American Scientist

This roundup summarizes some notable recent items about scientific research, selected from news reports compiled in Sigma Xi’s free electronic newsletters.

Sonar, Not the Moon, Flusters Whales

Navy sonar was to blame for a near mass stranding of melon-headed whales (Peponocephala electra) in 2004, says a new study. That’s what biologists thought at the time, when agitated whales swam into a shallow Hawaiian bay near a naval training exercise. Then they found out that, at the same time, another pod of P. electra entered shallow water 6,000 miles away. If one stimulus, such as a full moon, motivated both groups, sonar would be off the hook. Unlike the whales in Hawaii, though, those in the other group were relaxed and never came close to beaching. And a review of 23 different P. electra strandings showed no link to moon phase. Beaked whales beach in response to sonar, but this is the first time melon-headed whales have been known to react in the same way.

Brownell, R. L., Jr., et al. Behavior of melon-headed whales, Peponocephala electra, near oceanic islands. Marine Mammal Science 25:639–658 (July)

A Very Picky Fungus

Ophiocordyceps fungi turn ants into zombies. An infected ant leaves its colony to die, whereupon a fungal fruiting body grows from its head. But until now, no one realized how precisely the fungi control their ant hosts. The Asian carpenter ant Camponotus leonardi normally forages high in forest canopy. But in a study of 51 zombie C. leonardi, all the doomed ants sought the undersides of leaves ten inches above the ground, and bit down on a leaf vein before they died. Most ants chose northwest-facing leaves. When researchers moved dead ants to the forest floor or canopy, the fungus didn’t develop properly, suggesting that it has good reason to steer its hosts so meticulously.

Andersen, S. B., et al. The life of a dead ant: The expression of an adaptive extended phenotype. The American Naturalist 174:424–433 (September)

Better than Typing?

Keyboards, farewell! With a special glove and a couple of algorithms, computers can translate muscle activity, generated while writing, directly to typeface. Six volunteers donned a set of electrodes that recorded signals from eight muscles in the forearm and hand, then wrote on a digitized tablet. After initial “training,” the computer could reconstruct a person’s penmanship from the electrode recordings alone. A second program learned to convert the electrical patterns directly to a standard font with up to 97 percent accuracy. The device’s inventors say it could supplement keyboards—and may also assist patients with impaired handwriting.

Linderman, M., et al. Recognition of handwriting from electromyography. PLoS ONE 4(8):e6791 (August 26)

Unlikely Planet Mystery

Astronomers should not be seeing this: Nearby in the Milky Way, a giant planet orbits its star in less than one Earth day. Tidal interactions make the star and planet bulge toward one another—but because the planet orbits faster than the star spins, the star’s bulge should fall behind the planet’s. Misaligned bulges produce torque, which should slow the planet down until it spirals into the star—within a million years. Astronomers figure they had a one in 1,000 chance of spotting the planet so close to its demise. Maybe they were just lucky, in which case they will see the planet’s orbit change within a decade. But maybe the planet has longer to live. In that case, physicists will have to explain why the star isn’t dragging the planet in as fast as predicted.

Hellier, C., et al. An orbital period of 0.94 days for the hot- Jupiter planet WASP-18b. Nature 460:1098–1100 (August 27)

The Origin of Malaria

Humans can thank chimpanzees for our deadliest form of malaria, caused by Plasmodium falciparum. This parasite’s closest relative is P. reichenowi, which infects only chimps. Biologists assumed that the two parasites evolved from a common ancestor millions of years ago, but that idea was based on only one sample of chimp malaria. Now, researchers have tested 94 chimpanzees and found eight more strains of P. reichenowi. DNA sequences from these strains indicate that P. falciparum is just one branch on the P. reichenowi family tree. This pattern suggests that malaria hasn’t always infected humans. Rather, a mutant strain of P. reichenowi jumped to humans more recently—and only once.

Rich, S. M., et al. The origin of malignant malaria. Proceedings of the National Academy of Sciences 106:14902–14907 (September 1)

Plants Tell Ancient City’s Secrets

By the seventh century A.D., the Roman metropolis of Altinum was overcome by barbarian invasions. Its inhabitants fled to islands in a nearby lagoon, populating what is now Venice. Although historical records tell Altinum’s story, its physical remains have disappeared. Now the corn and soy crops that cover the site have provided a detailed glimpse of the lost city. During a 2007 drought, researchers took aerial infrared photos to gauge the crops’ water stress. Plants growing over compacted soil and bricks were pale in the photos, while those growing over canals and pits remained dark and well hydrated. The stressed plants traced a perfect map of Altinum, including city walls, theaters and canals—precursors of those later built in Venice.

Ninfo, A., et al. The map of Altinum, ancestor of Venice. Science 325:577 (July 31)

Seeing Red (and Green).

Gene therapy has given two color-blind male monkeys the ability to see red and green. Unlike females, male squirrel monkeys (Saimiri sciureus) are all color-blind and can’t find red and green dots on a computer screen—even with a grape-juice incentive. Researchers injected two male monkeys’ retinas with a virus carrying a human gene that codes for a red-detecting photoreceptor. Twenty weeks later, the male monkeys were finding red and green dots just as well as females. Researchers are encouraged that adult monkeys’ brains could process the new color. If humans’ brains are as flexible, gene therapy may hold promise for curing visual impairment, even in adults.

Mancuso, K., et al. Gene therapy for red-green colour blindness in adult primates. Nature (published online September 16)