18 | NewScientist | 3 March 2012

Giant flea gave dinosaurs the itch

IT’S amazing what you find when you scratch about in old rocks – the oldest and largest flea ever discovered, for instance, which has turned up in Jurassic rocks in China. Warm-blooded animals have been itching to get rid of the pests ever since.

At 20.6 millimetres long, the 165-million-year old fossils dwarf the largest living flea – a 12 mm species which plagues the mountain beaver of North America. The fossil beasts are so large they may have lived on feathered dinosaurs rather than the small mammals that scuttled across the Mesozoic landscape (Nature, DOI: 10.1038/nature10839). “Small hosts – mice, shrews, small bats – never have any large [external] parasites, and certainly never anything the size of these wonderful, extinct fleas,” says David Grimaldi at the American Museum of Natural History, New York, who was not involved in the find.

Mammals probably did not escape the blood suckers for long. The most primitive fleas alive today all live on mammals, which suggests their ancestors quickly hopped from feathered dinosaurs to our furry forerunners.

Drug offers larger window to treat strokeA DRUG which minimises brain damage when given three hours after stroke has proved successful in monkeys and humans.

A lack of oxygen in the brain during a stroke can cause fatal brain damage. There is only one approved treatment – tissue plasminogen activator – but it is most effective when administered within 90 minutes after the onset of stroke. Immediate treatment isn’t always available, however, so drugs that can be given at a later time have been sought.

In a series of experiments,

Michael Tymianski and colleagues at Toronto Western Hospital in Ontario, Canada, replicated the effects of stroke in macaques before intravenously administering a PSD-95 inhibitor, or a placebo. PSD-95 inhibitors interfere with the process that triggers cell death when the brain is deprived of oxygen.

To test its effectiveness the team used MRI to measure the volume of damaged brain for 30 days following the treatment, and conducted behavioural tests at various intervals within this time.

IS IT possible to tell whether a planet hosts life just from its glow? A new analysis of Earthshine, sunlight reflected off Earth then bounced back by the moon, suggests this is a viable way to seek life on exoplanets.

Life co-exists with certain chemicals that leave their imprint on the light Earth reflects, while plants reflect light differently to rocks. The trouble is that exoplanets are too faint compared with their host stars for such distinctions to be detected.

So Michael Sterzik of the European Southern Observatory in Santiago, Chile, and colleagues used a

spectrograph mounted on the Very Large Telescope to examine polarised Earthshine, its light waves aligned in one plane. The reflection of light off a planet’s surface and passage through the atmosphere cause it to become polarised, making it visible amid the glare of unpolarised starlight.

The team found light signatures of oxygen, ozone and water, as well as an increase in reflected wavelengths characteristic of vegetation (Nature, DOI: 10.1038/nature10778). Future telescopes such as the European Extremely Large Telescope could look for these signs in exoplanet-shine.

Earthshine holds clues for alien hunters

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Monkeys treated with the PSD-95 inhibitor one hour after stroke had 55 per cent less damaged tissue in the brain after 24 hours and 70 per cent less after 30 days, compared with those that took a placebo. These animals also did better in behavioural tests. Importantly, the drug was also effective three hours after stroke (Nature, DOI: 10.1038/nature10841).

An early stage clinical trial in humans, run by firm NoNO in Ontario has also seen positive results.

Red Planet’s got moves like Jagger

ROLLING stones on Mars suggest the Red Planet still rocks with quakes, which could be good for life.

At about half the diameter of Earth, Mars is thought to have radiated away its internal heat quickly, essentially dying geologically many millions of years ago. But boulders that rolled into faults and channels in a region called Cerberus Fossae suggest the planet’s rock ‘n’ roll days may not be over quite yet.

Gerald Roberts at Birkbeck, University of London, and colleagues compared the distribution of the boulders to that of boulders displaced by the 2009 earthquake in mountainous L’Aquila, Italy. In that quake, the size and number of boulders decreased with distance from the epicentre. The same pattern is seen around Cerberus Fossae (Journal of Geophysical Research, DOI: 10.1029/2011JE003816).

“This is consistent with the hypothesis that boulders had been mobilised by ground-shaking,” Roberts says.

The quakes may have occurred only months ago, since the boulders left trails in the Martian dust that had not yet been swept away by wind. If so, it might signal that some magma still flows beneath a nearby dormant volcano. That could be good for the search for Martian life, since magma could melt ice, providing wet, life-friendly habitats.

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