March 25, 2013
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.
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.
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.
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!
February 1, 2012
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.
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.
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
June 20, 2011
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.
March 25, 2011
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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August 20, 2010
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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