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16 | NewScientist | 18 August 2012 THE discovery of the specialist stem cells behind our most advanced cognition could pave the way for new treatments for schizophrenia. Scientists have identified a type of cell that seems to be responsible for the neurons that give rise to higher brain functions like problem-solving. The cerebral cortex of the brain is layered like an onion, with neurons in different layers responsible for distinct levels of cognitive function. Neurons in the inner layers deal with basic sensory and motor signals. Outer layer neurons play a role in higher-level brain processes. It was thought that different layers of neurons are generated in successive waves by a single type of stem cell. However, when Ulrich Mueller at the Scripps Research Institute in La Jolla, Lack of sleep fires sandpiper passion MALE pectoral sandpipers lose sleep over sex – which is a good thing for these birds. Pectoral sandpipers (Calidris melanotos) breed in the Arctic, where the sun never sets during the breeding season. This may have encouraged males to evolve the ability to go without sleep. Bart Kempenaers of the Max Planck Institute for Ornithology in Seewiesen, Germany, and colleagues tracked 149 birds living near Barrow in Alaska. The males could be active almost constantly for 19 days – a record in the animal kingdom. The team then monitored the brain activity of 29 males and found that the most wakeful males bred with more females and sired more young (Science, doi.org/h5z). “We thought sleep loss has an adverse effect on performance,” says team member Niels Rattenborg. “Yet certain males sleep little and perform the best.” The teeth that can bend over backwards to avoid breaking TEETH are typically the hardest material in the body, but not so for some suckermouth catfish (Loricariidae). Their pearly whites do something wholly untoothy: bend. Adaptations to avoid broken or chipped teeth are common enough – the teeth of sharks and rays, for example, are slightly loose. But this is the first published report of bendable teeth. It makes sense for catfish to have them, though, since they scrape food off rocks and other hard surfaces with their mouths – a habit that could easily break rigid teeth. Tom Geerinckx, an evolutionary morphologist at Ghent TOM GEERINCKX/GHENT UNIVERSITY IN BRIEF A specialist stem cell for self-awareness California, and his colleagues studied the developing brains of mouse embryos, they found that neurons in the upper layers of the cortex are produced by a different type of stem cell (Science, DOI: 10.1126/science.1223616). “Maybe the invention of this new type of stem cell was important in driving brain evolution,” says Mueller. Upper layer neurons are often affected in psychiatric disorders. Understanding their development may lead to improved treatments. University in Belgium, extracted teeth from five species of scraping suckermouth catfish and analysed their composition and microstructure. He found that each tooth had a bendable section containing more collagen and significantly less calcium, phosphate and magnesium than the rest of the tooth. The work will appear in Physiological and Biochemical Zoology. “[The] teeth are very long and skinny and they have a built-in section that’s flexible. That’s absolutely mind-blowing,” says Peter Wainwright of the University of California, Davis. Such teeth may not be unique, though. Wainwright suggests they are also found in some common reef fish that feed by scraping rocks. “I’ve personally tweaked their teeth and holy cow, they’re bendable,” he says. FROGS are made more vulnerable to a deadly fungus by an unpredictable climate. Chytridiomycosis, a disease caused by a fungus, is a threat to many amphibians. Thomas Raffel of Oakland University in Rochester, Michigan, exposed frogs to the fungus. Some were kept at constant temperatures, others experienced regular temperature changes, and others random temperature changes. Frogs exposed to random temperature changes experienced higher levels of infection (Nature Climate Change, DOI: 10.1038/ nclimate1659). Climate change is expected to increase climate variability, which could speed the decline of some species, says Raffel. Capricious climate is fatal for frogs
