Wild Things: Life as We Know It
Parasitic plants, zebra tarantulas and wobbles in Earth's orbit
- By Smithsonian magazine
- Smithsonian magazine, December 2006, Subscribe
Zebra tarantulas secrete silk through their feet to increase traction, scientists say. S. Niederegger
New Spin
Mammal species rise and fall with a baffling regularity—most survive about 2.5 million years and then go extinct. Now a study led by Utrecht University in the Netherlands offers an explanation: wobbles in Earth's orbit. The scientists analyzed the fossil record of rodents from Spain over 22 million years. Extinctions tended to coincide with either a shift in Earth's tilt, which occurs every 1 million years, or an increased roundness of its orbit, which occurs every 2.5 million years; both cool the Northern Hemisphere. We are entering a round orbit phase, but extinctions implied by this study may not begin for tens of thousands of years.
Where'd You Get That Smile?
Ever notice how a little girl frowns just like her mother? Common sense suggests that her expression is mostly learned, the product of years of mimicking her parents. But a new study from the University of Haifa in Israel shows other forces at work. Scientists filmed interviews with 21 congenitally blind people and found that their signature facial expressions were strikingly similar to those of close relatives. Thus frowns, smiles and scowls may be part of one's genetic inheritance.
Jeepers Creeper
While studying zebra tarantulas, researchers in Germany saw something unexpected: footprints. They were silky secretions left by tiny structures in the tarantula's feet as it climbed up a glass plate. Previously, spiders were thought to produce silk only in special abdominal organs. Why the sticky feet? The Max Planck Institute scientists say these hefty spiders—weighing up to seven grams—need added traction on slippery leaves in their rain forest habitat.
Observed
Name: Cuscuta pentagona, a parasitic plant better known as dodder
Recently Seen On: The Agriculture Department's top noxious weeds list
Now Known As: The plant kingdom's first known sniffer dog
Its Nose Knows?: Yes: C. pentagona can actually detect airborne chemicals emitted by its preferred host, a tomato plant, says a new study from Pennsylvania State University. C. pentagona seedlings may seem pathetic—they have no roots and little means of performing photosynthesis—but “sniffing” steers them toward hosts quickly, before their own limited energy stores run out.
That's Insidious: Well, yes and no. The discovery may speed up the development of ways to control this noxious pest, which can depress tomato yields 90 percent.
Free as a Bird
In the Colombian Andes, ornithologist Thomas Donegan, of the conservation group Fundación ProAves, discovered a new subspecies of the yellow-breasted brush-finch. The find adds a nuance to avian taxonomy, but the key is what happened next: he let the bird go. Biologists have traditionally established new types of animals with a preserved (dead) specimen. Authorities ruled in 1999 that scientists may use evidence from living specimens, and Donegan is only the third one to do so. He photographed the bird and sampled its DNA, the ultimate ID.
Subscribe now for more of Smithsonian's coverage on history, science and nature.
| Tweet | Digg |
Comments