Wetlands' Emissions Problem
Wetlands may be hazardous to your health. That's the conclusion of new research showing that unsullied salt marshes--and even ordinary soils--naturally emit a large fraction of the substances that destroy ozone in the atmosphere.
Of course, the biggest threat to the ozone layer, which absorbs a lot of ultraviolet radiation before it can damage living things on Earth, is the class of compounds called chlorofluorocarbons (CFCs). Most of them have been phased out by international agreement.
But there is also a large group of natural ozone-cracking substances produced by algae, bacteria and plants. Methyl chloride and methyl bromide are the biggies, together accounting for as much as one-fourth of ozone depletion. And a whopping amount of the methyl duo, three separate teams of scientists reported in the Jan. 20 issue of Nature, is generated by completely natural processes, including the biochemistry of salt-marsh plants, coastal ecosystems in the tropics and the breakdown of organic matter in soil.
Salt marshes are top producers. "Such ecosystems," wrote scientists from the Scripps Institution of Oceanography in La Jolla, Calif., "even though they constitute less than 0.1% of the global surface area, may produce roughly 10% of the total" atmospheric load of methyl chloride and methyl bromide.
Evolution and the Male
The human male's reproductive system appears to have evolved extremely quickly, according to new research.
Genes for traits related to male reproduction previously had been shown to evolve rapidly in fruit flies, mice and rats. So Chung-I Wu and colleagues from the University of Chicago compared genes involved in the production of sperm in humans, chimpanzees, gorillas and orangutans. They found that the male reproductive genes were much more different between humans and other primates than other genes not involved in male reproduction, indicating they had been evolving relatively rapidly.
"The pressure on a male to find a mate and fertilize her eggs is constant, and the stakes of success or failure are enormous," said Wu, whose work is reported in the Jan. 20 issue of Nature. "Presumably, genes governing male reproduction are under continuous pressure to evolve ways to outcompete other males when it comes to fathering offspring."
Hubble in the Heavens
The Hubble Space Telescope has resumed studying the heavens after spacewalking astronauts repaired the orbiting observatory last month. From Jan. 10 through Jan. 13, the updated telescope took a series of new pictures of remote galaxies and a colorful dying star, which are being released today. The dying, sun-like star, located 5,000 light-years from Earth, is dubbed the "Eskimo Nebula" because it resembles a face inside a furry parka when viewed from Earth-based telescopes. In the Hubble image, the "furry" features look like giant comets all pointing away from the central star like the spokes of a wheel.
"The clumps that form the comet heads all seem to be located at a similar distance from the star," said J. Patrick Harrington, a planetary nebula expert at the University of Maryland at College Park. "This fact will be important in developing a theory of why the clumps formed in the first place."
Aggression and Hormone Level
Boys who are very aggressive have significantly lower levels of a stress hormone in their saliva, offering a possible clue to a possible biological basis of antisocial behavior.
Keith McBurnett of the University of Chicago and colleagues studied 38 boys age 7 to 12 who had a history of behavior problems. The researchers took saliva samples from the boys twice over a four-year period to measure the amount of the stress hormone cortisol. Boys with a proclivity toward violence had significantly lower levels of cortisol.
"Boys with low cortisol concentrations at both time points exhibited triple the number of aggressive symptoms and were named as most aggressive by peers three times as often as boys who had higher cortisol concentrations," the researchers wrote in the January issue of the Archives of General Psychiatry. They also began antisocial behavior at a younger age.
Cortisol is normally released in response to fear, such as fear of punishment for misbehavior. Low levels, the researchers say, may indicate the boys do not fear the possible consequences of their actions.
CAPTION: The Hubble Space Telescope captured this view of a dying, sun-like star called the "Eskimo Nebula."