Science  24 Aug 2012:
Vol. 337, Issue 6097, pp. 898

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  1. Zoos Help Germs Jump Species Barrier

    Jerka, in 2007


    An international team of researchers has implicated a surprising culprit in the case of a dead polar bear: a zebra virus.

    In June 2010, Jerka, a 20-year-old polar bear in a zoo in Wuppertal, Germany, suffered seizures and died a few days later. In the animal's brain, scientists found only one candidate pathogen, a recombinant form of two herpes viruses found in zebras, EHV1 and EHV9, they reported last week in Current Biology. How the polar bear became infected is unclear, because zebras and bears had no direct contact and no keepers cared for both. One possibility, the authors suggest, is that rodents might have carried the virus from one enclosure to the other.

    “This case illustrates that when you are bringing animals from different continents together in a zoo, you are also giving pathogens the opportunity to recombine and jump to another host,” says lead author Alex Greenwood of the Leibniz Institute for Zoo and Wildlife Research in Berlin. The frequency of such events is probably underestimated, he suggests, because most zoo animal deaths do not trigger such an intense investigation.

  2. Older Dads Pass On More Mutations

    A group of Icelandic families with a high rate of schizophrenia and autism spectrum disorders (ASD) have helped researchers pin down an older father's impact on his offspring's genetics. For every extra birthday the father has had, his child carries an average of 2.01 additional mutations.

    The work, published this week in Nature by the Icelandic company deCODE genetics, backs up studies suggesting that a father's age correlates with a child's increased risk of these disorders. Sperm from older men is thought to be more likely to carry spontaneous, or de novo, mutations. “The large linear effect of more than two extra mutations per year,” the researchers write, “is striking.” They nailed the number down by sequencing and studying 78 families, which included 65 offspring who had either schizophrenia or ASD. Nearly 2000 other Icelanders served as controls.

    Older mothers seemed slightly more likely to pass on de novo mutations to their children. But it was the dads who primarily determined how many of these mutations their children ended up with.

  3. No Star Left Behind

    Contrary to expectations, the brightest supernova in recorded history left no star in its wake, say astronomers who have searched the celestial wreckage. In 1006, observers watched a star explode in the constellation Lupus. The explosion was a Type Ia supernova, the most luminous variety; it occurred when a small, dense star known as a white dwarf blew up about 7000 light-years from Earth. Such a supernova is supposed to result when a larger companion star dumps material onto the white dwarf, triggering a runaway nuclear reaction that annihilates the smaller star. However, as astronomers will report in The Astrophysical Journal, a thorough search for the companion, which should have survived the explosion, has turned up nothing—suggesting instead that two white dwarfs that were in orbit around each other merged and blew up, and hinting that more Type Ia supernovae may stem from double white dwarfs than astronomers had thought.