Male cichlids are mainly freshwater fish that may go after other fish who dare cross their path. A male cichlid will even lunge if that “other fish” happens to be himself: When some types of these cichlids see their own reflections in a mirror, they respond as aggressively as when they encounter a real fish opponent.

Male cichlids get hostile when they meet a real male (shown here) or when they encounter their own reflection. But their reflection provokes activity in their brains that could be connected with fear.

Todd Anderson

A new study suggests that even though these two situations may look the same, a fish’s brain actually reacts differently in each case. Researchers from Stanford University recently studied male cichlids that fight their own reflections. The team observed that the part of the brain associated with fear and other negative emotions becomes active when the fish fight their mirror images.

Julie K. Desjardins, one of the scientists who worked on the study, says it’s not clear whether the research is finding “fear”— that is, the scientists are not sure that the fish are afraid of themselves. Even if it’s not fear, the fish is having a negative response, something besides the aggression it usually shows toward another fish, she told Science News.

The study by Desjardins and Russell Fernald, her colleague at Stanford, is the first to show that a fish’s brain reacts differently when the fish sees its own reflection. That doesn’t mean, however, that the fish recognizes itself.

Scientists use mirrors to try to study the consciousness of animals. Previous studies have shown that great apes, elephants, dolphins and magpies (a type of bird) look into a mirror and know they see themselves, Diana Reiss told Science News. Reiss is a scientist at Hunter College in New York City who tries to understand animal cognition, or how animals think. She says not every animal knows its mirror self — monkeys and fish, for example, don’t seem to recognize themselves in the mirror.

In the new study, Desjardins and Fernald did not observe a difference in the behaviors of fish going after other fish compared with fish going after their own reflections. And when the scientists looked at hormones in the fish, they didn’t see a difference. But when they looked in the fish’s brain, using a technique called immediate early gene (IEG) expression, they found a difference.

With this technique, the scientists watched particular genes in the fish that were associated with particular regions of the brain. Measuring IEG helped the scientists to determine which areas of the brain were more active than others. “It’s a kind of fishy MRI,” Desjardins told Science News. MRI stands for magnetic resonance imaging, a tool that gives scientists an idea of what’s going on inside the brain.

When a fish went after its own reflection, the scientists found that the fish brain was especially active in a region similar to the amygdala. In human beings and other animals, the amygdala is associated with fear and other negative emotions.

When the male cichlids went after other fish, they didn’t have the same activity in their amygdala regions — showing that their brains reacted differently when they looked themselves in the fishy face.

Using IEG expression to study fishy fear is new and unusual, but some older studies have shown similar results in other animals. Monkeys, for example, have not been shown to recognize themselves — but they do act differently around their own reflections than they do around other monkeys.

This experiment shows how mirrors can be used to study brain activity, even for animals that don’t recognize themselves.

Going Deeper:

Milius, Susan. 2010. “Mirror, mirror on the wall, you’re the scariest fish of all,” Science News, May 11. Available at http://www.sciencenews.org/view/generic/id/59094/title/Mirror%2C_mirror_on_the_wall%2C_youre_the_scariest_fish_of_all

Ornes, Stephen. 2010. “Pipefish power from mom,” Science News for Kids, February 17. Available at http://sciencenewsforkids.org/articles/20100217/Note3.asp

Bower, Bruce. 2008. “I, Magpie.” Science News, September 13. http://www.sciencenews.org/view/generic/id/35462/title/I%2C_Magpie

We’re sitting on the seventh floor of a building in downtown San Francisco, upstairs from the famous jewelry store Tiffany & Co. But Chatham didn’t buy these gems at a jewelry store. His company, Chatham Created Gems & Diamonds, made them in its laboratories.

Lab-made gemstones can appear similar to those that form in Earth. This sapphire was made by Chatham Created Gems & Diamonds.

Chatham Created Gems & Diamonds

Usually, gemstones form below Earth’s surface. They can stay buried for many millions of years. But Chatham and other scientists are creating gemstones on their own. They do this by mimicking the processes that occur underground or by coming up with entirely new processes. Lab-made gems have the same appearance and basic chemical structures as the natural ones, and they can be produced in months or even days.

Because these gems are created in the laboratory, researchers can control the gems’ formation very carefully. Some lab-grown gems are even purer or tougher than natural gemstones. And the gems are good for more than just jewelry. They can be used to make tools, such as lasers and drills. Lab-made diamonds could even help scientists improve electronic devices or detect dangerous bacteria in drinking water.

The first emerald that Carroll Chatham made in his father’s basement.

Roberta Kwok

An accidental emerald

But making gemstones isn’t easy.

Chatham’s father, Carroll Chatham, became interested in the problem when he was only a teenager. Carroll had read about a scientist who tried to create diamonds, and he wanted to try making diamonds too.

Carroll had already built a laboratory in his father’s basement. For his experiment, he heated up iron and a soft black material called graphite, then dropped the melted mixture into a very cold substance: liquid nitrogen. It exploded.

“Almost blew up his father’s house,” says Tom Chatham. The explosion was so strong that it also smashed all the windows in the house across the street.

Carroll didn’t give up. He decided to try making emerald instead. For a long time, he couldn’t get it to work. Then one day, he left an experiment running and went away to college. While he was gone, Carroll’s father shut off the power in the basement and cooled down the furnace holding Carroll’s mixture of chemicals. That turned out to be the missing step. When Carroll came back, an emerald had grown.

Cooking up a crystal

Most gemstones are hard pieces of mineral. In nature, some minerals form underground when hot liquid rock — magma — cools down. Some of the atoms and molecules in the liquid start attaching to each other in repeating patterns, creating a structure called a crystal. If the mineral is beautiful, durable and rare, it is often considered a gemstone. Gemstones also form when minerals are heated up, squeezed, or exposed to new chemical elements.

These diamonds were created by CVD, or chemical vapor deposition, which can form diamonds relatively quickly.

Carnegie Institution for Science

When volcanoes erupt or mountains form, the gemstones get pushed closer to the surface. Or, over time, the rocks above wear away, uncovering the gems underneath.

To make a gemstone in the lab, researchers can imitate the Earth’s process. Each gem has a “recipe” with certain chemical ingredients. For example, emerald can be made with aluminum oxide, beryllium, silica, and bits of chromium. Rubies contain aluminum oxide and a little chromium.

Scientists usually melt the ingredients or dissolve them in water or other chemicals. The mixture can get as hot as 1,000 degrees Celsius — 10 times hotter than the temperature needed to boil water. Then the liquid is slowly cooled down. The cooling takes energy away from the atoms and molecules in the mixture, and they start to come together into a crystal. The crystal actually “grows,” as if bricks were arranging themselves into a house.

Because they contain the same ingredients, lab-made and natural gems can be hard to tell apart. But there are tiny differences. For example, many natural gems contain very small amounts of water, but some lab-grown gems do not, says James Shigley, a geologist at the Gemological Institute of America in Carlsbad, Calif. And certain lab-made gems may have bits of platinum that wouldn’t be found in natural gems.

While gemstones are forming, they can get traces of other materials stuck inside them, called inclusions. Lab-made gems often contain fewer inclusions than natural gems because scientists can control the growth conditions. “Natural gems just represent a fortunate accident in the Earth,” says Shigley.

Big crush

Diamonds are a little different from other gemstones because it takes huge amounts of pressure for diamonds to form. Imagine if the Eiffel Tower was pointed upside down and resting on its tip. Now imagine all that weight is pressing down on a point a few centimeters wide. That’s how much pressure a natural diamond feels deep inside the Earth, says George Harlow, a mineralogist at the American Museum of Natural History in New York City.

And diamonds are made only of carbon, a chemical element found in all living things. If you arrange carbon atoms in layers like sheets of paper, you get graphite — a soft material used in pencil lead. But if you connect each carbon atom to four other carbon atoms in a three-dimensional structure, you get diamond — an incredibly hard material.

The company Advanced Diamond Technologies Inc. is using lab-made diamond to develop tiny sensors that can detect and signal that bacteria are present in drinking water.

Advanced Diamond Technologies Inc.

A company called Gemesis in Sarasota, Fla., has hundreds of diamond-making machines. The scientists start with a tiny “seed,” a piece of diamond about the size of a period at the end of a sentence. They put the seed into a ceramic container with graphite and a secret mixture of other chemicals. Finally, they close the container, squeeze it with blocks of metal, and heat it up.

When the graphite dissolves, it separates into individual carbon atoms. The carbon atoms start attaching to the seed, making it grow. “Four days later, out comes a diamond,” says Karl Pearson, the senior vice president of technology and engineering at Gemesis.

Microwaving a diamond

Other researchers are making diamonds using a method that is completely different from Earth’s. The process is called chemical vapor deposition, or CVD. With CVD, scientists can make bigger pieces of diamond faster. They can also make thin diamond layers that could be used in high-tech devices.

Researchers at the Carnegie Institution for Science in Washington, D.C., have been working on CVD for many years. They put a penny-sized diamond seed into a chamber and pump out all the air. Next, they inject two types of gas: hydrogen and methane. Methane contains both carbon and hydrogen atoms.

“Then we microwave it,” says Joe Lai, a materials scientist at the lab. The microwave is similar to the microwave you would use at home to heat up your food, only more powerful. The hydrogen and carbon atoms break apart and then form into one very bright, very hot ball of gas. Carbon atoms bond to the diamond seed, making it bigger and bigger.

The Carnegie researchers have improved the CVD process so that diamonds grow more quickly. In 2002, they showed that their CVD process could grow single diamond crystals about 100 times faster than the microwave method had before. And the team can make their diamonds tougher than natural diamonds by adding a chemical element called boron. The boron keeps cracks from spreading, so it’s harder to break the diamond apart.

Tattoos, teeth and cell phones

Lab-made gems can be used for more than just rings and necklaces. For example, some supermarkets use sapphire in the check-out scanners. When a cashier needs to find out the price of a product — say, a box of cookies — a laser beam shines through a sapphire plate to scan a code on the box. Without a hard material like sapphire, the plate would quickly get scratched, and the scanner wouldn’t work as well.

The company Gemesis uses special machines (one pictured) to make diamonds.

Gemesis

Rubies are special because they can create laser beams. If you place a ruby rod between two mirrors and flash a very intense light at it, the ruby will shoot out a beam of red light. Ruby lasers can help remove tattoos because the red light breaks down certain colors of tattoo dye in a person’s skin.

But perhaps the most amazing gem of all is diamond. Diamond is so hard that it is used to cut rock and drill for oil. If you have ever had a cavity filled at the dentist, a diamond-tipped drill may have been used to remove part of your tooth.

Diamond lets heat pass right through it, so a diamond stays cool. “I could take a blowtorch, heat up a diamond till it’s glowing hot, put it on a metal surface and pick it up a couple seconds later, and it won’t be hot at all,” says Lai. Instead of holding the heat, the diamond transfers the heat to the metal. And diamond is very stiff, meaning that it is hard to bend.

“It really is nature’s extreme material,” says John Carlisle, a physicist and chief technical officer at the company Advanced Diamond Technologies Inc. in Romeoville, Ill.

Some of these properties could make diamond useful in cell phones. With today’s cell phones, people can talk to friends, surf the Internet and download videos. When you do these things, the phone uses parts called acoustic filters. Currently, these filters can be made of materials such as quartz or ceramic. Each filter must vibrate at a certain rate in order for the phone to work. Some filters have to vibrate more than a billion times per second.

Because diamond is so stiff, it can vibrate at a very fast rate. Researchers are now working on creating tiny diamond filters, smaller than the width of a strand of hair. These filters could make the cell phone use less power, so the battery would last longer.

Diving boards for bacteria

Lab-made diamond could even be used to help find bacteria in the water that we drink. Bacteria are small organisms that you can’t see. Some of them can make you very sick.

Carlisle’s company is working with researchers at the University of Wisconsin–Madison and the University of Illinois at Urbana-Champaign on tiny sensors that will detect these bacteria. The sensors have diamond parts shaped as miniature diving boards. To “catch” the bacteria, the diving boards will be coated with molecules that make the bacteria stick to them.

People could put these sensors in water treatment plants or on sinks in their homes. If bacteria got stuck to them, the diving boards would vibrate a little more slowly than usual. That would send an electrical signal to tell people that the water may be dangerous to drink.

If the diving boards were made of other materials, such as silicon or gold, the molecules that catch the bacteria would fall off after awhile. But with diamond, the molecules stay attached. So researchers can leave the sensors in the water for a long time.

Lab-made diamonds could be better for high-tech devices than natural diamonds because it’s easier to get large amounts of diamond in the right shape and size. These diamonds could also be used in devices that help blind people see, in radar equipment for the military, and in advanced computers for sending secret information that can’t be decoded. “There’s just 101 uses for it,” says Carlisle.

Going Deeper:

The human body has a natural block to keep out bacteria that would cause infections: skin. But when the skin gets burned, it’s not only painful, it’s bad for the body. Burned skin cannot keep the bacteria out, so infections are common. That’s why doctors who treat burn victims have to look out for the slightest sign of dangerous infection.

Doctors often wrap burns in bandages for protection, but a recent study shows that a new kind of bandage can actually fight infection. Better yet, this new bandage can use the harmful bacteria against themselves — in other words, the infection-causing organisms cause their own deaths.

Toby Jenkins, a scientist at the University of Bath in England, worked on the study. Jenkins and his colleagues developed a material that contains tiny capsules. But these carefully designed packets aren’t what they seem: To a bacterium, these capsules look like cells just waiting to be invaded. What the little invaders don’t know, however, is that the capsules contain antibiotics, which are chemical compounds that can kill bacteria on contact.

The wound dressings would contain tiny vesicles that, when attacked by a bacterial toxin, would release antibiotics. These antibiotics would then kill the attacking microbes, preventing the wound from becoming infected.

Zhou et al./JACS 2010

The bacteria attack the cells by releasing toxins, or poisons. But when the bacteria attack the capsules, the capsules fight back — by releasing antibiotics that knock out any nearby bacteria.

It’s an unusual idea — using bacteria against themselves. Jenkins and the other scientists tested the material on two types of harmful bacteria. One was a type of Staphylococcus bacteria; the other was a type of Pseudomonas bacteria. When researchers placed scraps of the new material in a Petri dish with the bacteria, the bacteria barely grew at all, which is unusual.

This observation led the researchers to believe that the bacteria had attacked the fabric, and that the antibiotics had been released — which kept the bacteria from growing.

The scientists want the bandages to work specifically against dangerous bacteria, so they also tested the fabric on a harmless type of E. coli bacteria. When the scrap of fabric was placed in a Petri dish with E. coli, the bacteria grew quickly — showing that the trap didn’t fool the harmless bacteria.

The harmful bacteria probably released toxins that burst the capsules open, while the harmless E. coli left the capsules alone.

This early experiment shows that the material can selectively kill dangerous bacteria, but it’s too early to start using the material in hospitals.

“This is a nice approach and they’ve shown in principle that it works,” Christopher Batich, a biomedical engineer at the University of Florida in Gainesville, told Science News. Batich did not work on the study. While he’s excited about the results, he added that the real world is more complicated than this experiment. “You’d have to work with real bacteria and real wounds to see if it makes a difference,” he says.

Jenkins and his colleagues are back at work improving the healing fabric. In the not-so-distant future, this kind of antibacterial bandage may move from the laboratory to the hospital bed — and give burn victims a fighting chance against infection.

This story and other Science News for Kids features describing research in medicine and biology are supported with funding from The Lasker Foundation. The foundation and its programs are dedicated to the support of biomedical research toward conquering disease, improving human health and extending life.

Going Deeper:

Ehrenberg, Rachel. 2010. “Infection, kill thyself,” Science News, April 28. http://www.sciencenews.org/view/generic/id/58697/title/Infection%2C_kill_thyself

Ornes, Stephen. 2010. “The tell-tale bacteria,” Science News for Kids, April 7. http://sciencenewsforkids.org/articles/20100407/Note2.asp

Saey, Tina H. 2009. “Hitting the redo button on evolution,” Science News for Kids, February 11. http://sciencenewsforkids.org/articles/20090211/Note2.asp

Diet fads come and go, but in the end, there’s really only one rule for losing weight: Burn more energy than you consume. In April, scientists from California reported on a chemical that might help people burn fat. It’s called dihydrocapsiate, it comes from a pepper, and in a recent study it was shown to boost the body’s energy burn.

Its name, dihydrocapsiate (di-HI-droh-CAP-see-ate), isn’t easy to say. And Peter Piper never picked it. But it might be easy to find: It is a chemical cousin of capsaicin (kap-SAY-sin), the chemical that makes chili peppers so hot. But unlike its fiery family members, dihydrocapsiate won’t send you running for a glass of water if you eat it. In fact, you won’t even know it’s in your body.

Painful foods — like the ones that contain capsaicin — stimulate pain receptors in the mouth. Once stimulated by a fiery food, these pain receptors signal nerves, which send a message to the brain. Dihydrocapsiate, however, is too big to fit into the receptors and tickle those nerve endings, which means it enters and passes through the body without causing pain.

The main compound that gives peppers (pictured are red savina habaneros of New Mexico) their sting has a close cousin that may burn body fat without irritating the mouth or stomach.

NSF; Chile Pepper Institute

David Heber, a scientist at the University of California, Los Angeles reported on the dihydrocapsiate research in April during a meeting of scientists who study nutrition. He and his colleagues tested the chemical on 33 obese men and women. For four weeks, these volunteers consumed only 800 calories per day, and all of those calories came from a nutritious liquid, instead of from solid foods. These liquids did not contain any fat.

At every meal, the participants were also given pills. People in one group received pills that didn’t do anything. Drugs that don’t do anything are called placebos, and they help experimenters figure out whether the drug being tested really works. Other participants were given a small dose of dihydrocapsiate. Finally, other participants were given a high dose of dihydrocapsiate.

All of the pills looked the same, so neither the participants nor the doctors knew who had consumed placebos and who had consumed the pepper chemical.

After the end of the dihydrocapsiate-enhanced (or placebo-“enhanced”) diet, the scientists determined how much fat the participants were burning.

The scientists observed that not everyone burned the same amount of fat. People who were given high doses of dihydrocapsiate were burning more body fat than people who had been given placebos, UCLA’s Heber says. So much more, he says, that the people taking high doses of dihydrocapsiate may have been losing one more pound per month than the people taking placebos. But that’s a guess: The scientists didn’t measure that number, so they don’t know for sure.

Heber and his team think that the pepper chemical works by attaching itself to another type of receptor, this one in a person’s gut. This receptor helps send a message to the brain, which then starts a process that causes a body to burn, burn, burn calories. This process is the same that, when triggered by capsaicin, causes some people to sweat while they eat hot foods. The scientists say that capsaicin could have the same effect as the dihydrocapsiate, but capsaicin causes intense pain to a person’s mouth and gut.

Dihydrocapsiate could help people lose weight, delivering the positive effects of hot peppers without the fiery side effects. In theory, the chemical could be consumed safely and help a 100-pound person burn an extra 160 calories per day.

Of course, it would be very easy to undo these sizzling effects with one slice of cake or a sugary soft drink. A chemical like dihydrocapsiate may help a person burn more than he consumes — but it can’t change a person’s eating habits.

“As I always say,” Heber told Science News, “a supplement doesn’t make up for diet.”

This story and other Science News for Kids features describing research in medicine and biology are supported with funding from The Lasker Foundation. The foundation and its programs are dedicated to the support of biomedical research toward conquering disease, improving human health and extending life.

Going Deeper:

Raloff, Jane. 2010. “Chili pepper holds hot prospects for painfree dieting,” Science News, April 27. Available at http://www.sciencenews.org/view/generic/id/58689/title/Science_%2B_the_Public__Chili_pepper_holds_hot_prospects_for_painfree_dieting

Picked a pepper? Find out how hot it is using the Scoville scale: http://www.chilliworld.com/FactFile/Scoville_Scale.asp

Sohn, Emily. 2006. “Hot pepper, hot spider,” Science News for Kids, November 15. http://sciencenewsforkids.org/articles/20061115/Note2.asp

Sohn, Emily. 2009. “Greener diet,” Science News for Kids, February 25. http://sciencenewsforkids.org/articles/20090225/Note2.asp

It can be tough to figure out which types of fish — and how much — a person can eat. But with a little reading and good information, a person can still eat fish and be healthy. In recent weeks, researchers have come up with some advice for how to get the fishy benefits and avoid the toxic mercury.

Take tuna as an example. There are many different species of tuna, but grocery stores and restaurants often sell it without specifying which kind. But the amount of mercury tends to vary with the type of tuna. In one of the new studies, researchers studied 100 samples of sushi tuna purchased from grocery stores and restaurants. Jacob Lowenstein, a scientist at Columbia University in New York City, worked on the study. Sushi is a Japanese style of food presentation, usually involving fish that is served raw.

Some types of canned tuna contain the amount of mercury that EPA says is concerning, a recent study found.

TheGiantVermin/Flickr

Lowenstein and his colleagues studied the genetic material in the cells of the tuna. They discovered that the tuna came from three types: bigeye, bluefin and yellowfin species. As the scientists expected, bigger fish had more mercury. So tuna that came from yellowfin, the smallest type on average, had less mercury than tuna from bluefin, which are larger.

But the scientists were surprised to discover that restaurant tuna contained more mercury than fish from the grocery store. Worse, yet, restaurant tuna had, on average, more mercury than the maximum amount recommended by the U.S. Environmental Protection Agency, or EPA.

The EPA recommends that fish not contain more than 0.5 parts per million of mercury. The tuna from restaurants had 0.75 parts per million, on average, and some restaurant samples had levels as high as 1 to 2 parts per million. These numbers may seem small, but long term ingestion of even tiny amounts of mercury can lead to heart or nervous-system disease.

As a result of their study, Lowenstein and his colleagues recommend that government “health agencies should consider adding bigeye and bluefin tuna to mercury advisories.” These advisories caution that people, especially pregnant women and young children, should avoid certain types of fish. Mercury is neurotoxic, which means it can injure developing brains.

In another study, scientists from the University of Nevada Las Vegas looked at three kinds of canned tuna: solid-white, chunk-white and chunk-light. On average, light tuna had 0.28 parts per million, which is safely below the EPA’s recommendation.

But solid and chunk-white types averaged 0.5 parts per million, right at the level of concern. The researchers calculated that a 55-pound child can safely eat only one serving every two weeks.

The Nevada scientists recommend that government agencies be stricter about allowable mercury levels in fish. The EPA, the researchers recommend, should produce a clear policy that will tell people how much mercury they can consume — and where it comes from. The scientists would like to see a similar policy from the Food and Drug Administration (FDA). Right now, the FDA safety limit is 1 part per million, or twice that of the EPA.

In a third study, Edward Groth III studied FDA’s database that documents mercury contamination in 51 different types of fish and found that some types have 100 times the amount of mercury typically found in other types. This means there is no easy rule about mercury and fish — it depends on the species of fish and how contaminated the waters were in which it had lived. Groth produced a chart to make it easy for consumers to check the mercury content of the fish they’re about to eat or buy. The chart is small enough for a person’s pocket.

In June, experts from around the world will get together in Stockholm, Sweden, to develop a world policy on mercury. Mercury can come from natural sources, like volcanoes, but it is also pollution produced by industrial sources like coal-fired power plants.

Once mercury gets in the water and into the fish, it can get into you. But in this case, a little information can go a long way in keeping the mercury at bay.

Going Deeper:

Raloff, Janet. 2010. “Studies aim to resolve confusion over mercury risks from fish,” Science News, April 21. http://www.sciencenews.org/view/generic/id/58464/title/Studies_aim_to_resolve__confusion_over_mercury_risks_from_fish

Ramsayer, Kate. 2005. “Cleaning up fish farms,” Science News for Kids, May 11. http://www.sciencenewsforkids.org/articles/20050511/Feature1.asp

Learn all about mercury: http://www.epa.gov/mercury/

Dreams can be familiar and strange, fantastical or boring. No one knows for certain why people dream, but some dreams might be connected to the mental processes that help us learn. In a recent study, scientists found a connection between nap-time dreams and better memory in people who were learning a new skill.

So perhaps one way to learn something new is to practice, practice, practice — and then sleep on it. (Warning: This research still doesn’t provide an excuse for falling asleep during class.)

“I was startled by this finding,” Robert Stickgold told Science News. He is a cognitive neuroscientist at Harvard Medical School who worked on the study. Neuroscience is the study of how the brain and nervous system work, and cognitive studies look at how people learn and reason. So a cognitive neuroscientist may study the brain processes that help people learn.

Volunteers who dreamed about a new task showed significant improvement in skill.

kodachrome25 / iStockphoto

In the study, 99 college students between the ages of 18 and 30 each spent an hour on a computer, trying to get through a virtual maze. The maze was difficult, and the study participants had to start in a different place each time they tried — making it even more difficult. They were also told to find a particular picture of a tree and remember where it was.

For the first 90 minutes of a five-hour break, half of the participants stayed awake and half were told to take a short nap. Participants who stayed awake were asked to describe their thoughts. Participants who took a nap were asked about their dreams before sleep and after sleep — and they were awakened within a minute of sleep to describe their dreams.

Stickgold and his colleagues wanted to know about NREM, or non-REM sleep. REM stands for “rapid eye movement,” which is what happens during REM sleep. This period of sleep often brings bizarre dreams to a sleeper, although dreams can happen in both modes of sleep. Stickgold wanted to know what people were dreaming about when their eyes weren’t moving, during NREM sleep. In other studies, scientists had found a connection between NREM brain activity and learning ability in rats and in people.

Four of the 50 people who slept said their dreams were connected to the maze. Some dreamed about the music that had been playing when they were working; others said they dreamed about seeing people in the maze. When these four people tried the computer maze again, they were able to find the tree faster than before their naps.

Stickgold suggests the dream itself doesn’t help a person learn — it’s the other way around. He suspects that the dream was caused by the brain processes associated with learning.

All four of the people who dreamed about the task had done poorly the first time, which makes Stickgold wonder if the NREM dreams show up when a person finds a new task particularly difficult. People who had other dreams, or people who didn’t take a nap, didn’t show the same improvement.

Going Deeper:

Bower, Bruce. 2010. “Dream a little dream of recall,” Science News, April 22. http://www.sciencenews.org/view/generic/id/58525/title/Dream_a_little_dream_of_recall

Gaidos, Susan. 2010. “Making light of sleep,” Science News for Kids, March 3. http://sciencenewsforkids.org/articles/20100303/Feature1.asp

Ornes, Stephen. 2009. “Brain cells take a break,” Science News for Kids, May 27. http://www.sciencenewsforkids.org/articles/20090527/Feature1.asp

This type of algae is kelp, and kelp forests are sometimes called the rainforests of the seas. This kelp forest is in Monterey Bay off the coast of California.

Tania Larson, U.S. Geological Survey

Algae may be easy to see, but appearances can be deceiving. There’s an ongoing problem with algae that has pestered scientists ever since they started trying to organize and classify the natural world. Different types of algae may look similar, but they’re actually very different organisms.

Algae may range in color from red to brown to yellow to green. Some types, like phytoplankton, are tiny and visible only under a microscope. Others types, like giant sea kelp, can grow to over 100 feet. Some types of algae are unicellular, which means the entire organism is made of one cell; others are multicellular.

Diatoms are one of the single-celled types of algae. Pictured is a scanning electron micrograph image of Diploneis puella.

USGS Geology and Environmental Change Science Center website

Strangest of all, there are types of algae that sometimes behave like plants — and sometimes behave like animals. Like a plant, these algae use photosynthesis to make food. (During photosynthesis, plants or algae use light from the sun to turn carbon dioxide and water into oxygen and food.) But when sunlight is not available, these organisms can still survive by eating other organisms — including other algae! (What would you call that? Cannibalgae?) That behavior is more like an animal because animals can’t synthesize their own food.

Algae are notoriously difficult to classify. So much so, say some scientists, that maybe the best idea is to stop using the word “algae” altogether — except that it’s been around so long it’s too late to change.

Your cousin Chlamy

In 2007, an international team of biologists looked at all the genes of a simple green alga called Chlamydomonas reinhardtii, or Chlamy for short. Genes carry the instructions of life “written” on tightly coiled molecules called DNA inside every cell. Chlamy’s genetic “instruction book” has about 15,000 genes, which is about 8,000 fewer genes than in humans. When the biologists compared Chlamy’s genes to other organisms, some interesting trends emerged.

A large number of Chlamy’s genes can also be found in flowering plants. But it might be surprising to know that roughly 35 percent of Chlamy’s genes can be found in both flowering plants and humans, the research team reported earlier this year. Plus, about 10 percent of Chlamy’s genes can be found in human cells but not plant cells.

No one is going to invite Chlamy to the family reunion, of course. And Chlamy isn’t that unusual — many different living things have identical genes. But Chlamy is interesting: It shows how evolution can deliver some surprising tricks, like producing algae that is genetically similar to humans and plants.

A red tide is a poisonous bloom of algae that can kill marine life.

NOAA

Scientists have always had trouble classifying algae. In ancient Greece, the philosopher Aristotle — probably the first scientist to try to organize all living things — simply placed algae in with plants. (Plants and animals were “beneath” humans, and humans were “beneath” angels.)

In the 18th century, a Swedish botanist named Carl Linnaeus suggested a system that grouped all plants together and grouped all animals together. Like Aristotle, Linnaeus called algae a plant. Linnaeus’ system also showed how similar animals — such as dogs and wolves, for example — could be grouped together. The system is still in use today, though it has been modified and changed significantly in the past 250 years. But even with hundreds of years of changes, algae stick out like a sore thumb.

“The study of algae has changed a lot, but it has always been a problem,” says Rick McCourt, a biologist at the Academy of Natural Sciences in Philadelphia. McCourt is also a phycologist, or a scientist who studies algae. (Phycology is the study of algae.)

McCourt points out that the algae problem goes back much farther than Linnaeus or even Aristotle. Much farther: The roots of algae’s identity crisis go all the way back to the beginning of life on Earth, billions of years ago.

Bacteria move in

About 3 billion years ago, Earth was a different planet. It was not populated by people, animals or plants, and the atmosphere was mostly carbon dioxide. Earth’s inhabitants were microorganisms such as bacteria, so small they’re impossible to see without the help of a microscope.

So how did that Earth become the planet on which we live? Many scientists who study evolution blame one particular organism called cyanobacteria. (Sometimes known as blue-green algae or blue-green bacteria, these microorganisms were grouped together with algae until just a few years ago.)

When cyanobacteria, or blue-green bacteria (pictured is the cyanobacteria Gloeotrichia stained with sytox green), invaded another organism, algae was the eventual result.

Barry H. Rosen, USGS

“Blue-green bacteria changed the world more than any other group of organisms,” says Brent Mishler, a phycologist at the University of California, Berkeley. Blue-green bacteria were capable of photosynthesis, he says, which means they started taking carbon dioxide and adding oxygen to the atmosphere.

Scientists think that blue-green bacteria are also responsible for algae. Here’s how: These bacteria may have been the first organisms to stay alive through photosynthesis. That means they used sunlight, water and carbon to make their own food.

Other organisms regularly fed on the blue-green bacteria as well. One of these organisms was the ancient ancestor of green algae. But this ancient alga wasn’t green back then — it was colorless.

And one time, when this algal ancestor ate one of these blue-green bacteria, something strange happened. The organism didn’t digest the bacteria — it absorbed it.

Instead of becoming dinner, that bacteria became a permanent resident inside the other organism. Biologists believe that bacteria-inside-an-organism is the oldest ancestor of all green algae. These two organisms each had their own set of genes, but after millions of years and many, many, many generations, the genes mixed and both sets became essential for the alga’s survival. The two organisms had become a single organism.

“It’s the only explanation that makes sense,” says McCourt. “Everything we call green algae descended from a single ancestor, maybe from a single cell, long ago in the ocean or in the freshwater.”

Green algae isn’t the only type of algae. Other types — including brown algae, red algae and diatoms — also evolved in a similar way. “What makes all the algae groups algae is that some of the cyanobacteria went and lived inside them,” Mishler says. “But they were invaded separately.”

Different types of algae may not be related in ancient, ancient history, but every type of algae evolved from an organism that, once upon a time, was invaded by blue-green bacteria. These invaded organisms were not necessarily similar. Green algae and brown algae, for example, are often grouped together because they both use photosynthesis to make food, and because they’re both found in the water. But they have very different family histories. Green algae evolved after one type of organism was invaded by cyanobacteria, and brown algae evolved after a different organism was invaded.

This distinction explains why there are so many different kinds of algae — and why the algae family is still hard to pin down. Scientists have shown that many different types of algae are related only distantly, despite the fact that they may look similar.

And some of these scientists say algae’s classification problem isn’t with algae at all, but with the system we use to organize living things. These scientists advocate for a new system — one based on evolutionary ancestors, rather than on the current appearance and structure of an organism.

Changing classification systems

The original invasion that gave us algae happened billions of years ago, but since then, algae’s evolutionary story has been filled with similar invasions. Even today, it’s easy to see how algae too have invaded other species.

Mishler points out that algae are responsible for the brightly colored plumes that can be observed on giant clams or the vibrant appearance of coral. Algae also live inside octopi. “There’s a parallel story over and over again, with algae invading a host,” says Mishler. “They like to live in other organisms.”

Earlier this year, scientists found an invasion in the making: A sea slug that regularly feasts on algae was found to have absorbed algal genes — the ones used to do photosynthesis.

But just because the invader is the same for all these host organisms doesn’t mean the host organisms are related; it just means they’ve been invaded. And if the evolutionary development of algae is considered, then maybe “algae” shouldn’t be its own group of organisms.

Some biologists, like Mishler, say it’s time to change the system that we use to organize the living world. A better way, they say, would be to organize living things according to how they evolved.

The problem in classifying algae is just one example of the issues that scientists who care about naming things grapple with. And their work is just starting. Dozens of new plant and animal species are found every year, and each one of those new species has to be studied, classified and named.

The system for classifying organisms also gives those organisms their names. It’s important that scientists agree on the same names. “Unless you can name something you really can’t talk about it,” says McCourt. “Giving a species a name is necessary in order to study and understand what it’s doing.”

“If a young scientist wanted to get a good career and go outside and do adventurous things, this would be an exciting career,” says Mishler. “It’s one of the older careers in biology, but it’s still not finished.”

And there will always be new species to find: “There are probably more organisms out there we don’t know than those we do know,” Mishler says.

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However, certain gases in our atmosphere, such as carbon dioxide, methane and water vapor, work like a blanket to retain much of that heat. This helps to warm our atmosphere. The gases do this by absorbing the heat and radiating it back to Earth’s surface. These gases are nicknamed “greenhouse gases” because of their heat-trapping effect. Without the “greenhouse effect,” Earth would be too cold to support most forms of life.

But you can have too much of a good thing. Carbon dioxide is released when we use fossil fuels, such as coal, oil and natural gas. We burn these fuels, made from the ancient remains of plants and animals, to run electricity-generating plants that power factories, homes and schools. Products of these fossil fuels, such as gasoline and diesel fuel, power most of the engines that drive cars, airplanes and ships.

By examining air bubbles in ice cores taken from Antarctica, scientists can go back and calculate what the concentrations of carbon dioxide in the atmosphere have been throughout the last 650,000 years. The amount of carbon dioxide in the atmosphere has been climbing to where today it is 30 percent greater than 650,000 years ago. That rise in carbon dioxide “is essentially entirely due to the burning of fuels,” Susan Solomon says. She’s a senior scientist with the National Oceanic and Atmospheric Administration, in Boulder, Colo., and studies factors that affect climate.

Humans have further increased the levels of greenhouse gases in the air by changing the landscape. Plants take up carbon dioxide to make food in a process called photosynthesis. Once cut down, they can no longer take in carbon dioxide, and this gas begins building up in the air instead of fueling the growth of plants. So by cutting down trees and forests for farmland and other human uses, more carbon dioxide is also added into the atmosphere.

“We’ve always had some greenhouse gases in the atmosphere,” Solomon says. “But because we’ve burned a lot of fossil fuels and deforested parts of the planet, we’ve increased the amount of greenhouse gases, and as a result have changed the temperature of the planet.”

Lice are tiny and itchy, and they feast on human blood. So it’s hard to imagine that these insects could be useful. Head lice, which can grow to be about the size of a sesame seed, live on the head. Body lice live in clothing. These two types of lice are similar but not identical, and the difference between them may help explain something about humans.

In a recent study, scientists used a genetic study of head and body lice to estimate when people started wearing clothes.

Body lice and head lice have a common ancestor, which means that if you were to travel back far enough in time and study lice, you wouldn’t find both body lice and head lice — only head lice. At some point in the distant past, there was a split. Some head lice stayed head lice; others started to change in microscopic ways and set the stage for later generations to  became body lice.

One type of human louse (left) lives on the scalp, and the other (right) lives on clothes.

SNK archives; S. Tuepke/Max Planck Institute for Evolutionary Anthropology

According to the recent study, body lice first appeared about 190,000 years ago. Some researchers have long suspected body lice, which live in the folds of clothing, appeared shortly after people started wearing clothes. So, the researchers propose, people probably started wearing clothes about 190,000 years ago, since it wasn’t long before the body lice moved in.

Before this study, scientists estimated that people started wearing clothes somewhere between 40,000 and 1 million years ago — a pretty wide range.

The changes that made body lice possible happened in the DNA of the lice. Inside almost any cell of a living organism is DNA, or deoxyribonucleic acid, the biological structure holding the instructions for life. DNA looks like a spiral staircase, where the supports are made of one type of chemical compound and the rungs are made of another.

These “instructions” are written in DNA. Carrying out the instructions for life are genes, which contain DNA. Every time lice — or any living thing — reproduce, the offspring’s genes are slightly different from the parents’. These changes are called mutations, and mutations make evolution possible. Over time, these mutations build up, eventually causing existing organisms — like some head lice long ago — to change enough to become new organisms — like body lice. In the new study, the scientists looked at DNA both in the nuclei of louse cells and in the mitochondria, which are the energy factories inside cells.

Andrew Kitchen, a scientist at Pennsylvania State University in University Park, led the new study. Speaking to Science News, Kitchen said that, with this new evidence, scientists can begin to understand how early humans were able to live in northern regions, which are cold — and would have required clothing.

If the new study is correct, then body lice as we know them today are only a little younger than Homo sapiens — which is the scientific name for human beings. The first Homo sapiens showed up about 200,000 years ago.

Of course, the new study makes lice more interesting — but not any less itchy or disgusting. So for the time being, let’s just leave the lice in the laboratory.

Going Deeper:

Bower, Bruce. 2010. “Lice hang ancient date on first clothes,” Science News, May 8. Available at http://www.sciencenews.org/view/generic/id/58435/title/Lice_hang_ancient_date_on_first_clothes

McDonagh, S. 2003. “Of lice and old clothes,” Science News for Kids, Aug. 27, Available at http://www.sciencenewsforkids.org/articles/20030827/Note3.asp