News Scan Briefs; March 2006; Scientific American Magazine; by JR Minkel, Charles Q. Choi; 2 Page(s)

Despite bacteria's ubiquity, their diversity in the world's soils is poorly understood. To get a handle on what makes the organisms thrive, Duke University researchers trekked far and wide to collect a few centimeters of dirt from 98 locations across North and South America, then analyzed each sample for genetic variation. To their surprise, the strongest predictor of high diversity was neutral pH. The acidic soil of the Peruvian Amazon, for example, harbored one half to one third as many species as did the neutral dirt of the arid American Southwest. "There are a lot of variables that didn't turn out to be very important," says co-author Robert Jackson, who adds that a more exhaustive search of different habitats might turn up other stimulators of diversity, such as carbon abundance. The report was published online January 9 by the Proceedings of the National Academy of Sciences USA.

The narwhal sports an eight-foot-long spiraled tooth that makes it resemble a unicorn of the sea. Some thought that the whale, typically 13 to 15 feet long, used it to break arctic ice; others theorized that it served as a lance in male jousts. The tooth, in fact, may be a giant sensor for navigating and hunting. Through electron microscopy of two male tusks, researchers from Harvard University, the Smithsonian Institution, and the National Institute of Standards and Technology discovered that a single horn possesses some 10 million nerves running from its surface to its core. Instead of inflicting the narwhals with a massive ice cream headache, this sensitive tooth appears capable of detecting changes in water temperature, pressure and particle gradients linked with salinity and prey. Their findings surfaced last December at the 16th Biennial Conference on the Biology of Marine Mammals in San Diego.