Par Laurent Sacco, Futura-Sciences

La découverte d'un nouveau fossile de dinosaure dans le désert de Gobi, appartenant à une espèce apparentée aux fameux vélociraptors de Jurassic Park, confirme que les oiseaux sont apparus à la suite d'une miniaturisation progressive des dinosaures à plumes. Le nouveau venu a été baptisé Mahakala et il est âgé de 80 millions d'années.

http://www.futura-sciences.com/fr/sinformer/actualites/news/t/paleontologie/d/mahakala-le-nouveau-dinosaure-oiseau-miniature_12867/  

13 September 2007; | doi:10.1038/news070910-9 / http://www.nature.com/news/2007/070910/full/070910-9.html

Fish for sale

Non-profits auction species names for conservation.

Geoff Brumfiel

Launch the slideshow Gerry Allen / CI

Over the years, philanthropists have lent their names to art galleries, schools and hospitals. But in a watershed auction, the world's rich will be able to add their names to several new species of fish - all in the name of charity.

On Thursday 20 September, an auction to name ten new species of fish is being held by the Monaco-based Monaco-Asia Society, a non-profit organization devoted to Asian causes and Conservation International, based in Arlington, Virginia. The fish are a few of the dozens discovered by Conservation International during expeditions to reefs off the coast of Indonesia's Papua Province in 2006.

Bidders will arrive from around the world for a gala at Monaco's Oceanographic Museum, which sits on a bluff high above the Mediterranean Ocean. Prince Albert II will be in attendance, and auction house Christie's will oversee the bidding pro-bono.

This isn't the first auction for a species name. For example, in 2005 an anonymous online bidder won the right to name a new kind of Bolivian monkey for a charitable donation of US$650,000. But this is the first time that multiple species will be auctioned in a single event, according to Monaco-Asia Society president Francesco Bongiovanni.

There's nothing wrong with naming an animal after the rich and famous, says Andrew Polaszek, executive secretary at the International Commission on Zoological Nomenclature in London. The only technical requirements, he says, are that the name must have a generic and specific part and be published in a paper or monograph - something that Conservation International will presumably do. Species are routinely named after famous scientists, and one species of cave beetle is even named after Adolf Hitler. He says that "you can essentially name a species anything you want".

Bongiovanni says he hopes the gala will raise US$1.2-1.4 million for further expeditions and conservation efforts in the region. But is it fair to name a species after a wealthy patron, rather than the scientist who discovered or described it? Bongiovanni says yes - especially because it is all for the greater good of the fish. "At the end of the day," he says, "these species need names."

13 September 2007; | doi:10.1038/news070910-11 / http://www.nature.com/news/2007/070910/full/070910-11.html

Salmon parents give birth to trout

Genetic technique creates viable fish sperm and eggs.

Nicola Jones

Trout juveniles at 6 months old, generated from surrogate salmon parents. Science

Researchers have succeeded in making salmon couples give birth to trout - using a technique that they argue could help to preserve rare species of fish.

Goro Yoshizaki and his colleagues at the Tokyo University of Marine Science and Technology in Japan had previously shown that male salmon could be injected with cells from closely-related trout to produce viable trout sperm. When the sperm were introduced to trout eggs, healthy trout offspring were produced.

Now the researchers have taken the work a step further, showing that salmon can be not only the biological fathers but also the mothers of trout offspring. The new work, published in Science, shows how two sterile masu salmon (Oncorhynchus masou) can together produce nothing but healthy rainbow trout (O. mykiss).

The technique relies on the injection of trout spermatagonia - the early, stem-cell stage of sperm - into salmon embryos, so that the growing salmon produce trout sperm and eggs. The technique could be very useful for storing back-up genetic material of different fish species that are today under threat, because spermatagonia can be easily cryopreserved, says David Penman, a fish geneticist at the University of Stirling, UK.

With many plants and animals, seeds, sperm and eggs can be cryopreserved to later resurrect a species that has died out. "The problem with gene-banking when you come to fish, is that it's almost impossible with eggs," says Penman. "The eggs are very big, very yolky," he says, which makes them nearly impossible to freeze.

If Yoshizaki's technique is broadly applicable to other fish, it will mean that their eggs don't need to be preserved - they could be made at a later date, in a surrogate fish.

The sperm that turned

Injecting trout spermatogonia into a salmon embryo. Science

If trout spermatagonia are injected into normal male salmon embryos, the fish will grow up to produce a mix of different types of sperm - some salmon, and some trout. In the team's previous work, when sperm from male salmon treated with primordial germ cells (an even earlier stage of sperm) were used to fertilize trout eggs, just 0.4% of the resulting offspring were healthy trout. The rest were hybrids that did not survive.

To increase this percentage, the team turned to salmon designed to have three sets of chromosomes instead of the usual two, making them sterile. When they are injected with spermatagonia, the only viable sperm the males later produce comes from these injected cells - making them 100% trout.

The group also met with success doing the same thing with sterile female salmon. When the female fish were injected as embryos with spermatagonia, the eggs they produced were all trout eggs.

The fact that an early form of sperm could be used to prompt the growth of eggs shows just how flexible these fish are to this type of treatment, notes Penman. "It's really amazing to see that they injected spermatagonia and got eggs - the fish are very plastic."

When mated, these salmon parents produced healthy trout offspring, which in turn mated to give a healthy second generation.

Save the fish

Yoshizaki and his colleagues hope the technique could be used to help save endangered fish.

"There are lots of species of fish that are threatened," says Penman. He says he thinks that to use this approach properly will mean thinking about cryopreserving a lot of material, to save all species and ensure that resulting populations are not too inbred. And some species are likely to be easier to work with than others, he adds. "If you don't happen to have a closely related recipient [for a surrogate] then you'd struggle. There are some groups where there are lots of close relatives, but some where there are only a few," he says.

"It's better to look at all the aspects of conservation biology - but this will be a useful additional technique, as a backup," Penman says.

Reference : Okutsu, T., Shikina, S., Kanno, M., Takeuchi, Y.& Yoshizaki, G.,Science 317,1517(2007). 

13 September 2007; | doi:10.1038/news070910-10 / http://www.nature.com/news/2007/070910/full/070910-10.html;jsessionid=130005018281DDD191001F471D2C3680

Gene knockout extends life of mice with ALS

Deleting a single gene almost doubles lifespan.

Heidi Ledford

Not many drugs for neurodegenerative disease tested on mice work in people. Punchstock

Knocking out a single gene nearly doubles the lifespan of mice with the animal model of Lou Gehrig's disease, suggesting that the gene may one day become a target for therapies in humans.

Lou Gehrig's disease, otherwise known as amyotrophic lateral sclerosis (ALS), is a neurodegenerative disease that gradually erodes motor control. Death usually follows within three to five years of diagnosis. There is no cure, and the only drug available that slows progression of the disease, riluzole, prolongs survival only by a few months.

Mice develop ALS-like symptoms when they have a mutation in a gene called SOD1 - a mutation that causes about 1-2% of human ALS cases. Research using these animal models has suggested that chemically reactive forms of oxygen that can damage cells also contribute to the disease.

Several proteins present in the bodies of mice and people are known to generate reactive oxygen species as part of their normal function in cell signalling and inflammation. So John Engelhardt and his colleagues at the University of Iowa in Iowa City decided to look closely at two of these - Nox1 and Nox2 - to see whether turning down the amount of such proteins could slow the progression of ALS symptoms.

It did - dramatically. The team found that ALS mice lacking the gene that creates Nox2 produced fewer reactive oxygen species and lived on average for 229 days - 97 days longer than those who had normal levels of Nox2.

In an unexpected twist, many of the mice that lacked Nox2 also suffered from aggressive eye infections that, if left untreated, were often fatal. The reason for this is not known.

Double whammy

Eliminating the gene for Nox1 also extended lifespan, but only by 33 days. These results are still exciting, says neurologist Serge Przedborski of Columbia University in New York, because Nox1 is expressed, in part, in blood vessels, and there are hints that something might be going on in these vessels that affects the disease.

Work published last year by Przedborski also showed that eliminating Nox2 prolongs life in ALS mice, but the effect found in that research was much smaller: the mice only survived an additional 13 days. Differences between the two results could stem from the different genetic backgrounds of the mice used, says Engelhardt.

Przedborski says the new results are encouraging. The relatively small increase in lifespan that he had previously observed had discouraged his research team from pushing towards human trials. "In light of this paper, I think we probably were wrong," says Przedborski. The new data make a stronger case for pursuing Nox2-targeting drugs, he says.

Lessons learned

The results are potentially valuable for designing new therapies, agrees neurologist Jeffrey Rothstein of Johns Hopkins University in Baltimore, Maryland, but researchers should use caution before extrapolating from mice to humans. More than 100 drugs have been studied in ALS mice, many of which increased survival. About a dozen of those have been tested in humans, but so far only riluzole has proven consistently effective.

And then there are the lessons learned from minocycline, an antibiotic that performed better than riluzole in mice, yet worsened symptoms in humans. Minocycline dampens the activity of neuronal immune cells called microglia. Nox2 is also expressed in these cells, and that, says Rothstein, should raise a red flag about drugs that reduce Nox2 expression.

That's true, says Engelhardt. But minocycline also had very broad anti-inflammatory activity, and a drug that targets a single gene, such as Nox2, may not produce the same side effects. "Specificity for any drug is key," he says.

References

1. Marden, J.J., et al. J. Clin. Invest doi:10.1172/JCI31265 (2007).
2. Wu, D.C., et al. Proc. Natl Acad. Sci. USA 103 , 12132 - 12137 (2006).

 

12 September 2007; | doi:10.1038/news070910-7 / http://www.nature.com/news/2007/070910/full/070910-7.html

Neanderthals 'not killed by climate change'

Study suggests demise did not coincide with climate cooling.

Michael Hopkin

Just the two of us: Did Homo sapiens (right) wipe out neanderthals (left) ? NPG

Whatever it was that sealed the fate of the Neanderthals, it looks unlikely to have been climate change. That is the verdict of a new study that used climate records from Venezuela to deduce what happened at the Neanderthals' last stand at the southern tip of Europe.

The research suggests that a switch to a cold, dry climate was probably not the telling factor in the demise of the Neanderthals, because of all the probable dates for their extinction, most do not lie near major cold events in the climate record.

Neanderthals (Homo neanderthalensis) lived in Europe until around 30,000 years ago - not long after Homo sapiens arrived on the scene 40,000 years ago. The Neanderthals are thought to have lasted longest in the region around Gibraltar, off the southern tip of Spain.

"There are different factors that have been invoked to explain the Neanderthal extinction," says Chronis Tzedakis of the University of Leeds, UK, who led the new research. "Clearly the appearance of anatomically modern humans is the prime suspect, but given that the extinction happened during the last glacial period, when climate was changing, what we know is that the climate was extremely unstable at that time."

The main problem with testing the different theories comes from the difficulty in dating accurately the age of Neanderthal fossils and tools to compare their ages with records of past climate.

This is because 'radiocarbon dating' used on Neanderthal remains - in which researchers measure the amount of the radioactively decaying isotope carbon-14 in a sample to determine its age - is not directly related to calendar years. For very old samples, it can be used to tell whether one object is older than another, but not to determine their exact ages.

Like with like

Tzedakis and his colleagues got around this problem by comparing the radiocarbon dates of Neanderthal tools from Gorham's Cave in Gibraltar, with a very accurate set of radiocarbon dates of ocean sediments, in which the lives of tiny sea-creatures record the climate of the time. These well-dated sediments happen to come from Cariaco Basin, Venezuela.

The researchers report in Nature, that of the three main radiocarbon dates given as possible extinction times for the Neanderthals - 32,000 years, 28,000 years and 24,000 years - only the most recent seems to have occurred at the same time as a climate shift. This most recent date is also the most controversial, meaning that it is generally more likely that it was competition with modern humans, rather than the bitter cold, that did for the Neanderthals.

"The take-home message is that we can eliminate catastrophic climate change as a factor for Neanderthal extinction," Tzedakis says.

The same method can be applied to assess the climatic conditions during any 'snapshot' event that is represented by accurately carbon-dated samples, Tzedakis adds. The climate in Venezuela is reflective of the climate in Europe, he adds, because many of Europe's climate shifts involved changes in the Gulf Stream, which influences climate from tropical America to the northern reaches of the Atlantic Ocean. And large climate swings, from warm and wet to cold and dry, tended to occur more or less all at once globally. "Changes from one condition to the other were extremely abrupt - of the order of a few decades," Tzedakis explains.

Reference : Tzedakis, P.C., Hughen, K.A., Cacho, I.& Harvati, K., . Nature 449 , 206 - 208 (2007).