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There are hardly any old fish left in the sea – and that's bad
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IN BRIEF Third-hand smoke damages organs
There are hardly any old fish left in the sea – and that’s bad THERE aren’t just fewer fish in the sea: there are far fewer old fish, too. Their numbers in fisheries around the US and Europe have fallen by an average of 72 per cent. Lewis Barnett at the University of Washington in Seattle and his colleagues looked at records covering 63 fisheries, spanning 24 to 140 years. They used several methods to work out the age of the fish, including examining otoliths: “stones” in their ears that grow annual rings, just like trees do. A 2010 study of 10 fisheries found a 25 per cent fall in old fish. But Barnett used models to estimate numbers
before large-scale fishing began – revealing the stark long-term decline. In some species, like Atlantic cod, populations of older fish fell over 95 per cent (Current Biology, doi.org/cc5t). Losing older fish may not sound bad, as they might be near death. But old fish tend to produce more offspring per spawning. They also adapt to changing conditions better, for instance by spawning at different times and locations. This makes short-term environmental change less likely to affect the population badly. Having only a few old fish leaves fisheries prone to collapse, but they can be saved. One way is to regularly stop fishing in certain areas to let numbers recover. Alternatively, “slot limits” could set minimum and maximum sizes of fish that can be harvested.
DNA robot delivers molecule cargo A robot made from a single strand of DNA could one day ferry medicines to diseased cells through the bloodstream or build chemical compounds in molecular factories. Lulu Qian at the California Institute of Technology and her colleagues have created a DNA robot that consists of a leg with two feet attached to two arms for carrying cargo. To test it, the team 18 | NewScientist | 23 September 2017
created a flat 58-by-58-nanometre surface with little DNA stepping stones for it to hop between. The robot successfully picked up six fluorescent dyes – three yellow and three pink – and moved them to one of two destinations (Science, doi.org/cc52). A single step between stones, which are 6 nanometres apart, takes 5 minutes, so covering the entire surface took a whole day.
But adding an enzyme could give the robot the extra thrust of a chemical motor. “This is one of the first steps towards developing general-purpose DNA robots,” says Qian. “This is the ultimate example of minuscule robotics, and yet it is still programmable and predictable,” says Robert Cross at the University of Warwick, UK. Specific signals could be used to get the bots to deliver a drug to cells that show signs of disease.
EXPOSURE to the chemicals that cigarette smoke leaves behind on clothing and furniture seems to increase the risk of liver damage and diabetes in mice. Manuela Martins-Green at the University of California, Riverside, and her team exposed fabric to levels of smoke similar to those found in smokers’ homes. Mice living in cages with these fabrics for up to six months had more cell damage in their liver and brain than mice who weren’t exposed to this third-hand smoke. The exposed animals also had a 30 per cent rise in fasting blood glucose and insulin. Both measures are known to increase the risk of diabetes (Clinical Science, doi.org/cc5m). The results are biologically plausible, says Taylor Hays at the Mayo Clinic in Rochester, Minnesota, but further study is needed before we know if it also affects humans.
Brown dwarf has star quality A MAGNETIC disturbance has been directly observed on a brown dwarf for the first time. These objects straddle the line between stars and planets, but this slots them more in the star category. Svetlana Berdyugina at the University of Freiburg, Germany, led a team that used observations from the Keck telescope to view the magnetism of a brown dwarf 55 times the mass of Jupiter (arxiv. org/abs/1709.02861). The field is bigger than those of strong sunspots. She says this is because brown dwarfs are relatively dense compared with stars. This work shows that brown dwarfs exhibit strong magnetic fields and possibly, like stars, interact with the discs of gas and dust around them in their youth.
IN BRIEF Third-hand smoke damages organs
There are hardly any old fish left in the sea – and that’s bad THERE aren’t just fewer fish in the sea: there are far fewer old fish, too. Their numbers in fisheries around the US and Europe have fallen by an average of 72 per cent. Lewis Barnett at the University of Washington in Seattle and his colleagues looked at records covering 63 fisheries, spanning 24 to 140 years. They used several methods to work out the age of the fish, including examining otoliths: “stones” in their ears that grow annual rings, just like trees do. A 2010 study of 10 fisheries found a 25 per cent fall in old fish. But Barnett used models to estimate numbers
before large-scale fishing began – revealing the stark long-term decline. In some species, like Atlantic cod, populations of older fish fell over 95 per cent (Current Biology, doi.org/cc5t). Losing older fish may not sound bad, as they might be near death. But old fish tend to produce more offspring per spawning. They also adapt to changing conditions better, for instance by spawning at different times and locations. This makes short-term environmental change less likely to affect the population badly. Having only a few old fish leaves fisheries prone to collapse, but they can be saved. One way is to regularly stop fishing in certain areas to let numbers recover. Alternatively, “slot limits” could set minimum and maximum sizes of fish that can be harvested.
DNA robot delivers molecule cargo A robot made from a single strand of DNA could one day ferry medicines to diseased cells through the bloodstream or build chemical compounds in molecular factories. Lulu Qian at the California Institute of Technology and her colleagues have created a DNA robot that consists of a leg with two feet attached to two arms for carrying cargo. To test it, the team 18 | NewScientist | 23 September 2017
created a flat 58-by-58-nanometre surface with little DNA stepping stones for it to hop between. The robot successfully picked up six fluorescent dyes – three yellow and three pink – and moved them to one of two destinations (Science, doi.org/cc52). A single step between stones, which are 6 nanometres apart, takes 5 minutes, so covering the entire surface took a whole day.
But adding an enzyme could give the robot the extra thrust of a chemical motor. “This is one of the first steps towards developing general-purpose DNA robots,” says Qian. “This is the ultimate example of minuscule robotics, and yet it is still programmable and predictable,” says Robert Cross at the University of Warwick, UK. Specific signals could be used to get the bots to deliver a drug to cells that show signs of disease.
EXPOSURE to the chemicals that cigarette smoke leaves behind on clothing and furniture seems to increase the risk of liver damage and diabetes in mice. Manuela Martins-Green at the University of California, Riverside, and her team exposed fabric to levels of smoke similar to those found in smokers’ homes. Mice living in cages with these fabrics for up to six months had more cell damage in their liver and brain than mice who weren’t exposed to this third-hand smoke. The exposed animals also had a 30 per cent rise in fasting blood glucose and insulin. Both measures are known to increase the risk of diabetes (Clinical Science, doi.org/cc5m). The results are biologically plausible, says Taylor Hays at the Mayo Clinic in Rochester, Minnesota, but further study is needed before we know if it also affects humans.
Brown dwarf has star quality A MAGNETIC disturbance has been directly observed on a brown dwarf for the first time. These objects straddle the line between stars and planets, but this slots them more in the star category. Svetlana Berdyugina at the University of Freiburg, Germany, led a team that used observations from the Keck telescope to view the magnetism of a brown dwarf 55 times the mass of Jupiter (arxiv. org/abs/1709.02861). The field is bigger than those of strong sunspots. She says this is because brown dwarfs are relatively dense compared with stars. This work shows that brown dwarfs exhibit strong magnetic fields and possibly, like stars, interact with the discs of gas and dust around them in their youth.