Smithsonian.com

The results of Smithsonian‘s 7th Annual Photo Contest were announced earlier this week. The winner in the Natural World category, Hidden frog (above), was taken last September by Laurie McAndish King of Novato, California:

King was experimenting with a new camera in a local Mendocino County garden when a frog paused for a moment on the leaves of a nearby plant. She snapped; it hopped. “I’ve gone halfway around the world looking for new experiences,” she says. “This photo will always remind me of the beauty in my own backyard.”

It’s an important lesson—you don’t need to go very far to find fantastic things—and one that plays out in the photo that won the Grand Prize, Young monks from Myanmar. For the photographer, Kyaw Kyaw Winn, from Yangon, Myanmar, monks are a common sight, but he found something particularly special.

Keep looking around. If you find something interesting and manage to capture it in a photo, consider sending it in. Our 8th Annual Photo Contest runs until December 1.

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A late-stage tadpole of Xenopus tropicalis on the cover of today's Science (credit: Siwei Zhang, Jingjing Li, Enrique Amaya)

I never found it very shocking that humans and chimpanzees share 96 percent of their genes. After all, chimps are our closest neighbors on the huge family tree of animals. But we also share genes with other organisms, and sometimes this can get pretty surprising (just check out Carl Zimmer’s article from Tuesday’s New York Times).

Scientists have now completed a draft sequence of the frog Xenopus tropicalis and found that the amphibian’s genome contains remarkable similarities to those of the mouse, the chicken and, yes, even the human genome. There are large swaths of DNA that have been conserved through 360 million years of evolution. That was when the last common ancestor of amphibians, birds and mammals lived.

The X. tropicalis frog isn’t the species used most often in lab studies, however. That would be the frog X. laevis. It’s been widely used in research on cell development because of its large eggs and transparent tadpoles (like the one above). But the genome of X. tropicalis is only half the size, so sequencing it was faster and cheaper. And it will still be useful in studies of the Western clawed frog and to sequence that species’ genome all the more quickly.

Why is the frog genome important? It may contain clues to human health: there are at least 1,700 frog genes that, when found in humans, are associated with disease.

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A male midwife toad carries fertilized eggs on his legs. (© blickwinkel / Alamy)

Before Charles Darwin, there was Jean-Baptiste Lamarck, the French naturalist who proposed that an organism could pass to its offspring characteristics that it acquired during its lifetime. The classic example is the idea that giraffes got their long necks by gradually stretching them over successive generations in response to the need to reach food high in the trees. Darwin’s theory—which held, in contrast, that giraffes with the longest necks were more likely to survive and reproduce—eventually won out, though Lamarckism persisted well into the 20th century (particularly in the Soviet Union, where it was revived as Lysenkoism).

One proponent of Lamarckism in the 1920s was Austrian biologist Paul Kammerer, who undertook a series of experiments on amphibians, including the midwife toad. These toads are special because they copulate on land and then the male keeps the eggs out of the water by carrying them around, on land, stuck to his own legs.

By placing the toads in an arid, hot environment, Kammerer induced the toads to mate in the water. Under these conditions, the toads simply deposited the eggs into the water—the male did not carry them—and only a few hatched into tadpoles. But later generations who grew up under normal conditions preferred to copulate in the water, and some males developed a trait called “nuptial pads” on their forelimbs (black spots that are used for gripping females and are common on water-dwelling toads). Kammerer believed that this was evidence that Larmarckian evolution was real.

In 1926, however, a herpetologist determined that the nuptial pads on the only specimen remaining from Kammerer’s experiment were simply black spots created by injections of India ink. And six weeks after the herpetologist’s paper appeared in Nature, Kammerer killed himself.

Kammerer denied injecting the frog, but his experiments were never repeated and he is often held up as an example of Lamarckian fraud. Nothing was ever proven, though, and nuptial pads have since been found in a wild midwife frog, proving they are a possible trait. Now, in a new paper, University of Chile biologist Alexander Vargas argues that Kammerer’s experiments produced intriguing evidence of epigenetics, in which a gene’s expression can change but not its underlying sequence, years before scientists discovered this non-Mendelian form of inheritance.

In Kammerer’s time, traits were thought to be inherited in a strict Mendelian fashion, in which genes obey statistical laws. We now know that genetics are far messier; the DNA sequence of a gene is only one part of the picture. For instance, with DNA methylation, a methyl group attaches to DNA resulting in less expression of the gene. Environmental factors can influence DNA methylation, and this can look something like Lamarckian evolution.

Vargas argues that moving the toad eggs from land to water changed their environment, and that change could have caused alterations in gene methylation. And epigenetic mechanisms are now known to influence some of the features that became altered in Kammerer’s toads, such as adult body size and egg size. “Rather than committing fraud,” Vargas writes, “it seems that Kammerer had the misfortune of stumbling upon non-Mendelian inheritance at a time in which Mendelian genetics itself was just becoming well accepted.”

A female Urspelerpes brucei (Photo courtesy of Bill Peterman).

Georgia is a hotspot for salamanders; about 10 percent of the 560 species found worldwide inhabit the southern state. And now scientists can add one more to the Georgian list: Urspelerpes brucei.

Two graduate students were hunting for another salamander species in the foothills of the Appalachian Mountains when they came across the tiny amphibian. At the time, they knew only that it was not a species known to inhabit the area. Genetic studies revealed that it was different enough from any known species to get its very own genus, the first new genus of salamanders to be found in the United States in 50 years.

The new salamander species, which is described in an article in the Journal of Zoology, has several novel characteristics.

“The genetic data revealed that this was far more unusual than any of us suspected, which is why we described it in its own genus,” says [biologist Carlos] Camp [of Piedmont College in Georgia].

But the amphibian also looks strikingly different to other species.

For a start, it has the smallest body size of any salamander in the US. It is also the only lungless salamander in the US whose males have a different colour and pattern than females, a trait more characteristic of birds.

Males have a pair of distinct dark stripes running down the sides of the body and a yellow back. Females lack stripes and are more muted in colour.

Males also have 15 vertebrae, one less than females. Yet while most species of lungless salamander have male and females of differing sizes, those of Urspelerpes brucei are close to being equal in size.

Uniquely for such a small lungless salamander, Urspelerpes brucei has five toes, whereas most other small species have reduced that number to four.

The behaviour and lifestyle of the salamander remain a mystery.