Editors' Choice

Science  04 Jul 2014:
Vol. 345, Issue 6192, pp. 43
  1. Zoology

    Butterflies steer with magnetic compass

    1. Carolyn Gramling

    Migrating monarchs head south each fall

    PHOTO: ADAM SKOWRONSK/FLICKR

    Each fall, eastern North American monarch butterflies migrate 4000 kilometers south to central Mexico. In daylight, the butterflies navigate by the Sun's position and their antennal circadian clocks. But under overcast skies, they rely instead on a magnetic compass, Guerra et al. found. The team put monarchs in a flight simulator surrounded by a magnetic coil, measuring responses to horizontal, vertical, and intensity changes in the magnetic field. Monarchs, they found, navigate north or south using the change in dip of Earth's magnetic field lines with latitude. And as in birds, the compass is light-sensitive; monarchs need ultraviolet-to-blue wavelengths to find their way.

    Nat. Comm. 10.1038/ncomms5164 (2014).

  2. Risk Perception

    How many words equal a number?

    1. Gilbert Chin

    The probability that an event will occur can be expressed in words (“very unlikely”) or in numbers (“<10%”). Budescu et al. show that to communicate clearly to a lay audience, it is better to use words and numbers together than words alone. They asked 10,000 adults across 25 countries to give their numerical interpretation of probability terms (very unlikely, unlikely, likely, or very likely) used in Intergovernmental Panel on Climate Change (IPCC) statements. With only words, people interpreted unlikely events to be more likely than the IPCC intended, and vice versa. When the experimenters used both words and numerical ranges, however, the respondents estimated probabilities more accurately.

    Nat. Clim. Change 4, 508 (2014).

  3. Arterial Innervation

    Netrin-1 helps to get the blood flowing

    1. Beverly A. Purnell

    In moments of crisis, you might remind yourself to breathe, but generally this and other functions controlled by the autonomic sympathetic nervous system, such as swallowing or maintaining blood flow to the heart and central nervous system, proceed without thought. To function properly, the autonomic sympathetic nervous system requires nerves and blood vessels to coordinate with each other as they grow. Using genetic and pharmacological approaches, Brunet et al. find that the protein netrin-1, produced by arteries, directs sympathetic neurons to develop normally around arteries. This parallels netrin-1's role in guiding neuronal axons toward their correct targets.

    J. Clin. Invest. 10.1172/JCI75181 (2014).

  4. Cancer Immunology

    Blocking IL-22 to stop cancer spread

    1. Kristen L. Mueller

    Cancer metastasis, when tumors spread from their primary location, is almost always deadly, so patients need anti-metastatic therapies. Cancer stem cells (cells within the tumors that can renew themselves) may drive metastasis. Kryczek et al. now report that CD4+ T cells within human colorectal cancer tissues produce the protein interleukin-22 (IL-22), which helps to maintain colorectal cancer stem cells. IL-22 blockade slowed down colon cancer in mice, whereas IL-22 made the cancer grow. And IL-22 helped tumor cells express stem-cell genes through epigenetic changes to these genes. Colon-cancer patients with these epigenetic modifications also had worse prognoses, which suggests that blocking IL-22 may provide therapeutic benefit.

    Immunity 40, 772 (2014).

  5. Ecology

    Casting new shade onto ecosystem threshholds

    1. Julia Fahrenkamp-Uppenbrink

    As environmental conditions change, ecosystems can suddenly enter a different and potentially unfavorable state. Researchers have captured such threshold crossings in whole-lake experiments, but it's much harder to study them experimentally in the dynamic open ocean. Thrush et al. cast shade on marine sandflats in New Zealand and looked at what happened to two species of bivalves. They found changes in how the bivalves interacted, in the primary producers that they feed on, and in their physical and chemical environment. Shading causes a loss of positive feedbacks; within about 100 days, the interaction network had shifted to a new configuration. The comparatively simple experimental system helps to identify the risks of threshold crossings.

    Bivalves on marine sandflats in New Zealand

    PHOTO: S. THRUSH ET AL. ECOLOGY 95, 6 (JUNE 2014) © 2014 ECOLOGICAL SOCIETY OF AMERICA

    Ecology 95, 1451 (2014).

  6. Microbial Genetics

    Worming into host immune responses

    1. Caroline Ash

    The whipworm Trichuris trichirura

    PHOTO: CNRI/SCIENCE SOURCE

    Among the variety of parasitic worms that can infest human beings, whipworms, or trichurids, are distinct. They partially burrow into the gastrointestinal wall and immediately influence host immune responses. The worms need to persist in the gut to reproduce, which means they have to dampen their hosts' immune responses. To find the substances the worms use to modulate their hosts, Foth et al. sequenced the genomes of mouse- and human-infecting trichurid species and analyzed how mouse tissues responded to low-level persistent infections. The worms produced a suite of serine protease enzymes, which split intestinal glycoproteins apart, helping the worms invade the intestine. Mice responded with a muted immune response, creating an inviting environment for the worms.

    Nat. Genet. 10.1038/ng.3010 (2014).

  7. Education

    A research paper in seven moves or less

    1. Melissa McCartney

    Genre analysis and argumentation theory, mainstays of literature classes, rarely appear in science classrooms. To teach students how to read primary research papers efficiently, Lacum et al. showed students which rhetorical moves occur in research articles and how to identify them. The authors created a scientific argumentation model (SAM), which provided a detailed description of seven possible rhetorical moves scientific authors use to argue: motive, objective, main conclusion, implication, support, counter-argument, and refutation. They then showed students how to identify these moves in a research article. A pre- and post-test that evaluated the teaching method showed a significant increase in how well students could identify these moves.

    CBE Life Sci. Educ. 13, 253 (2014).

  8. Astronomy

    Nova seems shell-shocked after outburst

    1. Margaret M. Moerchen

    With a generous companion star, even a runty white dwarf can quickly reach explosive stature. That's probably what happened to the unusual recurring nova T Pyx, which had its sixth recorded outburst in 2011. Chomiuk et al. used the Swift and Suzaku satellites to observe the x-ray brightness of this system over the first few hundred days after its discovery. The high- and low-energy x-ray behavior suggest that the white dwarf ejected two shells of material in successive thermonuclear events. In the team's model, the second shell expanded 50% faster than the first, and its inevitable catch-up produced a shock responsible for the x-ray emission. The reason for this stalled secondary explosion is still unclear.

    Astrophys. J. 10.1088/0004-637X/788/2/130 (2014).

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