. That’s the conclusion of a mathematical model of flu transmission by an international team of researchers.

The findings also suggest that countries that stockpile just one of the two commonly used flu drugs may have trouble controlling a major pandemic.

“If you can hold off using your primary drug until the cumulative number of cases reaches a sufficiently high number, you reduce the spread of resistance and the final number of cases,” says team member at the University of Hong Kong. But only, he warns, if the index country, Mexico, follows that strategy

“The key is to make sure the source population has good control of antiviral drugs, then all countries downstream benefit. If the source loses control then these strategies won’t work,” he says.

Resistance risk

Two anti-flu drugs are commonly stockpiled for use in a flu pandemic: oseltamivir, which is sold as Tamiflu, and zanamivir, which is sold as Relenza. Both work by inhibiting an enzyme called neuraminidase that the virus needs to replicate, but they act on different parts of the enzyme and resistance to one drug does not confer resistance to the other.

The Mexican H1N1 strain is currently , but no one knows how long that will last.

The Wu team conducted their study after noticing that despite concerns about resistance, many countries stockpile just one drug, usually oseltamivir. There are some exceptions, however, including Australia and the UK, which stockpile both drugs.

Viruses are notorious for their ability to develop resistance to drugs. Last year, an H1N1 flu strain that caused some seasonal flu rapidly developed resistance to oseltamivir. By December, “close to 100 per cent of H1N1 in Australia and the US, and many other parts of the world, were resistant to Tamiflu”, says , an infectious disease expert at the University of New South Wales in Sydney, Australia.

One drug or two?

To work out whether initially treating patients from a smaller stockpile of a secondary anti-flu drug could delay the emergence of resistance, the Wu team ran a mathematical model of a flu outbreak in a theoretical “closed” population of 6.8 million – the size of Hong Kong.

In the model, doctors either prescribed just one drug, both drugs in combination, or prescribed one, then switched to the other when supplies of the first drug ran out.

The two strategies that used more than one drug decreased the number of people who finally became infected from 68 to 58 per cent. It also reduced the chance of resistance emerging from 38 to just two per cent, which would translate into a significant number of lives saved, says Wu.

When the model included international travel between the “index” population and 105 large cities to take into account the possibility that people might spread resistant strains, the two strategies that used more than one drug reduced the final number of people infected and the emergence of resistance to a similar degree, but only if the index country also used that strategy.

According to Wu, it is probably not too late for Mexico to start to employ the two-phase strategy. “We’re still at the early stages, Mexico is not using a lot of drugs, and we haven’t seen resistant cases yet, he says.

Cross-resistance

As the safety of using two drugs together has not been assessed, the most practical strategy would be to use a limited supply of one drug first, and then switch to the other, says Wu. Zanamivir, which is less popular because it has to be inhaled, is the obvious drug of choice for the limited-supply drug. However, it has not been approved to treat young children.

“Cross-resistance to both drugs at the same time is highly unlikely, so using the two drugs cleverly might be able to delay the emergence of resistance,” says epidemiologist at Melbourne University, Victoria, Australia, who was not involved in the study.

McVernon’s team have previously used mathematical modelling to show that by using one of the drugs to treat active flu infections, and the other to prevent infection.

“In Australia, where the stock pile is enough for 40 per cent of population, we are keen to use drugs to prevent cases and spread early on, because it’s far more effective at limiting the pandemic,” she says.

Unethical solution

The Wu model only considers drug resistance that is caused by treatment with the drug, and not resistance that emerges from mixing of viruses, or natural mutation.

Wu points out that simply avoiding using either drug until numbers of sick people had reached a certain threshold would have the same effect as using two drugs in succession. “But medically that would be unethical, so you need to use a second drug,” he says.

“In a scenario where lots of drugs are being used over a short period of time, drug resistance will probably emerge, and efficacy would be substantially weakened,” says Wu.

The modelling study was carried with researchers from Harvard University and the Health Protection Agency in London, as well as the University of Hong Kong.

Journal reference: (in press)

The bid to produce green power on a commercial scale using heat mined from subterranean rocks – or “hot rocks” – has suffered a major setback, with the breach of a four-kilometre-deep well on Friday in the Cooper Basin in South Australia.

Mining heat from subterranean rocks could one day provide continuous, affordable energy anywhere on Earth, and , the Brisbane-based company that operates the South Australia well, is widely tipped as being closest to making the technology cost effective.

Geodynamics holds the rights to a potential power supply of up to 10 gigawatts trapped in a 1000-square kilometre slab of hot granite deep under the town of Innamincka in South Australia.

The company was in the final stages of commissioning a demonstration one-megawatt power plant for Innamincka when the rupture occurred, and steam started to escape from the well.

Drilling deep wells into hot rocks and circulating water to mine heat is technically challenging, and the cause of the breach is still unknown.

“We’ve mobilised a team from the US to investigate,” a company spokesperson says.

But last week it rose from the dead with ecologists reporting the discovery of three of the creatures and declaring that the species was never feared extinct. But its future is far from certain.

“They have a very limited range – most likely due to an inability to tolerate high temperatures – so they are at risk from future temperature extremes,” says ecophysiologist of James Cook University in Cairns, Australia.

of James Cook University in Townsville agrees. “There has been a massive decline in one population. One more hot summer could wipe [that population] out.”

Media confusion

Last December, the story took on a life of its own when Williams made an off-the-cuff remark to a local journalist that the possums may already be extinct from the Carbine plateau in the Daintree National Park in northern Queensland. With no sightings in three years, the fear was that the population had been wiped out by record temperatures in 2005.

However, there is a second population of lemuroid ringtail possums (Hemibelideus lemuroides) living on the Atherton tablelands, roughly 100 kilometres south. This population remains in relatively good health.

The story became further confused because roughly 40% of lemuroid ringtail possums living on the Carbine plateau are white, the rest brown – many reports equated the different colours with different species.

These points became irrelevant two weeks ago, though, when, during a last ditch attempt to find whether any of the Carbine plateau population had survived, Williams spotted three of the possums.

“They’re hanging in there. But we are completely certain that the species has severely declined – this is not a false alarm,” Williams says.

Rapid decline?

Last year the lemuroid ringtail possum was declared not to be at high risk of extinction by the , an influential although recently criticised barometer of extinction risk.

Although the Red List assessment was published in 2008, it “was done in 2006, or very early 2007”, so could now be out of date, agrees of the University of the Sunshine Coast in Queensland, one of the Red List assessors.

He cautions, however, that a road built in the late 1980s through the region occupied by the Carbine plateau population may have made it temporarily easier to count the animals, and that could be a “confounding factor”.

Possums are usually counted by shining spotlights from the road into the rainforest, so sightings may have become less frequent as the forest canopy grows back, he says.

Eat them alive, or at least get predatory ants to do it for us – that’s the latest proposal for dealing with the invasion of tropical Australia by toxic cane toads.

And in an unrelated move, Townsville in North Queensland called on its citizens to take part in a mass capture program – the Toad Day Out on Sunday – leading to the humane destruction of 362 kilograms (798 pounds) of toads, which is around 3600 individuals, according to .

Cane toad (Bufo marinus) young are more susceptible to being eaten by Australian (Iridomyrmex purpureus) than the young of native frogs, raising the possibility that meat ants might make a safe biocontrol agent, according to a team led by of the University of Sydney.

“The next step is to work out whether we can manipulate habitats – perhaps by using bait to bring toads and ants together more frequently – to increase the kill rate,” says Shine.

Toxic wave

According to ecologist of James Cook University in Townsville, the proposal is interesting, but “you would try it cautiously”.

“Ants are generalist predators, so if you increased their numbers, you may see an effect on native animals apart from frogs,” he says. “As we grow to understand [cane toad] biology more fully, other possible control mechanisms will emerge.”

Since their introduction in 1935 to control sugar cane pests, cane toads have spread through most of tropical Australia, eating and poisoning native animals.

Previous suggestions on how to control them have included importing exotic diseases, raising concerns that the diseases themselves could end up causing as much havoc as the cane toad. Being natives to the continent already, meat ants are likely to be safer, says Shine.

Toxin no defence

Shine’s proposal is based on lab studies confirming field observations that meat ants and cane toadlets are active in the day – a time when most native froglets are inactive.

When housed together, cane toadlets also made physical contact with ants significantly more often than native frogs. And when the ants attacked, which they did at the same rate whatever the species, the cane toads moved away more slowly, allowing the ants to hold on for significantly longer: for more than 5 seconds compared to 1 second for native frogs.

Tests of sprint speed and endurance of 40 young cane toads and 40 young of each of seven native frogs, found the toads to be significantly slower. They also had the lowest endurance of all species – refusing to hop when tapped after little more than one minute – bar the ornate burrowing frog (Opisthodon ornatus). However, ornate burrowing froglets were by far the most vigilant of all the species, moving away when ants approached to within 10 centimetres, says Shine.

Not surprisingly, toadlets were also worse than native frogs at escaping a simulated ant attack – being tapped five times on their bottoms with a pen.

“They’ve evolved in a world without big predatory ants, so instead of hopping away like a sensible frog, they just freeze. That makes sense if [the predator] is affected by your toxin, but the ants aren’t,” says Shine.

Prolific breeders

Cane toads at Australia’s invasion front have evolved longer legs and are faster. However, they are long way from being able to escape meat ants by developing the tactics of native frogs, which can often jump several times their body length, says Shine. “By the second hop, they are in a different world. Cane toads have short stubby legs, and walk rather than hop.”

According to Shine, the Townsville initiative will likely reduce numbers, but only in the short term. “There’s been a tremendous community effort,” he says, but “with females laying up to 30,000 eggs in a single clutch, it’s not a long-term strategy.”

Journal reference: (DOI: 10.1111/j.1365-2435.2009.01556.x)