A GROUP of octopuses in Europe are having an "I Love the '80s" moment.
The 25 octopuses have been given Rubik's Cubes - those annoying puzzles that baffled and defeated countless people during the 1980s - as well as balls and other toys to play with.
Researchers are hoping to determine whether octopuses, like humans, have a dominant arm - er, tentacle - or if they are "octidextrous".
"While octopuses might not fare well on a standard IQ test, it's not because they're dumb," says Slate.com science writer Carl Zimmer. "But because their behaviour is the product of hundreds of millions of years of evolution under radically different conditions than the ones under which our own brains evolved."
In the underwater world, octopuses and their cephalopod cousins, squid and cuttlefish, are smart cookies.
Researchers have discovered that octopuses have excellent memories; they play, just like dolphins and dogs; and they can learn by watching others.
One octopus in a German zoo learned how to open jars of shrimp by copying zoo workers.
A paper by Canadian biologist Jennifer Mather, in the journal Consciousness and Cognition, argues that octopuses combine their memories and perceptions to clue in to what is happening to them. In other words, they possess primary consciousness.
Hungry seals 'steer by the stars' By Jennifer Carpenter Science reporter, BBC News
Seals can identify a single star in the night sky and navigate by it, scientists have discovered.
Navigating in the open ocean is essential for seals to move between foraging grounds that may be hundreds of kilometres apart.
This is the first evidence that marine mammals, like humans, use stars to navigate in open water, say scientists.
The European team has published details of its work in the journal Animal Cognition.
The researchers, headed by Dr Guido Dehnhardt of University of Rostock in Germany, simulated a night sky above two captive male seals and monitored the movements of the animals through six hidden infrared cameras.
"Initially, the seals were guided to one of the brighter stars by a laser pointer, and encouraged to swim towards it," said Bjorn Mauck of the University of Southern Denmark and one of the team-members.
Once the seals got the hang of navigating by the one star, the night sky above them was swivelled around and the seals were watched to see if they could still orientate themselves.
"With a little practice the seals swam in the right direction 100% of the time," said Dr Mauck.
In the wild, seals' foraging trips can take several days and so they often find themselves in open water with no visible landmarks for nights on end. How these wild seals learn the relationship between a star and their feeding ground is still unknown.
"Seals might learn the position of the stars relative to foraging grounds during dawn and dusk when they can see both the stars and landmarks at the coast," suggests Dr Mauck.
The researchers think that marine mammals might use star paths, or "kaveingas" as Polynesian seafarers call them.
These people navigate by heading towards a star on the horizon until it moves too high to see, and then swap over to follow another star, and so on, guiding their way until dawn.
Seals, sealions and whales are often seen elevating themselves out of the water as they swim in open ocean. This act of coming out of the water vertically and staying above the surface momentarily, in the same way a human treads water, could allow marine mammals to set their course, the researchers speculate.
Life In A Bubble: Mathematicians Explain How Insects Breathe Underwater
The Fisher spider Dolomedes triton uses an air layer, approximately 0.2 mm thick, as an oxygen supply. (Credit: John Bush and Morris Flynn)
ScienceDaily (July 31, 2008) — Hundreds of insect species spend much of their time underwater, where food may be more plentiful. MIT mathematicians have now figured out exactly how those insects breathe underwater.
By virtue of their rough, water-repellent coat, when submerged these insects trap a thin layer of air on their bodies. These bubbles not only serve as a finite oxygen store, but also allow the insects to absorb oxygen from the surrounding water.
"Some insects have adapted to life underwater by using this bubble as an external lung," said John Bush, associate professor of applied mathematics, a co-author of the recent study.
Thanks to those air bubbles, insects can stay below the surface indefinitely and dive as deep as about 30 meters, according to the study co-authored by Bush and Morris Flynn, former applied mathematics instructor. Some species, such as Neoplea striola, which are native to New England, hibernate underwater all winter long.
This phenomenon was first observed many years ago, but the MIT researchers are the first to calculate the maximum dive depths and describe how the bubbles stay intact as insects dive deeper underwater, where pressure threatens to burst them.
The new study, which appears in the Aug. 10 issue of the Journal of Fluid Mechanics, shows that there is a delicate balance between the stability of the bubble and the respiratory needs of the insect.
The air bubble's stability is maintained by hairs on the insects' abdomen, which help repel water from the surface. The hairs, along with a waxy surface coating, prevent water from flooding the spiracles—tiny breathing holes on the abdomen.
The spacing of these hairs is critically important: The closer together the hairs, the greater the mechanical stability and the more pressure the bubble can withstand before collapsing.
However, mechanical stability comes at a cost. If the hairs are too close together, there is not enough surface area through which to breathe.
"Because the bubble acts as an external lung, its surface area must be sufficiently large to facilitate the exchange of gases," said Flynn, who is now an assistant professor of mechanical engineering at the University of Alberta.
The researchers developed a mathematical model that takes these factors into account and allows them to predict the range of possible dive depths. They found that there is not only a maximum depth beyond which the bubble collapses, but a minimum depth above which the bubble cannot meet the insect's respiratory needs.
Though the researchers found that the insects can go as deep as 30 meters below the surface, they rarely venture deeper than several meters, due to environmental factors such as amount of sunlight, availability of prey and the presence of predators.
The researchers first took an interest in the external lung phenomenon when they accidentally captured one of the underwater breathers while looking for water striders. A few years ago, Bush and colleagues figured out how the striders use surface tension to glide across the water's surface.
Other researchers have explored systems that could replicate the external lung on a larger scale, for possible use by diving humans. A team at Nottingham Trent University showed that a porous cavity surrounded by water-repellent material is supplied with oxygen by the thin air layer on its surface. The surface area required to support human respiration is impractically large, in excess of 100 square meters; however, other avenues for technological application exist. For example, such a device could supply the oxygen needed by fuel cells to power small autonomous underwater vehicles.
Male Fish Deceive Rivals About Their Top Mate Choice
ScienceDaily (Aug. 1, 2008) — When competitors are around, male Atlantic mollies try to hide their top mate choice, reveals a new study published online on July 31st in Current Biology, a Cell Press journal.
They feign disinterest in females after onlookers enter the scene. What's more, after encountering a rival, the tricky males direct their first sexual advances toward females that really aren't their first pick. Male mollies are known to copy other males' mate choices, the researchers noted.
"I find it particularly interesting that fish are capable of such a sophisticated behavior," said Martin Plath of the University of Potsdam in Germany and the University of Oklahoma. "The study highlights that traits that we typically ascribe to humans only can also be found in other, seemingly simpler animals and that no consciousness or self-awareness is needed for a behavior like deception to occur."
Deception among animals has been seen before, he noted. For instance, ravens try to trick rivals about where they hide food. Male pied flycatchers also may deceive females about whether they've already mated so as to have another go. Nevertheless, Plath said, the new study may be the first to show that males deceive other males about their preferred mate.
The new findings came as a surprise to the researchers. Plath had expected to corroborate earlier findings of his team, showing that male Atlantic mollies curb sexual activity when other males are around, acting as though they've lost interest in the opposite sex altogether. That previous study didn't allow full contact among the fish, however, and was therefore not well-suited to detect deception.
In the new study, the researchers first placed two "stimulus" females into a tank. They then introduced a male and observed his sexual advances—including nipping and mating attempts—for five minutes, repeating the experiment several times with different individuals. Immediately after those trials, they repeated the experiment, this time including an "audience male" in half of the encounters. Those onlookers could watch, but they couldn't interfere.
In the first experiments, males more often directed their initial advances toward the larger of the two females, they found. In the presence of another male, however, the focal male's interest in the females suddenly slumped and, when it did make a move, it was initially directed toward the punier, apparently less-preferred female.
The researchers suggest that deceptive signals may be a powerful mating strategy used by males to lead competitors away from preferred females, thereby increasing the chance that the deceivers will father the offspring, they said.
"Future studies will need to evaluate the potential for male mate choice copying and deception in natural populations, because male mate choice copying cannot be evolutionarily stable if males always have an opportunity to deceive rivals," they said. After all, if males always attempt such deception, any competitor who didn't fall for the ruse would have easy access to the choicest mating partner.
The researchers include Martin Plath, University of Potsdam, Potsdam, Germany, University of Oklahoma, Norman, OK; Stephanie Richter, University of Potsdam, Potsdam, Germany; Ralph Tiedemann, University of Potsdam, Potsdam, Germany; and Ingo Schlupp, University of Oklahoma, Norman, OK.
How Some Bacteria May Steal Iron From Their Human Hosts
ScienceDaily (Aug. 2, 2008) — Like their human hosts, bacteria need iron to survive and they must obtain that iron from the environment. While humans obtain iron primarily through the food they eat, bacteria have evolved complex and diverse mechanisms to allow them access to iron.
A Syracuse University research team led by Robert Doyle, assistant professor of chemistry in The College of Arts and Sciences, discovered that some bacteria are equipped with a gene that enables them to harvest iron from their environment or human host in a unique and energy efficient manner. Doyle's discovery could provide researchers with new ways to target such diseases as tuberculosis.
The research will be published in the August issue (volume 190, issue 16) of the Journal of Bacteriology, published by the American Society for Microbiology.
"Iron is the single most important micronutrient bacteria need to survive," Doyle says. "Understanding how these bacteria thrive within us is a critical element of learning how to defeat them."
Doyle's research group studied Streptomyces coelicolor, a Gram-positive bacteria that is closely related to the bacteria that causes tuberculosis. Streptomyces is abundant in soil and in decaying vegetation, but does not affect humans. The TB bacteria and Streptomyces are both part of a family of bacteria called Actinomycetes. These bacteria have a unique defense mechanism that enables them to produce chemicals to destroy their enemies. Some of these chemicals are used to make antibiotics and other drugs.
Actinomycetes need lots of iron to wage chemical warfare on its enemies; however, iron is not easily accessible in the environments in which the bacteria live— e.g. human or soil. Some iron available in the soil is bonded to citrate, making a compound called iron-citrate. Citrate is a substance that cells can use as a source of energy. Doyle and his research team wondered if the compound iron-citrate could be a source of iron for the bacteria. In a series of experiments that took place over more than two years, the researchers observed that Streptomyces could ingest iron-citrate, metabolize the iron, and use the citrate as a free source of energy. Other experiments demonstrated that the bacteria ignored citrate when it was not bonded to iron; likewise, the bacteria ignored citrate when it was bonded to other metals, such as magnesium, nickel, and cobalt.
The next task was to uncover the mechanism that triggered the bacteria to ingest iron-citrate. Computer modeling predicted that a single Streptomyces gene enabled the bacteria to identify and ingest iron-citrate. The researchers isolated the gene and added it to E. coli bacteria (which is not an Actinomycete bacteria). They found that the mutant E. coli bacteria could also ingest iron-citrate. Without the gene, E. coli could not gain access to the iron.
"It's amazing that the bacteria could learn to extract iron from their environment in this way," Doyle says. "We went into these experiments with no idea that this mechanism existed. But then, bacteria have to be creative to survive in some very hostile environments; and they've had maybe 3.5 billion years to figure it out."
The Streptomyces gene enables the bacteria to passively diffuse iron-citrate across the cell membrane, which means that the bacteria do not expend additional energy to ingest the iron. Once in the cell, the bacteria metabolize the iron and, as an added bonus, use the citrate as an energy source. Doyle's team is the first to identify this mechanism in a bacteria belonging to the Actinomycete family. The team plans further experiments to confirm that the gene performs the same signaling function in tuberculosis bacteria. If so, the mechanism could potentially be exploited in the fight against tuberculosis.
"TB bacteria have access to an abundant supply of iron-citrate flowing through the lungs in the blood," Doyle says. "Finding a way to sneak iron from humans at no energy cost to the bacteria is as good as it gets. Our discovery may enable others to figure out a way to limit TB's access to iron-citrate, making the bacteria more vulnerable to drug treatment."
Olfactory Fine-tuning Helps Fruit Flies Find Their Mates
Normal fruit flies (left) quickly found a female at the center of the testing arena, whilst flies unable to calibrate their olfactory systems (right) wandered aimlessly. Track color depicts time beginning with violet and ending with red. (Credit: Cory Root/UCSD)
ScienceDaily (Aug. 2, 2008) — Fruit flies fine-tune their olfactory systems by recalibrating the sensitivity of different odor channels in response to changing concentrations of environmental cues, a new study has shown. Disable this calibration system, and flies have trouble finding a mate, the researchers found.
Just like overly bright light can wash out a photographic image, strong smells can overwhelm the olfactory system and eliminate an animal's ability to detect subtle differences, such as changes in concentration that would allow it to track a scent.
Now neurobiologists at UC San Diego, Stockholm University and the National Institute of Child Health and Human Development have evidence that the fly nervous system can dampen its response to intense smells to prevent strong signals from overloading the circuits, they report in the July 31 issue of Neuron.
"We found a feedback mechanism in the olfactory system," said Jing Wang, assistant professor of biology at UCSD and senior author of the paper. "This system may be useful for the fly to navigate the olfactory landscape. Odor concentrations can change very dramatically, and this is how they deal it."
Olfactory neurons selectively respond to particular chemicals, such as ethyl hexanoate, which smells like ripe bananas, or food to a fruit fly.
"We applied natural odors to the antennae, odors that the fly would normally smell," said Cory Root, a graduate student in biology at UCSD and first author of the paper.
When Root wafted concentrated banana smell onto the flies' antennae, he found increases in signaling by a molecule called the GABAB receptor, which helps to inhibit neurons from sending signals, and he confirmed that cells with increased signaling by GABAB receptors released neurotransmitter less easily.
Other strong fruity smells and a male pheromone, a chemical sex attractant, also shifted subsequent neural responses to those stimulants, adjusting the response range to detect differences between higher levels of these odors.
But carbon dioxide, a stress signal in flies, shifted the response very little. "It's like evolution has taken advantage of the system to adjust some channels up and down without affecting other channels," Wang said. "If you want high sensitivity to CO2 then you can eliminate the feedback receptor in those neurons. For other odors such as pheromone, which is important for finding other flies, a good tracking system is needed."
When the team knocked down levels of the receptor molecule within the specific olfactory neurons tuned to pheromones using molecular biological techniques they found that the fly neural system failed to adjust to chemical overloads. And without the fine tuning, male flies had difficulty finding females.
Most normal flies let loose in an area with an immobilized female quickly locate her and attempt to mate, even in the dark. But when Root and colleagues disabled the calibration system, most males wandered aimlessly.
"Flies that lack inhibition in their pheromone sensing neurons often fail to find the female," Root said. "The control flies are strikingly different. Soon after they get accustomed to the new arena they zoom in on the female and immediately start courting her."
Only half as many of the disabled flies he tested made contact with the female within the 30 minute testing period, despite being confined to a plastic dish only 40 millimeters wide.
The Whitehall Foundation and the National Institute for Deafness and Other Communication Disorders funded this research. Jing Wang is a Beckman investigator, Hellman faculty scholar and Searle Scholar.
In Lean Times, Flies Can't Survive Without Their Sense Of Smell
New research shows that fruit flies with a normal sense of smell have a survival advantage over those that don't. (Credit: iStockphoto)
ScienceDaily (Aug. 2, 2008) — It's not just bomb-sniffing dogs; animals everywhere rely on their sense of smell. Now, Howard Hughes Medical Institute and Rockefeller University researchers show just how important olfaction is, proving that fruit flies with a normal sense of smell have a survival advantage over those that don't. The findings, to appear in the July 31 advance online issue of Current Biology, may be useful in controlling insect populations and reducing insect-borne disease.
"You observe animals using the sense of smell to find food and you assume that this sensory modality must be important for survival, but what we wanted to do is demonstrate it scientifically and in a rigorously controlled way," says Leslie Vosshall, head of the Laboratory of Neurogenetics and Behavior. "To our knowledge, that has never been proven before."
The researchers worked with two strains of genetically modified fruit flies: one that couldn't smell and another that had a simplified olfactory system. The odor-blind fruit flies lacked Or83b, a protein in the fly nose that works in tandem with most other odorant receptors to detect a complex array of odors. So fruit flies without this protein could smell hardly anything at all. The other strain had Or83b, but only one working odorant receptor.
In previous work, Vosshall had observed that both strains survived as well as fruit flies that had a normal sense of smell. "That was the puzzle," says Vosshall, who is also a Howard Hughes Medical Institute investigator. "If smell is so important, then why are these odor-blind animals doing as well as the animals that have a very good nose?"
To find out the answer, Vosshall and her colleagues made the fruit flies lives more difficult.
In the first experiment, the researchers placed five times the original number of fruit flies in each cage but didn't add more food. Under these conditions, the survival rate of each fruit fly strain was equally low. But when the researchers placed a second bolus of food at the opposite ends of each strain's cage, the situation changed: The fruit flies that couldn't smell continued to die while the fruit flies that had a normal sense of smell lived on. Those with the simplified olfactory system fared in between.
"When the first cup of food was exhausted, the animals with the normal sense of smell started to forage and very efficiently found that second cup - much more so than those with the simple nose," explains Vosshall. "The odor blind animals didn't have a sense of smell to guide them."
In the second experiment, the scientists went a step further: They placed odor-blind flies in the same cage as the normal fruit flies, so that the two strains had to compete for limited food. When there was only one cup of food, the survival rates of both strains were equally low. Since the flies hatch directly on a food source, neither strain carried a competitive advantage for survival. But when the researchers introduced a second cup of food into the cage, the odor-blind fruit flies were massively out-competed. The results were similar with the simple-nosed animals.
"It's a simple demonstration that in times of plenty, the sense of smell is irrelevant for survival," says Vosshall. "But in times of scarcity, when you really need to use that sensory modality to forage for food, those without it have a competitive disadvantage."
This research was supported by the National Institutes of Health.
1. Kenta Asahina, Viktoryia Pavlenkovich, and Leslie B. Vosshall. The Survival Advantage of Olfaction in a Competitive Environment. Current Biology, 2008; in press
Australian Bird Research Could Rewrite 'Ring Theory' Of Speciation
A crimson rosella. (Credit: Mathew Berg, Deakin University)
ScienceDaily (July 30, 2008) — New research has uncovered how different populations of the bird crimson rosella are related to each other – a discovery which has important implications for research into how climate change may affect Australia’s biodiversity.
Published in the journal Proceedings of the Royal Society B, the research investigates the genetic and geographical relationships between different forms of crimson rosellas and the possible ways that these forms may have arisen.
Dr. Gaynor Dolman of CSIRO’s Australian National Wildlife Collection says there are three main colour ‘forms’ of the crimson rosella – crimson, yellow and orange – which originated from the same ancestral population and are now distributed throughout south eastern Australia.
“Many evolutionary biologists have argued that the different forms of crimson rosellas arose, or speciated, through ‘ring speciation’,” she says.
The ring speciation hypothesis predicts that a species that spreads to new areas may eventually join back up with itself, forming a ring. By that time, the populations at the join in the ring may be two distinct species and unable to interbreed, despite continuous gene flow, or interbreeding, between populations around the ring.
“We found that in the case of crimson rosellas, their three separate genetic groups don’t show a simple link to the geographical distribution of the colour forms,” Dr Dolman says.
“For example, orange Adelaide and crimson Kangaroo Island rosellas are separated by 15km of ocean but are genetically similar. Conversely, genetic dissimilarity was found in the geographically linked yellow and orange populations in inland south eastern Australia. We rejected the ring hypothesis because it predicts only one region of genetic dissimilarity, which should occur at the geographical location of the join in the ring, around the headwaters of the Murray and Murrumbidgee Rivers. However, it is possible that crimson rosellas formed a ring at some stage in their evolutionary history, but that the evidence has been lost through climatic or environmental changes,” she says.
Wildlife genetic research of this kind is increasing our understanding of the biogeography and evolution of Australia’s terrestrial vertebrates, helping Australia sustainably manage its biodiversity and ecosystem functions in the face of land use and climate change.
This work involved a team of researchers from CSIRO, Deakin University and the South Australian Museum.
Dual-use Sexual Attraction And Population-control Chemicals Found In Nematodes
Wild-type C. elegans hermaphrodite stained to highlight the nuclei of all cells. (Credit: Image courtesy of Wikimedia Commons)
ScienceDaily (Aug. 1, 2008) — Organisms ranging from humans to plants to the lowliest bacterium use molecules to communicate. Some chemicals trigger the various stages of an organism's development, and still others are used to attract members of the opposite sex. Researchers at the California Institute of Technology have now found a rare kind of signaling molecule in the nematode worm Caenorhabditis elegans that serves a dual purpose, working as both a population-control mechanism and a sexual attractant.
The discovery, published online July 23 in the journal Nature, could lead to new ways to control parasitic nematodes, which affect the health of more than a billion people and each year cause billions of dollars in crop damage.
Caenorhabditis elegans worms have long been a favorite model organism among developmental biologists, in part because of their small size (1 mm long), simple nervous system, and ease of care. The normally soil-dwelling worms are almost always hermaphrodites--females that are capable of making sperm, with which they can fertilize their own eggs. About one in every 1000 worms is a true male.
Researchers studying C. elegans had long noted that hermaphroditic worms, left to wander about in a culture plate, will secrete a chemical that strongly attracts males. When males are exposed to the chemical, dubbed "worm sweat" by C. elegans researchers, "males will act as if their desired mate is near, and start blindly feeling around to locate it," says molecular geneticist Paul W. Sternberg, the Thomas Hunt Morgan Professor of Biology at Caltech and an investigator with the Howard Hughes Medical Institute.
Jagan Srinivasan, a postdoctoral research scholar at Caltech, Sternberg, and his colleagues at the University of Florida, the United States Department of Agriculture, and Cornell University, assayed and analyzed worm sweat and found that it consisted of a blend of three related chemicals, called ascarosides. The chemicals looked suspiciously like another compound previously known to be involved in triggering an alternative developmental state in the nematodes, a spore-like condition called the "dauer stage"--from the German word for "enduring"--that represents a form of worm population control.
"When worm larvae are stressed out and hungry and crowded," Sternberg says, "they enter the dauer stage." In this alternate state, the worm larvae can withstand harsh environmental conditions. "The dauer stage is important because it is the infective stage in a lot of parasitic nematodes," he says.
The scientists found that purified samples of the chemicals, dubbed ascr#2, ascr#3, and ascr#4, induced sexual excitement among males, but only when the chemicals were combined, and only when presented to the worms in very dilute form. At higher concentrations, 100 to 1000 times stronger, males were repelled, sexual reproduction ceased, and existing worm larvae entered their hibernating stage.
"This is the first glimpse into the chemical code that nematodes are using to communicate," says Sternberg. Adds Srinivasan, "It is the first time that two distinct and different life history traits--reproduction and developmental arrest--have been found to be regulated by the same family of molecules, suggesting a link, which we had not suspected, between the corresponding pathways."
The discovery offers hope for a solution to a global nematode scourge. Hundreds of thousands of nematode species occupy the earth, and many are pests or parasites whose activities cause disease or economic hardship, with damage amounting to billions of dollars per year. For example, hookworm, a parasitic nematode that lives in the small intestine of humans, is believed to infect one billion people worldwide and in developing countries is the leading cause of illnesses in babies, children, pregnant women, and malnourished individuals; the soybean cyst nematode, which attacks the roots of soybean plants, causes half a billion dollars worth of crop loss each year in the United States alone.
By decoding some of the signals that nematodes use to communicate, scientists may be able to offer new strategies to control the pests. One option could be to create chemical attractants derived from pheromones, similar to the pheromone-based substances that now are used to lure fruit flies and other bugs into traps. Alternatively, Sternberg says, compounds could be developed "that interfere with the chemical signaling involved in the reproductive process," thereby preventing the organism from multiplying.
The paper, "A blend of small molecules regulates both mating and development in Caenorhabditis elegans," was published July 23 in the early online edition of Nature and will appear in the August 28 print edition. The work was supported by the Human Frontiers Science Program, the National Institutes of Health, and the Howard Hughes Medical Institute.
1. Srinivasan et al. A blend of small molecules regulates both mating and development in Caenorhabditis elegans. Nature, 2008; DOI: 10.1038/nature07168
LONDON, Aug. 5, 2008 (Reuters) — Dogs find human yawns contagious, suggesting they have a rudimentary capacity for empathy, British scientists said on Wednesday.
File photo shows stray dogs resting in the warm spring sunshine in Red Square in Moscow March 29, 2007. REUTERS/Denis Sinyakov
Although yawning is widespread in many animals, contagious yawning -- a yawn triggered by seeing others yawning -- has previously only been shown to occur in humans and chimpanzees.
It turns out, however, that man's best friend is highly sensitive to catching human yawns, with 72 percent of 29 dogs tested yawning after observing a person doing so.
Writing in the journal Biology Letters, Atsushi Senju and colleagues at London's Birkbeck College said this behavior showed dogs were skilled at reading human social cues and "may relate to their capacity for empathy."
Tuning In To A New Language On The Fly: Effects Of Context And Seasonality On Songbird Brain
Two Zebra finches on a rope having a chat. Researchers found that exposure to a changed acoustic and social environment can rewire the way the brain processes sounds. (Credit: iStockphoto/Andrew Corney)
ScienceDaily (Aug. 5, 2008) — Research conducted at Rutgers University has shown that exposure to a changed acoustic and social environment can rewire the way the brain processes sounds. Beginning in the cochlea of the inner ear, nerve cells of the auditory system parse incoming sounds into their different components.
Study of the responses of individual brain cells has shown that they respond best to a particular frequency (pitch) of sound, less well to nearby frequencies, and poorly to distant sound frequencies. The range of effective frequencies can be measured as the "tuning width." Cells with similar tuning are found together, producing an orderly map of all the possible frequencies spread out across the auditory part of the brain.
These tuning properties were used to study the way experience can change the brain in two species of songbirds. Songbirds provide the best-developed animal system for studying vocal learning because juvenile birds learn to sing by hearing and imitating adults, much as human infants do. The songbird brain contains an area similar to the mammalian auditory cortex (the NCM) that is specialized to discriminate and remember the songs of other birds of the same species.
In this study, adult zebra finches (which normally live in a single-species colony) were moved to a canary colony, and adult canaries were moved to a zebra finch colony. These birds experienced a novel environment because canaries and zebra finches produce learned species-typical vocalizations that differ in their acoustic components. Other birds of each species remained in their home colony and still others were placed in individual isolation.
After nine days of altered experience, the tuning width was assessed in the brains of these animals and was found to be significantly different from birds that remained at home. In birds of both species that experienced life in a foreign colony, the tuning became narrower (i.e. more selective). In canaries, which can learn new song elements in adulthood, these effects were also influenced by season, and may reflect the role of vocal imitation in the seasonal breeding behavior of this species. Isolation had the opposite effect: the tuning became wider (i.e. less selective).
In other words, when a bird is exposed to a new acoustic and social environment, basic auditory properties in its brain change to become more finely tuned. In human terms, a possible analogy for this experiment is when a person travels to a foreign country where an unfamiliar language is spoken. The individual has to pay close attention and gradually begins to make out the words in the speech stream (and perhaps to recognize a few from the phrase book). This process of "tuning in" to the new sound and social environment may involve increased sensitivity to fine acoustic details and may produce measurable tuning changes such as those observed at the neural level in these songbirds.
In contrast, the songbirds' tuning coarsened in the impoverished, monotonous environment provided by being housed in isolation.
The researchers suggest that these songbird results provide a useful experimental model of sensory plasticity accessibility, which is worthy of further study. Consistent with observations in other sensory systems, the tuning map in the brain is not rigid, but adjusts dynamically to current experience. Journal reference:
1. Terleph TA, Lu K, Vicario DS. Response Properties of the Auditory Telencephalon in Songbirds Change with Recent Experience and Season. PLoS One, 3(8): e2854 DOI: 10.1371/journal.pone.0002854
LONDON, Aug. 6, 2008 (Reuters) — Even viruses can go down with a viral infection, French scientists reported on Wednesday, in a discovery that may help explain how they swap genes and evolve so rapidly.
A new strain of giant virus was isolated from a cooling tower in Paris and found to be infected by a smaller type of virus, named Sputnik, after the first man-made satellite.
Sputnik is the first example of a virus infecting another virus to make it sick.
Bernard La Scola and colleagues from the Universite de la Mediterranee in Marseille reported in the journal Nature that Sputnik was able to achieve a remarkable degree of gene mixing by "looting" genes from its host virus and other organisms.
Viruses are already known to infect and sicken bacteria but this is the first example of a virus infecting one of its own kind.
The finding may shed light on how viruses mutate so quickly -- a feature that can make them difficult to tackle with drugs and vaccines.
It also lends weight to the argument that viruses are true living organisms, despite not having cells.
"There's no doubt this is a living organism. The fact that it can get sick makes it more alive," said Jean-Michel Claverie, a virologist at the CNRS UPR laboratories in Marseilles.
Positive-feedback System Ensures That Cells Divide
A positive-feedback system ensures that a cell that has made the decision to divide finishes what it has started. (Credit: Image courtesy of Rockefeller University)
ScienceDaily (Aug. 7, 2008) — In the life of every cell, there’s a point of no return. Once it enters the cell cycle and passes a checkpoint known as “Start,” a cell will follow the steps it needs to divide — no matter what changes might occur in its environment.
Now scientists at Rockefeller University show that a positive-feedback system ensures that a cell that has made the decision to divide finishes what it has started.
Part of the decision process includes activating more than 200 genes simultaneously, a formidable problem considering the noisy environment of the cell. “Given how difficult it is for a cell to activate just one gene, activating 200 at the same time seems like a very difficult task,” says Jan Skotheim, a postdoc who collaborated on the research with Frederick Cross, head of the Laboratory of Yeast Molecular Genetics, and Eric Siggia, head of the Laboratory of Theoretical Condensed Matter Physics. “And the way the cell solves this challenge is through positive feedback. It keeps all these events in sync.”
Positive-feedback mechanisms allow cells to adapt to changes in their environment rapidly and efficiently. In the case of cell division, the key is a pair of molecules called Cln1 and Cln2, part of a family of proteins known as G1 cyclins. Skotheim and his colleagues, including graduate student Stefano DiTalia, show that when budding yeast (Saccharomyces cerevisiae) cells sense that they are big enough to divide, they synthesize an activator molecule that triggers a positive feedback system in which Cln1 and Cln2 advance their own expression.
“So what happens is that the very rapid ramp-up of the G1 cyclins during Start lead to all those target genes getting fired synchronously,” says Skotheim. “It’s a function of positive feedback that hasn’t been thought of before: synchrony and coherence.”
For the genes to be fired synchronously, a protein called Whi5 must be exported from the nucleus, and kept out until the two daughter cells are born. During Start, which lasts approximately three minutes, Cln1, Cln2 and the activator molecule all collaborate to kick out Whi5. Once out, Cln1 and Cln2 must continue to advance their own expression in order to keep Whi5 out. Then, the moment the two daughter cells separate, the G1 cyclins are inactivated, Whi5 enters back into the nucleus and the complex detaches. In previous work, the team showed that the export of Whi5 is the molecular event that signals Start. Now they show that a positive-feedback mechanism is what drives it.
In the past, when scientists tested the possibility that positive feedback could be behind cell division, the results always came out negative. But Skotheim took a different approach from that of his predecessors. Instead of averaging the results across many cells, he looked at data from individual cells, an approach that minimizes data loss.
Working with two strains of single-celled budding yeast, only one of which had Cln1 and Cln2, the researchers observed that most cells without the two molecules had less predictable divisions. They took longer to start dividing, and when they finally passed Start, the time it took them to complete the process varied considerably. Some cells, in fact, didn’t bud at all.
“By looking at averages, previous attempts to find a potential positive-feedback loop had obscured what was going on,” explains Skotheim. “By studying single cells, we regained the lost information and found the opposite of what others had found: that positive feedback drives and coordinates a cell’s commitment to divide.”
Vine Invasion? Ecologists Look At Coexistence Of Trees And Lianas
By studying lianas, UWM ecologist Stefan Schnitzer hopes to answer the question of what mechanisms determine the distribution and abundance of lianas, and maintenance of plant diversity, in tropical forests. (Credit: Photo by Marcos Guerra/Center for Tropical Forest Science, Smithsonian Tropical Research Institute)
ScienceDaily (Aug. 8, 2008) — Among the hundreds of species of woody vines that University of Wisconsin–Milwaukee ecologist Stefan Schnitzer has encountered in the tropical forests of Panama, the largest has a stalk nearly 20 inches in circumference.
"That's like a large tree," says Schnitzer. "And because it winds itself up to the forest canopy and spreads, it can cover as much canopy area as a community of trees."
Such vines, called lianas, concentrate their energy on extending high and wide, and plunging their roots deep into the earth, rather than on building a thick trunk, says Schnitzer, an assistant professor of biological sciences at UWM who specializes in the vines and forest diversity.
They are essentially structural parasites, he says. But tropical lianas, even more so than their temperate counterparts (like kudzu, grapevine and poison ivy), are important players in tropical forest dynamics.
Growing evidence suggests that lianas are becoming more abundant with rising levels of carbon dioxide (C02) in the atmosphere, choking out trees. While all plants remove C02 from the atmosphere and store it, vines do not sequester as much as trees do – so vines may cause a net forest-wide loss in carbon.
Scientists would like to know if lianas really are becoming more numerous in tropical forests and what – if any –effects that would have on C02 and climate change.
One problem in testing the theory of lianas on climate change, says Schnitzer, is that scientists aren't sure whether C02 is acting on lianas or the other way around. To find out more, he is involved in one of the most comprehensive community-level studies on liana-tree interactions ever conducted.
Lianas vs. trees
Schnitzer's study in central Panama aims to better understand the impact of lianas on forest regeneration by first looking at the abundance and distribution of the vines.
The project is backed by the Smithsonian Tropical Research Institute and its Center for Tropical Forest Science. It has three years of financial support from the National Science Foundation (NSF) and two rounds of UWM Research Growth Initiative grants.
With collaborator Stephen Hubbell and graduate students Suzanne Rutishauser and Sasha Wright, Schnitzer is conducting a census of all lianas 1 centimeter in diameter or larger on a 50 hectare plot on Barro Colorado Island – nearly 50,000 individuals have been tagged, mapped, measured and identified to species.
The researchers will match a map of liana abundance on their Panamanian plot with an existing dataset on 25 years of tree growth and mortality for nearly a quarter million trees and saplings. They will also conduct a separate study of liana removal in an adjacent forest. In that study, they will quantify how lianas contribute to forest-level CO2 sequestration.
Thriving in drought
"It appears to be true that lianas grow more rapidly at higher levels of C02," Schnitzer says. "But there could be other explanations for the increase in lianas, too. Weather could be a factor."
His hypothesis is that tropical lianas thrive during seasonal droughts, when trees suspend their growth and lose their leaves, giving the lianas a competitive advantage in those locations. In fact, he found the growth rate of lianas is seven times that of trees in dry conditions, compared to only twice that of trees in the rainy season.
One reason may be that lianas have a more efficient root system than trees, but Schnitzer says more information is needed. He and his collaborators are using probes inserted into lianas to collect data on the flow of the water inside the vines' vascular system throughout the year in order to determine how lianas respond to drought.
"If lianas can grow far more than trees during seasonal droughts, then global increases in drought from such events as El Niño or La Niña may be responsible for the documented increases in liana abundance," Schnitzer says. He hopes to test this hunch when funding is secured, by monitoring liana growth rates and internal water flow in a number of wet and dry forests. Panama, where one side of the isthmus is far wetter than the other, provides a perfect natural location for such a study.
By studying lianas, Schnitzer hopes to answer the larger question of what mechanisms determine the distribution and abundance of lianas, and maintenance of plant diversity, in tropical forests.
With so many variables clouding issues of diversity and abundance, Schnitzer's investigative approach is to test his theories on the organism that is most different from the others – like lianas.
"If you can't figure out what's going on in the ecological system, then look at the oddball, the deviant– something that doesn't fit the model," he says.
Gene For Sexual Switching In Melons Provides Clues To Evolution Of Sex
Scientists have isolated the melon sex determination gene and determined its function. (Credit: iStockphoto)
ScienceDaily (Aug. 8, 2008) — A newly discovered function for a hormone in melons suggests it plays a role in how sexual systems evolve in plants. The study, conducted by French and American scientists, appeared recently in the journal Science.
Scientists from several French institutions, led by Abdel Bendahmane of the National Institute for Agricultural Research (INRA), isolated the melon sex determination gene and determined its function. As part of this collaborative effort, New York University biologists Jonathan Flowers and Michael Purugganan, who are part of NYU's Center for Genomics and Systems Biology, conducted the evolutionary analysis of the study.
Because plants' sexual systems are varied—species may possess various combinations of male, female, or hermaphrodite systems—their evolution has long been of interest to scientists. This is especially the case in melons, whose sexual system—andromonoecy—carries both male and bisexual flowers and appears to have evolved recently. In this study, the researchers sought to understand what determines the recent formation of melons' new sexual system.
"If we can understand how different sexual systems in plants have evolved, we can then begin to understand how sex in general evolves," explained Purugganan.
The researchers focused on the role played by the hormone ethylene, which is known to help fruit ripen. The French group determined that an enzyme involved in making this gaseous hormone is also involved in the evolution of the sexual switch of female flowers to hermaphrodites. The finding links hormone levels to sex determination in flowers.
The scientists also sought to determine if the change in ethylene levels, and therefore the resulting sexual system, was the result of evolutionary selection. The key was in looking at the ethylene enzyme gene, called CmACS-7, which had the mutation that causes the sex change in melons.
After examining the molecular diversity in this gene, comparing it with other genes in the melon genome, and using mathematical modeling, the researchers concluded that the level of molecular variation at the sex determining ethylene enzyme gene was unlikely to have occurred by chance. Instead, the pattern was consistent with evolutionary selection favoring the sex switch mutation in melons.
"Humans and other mammals generally have only two sexes – males and females," observed Purugganan. "But other species, including plants, can evolve bewildering arrays of sexual combinations."
This study, he suggests, provides us with new insights into the molecular basis for sex determination and allows us to understand the advantages of different sexual systems.