From: California Academy of Sciences
Published January 7, 2005 12:00 AM

Sticky Gecko Feet Repel Grime, and Other Stories

Geckos can climb vertical walls thanks to their sticky feet. Yet geckos never need to groom their feet. Despite these adhesive tendencies, the gecko's tacky toes repel grime automatically, according to new research by Kellar Autumn and Wendy Hansen of Lewis & Clark College. Previously, Autumn discovered that the gecko uses millions of spatula-shaped, microscopic hairs on its feet to cling to walls. These hairs, or setae, allow gecko feet to grip surfaces very closely, allowing weak molecular forces to support the gecko despite gravity. In the study, the researchers observed that geckos were able to shed tiny silica spheres from their feet after just five steps on a clean surface. The setae retained this self-cleaning property even after they were detached from the gecko's feet. The scientists calculated that a minimum number of setae were required to generate enough force to attract dirt, but that individual dirt particles, in turn, were too small to be attracted by so many hairs. The findings, reported in the Proceedings of the National Academy of Sciences, should help scientists develop self-cleaning, reusable adhesives.


Great Eagle Ruled Ancient New Zealand


One of the world's smallest eagles morphed into one of the world's largest birds of prey after immigrating to an island, according to a new genetic study. Researchers from Oxford University, United Kingdom, and the University of Canterbury, New Zealand set out to find the ancestors of the now-extinct Haast's eagle, which had a wingspan of more than three meters and ruled prehistoric New Zealand skies. They extracted DNA from 2,000-year-old fossil eagle bones, and compared it to genes from other birds of prey in the region. To their surprise, the 10 kilogram Haast's eagle turned out to be most closely related to the little eagle of New Guinea and Australia, which usually weighs less than 1 kilogram. Calculations of mutation rates suggest that the two birds probably shared a common ancestor less than a million years ago. If so, Haast's eagle ballooned to more than 10 times its size in an astonishingly short period of time. Haast's eagle was once the island chain's top predator and dined on 200-kilogram flightless birds called moas. Like its staple prey, the eagle went extinct soon after humans arrived on the island about 700 years ago. The research was reported in the journal PLoS Biology.


Cassini Gets Closest Look Ever At Saturn Moon


New Year's Day 2005 brought scientists their best look yet at one of Saturn's strangest moons. The European Space Agency space probe Cassini flew within 123,400 kilometers of Iapetus, Saturn's third largest moon. Cassini sent back images of a harlequin world half sparkling white and half inky black. The moon's dark side is the one facing the direction of orbital motion around Saturn. That hemisphere is coated in an organic, or carbon-based, substance of unknown origin. Some scientists believe the material began as dust ejected by an impact on an outer moon in the Saturnian system. According to this theory, the dust moved inward and eventually splattered half of Iapetus. Other scientists believe the organic molecules originated from within Iapetus itself and was spewed onto the surface by some type of volcanism. The new images should help scientists rule out some theories. The Cassini views also show a line of mountains around the moon's equator that may be as tall as the Himalayas, and what appears to be an impact crater 400 kilometers across.


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Sleep Patterns Can Mark End Of Adolescence


Teens have a well-deserved reputation as slugabeds. The same kids that once awoke bright and bushy tailed for first grade tend to snooze through early classes in high school. But adolescent laziness may be a biological imperative. Till Ronneberg of the University of Munich, Germany has found characteristic changes in sleep/wake patterns throughout the maturation process. Ronneberg asked 25,000 people ages eight to 90 to track the hour when they went to bed, and when they awoke. He then calculated the midpoint of those sleep cycles--the hour halfway between bedtime and waking--for each subject on days without school or work obligations. He found that youngsters typically slept later and later until about age 20, when they began to awaken earlier again. On average women began waking earlier at a younger age (19.5 years) than men (20.9 years.) The fact that females also tend to mature faster than males suggests that the trend is biological and not caused by social habits. Ronneberg reports in the journal Current Biology that this abrupt shift in sleeping patterns may serve as biological marker of adolescence--an historically murky life threshold.


Strange Deepwater Coral Reef Found


Scientists have found a large coral reef 250 feet down in the Gulf of Mexico. Located near the Dry Tortugas islands off of Key West, it is the deepest coral reef found to date in U.S. waters. The lack of light at such depths has left its mark on the corals. Instead of growing in vertical high-rises toward the sun, this reef's blue and brown corals sprawl horizontally in an effort to maximize light-gathering ability. Both deep and shallow-water fishes swarm in huge numbers around the reef. Species include giant red grouper, damselfish, angelfish, hogfish, and bass. The reef extends in a 3-mile-wide, 20-mile long swath along a submarine formation known as Pulley Ridge. It was first spotted in 1999 by scientists from the University of Florida but was not confirmed as a coral reef until researchers from the U.S. Geological Survey got a closer look at it last year. The Gulf of Mexico Fishery Management Council is considering ways to protect the reef, including reducing trawling in its vicinity.


Whistling Language Processed Like Words


Instead of shouting to one another across the fields, the shepherds on one of Spain's Canary Islands converse in whistles. Known as Silbo Gomero, the language is a modified version of Spanish reduced to two vowels and four consonants. To the untutored ear, it sounds like music. But scientists from the University of La Laguna, Spain, and the University of Washington say the brain processes Silbo Gomero just like a language. In the study, the researchers monitored the brain activity of five Spanish-speakers and five shepherds fluent in Silbo Gomero using functional magnetic resonance imaging. The brains of both groups reacted equally to sentences spoken in Spanish. Their left hemispheres were active in areas associated with language production and comprehension, while their right hemispheres were active in regions involved in linguistic processing. When listening to Silbo Gomero, the shepherds' brains produced the same bilateral response, while the brains of the other subjects did not. In other words, the shepherds were truly processing Silbo Gomero whistles as a language, demonstrating the brain's flexibility for interpreting language. The researcher was reported in the journal Nature.


Related Links:


Sticky Gecko Feet Repel Grime: Scientific American / New York Times
Great Eagle Ruled Ancient New Zealand: BBC
Cassini Gets Closest Look Ever At Saturn Moon: BBC
Sleep Patterns Can Mark End Of Adolescence: news@nature.com
Strange Deepwater Coral Reef Found: CNN (Associated Press)
Whistling Language Processed Like Words: Yahoo Daily News (Reuters)


Source: California Academy of Sciences


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