Fish can count, too

One, two, three...

Timeline, 2008: We tend to think of a few things we do as being uniquely human. And then we keep finding other organisms that can do them, too. Walking on two legs? Meet the orangutan, walking upright in the trees. Tool use? Crows can make a hook to fish meat out of a tube. The ability to talk? Seems that Neanderthals might have had that, also. OK, well what about counting, having number sense? Baby chickens share this trait with us. To the growing list of other animals that do as well—which includes dolphins, rats, and some monkeys—you can now add the mosquitofish.

Mosquitofish vs Munduruku

Yes, apparently fish can also count, in some cases as well as infants ages 6 to 12 months. In fact, when compared to some natives of the Amazon, the Munduruku, which have limited number language, the fish may even be comparable. The Munduruku people see no value in having a construct for counting beyond five. The mosquitofish, on the other hand, can count about that high and estimate with even higher numbers.

Number sense: It’s not just for people any more

Number sense can be broken down into three paths of perception. We can visually estimate what we see, as people do when they report crowd counts for huge parades or demonstrations. We can also visually count individual units, as we might do just looking at the fingers on one hand. And humans also have the ability to verbally count, theoretically to infinity given sufficient time. While mosquitofish obviously do not count out loud, they do appear to have visual estimation and counting abilities.

Neither is sexual harassment

Their estimation abilities first emerged as a result of sexual harassment. Researchers studying the guppy-like fish noticed that when a male harassed a female, the female fish would take refuge with a group of fish nearby. If there was a choice of groups, or shoals, of different sizes, she would choose the larger of the two. Of course, her ability to tell “larger” might have had nothing to do with actual numbers but instead with the area that the fish occupied. To assess this possibility, researchers performed a number of complex experiments. Their results showed that the females were not relying in occupied area to figure out which group had more fish. They really were using visual number estimation to decide.

In fact, they seem to use ratios in their determinations, but the ratios need to meet a threshold of difference for the estimations to work. For example, a mosquitofish seems able to distinguish a group of 16 fish as being larger than a group of 8 fish, a ratio of 2:1. But the fish cannot tell a group of 12 from a group of 8, proving unable to distinguish a 3:2 ratio.

Estimating, counting: These fish are brilliant

With lesser numbers, up to about four, however, the fish discard visual estimation and rely instead on actual visual counting. In what really was a clever set of experiments, the research team let an individual female fish spend an hour exploring two areas of an aquarium. In one area, she could see a group of four fish but could only see each fish one at a time. In the other area was a group of three fish, again only visible to the female one at a time. After letting her explore, the researchers then determined where the female spent more time. The fish spent about twice as long swimming close to the larger group. In other words, the fish seems to have counted the number of individuals in each group and based on their counting, figured out which area of the aquarium had the larger group.

Pretend you’re a fish

To get in tune with how meaningful this ability is, visualize the experiment yourself as a human (you’re human, right?). Stand in front of two open doorways. In one doorway, four people appear, one at a time. In the other doorway, three people appear, one at a time. You can count them, distinguishing each different individual, and can tell which doorway leads to the larger group of people. That’s how smart the mosquitofish is.

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Why we love our blankies

The box that "duplicated" precious objects

Timeline, 2007: My oldest son is like Linus. He will not part with his “fuzzy,” a blanket that has now survived almost six years of nightlong hugging, trips by plane, train, and automobile, a lonely overnight at a Gymboree, and endless variations on superheroes, ghosts, and pirate headwraps. A professor at the University of Bristol, working with another researcher from Yale, found that children appear to attach a property beyond the physical to these objects of their sleepytime need. The two professors, Bruce Hood and Paul Bloom (of Yale), tested children ages 3 to 6 who had an attachment toy, something that they slept with regularly and had owned for at least one-third of their lives.

For the study, the grownups played a trick on the children. They showed the kids a conjurer’s box with a lot of fancy knobs on it and told them that it was a copying machine that could duplicate objects. To demonstrate, the grownups placed a green block in the machine, fooled around with some of the knobs, and made the first box buzz. Then, the second box of the machine buzzed, and when the doors opened, there was an identical green block behind door number 2.

Linus was engaged in magical thinking

A total of 22 children had brought their attachment objects for the study. After witnessing the amazing abilities of the copying box, four of them simply refused to allow their special object to be “copied” at all. The remaining 18 did allow it, but when choosing between the “copy” and the original, only five selected the “copy.”

Another group of children had brought nonattachment objects for the study. Every child consented to the copying process, and when it came time to choose between their object and the “duplicate,” almost two-thirds opted for the “new” version. Once the study was completed, all children learned that the object they had selected was, in fact, their original toy or blanket.

The Queen’s chalice

The researchers also conducted a different set of experiments in which they placed a goblet in the machine and told the child that it was special either because it was made of silver or had belonged to the “Queen,” presumably the Queen of England. Children who thought it was made of precious metal felt that the “copy” was worth the same as the original; however, children who were told that the original was the Queen’s thought it was of superior value to the “duplicate.”

What drives this kind of irrational, magical thinking? According to Hood, from the University of Bristol, humans are evolved to seek explanations for what cannot be seen, such as gravity. Because mechanisms for many natural phenomena cannot be directly observed but must be inferred, we rely heavily on our intuitive thinking to reach conclusions. This reliance leaves the door open to believing supernatural explanations for what we otherwise cannot explain. Attachment objects may be a substitute for a child who sleeps separately from his mother. But children also appear to confer on the object an “essence,” some meaning beyond its physical worth, something that makes it different from an exact physical duplicate.

The killer’s cardigan

Children are not alone in their reliance on credulity. Grownups use superstition as a way to cope with situations or feel more control over them or to explain the unexplainable. Hood demonstrated the adult tendency to believe an “essence” very clearly in a recent presentation. He offered audience members the chance to earned a quick $25 just for putting on a worn old blue cardigan. Numerous volunteers raised their hands. When he then mentioned that the cardigan had been the property of a notorious mass murderer, most volunteer hands disappeared. The few people who did put on the sweater, which had not really belonged to a murderer, found that the other members of the audience avoided them while they wore it. Scientists are not immune—plenty of us would simply refuse to exchange our wedding rings for an exact copy, for example, even though physically, it is no different from the original we wear on our ring finger.

Nematode may trick birds with berry-bellied ants

Comparison of normal worker ants (top) and ants infected with a nematode. When the ant Cephalotes atratus is infected with a parasitic nematode, its normally black abdomen turns red, resembling the many red berries in the tropical forest canopy. According to researchers, this is a strategy concocted by nematodes to entice birds to eat the normally unpalatable ant and spread the parasite in their droppings. (Credit: Steve Yanoviak/University of Arkansas)

Timeline, 2008: Host-parasite relationships can be some of the most interesting studies in biology. In some cases, a parasite requires more than one host to complete its life cycle, undergoing early development in one host, adult existence in another host, and egg-laying in still another. There’s the hairworm that turns grasshoppers into zombies as part of its life cycle, and the toxoplasma parasite, which may alter the behavior of humans and animals alike. Often, the infection ends with the host engaging in life-threatening behaviors that lead the parasite to the next step in the cycle.

A recent discovery of a most unusual host-parasite relationship, however, results in changes not only in host behavior but also in host appearance. The infected host, an ant living in the forest canopy in Panama and Peru, actually takes on the look of a luscious, ripe fruit.

Berry-butted ants

Researchers had traveled to the Peruvian forest on a quest to learn more about the airborne acrobatics of these ants, Cephalotes atratus. This ant is a true entomological artist, adjusting itself in midair if knocked from its perch. Re-orienting its body, it can glide back to the tree trunk, grabbing on and climbing to where it belongs, avoiding the dangers of the forest floor.

As the investigators monitored the colony, they became aware of some odd-looking members of the group. These ants had large red abdomens that shimmered and glowed and looked for all the world like one of the tropical berries dotting the forest around them. Curious about these odd ants, the scientists took some to the lab for further investigation. Ant researchers are an obsessive breed, and they had even placed a bet over whether or not these berry-bellied ants were a new species.

A belly full of another species’ eggs

When they sliced open one of the bellies under a microscope, what they found surprised them. Inside, a female nematode had packed the ant’s abdomen full of her eggs. The bright red belly was an incubator and, the researchers surmised, a way station on the nematode’s route to the next step in its life cycle. This was the same old C. atratus with a brand new look.

Tropical birds would normally ignore these ants, which are black, bitter, and well defended with a tough, crunchy armor. But any tropical bird would go for a bright, red, beautiful berry just waiting to be plucked. The scientists found that in addition to triggering changes to make the ant belly look like a berry, the nematode also, in the time-honored manner of parasites, altered its host’s behavior: the berry-bellied ants, perched on their trees, would hold their burgeoning abdomens aloft, a typical sign of alarm in ants. A bird would easily be tricked into thinking that the bug was a berry. One quick snap, and that belly full of nematode eggs would be inside the belly of a bird.

Poop: A life cycle completed

And then the eggs would exit the bird the usual way, ending up in the bird’s feces. The ants enter the picture again, this time collecting the feces and their contents as food for their colony’s larvae. The eggs hatch in the larvae and the new nematodes make their way to the ant belly to start the cycle anew.

The nematode itself is a new find, a new species dubbed Myrmeconema neotropicum. And it seems that earlier discoverers of the berry-bellied ants also thought they had a new species on their hands: the researchers turned up a few previous berry-bellied specimens in museums and other collections labeled with new species names. No one had thought that the difference in appearance might be the result of a parasitic infection: this relationship is the first known example of a parasite causing its host to mimic a fruit.

Birds remain the missing link

There is one hitch to the newly discovered nematode-ant-bird association: the researchers never actually saw a tropical bird snap up a juicy, fruit-mimicking ant. They report seeing different species of birds scan the bushes where such ants sheltered, but there were never any witnessed ant consumptions. Thus, this inferred piece of the puzzle—the involvement of birds and their droppings in the life cycle of this nematode—remains to be proven.

Asymmetrical features associated with anger

Don’t anger the asymmetric

After you read this piece, you will probably break out the measuring tape and try to figure out how prone to anger you are, because recent research indicates that anger can be measured in inches.

Using a clever ruse, researchers at Ohio State University found in 2004 that the more asymmetrical a person is in some physical features, the more likely that person is to become angry at rejection. In addition, the scientists found a role for testosterone and sex in these responses.

They duped 51 men and 49 women into thinking that they were attempting to raise money for a (false) charity. Participants had to make two phone calls in an effort to obtain a donation and expected to receive a reward if they were successful. Instead of the person on the other end of the phone being someone in the middle of his dinner, it was really a researcher, pretending to be a solicitee. At the first phone call, the solicitee pretended to be sympathetic, but politely said that he or she had no money to give. For the second phone call, the responder behaved rudely, saying the donation would be a waste of money. The first response was considered a low-provocation incident, and the second a high-provocation response.

Who hangs up phones any more?

When the unknowing study participants hung up the phone, the force of their hang-up was measured, as were their testosterone levels. Additionally, after the exercise, they had a choice of three letters to send to the people they had called; one letter was polite, one moderately pleasant, and the third accusatory and angry.

After collecting data on the ankles, foot width, ear height and width, palms, wrists, and fingers of the participants, the researchers looked for correlations between asymmetry of these characteristics and an angry response, as measured by the force of the telephone hang-up. They found that asymmetrical people became angrier and slammed the receiver more than symmetrical people. In addition, asymmetrical men hung up with more force under the low-provocation scenario, and asymmetrical women hung up with more force after confronting the rude responder.

Oh, testosterone and anger again?

Testosterone levels also played a role, with higher levels causing a more pronounced anger response, and again, the response showed a sex-bias. High-testosterone men were more likely to hang up forcefully after the low-provocation incident, and high-testosterone women after the high-provocation scenario.

What does it all mean? Are the asymmetric people sensitive to rejection, and thus, easily angered by it? Perhaps. But the researchers hypothesize that stress during embryonic development disrupts the embryo on several levels, from physical symmetry to neuronal connections. Scientists have long thought that shifts from symmetry during embryonic development—for example, the right-hand fingers developing a greater length than the left-hand fingers—occur because stressors send developmental signals awry. If the signals operate and are received correctly, both sides should develop the same way; but cigarette smoke, alcohol, and other stressors can disrupt these signals, and asymmetry—and quick anger—can be the result.

Testosterone and asymmetry

One intriguing finding of the study was that the asymmetry results reflected the testosterone levels of the participants. This outcome brings questions of the relationships among the hormonal parameters of development, their disruption, and later manifestations of these interactions.

If you’re wondering why men got so angry with the polite responder and women more so with the rude responder, here’s the researchers’ explanation: Men are quick to react with anger, but are not as comfortable as women with high-anxiety situations. So, when the tension amps up, men back off, but women may actually become more aggressive.

And those letters? More than a third of the participants wanted to send the rudest letter, regardless of their sex or levels of symmetry or testosterone. Perhaps they were merely foreshadowing the anger that now pervades American politics today.

With clones like these, who needs anemones?

Finding Nemo makes marine biologists of us all

I once lived a block away from a beach in Northern California, and when my sons and I wandered the sands at low tide, we often saw sea anemones attached to the rocks, closed up and looking much like rocks themselves, waiting for the water to return. My sons, fans of Finding Nemo, still find these animals intriguing because of their association with a cartoon clownfish, but as it turns out, these brainless organisms have a few lessons to teach the grownups about the art of war.

Attack of the clones

Anemones, which look like plants that open and close with the rise and fall of the tides, are really animals from the phylum Cnidaria, which makes them close relatives of corals and jellyfish. Although they do provide a home for clownfish in a mutualistic relationship, where both the clownfish and the anemone benefit from the association, anemones are predators. They consist primarily of their stinging tentacles and a central mouth that allows them to eat fish, mussels, plankton, and marine worms.

Although anemones seem to be adhered permanently to rocks, they can, in fact, move around. Anemones have a “foot” that they use to attach to objects, but they also can be free-swimming, which comes in handy in the art of sea anemone warfare. (To see them in action, click on video, above.)

Sea anemone warfare could well be characterized as an attack of the clones. These animals reproduce by a process called lateral fission, in which new anemones grow by mitosis from an existing anemone, although they can engage in sexual reproduction when necessary. But when a colony of anemones is engaged in a battle, it consists entirely of genetically identical clones.

Yet even though they are identical, these clones, like the genetically identical cells in your liver and your heart, have different jobs to do in anemone warfare. Scientists have known that anemones can be aggressive with one another, tossing around stinging cells as their weapons of choice in battle. But observing groups of anemones in their natural environment is almost impossible because the creatures only fight at high tide, masked by the waves.

To solve this problem, a group of California researchers took a rock with two clone tribes of anemones on it into the lab and created their own, controlled high and low tides. What they saw astonished them. The clones, although identical, appeared to have different jobs and assorted themselves in different positions depending on their role in the colony.

Battle arms, or “acrorhagi”

The warring groups had a clearly marked demilitarized zone on the rock, a border region that researchers say can be maintained for long periods in the wild. When the tide is high, though, one group of clones will send out scouts, anemones that venture into the border area in an apparent bid to expand the territory for the colony. When the opposition colony senses the presence of the scouts, its warriors go into action, puffing up large specialized battle arms called acrorhagi, tripling their body length, and firing off salvos of stinging cells at the adventuresome scouts. Even warriors as far as four rows back get into the action, rearing up the toss cells and defend their territory.

In the midst of this battle, the reproductive clones hunker down in the center of the colony, protected and able to produce more clones. Clones differentiate into warriors or scouts or reproducers based on environmental signals interacting with their genes; every clonal group has a different response to these signals and arranges its armies in different permutations.

Poor Stumpy

Warriors very rarely win a battle, and typically, the anemones maintained their territories rather than achieving any major expansions. The scouts appear to run the greatest risk; one hapless scout from the lab studies, whom the researchers nicknamed Stumpy, was so aggressive in its explorations that when it returned to its home colony, it was attacked by its own clones. Researchers speculated that it bore far too many foreign stinging cells sustained in the attacks, thus resulting in a case of mistaken identity for poor Stumpy.

Crazy cat lady may have microbe to blame

Toxoplasma gondii is the cat-borne parasite responsible for causing toxoplasmosis and a host of other problems in humans. This close relative of the malaria-causing protozoan may drive human behavior and immunity, in addition to causing acute illness and devastating birth defects. Recent research points to a single gene underlying this parasite’s virulence in the human host. It’s scary yet fascinating to think that a single gene from a single organism could have such dramatic effects on our species.

Warning pregnant women away from litter boxes

Because T. gondii infection can result in serious fetal defects, many pregnant women have heard of toxoplasmosis, an illness that often goes unnoticed in the afflicted person. Pregnant women are warned away from cat litter boxes and even away from gardening because contact with cat feces can mean contact with the parasite. T. gondii spends the sexual part of its life cycle in cats, but for its asexual life, it can parasitize a number of hosts, from pigs to lambs to mice to people. People also can acquire the infection from eating undercooked meat or drinking contaminated water. In some countries, like Brazil, up to 60% of the population has been exposed to T. gondii; in the United States, about 33% of people tested have antibodies to the parasite, indicating past infection.

Link between parasite and schizophrenia

The “crazy cat lady” has practically become a social stereotype in the United States and other countries, conjuring the image of a woman who lives with 25 cats and talks to herself a lot. But researchers investigating schizophrenia have actually identified a potential link between people who are exposed to Toxoplasma infection and the manifestations of schizophrenia; for example, several studies have identified higher levels of antibodies to the parasite in people with schizophrenia, and infection with Toxoplasma can cause damage to brain cells that is similar to the damage seen in patients with schizophrenia. Toxoplasmosis can also sometimes lead to symptoms of psychosis.

The fact is that most people don’t know they have toxoplasmosis because they have healthy immune systems. In people with compromised immunity, however, such as those with HIV, T. gondii can precipitate an extreme form of dementia that eventually kills them. The dementia is so severe that the sufferer eventually becomes completely unaware of his or her surroundings and lapses into a coma. The bug, however, also can affect the central nervous system in healthy people and is also linked to severe eye problems even in patients who are not immunocompromised. One researcher has claimed that infection with the parasite makes men dumber and women act like “sex kittens.”

ROP18: Watch out for this one

There are different strains of T. gondii, and investigators have noted that the Type 1 strain is most closely associated with disease. Studies of T. gondii, which has a genome with about 6000 genes, have pinpointed the virulence capacity of the strain to a single gene, dubbed ROP18. This gene encodes a kinase, one of a huge class of cell signaling proteins that add phosphates to molecules. Typically in cell signaling, kinases exist in a series, phosphorylating the next protein in the pathway, which helps maintain regulation of the signaling. The most virulent T. gondii strains have a form of the gene that differs from that carried by benign strains. Researchers speculate that this kinase interferes with a cell’s normal signaling, hijacking it for its own purposes, including growth and reproduction. The good news is that because kinases are so important in cell signaling, pharmaceutical companies have developed libraries of molecules that inhibit specific kinases, so one potential path to preventing toxoplasmosis is to discover an inhibitor of ROP18.

Rats get a little nutty from it, too

Not only has this parasite been linked to the ability to alter human behavior, but it also appears to alter rodent behavior in ways that favor its own reproduction. For example, rodents exposed to toxoplasma via cat feces actually become more likely to hang out near cat urine. If a cat eats the infected animal, the toxoplasmosis bug can then move into the sexual phase of its life cycle in the cat.

Magnetic fields and the Q

Sorry, not for Trekkies. This Q is chemical.

People have been concerned for years about magnetic fields having adverse health effects–or even have peddled magnets as being health beneficial. But although scientists have demonstrated repeatedly a chemical response to magnetic fields, no one has ever shown the magnetic fields directly affecting an organism.

The earth’s core is weakly magnetic, the result of the attraction between electric currents moving in the same direction. Nature presents plenty of examples of animals that appear to use magnetic fields. Some bacteria can detect the fields and use them for movement. Birds appear to use magnetic fields to navigate, and researchers have shown that attaching magnets to birds interferes with their ability to navigate. Honey bees become confused in their dances when the earth’s magnetic fields fluctuate, and even amphibians appear to use magnetism for navigation. But no one has clearly demonstrated the mechanism by which animals sense and use magnetic fields.

Do pigeons use a compass?

Some research points to birds using tiny magnetic particles in their beaks to fly the right way. But these particles don’t tell the birds which way is north; they simply help the bird create a topographical map in its head of the earth over which it flies. The magnetic particles tell a pigeon there’s a mountain below, but not that the mountain is to the north. The conundrum has been to figure out how the pigeon knows which way is north in the absence of other pointers, such as constellations.

The answer to the conundrum lies with the bacteria. Scientists in the UK have used the purple bacterium Rhodobacter sphaeroides to examine what magnetic fields do at the molecular level. These bacteria are photosynthetic, and absorb light to convert to energy in the same way plants do. The absorbed light triggers a set of reactions that carry energy via electrons to the reaction center, where a pigment traps it. Under normal conditions, as the pigment traps the energy, it also almost instantaneously converts it to a stable, safe form, but sometimes the energy can form an excited molecule that can be biologically dangerous. As it turns out, these reactive molecules may be sensitive to magnetic fields.

A radical pair…or dangerous triplet

A chemical mechanism called the “Radical Pair Mechanism” is the method by which the potentially dangerous molecules can form. In this mechanism, an electron in an excited state may pair with another type of electron in an excited state. If the two excited molecules come together, they can form what is called a “radical pair in a singlet state,” because they are two singlets that have paired. Under normal conditions, this pairing does not happen; in the photosynthetic bacterium, for example, a compound called a quinone (Q) inhibits formation of this pair or of an equally damaging triplet of one electron type or the other.

But when a Q is not present, the singlet or triplet state results. If the triplet forms, it can interact with oxygen to produce a highly reactive, biologically damaging singlet molecule that we know as a “radical.” You have probably heard of radicals in the context of antioxidants—they are the molecules that antioxidants soak up to prevent their causing harm. You may also have heard of carotenoid, a pigment that is an antioxidant. In a normal photosynthetic bacterium, the carotenoids present serve as the Q, the compound that prevents formation of the damaging radical.

A helpful effect of magnetic fields?

Where do magnetic fields come in? Previous work indicated an influence of magnetic fields on triplet formation, and thus, on radical formation. One excellent model to test the effects of fields in a biological system is to remove the Q, the molecular sponge for the triplets, and then apply magnetic fields to see whether triplets—and radicals—form.

That’s exactly what the researchers did, using a mutated form of R. sphaeroides that did not make carotenoids—the Q. The result? The stronger the field, the less radical product was made. They have demonstrated a magnetic field effect in an organism for the first time, and the effect was helpful, not damaging. Their next step, which they are working on, is examining whether or not the bacteria grow better in the presence of the fields.

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