American Scientist

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

A Little Salt Helps the Leaf Litter Go Down

Plants assimilate CO₂; when they die, decomposers release it again. But in salt-starved environments such as the Amazon, decomposers don’t keep up, and carbon accumulates in the leaf litter. That might be because, unlike plants, decomposers such as fungi and termites need sodium in their diets. Working in the Peruvian rainforest, a team of ecologists tested that idea by sprinkling 70 small plots with either salt water or stream water. In about two weeks, the salty plots saw a seven-fold increase in termites and lost more than 40 percent of their leaf litter. The authors speculate that increasingly fierce tropical storms could drop more sea salt inland—spurring faster decomposition and carbon release, thus speeding climate change.

Kaspari, M., et al. Sodium shortage as a constraint on the carbon cycle in an inland tropical rainforest. Proceedings of the National Academy of Sciences (published online November 2)

Hypnotic Milk

Saving morning breast milk to feed the baby in the evening could make for a sleepless night. That’s according a new study that examined daily fluctuations in the composition of human breast milk from 30 moms. The milk contains nucleotides—compounds best known as components of DNA, some of which also promote sleep. The most soporific of the nucleotides peaked at dusk and overnight, suggesting that babies who get breast milk at the same time it is produced will have a better sleep at night.

Sánchez, C., et al. The possible role of human milk nucleotides as sleep inducers. Nutritional Neuroscience 12:2–8 (February)

Archaeopteryx Demoted

It may be an iconic fossil, but it’s not a bird. So say researchers who extracted minute chips of leg bone from Archaeopteryx and other bird-like fossils, and put them under a microscope. Archaeopteryx’s bones were dense and reptilian, rather than air-filled and bird-like. And based on the growth rings in the bones, it took Archaeopteryx more than two years to grow up, compared to just a few weeks or months for modern birds. True avian physiology didn’t show up until 20 million years post-Archaeopteryx; that distinction goes to Confuciusornis, a Cretacious specimen now in need of a publicity campaign.

Erickson, G. M., et al. Was dinosaurian physiology inherited by birds? Reconciling slow growth in Archaeopteryx. PLoS ONE 4:e7390 (October 9)

Crying With a French Accent

There’s an oft-repeated saying that in Paris, incredibly, even the children speak French. Now it turns out the babies cry in French, too. Researchers compared the wails of 60 newborns from French- and German-speaking families, and found that their cries mimicked inflections common in their native tongues. Babies who had heard French from the womb uttered cries of increasing pitch and intensity, whereas German babies produced descending shrieks. It’s well known that fetuses hear the outside world, and newborns recognize aspects of their native language. But this is the earliest that babies have been found to mimic those sounds.

Mampe, B., et al. Newborns’ cry melody is shaped by their native language. Current Biology (published online November 5)

Can Bacteria Make You Fat?

Genetics, diet, exercise.… Complex factors affect bodyweight, and new studies suggest a role for intestinal microbes, too. In mice that harbor normal human gut bacteria in their intestines, a fatty, sugary diet (as opposed to a low-fat, high-fiber one) drastically altered bacterial metabolism and species composition. In an apparently vicious cycle, the rich diet favored microbes that promote more efficient calorie absorption. And those same microbes, when transferred to other mice, made them gain weight even on a low-fat diet. The results don’t prove that bacteria cause human obesity—but they do suggest it’s an important connection to investigate.

Turnbaugh, P. J., et al. The effect of diet on the human gut microbiome: A metagenomic analysis in humanized gnotobiotic mice. Science Translational Medicine 1:6ra14 (November 11)

A Superficial Supernova

Astronomers think they’ve spotted a whole new category of supernovae. Revisiting old data from a California telescope, they found a stellar explosion that faded three times faster than a typical supernova. It was also too dim and had an unusual composition of helium with traces of vanadium—but no hydrogen. Those features did, however, fit with the theoretical type .Ia supernova. Theoreticians recently predicted that when a white dwarf star collects helium from a smaller partner star, the helium could eventually detonate in a fast supernova that leaves the underlying star intact. To spot more such fleeting explosions, telescopes may need to revisit the same patch of sky more often.

Poznanski, D., et al. An unusually fast-evolving supernova. Science (published online November 5)

Bed Bug Turn-Ons and Turn-Offs

Male bed bugs (Cimex lectularius) can’t resist the puffy body of a well-fed, blood-filled bug, regardless of its sex. If the bloated beauty is a female, her suitor disregards her genital opening and punctures her abdomen to inject his sperm. But if the attractive bug is another male, even he is at risk of an abdominal piercing. Unless, that is, he releases a dose of alarm pheromone—a mixture of compounds previously thought to deter only predators. Researchers found that blocking a male’s pheromone glands left him susceptible to homosexual advances, whereas male-female pairs broke up when exposed to the alarm compounds. The arrangement saves males both wasted time and abdominal injury—and leaves one wondering why females don’t occasionally emit the same “bug off” message.

Ryne, C. Homosexual interactions in bed bugs: alarm pheromones as male recognition signals. Animal Behaviour (published online October 24)