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Birds seem to ‘see’ magnetic fields while navigating
IN BRIEF ‘Gatorade for frogs’ delays fungal killer
KIM TAYLOR/NATUREPL.COM
Birds navigate by ‘seeing’ magnetic field lines BIRDS that navigate using the Earth’s magnetic field rely more on their eyes than on the magnetic particles in their nostrils, an experiment on robins suggests. Rival theories of bird navigation have suggested both mechanisms. Now Henrik Mouritsen at the University of Oldenburg, Germany, and his team have show that eyes could be key. In one group of robins, the team removed cluster N, a brain region involved in processing signals from the “pair-forming photopigments” in the eyes thought to relay magnetic compass information. In another group, the team cut the trigeminal nerve, which sends signals to
the brain from the magnetic particles in the nostrils. The researchers then exposed the surgically treated and untreated robins to the Earth’s natural magnetic field, and also to a field which artificially rotated magnetic north 120 degrees anticlockwise. The robins lacking their nostril-to-brain connection weren’t tricked, locating the true and artificial magnetic norths just as well as the controls. But the robins without cluster N were unable to navigate. “The results raise the distinct possibility that this part of the visual system enables birds to ‘see’ magnetic compass information,” conclude the researchers (Nature, DOI: 10.1038/nature08528). “It goes a long way to demonstrating that the magnetic compass response is mediated by the eye,” says Verner Bingman of Bowling Green State University in Ohio.
Message from planets in distant galaxies WITH the discovery of planets around distant stars in the Milky Way now almost routine, it takes evidence of planets beyond our own galaxy to turn heads – and that’s what Erin Mentuch at the University of Toronto in Canada has produced. Mentuch analysed 88 remote galaxies whose light was emitted when the universe was between a quarter and half its current age – 18 | NewScientist | 31 October 2009
making them far too remote for their stars to be seen individually. The galaxies’ light output peaks at two distinct wavelengths. One represents the combined light of a galaxy’s stars; the other, at longer wavelengths, comes from the glow of its interstellar dust. In each case, Mentuch noticed a faint third component between the two peaks. Whatever produces this light is too cold to be stars and
too warm to be dust. The most likely source is circumstellar discs – embryonic solar systems around young stars. “It’s the most surprising result I’ve ever worked on,” says Roberto Abraham, who collaborated with Mentuch. The opportunity to study discs that existed so long ago could help reveal how the rate of planet formation across the universe has changed over time, says Mentuch. The work will appear in The Astrophysical Journal.
THE deadly fungal disease known as chytridiomycosis is killing frogs worldwide by impairing the animals’ ability to absorb electrolytes through their skin. In frogs with the disease, the skin’s ability to take up sodium and potassium ions from the water decreases by more than 50 per cent, Jamie Voyles of James Cook University in Townsville, Queensland, Australia, and his colleagues found (Science, DOI: 10.1126/science.1176765). This causes the levels of these ions in the frogs’ blood to fall by 20 and 50 per cent, respectively, leading to cardiac arrest and death. The researchers found that they could delay death by giving the diseased frogs an oral electrolytereplacement solution – a sort of froggy Gatorade. While this did not save the frogs, the findings are a first step towards finding an effective treatment for the disease, Voyles says.
Odd outbursts are dead stars talking MYSTERIOUS radio blips that come from apparently empty regions of space may be the voices of long dead stars. Thirteen unexplained radio blips have turned up in recent radio telescope observations. They emerged in spots where there are no stars or galaxies to be seen. The blips could be traces of a vast population of stellar corpses – neutron stars that roam largely unseen, suggests a team led by Eran Ofek of Caltech in Pasadena (arxiv.org/abs/0910.3676). Most of the galaxy’s estimated billion neutron stars are invisible. But if each produces a radio burst every few months, perhaps after absorbing interstellar gas, the close ones would be detected at the rate observed, the team calculates.
KIM TAYLOR/NATUREPL.COM
Birds navigate by ‘seeing’ magnetic field lines BIRDS that navigate using the Earth’s magnetic field rely more on their eyes than on the magnetic particles in their nostrils, an experiment on robins suggests. Rival theories of bird navigation have suggested both mechanisms. Now Henrik Mouritsen at the University of Oldenburg, Germany, and his team have show that eyes could be key. In one group of robins, the team removed cluster N, a brain region involved in processing signals from the “pair-forming photopigments” in the eyes thought to relay magnetic compass information. In another group, the team cut the trigeminal nerve, which sends signals to
the brain from the magnetic particles in the nostrils. The researchers then exposed the surgically treated and untreated robins to the Earth’s natural magnetic field, and also to a field which artificially rotated magnetic north 120 degrees anticlockwise. The robins lacking their nostril-to-brain connection weren’t tricked, locating the true and artificial magnetic norths just as well as the controls. But the robins without cluster N were unable to navigate. “The results raise the distinct possibility that this part of the visual system enables birds to ‘see’ magnetic compass information,” conclude the researchers (Nature, DOI: 10.1038/nature08528). “It goes a long way to demonstrating that the magnetic compass response is mediated by the eye,” says Verner Bingman of Bowling Green State University in Ohio.
Message from planets in distant galaxies WITH the discovery of planets around distant stars in the Milky Way now almost routine, it takes evidence of planets beyond our own galaxy to turn heads – and that’s what Erin Mentuch at the University of Toronto in Canada has produced. Mentuch analysed 88 remote galaxies whose light was emitted when the universe was between a quarter and half its current age – 18 | NewScientist | 31 October 2009
making them far too remote for their stars to be seen individually. The galaxies’ light output peaks at two distinct wavelengths. One represents the combined light of a galaxy’s stars; the other, at longer wavelengths, comes from the glow of its interstellar dust. In each case, Mentuch noticed a faint third component between the two peaks. Whatever produces this light is too cold to be stars and
too warm to be dust. The most likely source is circumstellar discs – embryonic solar systems around young stars. “It’s the most surprising result I’ve ever worked on,” says Roberto Abraham, who collaborated with Mentuch. The opportunity to study discs that existed so long ago could help reveal how the rate of planet formation across the universe has changed over time, says Mentuch. The work will appear in The Astrophysical Journal.
THE deadly fungal disease known as chytridiomycosis is killing frogs worldwide by impairing the animals’ ability to absorb electrolytes through their skin. In frogs with the disease, the skin’s ability to take up sodium and potassium ions from the water decreases by more than 50 per cent, Jamie Voyles of James Cook University in Townsville, Queensland, Australia, and his colleagues found (Science, DOI: 10.1126/science.1176765). This causes the levels of these ions in the frogs’ blood to fall by 20 and 50 per cent, respectively, leading to cardiac arrest and death. The researchers found that they could delay death by giving the diseased frogs an oral electrolytereplacement solution – a sort of froggy Gatorade. While this did not save the frogs, the findings are a first step towards finding an effective treatment for the disease, Voyles says.
Odd outbursts are dead stars talking MYSTERIOUS radio blips that come from apparently empty regions of space may be the voices of long dead stars. Thirteen unexplained radio blips have turned up in recent radio telescope observations. They emerged in spots where there are no stars or galaxies to be seen. The blips could be traces of a vast population of stellar corpses – neutron stars that roam largely unseen, suggests a team led by Eran Ofek of Caltech in Pasadena (arxiv.org/abs/0910.3676). Most of the galaxy’s estimated billion neutron stars are invisible. But if each produces a radio burst every few months, perhaps after absorbing interstellar gas, the close ones would be detected at the rate observed, the team calculates.