For the first time, a team of scientists has scanned an entire set of genes in a dog—a poodle belonging to two of the researchers. The results are still somewhat incomplete, but the data already show remarkable similarities between dogs and humans. The information could help scientists learn more about the 300 or so diseases that we share with dogs.

Scientists have deciphered DNA from cells belonging to Shadow, a 9-year-old standard poodle.

The Institute for Genomic Research

Cells in every animal contain long molecules called DNA, which are made of even tinier units called nucleotides. You can think of nucleotides as letters and genes as words. An entire set of genes is called a genome, which is like a library of information about an animal. Most genes are very similar from individual to individual within a species.

In recent years, scientists have spelled out, or sequenced, the entire genomes of people, mice, rats, and a few other animals. Now, scientists from The Institute for Genomic Research and The Center for the Advancement of Genomics have found a quick and inexpensive way to do the same for dogs.

Already, the results show that the human and dog are much more similar to each other at the genetic level than to the mouse. At the same time, knowing the details of the DNA structure is important in understanding the genes that contribute to diseases and traits among various breeds of dogs.

You know how people sometimes start looking like their pets? Those similarities, it now appears, might be more than skin deep.—E. Sohn

Going Deeper:

Travis, John. 2003. Letting the dog genome out: Poodle DNA compared with that of mice, people. Science News 164(Sept. 27):197. Available at http://www.sciencenews.org/20030927/fob5.asp .

You can learn more about mapping the dog genome at http://www.genomenewsnetwork.org/articles/11_01/Dog_feature1.shtml (Genome News Network).

Making it in a Tough Environment: You and Your Genes
http://www.niehs.nih.gov/kids/genes/home.htm
(National Institute of Environmental Health Sciences).

Several companies are racing to produce electronic paper and ink, complete with colors and moving images. One idea would be to create a newspaper like The Daily Prophet in the Harry Potter books. Its pages would hold video clips of baseball games, say, instead of just black-and-white photos.

A researcher examines small samples of a full-color display that, on a larger scale, might eventually bring video to newspapers and magazines.

Philips

Electronic paper is not a new idea. A company in Massachusetts called E Ink, for example, has been working for years on a technology that involves millions of tiny liquid-filled spheres, about as wide as a human hair. Jolts of electricity determine whether each microsphere looks black or white at any given time. Together, microspheres make up words and images. The technique seems promising for creating still images that can be changed when needed, but the process is too slow for good video.

Scientists in the Netherlands now report a new type of e-paper technology. By using layers of oil, the researchers say, they can make images that change fast enough to meet standard video requirements. They can also make brilliant colors. So far, however, each image is smaller than the fingernail on your pinkie.

Critics say the new technology requires too much power to be practical. But no one will know if that’s really true until larger screens are made.

For now, reading and watching TV will have to remain two separate activities. Keep your eyes open, though. In the future, TV watching and reading might be part of the same assignment.—E. Sohn

Going Deeper:

Weiss, Peter. 2003. The daily flicks: Morphing ink may bring video to newspapers. Science News 164(Sept. 27):195. Available at http://www.sciencenews.org/20030927/fob1.asp .

You can learn more about electronic paper and ink at http://computer.howstuffworks.com/e-ink.htm (How Stuff Works), http://www.media.mit.edu/micromedia/elecpaper.html (MIT Media Laboratory), and http://www2.parc.com/dhl/projects/gyricon/ (Xerox PARC).

Government and utility officials are still scrambling to explain a blackout that hit much of the northeastern United States in late summer. From Detroit to New York, lights went out. Refrigerators, traffic signals, elevators, and subway trains stopped working. Computers went dead.

Lightning over a darkened city.

Without electricity, people had trouble getting to work, shopping for groceries, and communicating with each other. Normal life pretty much shut down for a few days.

Electricity also plays a crucial role within the human body. A lightning bolt or shock can disrupt or shut down that flow, causing disability or death.

“Electricity is life,” says David Rhees, executive director of the Bakken Library and Museum in Minneapolis. The Bakken museum is dedicated entirely to the history and applications of electricity and magnetism in biology and medicine.

The museum has a lot to keep up with. As scientists learn more about the electrical signals that whiz through our bodies and the electrical pulses that tell our hearts to beat, they are finding new ways to use electricity to save lives.

Research on the nervous systems of animals and people are helping scientists design machines that help diagnose and treat brain conditions and other problems. New drugs are being developed to regulate the body’s electrical pulses when things go wrong in response to injury or disease.

Electricity everywhere

Electricity is everywhere, thanks to the unique structure of the universe. Matter, which is basically everything you see and touch, is made up of tiny units called atoms. Atoms themselves are made up of even tinier parts called protons and neutrons, which form the atom’s core, and electrons, which move around outside the core.

Protons have a positive electrical charge, and electrons have a negative electrical charge. Normally, an atom has an equal number of electrons and protons. The positive and negative charges cancel each other out, so the atom is neutral.

When an atom gains an extra electron, it becomes negatively charged. When an atom loses an electron, it becomes positively charged. When the conditions are right, such charge imbalances can generate a current of electrons. This flow of electrons (or electrically charged particles) is what we call electricity.

The first person to discover that electricity plays a role in animals was Luigi Galvani, who lived in Italy in the late 18th century. He found that electricity can cause a dissected frog’s leg to twitch, showing a connection between electrical currents traveling along an animal’s nerve and the action of muscles.

Quick signals

All animals that move have electricity in their bodies, says Rodolfo Llinas, a neuroscientist at New York University’s School of Medicine. Everything we see, hear, and touch gets translated into electrical signals that travel between the brain and the body via special nerve cells called neurons.

Electricity is the only thing that’s fast enough to carry the messages that make us who we are, Llinas says. “Our thoughts, our ability to move, see, dream, all of that is fundamentally driven and organized by electrical pulses,” he says. “It’s almost like what happens in a computer but far more beautiful and complicated.”

By attaching wires to the outside of the body, doctors can monitor the electrical activity inside. One special machine records the heart’s electrical activity to produce an electrocardiogram (EKG)—strings of squiggles that show what the heart is doing. Another machine produces a pattern of squiggles (called an EEG) that represents the electrical activity of neurons in the brain.

This recording of brain waves, called an EEG, represents the electrical activity of neurons in the brain.

One of the newest technologies, called MEG, goes even further. It actually produces maps of magnetic fields caused by electrical activity in the brain, instead of just squiggles.

Recent observations of patterns of nerve-cell action have given scientists a much better view of how electricity works in the body, Llinas says. “The difference between now and 20 years ago is not even astronomical,” he says. “It’s galactic.”

Now, researchers are looking for new ways to use electricity to help people with spinal injuries or disorders of the nervous system, such as Parkinson’s disease, Alzheimer’s disease, or epilepsy.

People with Parkinson’s disease, for example, often end up having tremors and being unable to move. One type of treatment involves drugs that change the way nerve cells communicate with each other. As part of another new treatment, doctors put tiny wires on the head that send electrical impulses into the patient’s brain. “As soon as you put that in,” Llinas says, “the person can move again.”

Philip Kennedy at Emory University in Atlanta has even invented a kind of “thought control” to help severely paralyzed people communicate with the outside world. His invention, called a neurotrophic electrode, is a hollow glass cone filled with wires and chemicals. With an implanted electrode, a patient who can’t move at all can still control the movement of a cursor across a computer screen.

Looking to the past

One way to help keep the medical field speeding into the future might be to cultivate an appreciation for the past. At least, that’s what the folks at the Bakken museum think.

Modern-day medical equipment powered by electricity.

When I recently visited the museum, Rhees and Kathleen Klehr, the museum’s public relations manager, took me down to a huge padlocked room in the basement called “The Vault.” Row upon row of shelves were crammed with rare, old books about electricity, early versions of pacemakers and hearing aids, and all sorts of weird devices. One was a shoe-store X-ray machine, powered by electricity, that showed you whether your foot fit comfortably into a new shoe.

Upstairs, the exhibits included a tank of electric fish and Hopi dolls dedicated to the spirit of lightning.

There’s also a whole room dedicated to a monster made famous in a book titled Frankenstein. Made from assorted human parts, the monster was brought to life by an electrical spark. When Mary Shelley wrote Frankenstein in 1818, electricity was still a relatively new idea, and people were fascinated by the possibilities of what they might be able to do with it.

Even today, the Frankenstein room, with its scary multimedia presentation, remains one of the Bakken’s most popular exhibits, Klehr told me. “It’s been centuries,” she says, “and everyone is still excited about Frankenstein.”

That’s something you might keep in mind the next time a blackout strikes. Without electricity, those monsters under your bed might have a lot less power over you!

Going Deeper:

Additional Information

News Detective: Emily goes to the hospital

Word Find: Spark of Life

Questions about the Article

Every day, life delivers its little injustices. “That’s not fair!” We’ve all said it at one time or another.

Now, a new study shows, some monkeys express the same sort of frustration. It’s the first time scientists have found a sense of fairness in a species other than humans.

Brown capuchin monkeys demand an honest deal.

Frans de Waal

Researchers Sarah Brosnan and Frans de Waal of the Yerkes National Primate Research Center in Atlanta spent 2 years training brown capuchin monkeys how to trade rocks for food. She gave a monkey a rock and then held out her hand. If the monkey returned the rock, she’d offer food.

Then, Brosnan worked with five female monkeys from the original group who knew each other but were not related. She would accept a rock from one monkey and give it a yummy grape in return, while a second monkey watched the exchange. When the second monkey gave Brosnan a rock, she would hand it a less-tasty cucumber. After a while, the shortchanged monkey started either rejecting the cucumber or refusing to trade at all. In 10 out of 25 trials, it would nix the deal.

Next, Brosnan gave a grape to the first monkey without even asking for payment. In these cases, the second monkey bailed on the rock-for-cucumber trade 20 out of 25 times.

The study suggests that a sense of fairness is an important skill with adaptive value: It keeps us honest and helps us cooperate. In other words, we might be programmed to get upset if the neighborhood bully tries to steal our Hallowe’en candy.—E. Sohn

Going Deeper:

Milius, Susan. 2003. Unfair trade: Monkeys demand equitable exchanges. Science News 164(Sept. 20):181. Available at http://www.sciencenews.org/20030920/fob5.asp .

You can learn more about the work of Frans de Waal and Sarah Brosnan and the Yerkes National Primate Research Center at http://www.emory.edu/LIVING_LINKS/ (Emory University).

Back then, a South American rodent called Phoberomys pattersoni grew to be as big as a bison, say researchers who recently found some new Phoberomys fossils in northwestern Venezuela. Analyses of the 8-million-year-old fossils suggest that the rodents could reach a weight of 740 kilograms, or more than 1,600 pounds.

About the size of a bison, this rodent grazed on aquatic grasses and roamed the riverbanks of Venezuela about 8 million years ago.

C.L. Cain/Science

Phoberomys belongs to the caviomorph family of rodents, related to modern-day guinea pigs, chinchillas, and capybaras, which at 50 kilograms, are today’s largest rodents. Researchers first learned about Phoberomys in 1980, but bone and tooth fossils weren’t complete enough for them to estimate the animal’s size.

The new fossil finds suggest that the enormous creatures could sit on their hind legs like modern rodents, using their front paws to handle objects. The researchers also found crocodile, fish, and freshwater turtle remains near the Phoberomys fossils, suggesting that the rodents probably spent part of their time in water eating aquatic grasses.

The researchers speculate that Phoberomys was able to get so huge because there weren’t any grazing animals such as horses or cows to compete with them. The rodents disappeared when ferocious predators arrived on the continent.

For us, their extinction is probably a good thing. It might be tough to clean up after your cat if it happened to drag one of these things into the house!—E. Sohn

Going Deeper:

Perkins, Sid. 2003. Ratzilla: Extinct rodent was big, really big. Science News 164(Sept. 20):179. Available at http://www.sciencenews.org/20030920/fob1.asp .

You can learn more about the capybara, the world’s largest rodent today, at http://www.rebsig.com/capybara/ (Ronald E. Boucher, REB Signal Technology).

Every summer, George spends 3 months living in a one-room cabin on top of Mt. Holmes, a 10,330-foot peak in the northwest corner of Yellowstone National Park.

By day, he looks for fires, takes weather readings, and talks to the rare hiker who makes the rigorous 9.6-mile trek to his hut. At night, he stokes a wood-burning stove and hunkers down against cold winds. Every few weeks, a helicopter delivers groceries, firewood, and propane fuel. He sometimes goes 2 or 3 weeks without seeing anyone.

George Henley with an Osborne Firefinder at his lookout atop Yellowstone’s Mt. Holmes.

Gabe Keller

“It gets lonely,” George says. “It’s the same view I see for years and years. I get tired of it sometimes. I sit here and think, ‘I’ll get out of here some day.’”

Luckily, he hasn’t left yet.

George is an important link in a national fire and weather reporting system, says Roy Renkin, a vegetation management specialist at Yellowstone.

Like George, other rangers are stationed at strategic vantage points in parks and on public lands all around the country. They keep records of wind, temperature, and humidity. They notice changes in the animals that show up from year to year. And, perhaps most important of all, at least in Yellowstone, they look for fires.

“They call in these smokes very quickly, before many people have a chance to see them,” Renkin says, referring to Yellowstone’s three firewatchers. “With the work they do, we’re able to initiate fire-management activities very soon after the fire gets observed.”

Wildfires flare up every summer all over the western United States. This past summer was especially dry in many areas, and numerous fires continue to blaze in California, Montana, Wyoming, and other states.

Experts disagree on how best to handle the blazes. Flames destroy property. They kill plants, animals, sometimes even people. Yet research continues to show that fire is a natural part of life. Entire ecosystems, in fact, may depend on it for survival.

Yellowstone wonders

Ever since Yellowstone became the first U.S. national park in 1872, it has been a prime tourist destination. It’s easy to see why. Old Faithful and other geysers spout water high into the air. Pungent gases bubble up through mud. Rivers of scalding hot water carve beautiful, alien landscapes that stink of sulfur.

Then, there are the animals. As we drove and hiked through the park, my friend Gabe and I felt like we were on a safari. We saw grizzly bears, elk, bison, wolves, antelope, and more.

An aerial view of Yellowstone’s Grand Prismatic Spring.

NPS Photo

We weren’t the only ones impressed by Yellowstone’s geology and wildlife. An 11-year-old girl named Tessa, whose family was visiting the park from Seattle, was so impressed by the steaming hot-spring pools that she was writing down their names in a notebook.

“Lots of minerals!” Tessa said, when I asked her what part of the park was her favorite. Her 10-year-old brother Wesley looked bored until he started listing the animals he had seen so far—black bears, elk, deer, grasshoppers, prairie dogs—and the animals he still hoped to see: moose, wolves, jackrabbits.

Wildfires large and small

Fires deserve just as much attention as rocks and bears, Renkin insists. “We see the effects of fire on the landscape everywhere we look,” he says. “Even when you are looking at trees that are green, they are all born from an earlier fire.”

Most fires are small, Renkin says. They usually burn themselves out before they cause too much damage. And even though 3 years out of every 10 are dry enough to be serious fire years, historical records show that really big fires strike the Yellowstone area only once every 200 to 400 years.

“We don’t get them very frequently,” Renkin says. “But when we do get them, we get them very, very hot, and we get total stand replacement.”

The summer of 1988 was a perfect example. That year, not a single drop of rain fell in August in the northern part of the park. “In 106 years of the fire record, we don’t see that anywhere,” Renkin says. “That was really something.”

At the same time, the park was full of big trees, some more than 200 years old. Renkin’s research has shown that old trees burn faster than young ones.

Together, those conditions were a recipe for disaster. More than 45 fires swept through Yellowstone that summer, Renkin says. Lightning ignited most of them. People started others. Fires burned for longer than 3 months and consumed more than 34,000 acres of forest until late summer rains and snow finally put them out.

“The sheer magnitude of these fires was so awesome,” Renkin says. “There were miles and miles of fire front moving along.”

Fire’s benefits

Even today, 15 years later, charred logs and dead trunks litter the park. On our hike to Mt. Holmes, Gabe and I passed through barren stands of blackened timber instead of lush blankets of trees that used to cover the base of the mountain. It saddened us that so many trees and animals had died in the blaze.

A Yellowstone forest fire.

NPS Photo

On a long time scale, however, the 1988 fires started a whole slew of important events. Big fires clear the way for what scientists call succession. Winds blow in new seeds that take root in the bare soil. Because heat rises, bulbs and other underground plant parts often survive and sprout again.

It takes fallen logs 70 to 100 years to decompose, Renkin says. During that time, nutrients seep back into the dirt to feed future generations of plants and animals.

Some plants even rely on fire to reproduce. Lodgepole pines, the most common tree in Yellowstone, have a type of pinecone that sits in the treetops for years. In order to open and release their seeds, the cones need heat from a fire to unseal the glue-like resin that keeps them shut.

For all of these reasons, rangers at Yellowstone usually leave fire alone. “It kind of takes the forest back to a starting point,” Renkin says, “and the whole process starts all over again.”

Life on a mountaintop

No one is in a better position to observe this cycle of life and death than George Henley.

Over the years, he has watched the decline of black bears in the park, for one thing. Bears used to be so common, he told us, that a mamma bear and her two cubs once broke into his house, when he lived in a different part of the park. George later found them sitting in the woods, eating his can of cocoa.

There are also unexpected sightings. He once alerted park rangers when a rare group of mountain goats appeared near his lookout.

George has become an expert at spotting fires and reading weather. After we had finished eating lunch in his hut, he showed us his equipment: thermometers to measure temperature and dew point, wooden sticks that he weighs to calculate moisture in the air, a weather vane to read wind direction, and more. He calls all his readings in to park headquarters at about 1:30 p.m. every day.

I was most impressed by the Osborne Firefinder—an ancient-looking contraption that spins around and allows him to pinpoint the location of a fire on a map. The day we arrived, the viewfinder was pointed at a small blaze way down in a valley to the southwest. It had been burning for two days. “It’s picking up pretty good,” George noted.

To pass the many hours he spends alone, George reads books, works on his ham radio, and keeps a journal. Daily journal entries cover the things that you notice when you live on a mountaintop: animals, weather, fires. On Friday, Aug. 21, 2001, for example, George wrote: “It was pleasant and sunny today, so I washed clothes.”

If only life could always be so simple.

News Detective: Emily hikes up Mt. Holmes

Word Find: Fires in Yellowstone

Questions about the Article

Going Deeper:

Kids who always snore when they sleep are four times more likely to get bad grades in school than are students who never snore, according to a new study.

Frequent snoring can lead to poor schoolwork.

A group of German scientists asked the parents of 1,129 third-graders whether their children snored always, frequently, occasionally, or never. The researchers also collected information about how well the students did in school.

Frequent and constant snorers did worse in math, science, and spelling than did occasional snorers and non-snorers, the data showed.

The researchers also tested whether the snorers might have a sleep disorder called intermittent hypoxia. Caused by low levels of oxygen in the blood, this disorder is fairly common. People who have it often snore. Still, kids who had the disorder didn’t get worse grades than did kids without it, the second study showed.

Snoring might just keep kids from sleeping well, the researchers think. Being tired would make it hard to pay attention and perform well in school. So, make sure to tell your doctor if you snore a lot. If the problem is extreme, surgery to remove the tonsils sometimes helps.

Whatever you do, don’t start snoring while you’re at school. Then, you’ll really be in trouble!—E. Sohn

Going Deeper:

Seppa, Nathan. 2003. Grades slipping? Check for snoring. Science News 164(Sept. 13):173-174. Available at http://www.sciencenews.org/20030913/note13.asp .

You can learn more about snoring at http://kidshealth.org/kid/health_problems/teeth/snoring.html (KidsHealth for Kids).

In times of stress, many people turn to french fries, ice cream, mac and cheese, and other fatty “comfort foods” to make themselves feel better. There might be important biological reasons for those cravings, according to a new theory.

Ice cream and other fatty sweets may help people face the stress of constant worries but, at the same time, cause them to gain weight.

Studies with animals and people have shown that stressful situations cause the body to churn out lots of extra hormones, including those known as glucocorticoids. These chemicals eventually shut down the stress response, and the animal relaxes.

If the stress lingers for days and days, however, glucocorticoids no longer shut down the stress response. Animals may then begin to seek out yummy foods. All of those extra calories get stored as fat around the waist. Then, in a feedback loop, this abdominal fat interferes with the action of the glucocorticoids, and the animal relaxes again. In this way, studies with rats show, comfort foods really can ease anxiety.

That’s the theory at least.

In our society, however, enduring stress is such an established fact of life and comfort foods are so easy to get that stressed-out people often gain weight. That increases their risk of heart disease, diabetes, and other health problems.

Pay attention to your cravings. If you catch yourself mindlessly reaching for the cookie jar, stop and take a few deep breaths. It may be time to take a vacation instead!—E. Sohn

Going Deeper:

Ramsayer, Kate. 2003. Sweet relief: Comfort food calms, with weighty effect. Science News 164(Sept. 13):165-166. Available at http://www.sciencenews.org/20030913/fob5.asp .

Sohn, Emily. 2003. In search of the perfect french fry. Science News for Kids (July 23). Available at http://www.sciencenewsforkids.org/articles/20030723/Feature1.asp .

You can learn more about stress at http://www.bam.gov/head_strong/top10Coping.htm and http://www.bam.gov/survival/physical_signs.htm
(BAM!/Centers for Disease Control and Prevention).

As Norman Eiley, our boat driver, prepared to cast anchor, a handful of sharks and stingrays swam beneath the boat’s wake. The 15 high school students I was traveling with started to squeal. “I never get to see sharks in the water!” said Emma Cooper-Mullin, 17, from Irvington, N.Y., with fins and snorkel in hand. “I really want to swim with one.”

Holding a nurse shark at the Hol Chan Marine Reserve in Belize.

AmbergrisCaye.com

Within minutes, we were all in the water, making that dream come true. For the next hour, we snorkeled with a handful of nurse sharks and southern stingrays at Shark Ray Alley—a shallow sandbar just south of Ambergris Caye, an island in northern Belize. Shark Ray Alley is part of the Hol Chan Marine Reserve. It is illegal to catch fish there. Instead, tourism is the main draw.

Every day, boats full of tourists arrive at Shark Ray Alley, where tour guides feed chunks of fish guts to the animals. As a result, the area’s sharks and rays—some bigger than we are—have become so used to people that they’ll swim right up to you and even let you touch them.

And that’s the problem. Just days before we snorkeled at Shark Ray Alley, Norman told me, a fisherman from the mainland had cruised in at 4 in the morning, caught 9 or 10 nurse sharks, and killed them to sell their fins and meat.

“People noticed them missing that day,” Norman said. “They were complaining—no sharks, no sharks, no sharks. Nobody has ever done something like this before on a large scale.”

Underwater national parks

Marine reserves, or sanctuaries, are supposed to prevent such incidents from happening. Like national parks under water, marine reserves are set up to protect designated areas of the ocean from fishing, instead favoring research, education, and tourism.

Published research on the benefits of marine reserves worldwide has exploded in recent years, says Jim Bohnsack, a fisheries biologist at the National Marine Fisheries Service in Miami. “The scientific community is 99 percent supportive of marine reserves,” he says. “They work for protecting biodiversity and protecting resources.”

The idea is that a carefully designed network of protected areas should help the health of the entire ocean. Fish and other creatures can grow up safely inside reserves before spilling over the edges, where they become fair game for fishermen.

The Hol Chan Marine Reserve protects fish and other sea creatures.

AmbergrisCaye.com

“It’s like an insurance policy,” Bohnsack says. “If you make mistakes, you have something in the bank, like a savings account, that can help resupply areas that have been overfished.”

In support of marine reserves, Bohnsack points to evidence that bigger fish tend to lay more eggs. So, fish inside reserves should be more likely to produce even more fish with stronger genes. In theory, everyone wins, including fishermen and conservationists.

“It’s like having your cake and eating it, too,” Bohnsack says.

Boosting conservation

Marine reserves also make sense economically, says Charles Acosta, an ecologist at Northern Kentucky University. By tracking lobsters, queen conch, and other animals with radio technology and using mathematical models to analyze population patterns, Acosta and his colleagues have come up with dollar figures to show fishermen that conservation will actually boost their business in the long run.

Acosta’s work has contributed to a debate over what marine reserves should look like. “One of our biggest, most important results has been that there is a limit that you cannot go below in terms of size of reserve,” he says. “If the reserve is too small, it will have no effect at all.”

A southern stingray.

AmbergrisCaye.com

Still, plans to create marine reserves are often controversial, especially in places like the Florida Keys, where the fishing industry has a lot of money at stake.

And even after reserves are established, enforcement is often difficult and more expensive than most developing countries can afford. At Hol Chan, a ranger zooms around all day long, collecting fees from snorkelers and divers who visit the area.

You can pay a fine of up to $500 if you get caught stealing even a piece of coral. Other reserves rely more on word-of-mouth and the honor principle for protection.

Sharks in the wild

Unfortunately, those kinds of systems can backfire, as the recent incident at Shark Ray Alley demonstrates. “To have all those sharks living in one place is setting them up for something like this to happen,” said Norman, who is also treasurer of the Belizean Tour Guide Association. He is now determined to track down and punish the shark poachers and to revise enforcement policies in Belize. “We all depended on the honesty of fishermen,” he said.

Besides, Norman added, maybe it’s better not to turn shark sightings into humdrum, everyday events. “It used to be when you saw a nurse shark it was like, ‘Wow!,’” he said. “But after going to Shark Ray Alley, it’s like ‘Oh, there’s another one.’ The element of surprise has changed.”

Given a choice between seeing a shark by chance in the wild and seeing a shark at a place like Sting Ray Alley, most of the students in our group reluctantly agreed. “I guess I would rather see sharks when no one else was around than at Shark Ray Alley,” Emma said on the boat ride back to Ambergris Caye.

Her classmate Cheryl Berman, an 18-year-old senior from Armonk, N.Y., wasn’t so sure. “I think both are pretty cool.”

Going Deeper:

Additional Information

Word Find: Swimming with Sharks

Questions about the Article

Scientists have discovered a poisonous frog that takes up a toxin from its food and makes the chemical even deadlier. It’s the first example of a frog using chemistry to make a poison for its own defense stronger.

This 4-centimeter-long green poison dart frog, Dendrobates auratus, can increase the power of a particular toxin that it picks up from its food.

Proceedings of the National Academy of Sciences, National Aquarium in Baltimore

Several types of frogs from South America, Australia, and Madagascar carry deadly poisons in their skin. When raised in zoos and aquariums, however, most of the frogs grow up to be totally harmless.

About 10 years ago, researchers from the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md., figured out that many poison dart frogs take up toxins from the food they eat, including ants and other insects. If such prey isn’t available, the frogs get no toxins to store in their skins.

More recently, scientists were working with a toxin called pumiliotoxin 251D, often found on the skin of the tropical frog known as the green poison dart frog (Dendrobates auratus). The scientists sprinkled the toxin on termites and fruit flies, which they then fed to captive frogs.

Later analyses of the frogs’ skins showed that about 80 percent of the pumiliotoxin 251D had been converted to a different toxin, called allopumiliotoxin 267A. The new toxin was five times more poisonous to mice than the original chemical.

Scientists were surprised by their findings. Any creature that tries to eat a wild Dendrobates would get an even bigger surprise. It’s quite possible that its frog-leg dinner would be its last!—E. Sohn

Going Deeper:

Milius, Susan. 2003. Skin chemistry: Poison frogs upgrade toxins from prey. Science News 164(Sept. 6):148-149. Available at http://www.sciencenews.org/20030906/fob5.asp .

You can learn more about the poison dart frogs at the following Web sites:

http://www.aqua.org/animals_bluepoisondartfrog.html (National Aquarium in Baltimore)

http://www.scz.org/animals/f/blufrog.html (Sedgwick County Zoo)

http://www.bsrsi.msu.edu/rfrc/tour/dendrobates.html (Rain Forest Report Card, Michigan State University)

http://www1.tip.nl/~t272198/index.htm (Digital Dendrobates, Q. Jansson)