Tadpole shrimp eggs can remain dormant for years, then burst into life when elusive desert rains arrive. Photo by Flickr user theloushe

As Easter draws near, we begin to notice signs of nature’s very own annual resurrection event. Warming weather begins “breeding lilacs out of the dead land,” as T.S. Elliot noted, and “stirring dull roots with spring rain.” Where a black and white wintery landscape just stood, now technicolor crocus buds peak through the earth and green shoots brighten up the azalea bushes.

Aside from this grand show of rebirth, however, nature offers several cases of even more overtly stunning resurrections. From frozen animals jumping back into action during spring thaws to life blooming from seemingly desolate desert sands, these creatures put a new spin on nature’s capacity for revival.

Resurrection fern

A resurrection fern, before and after watering. Photo by Flickr user Gardening in a Minute

As its name suggests, during a drought the resurrection fern shrivels up and appears dead, but with a little water the plant will burst back into vibrant life. It can morph from a crackled, desiccated brown into a lush, vibrant green in just 24 hours.

The fern doesn’t actually die, but it can lose up to 97 percent of its water content during an extreme dry spell. In comparison, other plants will usually crumble into dust if they lose more than 10 percent of their water content. Resurrection ferns achieve this feat by synthesizing proteins called dehydrins, which allow their cell walls to fold and reverse back to juicy fullness later.

Resurrection ferns are found as far north as New York and as far west as Texas. The ferns needs another plant to cling to in order to grow, and in the south it’s often found dramatically blanketing oak trees. A fallen oak branch covered in resurrection ferns are common features in southern gardens, though the ferns have also turned up in more uncanny locales: in 1997, astronauts took resurrection fern specimens onto the Space Shuttle Discovery to study how the plant resurrects in zero gravity. As investigators write (PDF), the fern “proved to be a hardy space traveler and exhibited regeneration patterns unaltered by its orbital adventure.” This earned it the title of “first fern in space.” 

Brine shrimp, clam shrimp and tadpole shrimp 

In the deserts of the western U.S., from seemingly life-barren rocks and sands, life blooms by just adding a little rain water. So-called ephemeral pools or “potholes” form tiny ecosystems ranging from just a few millimeters across to several meters deep. The ponds can reach up to 140 degrees Fahrenheit in the summer sun or drop below freezing during winter nights. They can evaporate nearly as quickly as they appeared, or linger on for days or weeks. As such, the animals that live there all have special adaptations for allowing them to thrive in these extreme conditions.

Ephemeral desert ponds in New Mexico. Photo: J. N. Stuart

Some of the potholes’ most captivating critters include brine shrimp (of sea monkey fame!), clam shrimp and tadpole shrimp. These crustaceans practice a peculiar form of drought tolerance: In a process known as cryptobiosis, they can lose up to 92 percent of their body water, then pop back into fully-functional action within an hour of a new rain’s arrival. To do this, the tiny animals keep their neural command center hydrated but use sugar molecules instead of water to keep the rest of their cells intact throughout the drought. Like resurrection ferns, brine shrimp, too, have been taken into space–they were successfully hatched even after being carried outside of the spacecraft. 

Most of these animals only live for about ten days, allowing them to complete their entire life cycle (hopefully) before their pool dries up. Their dried eggs are triggered to hatch not only when they’re hydrated again but also when oxygen content, temperature, salinity and other factors are just right. Some researchers, such as this zoologist quoted in a 1955 newspaper article, think that the eggs can remain dormant for several centuries and still hatch when conditions are right.

Wood frogs 

Some amphibians undergo their own sort of extreme hibernation in order to survive freezing winter temperatures. This suspended animation-like state allows them to slow down or stop their life processes–including breathing and heartbeat–just to the brink of death, but not quite. Wood frogs, for example, may encounter freezing conditions on the forest floor in winter. Their bodies may contain 50 to 60 percent ice, their breathing completely stops and their heartbeat is undetectable. They may stay like this for days, or even weeks. 

They achieve this through a specially evolved biological trick. When the frogs encounter the first signs of freezing, their bodies pull moisture away from its central organs, padding them in a layer of water which then turns into ice. Before it freezes, the frog also floods its circulatory system with sugar molecules, which act as an antifreeze. When conditions warm up again, they can make a complete recovery within a day, which researchers call “spontaneous resumption of function.” Here, Robert Krulwich explains the process: 

As seen through these examples, some creatures really do come back from the brink of death to thrive!

A cane toad is highly toxic and should not be eaten or even licked. Photo from Wikicommons.

American cane toads (Rhinella marina), native to Central and South America, are an invasive species in Australia. These toads contain a substance called “bufotoxin” that makes a lot of predators ill, sometimes fatally. (Warning: This is very poisonous stuff. Do not even lick a cane toad!)

Australian animals that eat this toad are typically poisoned by it, but one animal, the bluetongue skink (Tiliqua scincoides), appears to be able to eat the toad with few or no ill effects. Or, more exactly, some bluetongue skinks can eat the cane toads, depending on where they live.

Many animals and plants produce complex molecules (like bufotoxin) that have been shaped by natural selection to be toxic to predators. Some of our favorite spices, such as basil, chili peppers and other aromatic plants, owe their culinary properties to these molecular adaptations to herbivory. Only a few mammals produce molecular toxins, but many frogs and toads do.

The bluetongue skink. Note the blue tongue. Photo from Wikicommons.

If a weapon evolves in nature, there is a certain chance that a counter-weapon will also evolve. Many insects that feed on toxic plants have evolved the ability to sequester the poisonous molecules produced by those plants, rendering them harmless to the insect, and in some cases concentrating the undesirable substance in the insect’s own body to be used as a defense against insect-eating animals (usually other insects). Many mammals have enzymes in their digestive tract that detoxify plants that would otherwise be harmful. The evolution of toxicity and the evolution of anti-toxin strategies is considered an arms race between the eaten and the eaters.

So, it would be reasonable to suspect that the bluetongue skink has evolved a physiological mechanism to combat the bufotoxin produced by the cane toads. But it turns out that the explanation for the ability of some skinks to snack on the toxic toads is a little more complicated.

Another invasive species found in Ausralia is the ornamental “mother-of-millions” plant, a Bryophyllum from Madagascar. This plant produces a toxin that is chemically similar to bufotoxin. Why is it chemically similar to bufotoxin? This is probably a coincidence. If you have a large number of animals and plants producing toxins, sometimes there are going to be accidental similarities.

Mother-of-millions plant. Image from Wikicommons.

The mother-of-millions plant is invasive and found in the wild in certain areas of Australia, but it is not common everywhere. Bluetongue skinks that live where mother-of-millions is common appear to have adapted to eating them, and as such posses the ability to neutralize bufotoxin-like molecules. When these skinks encounter cane toads, they eat them without consequence. In fact, the skinks living in these area regularly eat both the mother-of-millions plants and the cane toads.

This research was was carried out by scientists at the Richard Shine Lab at the University of Sidney.

Price-Rees, Samantha J. Gregory P. Brown, Richard Shine, 2012. Interacting Impacts of Invasive Plants and Invasive Toads on Native Lizards. Natural History Editor: Craig W. Benkman. Published online Jan 25, 2012

The Glass Frog (Centrolenella colymbiphyllum) has skin so translucent that you can watch its heart beating (credit: Carl C. Hansen, Smithsonian Institution)

When I started working on this frog blog post (inspired by the adorable yet deadly poison dart frogs at the National Zoo), my knowledge of frogs was limited to Mr. Toad from The Wind in the Willows and Kermit. Obviously, I had a lot to learn. I have since discovered many amazing, surprising, disgusting and flat-out weird facts about frogs, and have collected the 14 best to share here with you:

1 )  One gram of the toxin produced by the skin of the golden poison dart frog could kill 100,000 people.

2 )  The female Surinam toad lays up to 100 eggs, which are then distributed over her back. Her skin swells around the eggs until they become embedded in a honeycomb-like structure. After 12 to 20 weeks, fully formed young toads emerge by pushing out through the membrane covering the toad’s back.

3 )  A frog completely sheds its skin about once a week. After it pulls off the old, dead skin, the frog usually eats it.

4 )  When Darwin’s frog tadpoles hatch, a male frog swallows the tadpoles. He keeps the tiny amphibians in his vocal sac for about 60 days to allow them to grow. He then proceeds to cough up tiny, fully formed frogs.

5 )  When a frog swallows its prey, it blinks, which pushes its eyeballs down on top of the mouth to help push the food down its throat.

6 )  The wood frog of North America actually freezes in the winter and is reanimated in the spring. When temperatures fall, the wood frog’s body begins to shut down, and its breathing, heartbeat and muscle movements stop. The water in the frog’s cells freezes and is replaced with glucose and urea to keep cells from collapsing. When there’s a thaw, the frog’s warms up, its body functions resume and it hops off like nothing ever happened.

7 )  A group of birds is called a flock, a group of cattle is called a herd, but a group of frogs is called an army.

8 )  The glass frog has translucent skin, so you can see its internal organs, bones and muscles through its skin. You can even observe its heart beating and its stomach digesting food.

9 )  There is a frog in Indonesia that has no lungs – it breathes entirely through its skin.

10 )  The waxy monkey frog secretes a wax from its neck and uses its legs to rub that wax all over its body. The wax prevents the skin of the frog from drying out in sunlight.

11 )   Most frogs have teeth, although usually only on their upper jaw. The teeth are used to hold prey in place until the frog can swallow it.

12 )  The biggest frog in the world is the Goliath frog. It lives in West Africa and can measure more than a foot in length and weigh more than 7 pounds – as much as a newborn baby.

13 )  There’s a type of poison dart frog called the blue-jeans frog; it has a red body with blue legs. It is also sometimes called the strawberry dart frog.

14 )  The red-eyed tree frog lays it eggs on the underside of leaves that hang over water. When the eggs hatch, the tadpoles fall into the water below.

The Last Prayer, by Charles Littlewood (Photographed June 2009, Micanopy, Florida)

Creatures eat other creatures all the time, but it’s not something that is often captured on film, at least not in such an attractive way that it makes the finals of a photo contest. Charles Littlewood of Silver Springs, Florida spotted this rat snake stalking a frog amid the cattails one day in June 2009. “I watched as it approached and marveled that the frog did nothing,” he says. Littlewood then took 185 shots with his camera and entered this one in Smithsonian magazine’s 8th Annual Photo Contest, where it’s one of the top entries in the Natural World category. “The photo demonstrates the persistence required to obtain the views of nature and the lessons to be learned from the participants,” Littlewood says.

There’s only a few days left to enter your vote for the Readers’ Choice Award in this year’s contest; voting closes on March 31. The Grand Prize, Readers’ Choice and category winners will be announced on July 1. And if you’ve captured your own amazing image, consider entering it into the 9th annual photo contest, which is open for submissions until December 1, 2011.

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A newborn Kihansi spray toad sits on the back of a female (Credit: Julie Larsen Maher/Wildlife Conservation Society)

The Kihansi spray toad (Nectophrynoides asperginis) is a fairly new species to science, discovered only in 1996. There were once as many as 21,000 of the toads living in a five-acre region around Kihansi Falls in the Udzungwa Mountains of eastern Tanzania. They could be found nowhere else in the world and are particularly special because the females give birth to fully formed baby toads, bypassing the tadpole stage.

About a decade ago, a dam built upstream cut off 90 percent of the flow of water to the region. Artificial sprinklers were set up to mimic the natural spray of the falls, but they were unreliable. This may have made the toads more susceptible to the chytrid fungus, which was detected in dead Kihansi spray toads in 2003. The sprinklers failed that year and a brief opening of the dam’s floodgates released water tainted with pesticides at high enough levels to potentially kill the toads. The Kihansi spray toad population crashed. In January 2004, just three toads could be found, and none have been seen since an unconfirmed sighting in 2005. The IUCN now lists the species as Extinct in the Wild.

Two populations of the toads now live in zoos: 5,000 at the Toledo Zoo and 1,500 at the Bronx Zoo. A third population was established just this week at a facility in Dar Es Salaam, Tanzania, as part of a program established by the two U.S. zoos, the Tanzanian government and the World Bank. One hundred toads were transferred to the Tanzanian facility in the hopes that they soon may be reintroduced to their previous home territory.

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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.