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Chemical tag to identify black-market caviar
IN BRIEF
ALEXANDER NATRUSKIN/REUTERS
FARMED sturgeon on special diets could undermine the market for illegal caviar and help save the species from extinction. International regulations introduced this year mean only caviar from farmed sturgeon can be traded legally. But as there is no way to tell if caviar is farmed or “wild”, the new rules offer scant hope for sturgeon in the Caspian Sea, where overfishing has reduced their numbers by 90 per cent in the past two decades. Until recently, the Caspian supplied 90 per cent of the world’s caviar. Sven Wuertz at the University of Kiel, Germany, and his colleagues put capric acid, a fatty acid, in the food of female sturgeon and found that the tracer accumulated in their eggs after 10 days. The amount of capric acid in the resulting caviar was too low to change its taste. Wuertz believes his team has hit on a cheap and simple tool to “tag” farmed caviar. Once fully tested, it could help the Convention on International Trade in Endangered Species, which at present relies on labelling to regulate where caviar comes from. The study is important, says Phaedra Doukakis, a caviar conservation biologist at Stony Brook University, New York, as ways to distinguish wild and aquacultured caviar are needed.
24 | NewScientist | 7 November 2009
What drives a lion to think, ‘I feel like a human tonight’ WHEN the food gets scarce, it’s every lion for itself. In 1898, according to numerous accounts and no fewer than three Hollywood movies, two male lions went on a 9-month killing spree around the Tsavo area of Kenya, devouring between 28 and 135 workers building the KenyaUganda railway. Now an analysis of bone and hair samples from the notorious duo has backed the theory that scarcity drives dietary specialisation, and shows that food preferences can diverge
within co-operating groups. By comparing the isotopic ratios of nitrogen and carbon in the lions’ remains with that of contemporary lions, humans and herbivore prey, Justin Yeakel of the University of California, Santa Cruz, estimates the lions ate around 35 people. The study also made a surprise finding. “One lion was consuming a lot of humans, and one was not,” Yeakel says (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0905309106). He attributes 24 deaths to one
cat, or 30 per cent of its diet, and 11 deaths to the other, just 13 per cent of its food. By the late 19th century, elephants in the area had been hunted away, causing grasslands to become overgrown woodlands and the number of ungulate prey to decline. Most lions probably left the region, but two turned maneaters, Yeakel speculates. “People are a dangerous food to go after,” he says. “One lion was able to figure out how to do it and wasn’t afraid, the other was not.” TOMMASO BONAVENTURA/CONTRASTO/EYEVINE
Caviar tag to save Caspian sturgeon
Evidence recovered from polluted DNA CONTAMINATED crime-scene DNA samples that would normally be written off as forensically useless can now be rescued, thanks to amplification enzymes that tolerate pollution. Before a profile can be obtained from a DNA sample recovered from a crime scene, it must be amplified using enzymes called polymerases. Pollutants such as tobacco or aluminium from drink cans can stop the enzyme working, but now Johannes Hedman and colleagues at the Swedish National Laboratory of Forensic Science have come up with some alternatives to the AmpliTaqGold enzyme, which is preferred by forensic labs. The team amplified 32 polluted samples of saliva using three other polymerases regularly used to process non-forensic samples. Of these samples, 20 showed statistically significant improvements in the quality of the profile compared with using AmpliTaqGold (Biotechniques, vol 47, p 351). Hedman suggests that employing these enzymes could be useful for samples that till now would not yield a complete DNA profile.
Quakes centuries apart may be linked SOME earthquakes can leave a legacy of aftershocks that last for centuries. Low-level seismic rumbles appear to foreshadow many quakes. Yet not always: the 2008 Sichuan quake in China (pictured) came out of the blue. These rumbles may not be precursors but aftershocks – readjustments at a fault following a larger event, in some cases centuries earlier. Seth Stein of Northwestern University in Evanston, Illinois, and colleagues analysed the rate of fault slip in various tectonic settings. At plate boundaries, motion rapidly “reloads” a fault with new stress
and changes conditions there, so tremors that can be clearly identified as aftershocks typically end within a decade, they found. Far away from plate boundaries, however, fault reloading is much slower, and aftershocks can continue for hundreds of years. The New Madrid fault in Missouri, for instance, may be experiencing aftershocks from a quake in the early 1800s (Nature, DOI: 10.1038/nature08502). Seismic activity away from plate boundaries “tells you more about where large quakes were than where the next one will be”, says Stein.
ALEXANDER NATRUSKIN/REUTERS
FARMED sturgeon on special diets could undermine the market for illegal caviar and help save the species from extinction. International regulations introduced this year mean only caviar from farmed sturgeon can be traded legally. But as there is no way to tell if caviar is farmed or “wild”, the new rules offer scant hope for sturgeon in the Caspian Sea, where overfishing has reduced their numbers by 90 per cent in the past two decades. Until recently, the Caspian supplied 90 per cent of the world’s caviar. Sven Wuertz at the University of Kiel, Germany, and his colleagues put capric acid, a fatty acid, in the food of female sturgeon and found that the tracer accumulated in their eggs after 10 days. The amount of capric acid in the resulting caviar was too low to change its taste. Wuertz believes his team has hit on a cheap and simple tool to “tag” farmed caviar. Once fully tested, it could help the Convention on International Trade in Endangered Species, which at present relies on labelling to regulate where caviar comes from. The study is important, says Phaedra Doukakis, a caviar conservation biologist at Stony Brook University, New York, as ways to distinguish wild and aquacultured caviar are needed.
24 | NewScientist | 7 November 2009
What drives a lion to think, ‘I feel like a human tonight’ WHEN the food gets scarce, it’s every lion for itself. In 1898, according to numerous accounts and no fewer than three Hollywood movies, two male lions went on a 9-month killing spree around the Tsavo area of Kenya, devouring between 28 and 135 workers building the KenyaUganda railway. Now an analysis of bone and hair samples from the notorious duo has backed the theory that scarcity drives dietary specialisation, and shows that food preferences can diverge
within co-operating groups. By comparing the isotopic ratios of nitrogen and carbon in the lions’ remains with that of contemporary lions, humans and herbivore prey, Justin Yeakel of the University of California, Santa Cruz, estimates the lions ate around 35 people. The study also made a surprise finding. “One lion was consuming a lot of humans, and one was not,” Yeakel says (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0905309106). He attributes 24 deaths to one
cat, or 30 per cent of its diet, and 11 deaths to the other, just 13 per cent of its food. By the late 19th century, elephants in the area had been hunted away, causing grasslands to become overgrown woodlands and the number of ungulate prey to decline. Most lions probably left the region, but two turned maneaters, Yeakel speculates. “People are a dangerous food to go after,” he says. “One lion was able to figure out how to do it and wasn’t afraid, the other was not.” TOMMASO BONAVENTURA/CONTRASTO/EYEVINE
Caviar tag to save Caspian sturgeon
Evidence recovered from polluted DNA CONTAMINATED crime-scene DNA samples that would normally be written off as forensically useless can now be rescued, thanks to amplification enzymes that tolerate pollution. Before a profile can be obtained from a DNA sample recovered from a crime scene, it must be amplified using enzymes called polymerases. Pollutants such as tobacco or aluminium from drink cans can stop the enzyme working, but now Johannes Hedman and colleagues at the Swedish National Laboratory of Forensic Science have come up with some alternatives to the AmpliTaqGold enzyme, which is preferred by forensic labs. The team amplified 32 polluted samples of saliva using three other polymerases regularly used to process non-forensic samples. Of these samples, 20 showed statistically significant improvements in the quality of the profile compared with using AmpliTaqGold (Biotechniques, vol 47, p 351). Hedman suggests that employing these enzymes could be useful for samples that till now would not yield a complete DNA profile.
Quakes centuries apart may be linked SOME earthquakes can leave a legacy of aftershocks that last for centuries. Low-level seismic rumbles appear to foreshadow many quakes. Yet not always: the 2008 Sichuan quake in China (pictured) came out of the blue. These rumbles may not be precursors but aftershocks – readjustments at a fault following a larger event, in some cases centuries earlier. Seth Stein of Northwestern University in Evanston, Illinois, and colleagues analysed the rate of fault slip in various tectonic settings. At plate boundaries, motion rapidly “reloads” a fault with new stress
and changes conditions there, so tremors that can be clearly identified as aftershocks typically end within a decade, they found. Far away from plate boundaries, however, fault reloading is much slower, and aftershocks can continue for hundreds of years. The New Madrid fault in Missouri, for instance, may be experiencing aftershocks from a quake in the early 1800s (Nature, DOI: 10.1038/nature08502). Seismic activity away from plate boundaries “tells you more about where large quakes were than where the next one will be”, says Stein.