Frog tadpoles have a good nose for danger: Scientists know that they go from headlong swimming to total stillness when they smell a predator. Now, researchers have discovered that frogs get that odoriferous training very early on. When they’re still embryos, they can learn to assess the threat level by sniffing for a predator’s pheromones.
Embryos put into water containing the odour of a salamander and the odour of injured tadpoles learned that the predator’s smell was a threat [BBC News]. The idea was to see if the amphibian embryos could learn to associate the smell of injured tadpoles with the smell of a predator. This type of learning behavior has also been observed in previous experiments with fish, larval amphibians, and larval mosquitoes, however this was the first study to document the behavior in embryos.
In an experiment sure to make PETA squirm, crushed tadpoles were mixed with water in which a tiger salamander had been swimming. Embryos were raised in this water with different concentrations of crushed tadpoles. Once the embryos had hatched into tadpoles, researchers tested their response to only the salamander odor. The tadpoles that were exposed to a higher concentration of the injured tadpole odour stayed motionless for longer in response to the salamander cue [BBC News].The scientists say this demonstrates that these tadpoles learned as embryos that salamanders were more dangerous predators. The researchers published their findings in the journal Behavioural Ecology and Sociobiology.
Atlantic bluefin tuna populations have declined so drastically that trade in the fish should be completely outlawed, says a new report. The population of the Atlantic tuna, a sushi staple, is now about 15 percent of the original stock size, says International Commission for the Conservation of Atlantic Tunas’ (ICCAT). The report has delighted conservation groups, who have criticized ICCAT’s regulation policies. The report was triggered by Monaco’s recent proposal to ban international trade in the Atlantic bluefin under the Convention on International Trade in Endangered Species (CITES) – a proposal that has gathered support from several other European countries [BBC News].
ICCAT has a history of setting quotas higher for the fish than scientists say is safe, while CITES seems to take a more proactive approach.Atlantic bluefin tuna are mainly caught from countries around the Mediterranean Sea, but most of the meat is consumed in Asia, particularly Japan. Japan has previously argued that commercial fish species should be controlled by bodies like ICCAT rather than CITES [BBC News]. In Japan, the fish are so highly prized that a single giant tuna can sell for more than $100,000 at the wholesale fish market. ICCAT will meet in 10 days to discuss the report.
Some migratory birds that have to navigate across continents have an extremely useful tool at their disposal–an internal compass that points unerringly towards magnetic north. Researchers already knew that some birds possess these biological compasses, but their mechanism has been unclear. “This is basically the sixth sense of biology, but no one knows how it works…. The magnetic sense is by far the least understood sense in the natural world,” [Science News], says study coauthor Henrik Mouritsen.
Now, researchers have determined that light-sensing cells in the eye convey the crucial message to a special visual center of a robin’s brain, called cluster N. Special proteins called cryptochromes in the birds’ eyes may mediate this light-dependent magnetic sensing, Mouritsen says. Light hitting the proteins produces a pair of free radicals, highly reactive molecules with unpaired electrons. These electrons have a property called spin which may be sensitive to Earth’s magnetic field. Signals from the free radicals may then move to nerve cells in cluster N, ultimately telling the birds where north is [Science News].
The naked mole rat is a species with a long list of peculiarities. The mole rat is about the same size as the more hirsute wild mouse, but lives seven times as long, sometimes reaching the ripe old age of 28. The creatures almost never poke their noses beyond the snug confines of their burrows and tunnels, and instead live out their lives underground in the dark. They’re also the only mammals who have a social structure that resembles an ants’ nest or beehive, where only one dominant female mates and reproduces.
Finally–and this is the part that most interests researchers–naked mole rats never get cancer.
A new study in the Proceedings of the National Academy of Sciences probed the mole rats’ robust good health, and determined how they beat cancer. The naked mole rat’s cells hate to be crowded, it turns out, so they stop growing before they can form tumors…. Normal human and mouse cells will grow and divide in a petri dish until they mash tightly against one another in a single, dense layer–a mechanism known as “contact inhibition.” Naked mole rat cells are even more sensitive to their neighbors, the researchers found. The cells stop growing as soon as they touch [ScienceNOW Daily News]. Researchers hope that the mechanism can one day lead to novel treatments for cancer, where cancerous cells won’t stop multiplying and form tumors.
Before one species of jumping spider, known as Evarcha culicivora, goes trolling for a mate, it firsts look to feast on blood-fattened mosquitoes. What happens next seems like something out of a bad video game: The delicacy gives the spider a special power–a sweet smell that the opposite sex finds irresistible.
In a new study, which will be published in the Proceedings of the National Academy of Sciences, researchers exposed E. culicivora specimens to the odors of others raised on blood-fed female mosquitoes and on three other diets: sugar-fed females, males and lake flies…. [The] tested spiders of both sexes were most strongly attracted to the odor of spiders reared on blood-fed female mosquitoes. But the attraction was only for spiders of the opposite sex [The New York Times]. Spiders would hang around blood-fattened spiders of the opposite sex four times longer than they would linger around those fed on another diet. The blood perfume effect might only be triggered by a gender specific hormone, the researchers suggest.
A new discovery about how mantis shrimp process light could give rise to new and more powerful consumer electronics, according to a new study. Mantis shrimp possess the animal kingdom’s most complicated eyes, capable of distinguishing between 100,000 colors — 10 times as many as humans — and seeing circular polarized light, or CPL, which can’t be detected by any other creature [Wired.com]. Circular polarized light is one of two forms of polarized light, or light waves that travel in a specific plane.
The specialized CPL detecting cells in shrimp eye are similar to the optical detectors found in DVD players; each can convert polarized light into other forms so it can be stored or processed. However, shrimp eyes can do this with all colors of circular polarized light across the spectrum, according to the study in Nature Photonics. The detectors in DVD and CD players can only recognize circular polarized light in a few colors. The research team thinks that in the future, optics devices might be beefed up by chemically engineered crystals that could mimic the light polarizing cells of the mantis shrimp eye.
The chytrid skin fungus is killing frogs around the world, and researchers worry that it is already driving some species to extinction–but until now, no one understood how the fungus killed. Now, new research shows that the fungus disrupts the flow of nutrients through the frogs’ skin, ultimately leading to cardiac arrest.
In the study, which will be published tomorrow in Science, the scientists found that the fungus interferes with the frogs’ ability to absorb electrolytes, the electrically conducive molecules that are vital for muscle and nerve function. Diseased green tree frogs had dramatically lower levels of potassium and sodium in their blood and urine. Says study coautor Wyatt Voyles: “It’s a failure of the electrical system, leading to mechanical failure. If you don’t have a normal electrical system pacing the heart, it won’t pump blood” [Wired.com].
Further experiments confirmed that the electrolyte imbalance led to a heart shutdown. The scientists took electrocardiogram recordings of the frogs’ hearts in the hours before death; and found changes to the rhythm culminating in arrest. Drugs that restore electrolyte balance brought the animals a few hours or days of better health, some showing enough vigour to climb out of their bowls of water; but all died in the end [BBC News]. Researchers’ next task will be to determine exactly how the fungus interferes with the electrolyte absorption: it could be a result of cell damage in the skin, or a toxin produced by the fungus.
Surprise, surprise. An independent analysis of the primate fossil that was unveiled amid extraordinary hype last May has found significant evidence that the lemur-like creature was not a direct ancestor of humans, after all. The 47-million-year old fossil described in May, which was given the scientific name Darwinius masillae and nicknamed Ida, was announced with unrestrained razzmatazz. She was the “eighth wonder of the world”, “our Mona Lisa” and an evolutionary “Rosetta Stone”, according to the researchers who unveiled her…. She was, they said, the “link” between us and the rest of the animal kingdom [The Guardian].
But Ida, who was the subject of both a book and a TV special that were released at the same time as the scientific paper describing the fossil, failed to wow many evolutionary biologists. Says Erik Seiffert, lead researcher of the new study: ”The suggestion that Ida [was]… specifically related to the higher primates, namely monkeys, apes and humans, was actually a minority view from the start. So it came as a surprise to many of us who are studying primate palaeontology” [BBC News].
Seiffert’s new analysis began with his attempt to identify another fossil primate, Afradapis longicristatus, which he found to be a close relation to Darwinius. The researchers then compared 360 specific anatomical features of 117 living and extinct primate species to draw up a family tree [AP]. The analysis showed that both primates are located on an early twig of the branch that produced lemurs, and far from the lineage that spawned monkeys and great apes [Wired.com]. What’s more, the researchers say that both species have no modern descendants.
By altering a female fruit fly’s pheromones, researchers have created an insect with so much sex appeal that it even attracts males of other species. But in a surprising twist, they didn’t boost the levels of some courtship chemical–instead they created flies that lacked all pheromones, which were then besieged suitors. The discovery suggests pheromones can be back-off rather than come-hither signals. The finding could lead to a better understanding of the chemical signals that help flies and other animals interpret the world, including how to select a mate and how to distinguish other species [Science News].
The study, published in Nature, also found that males who lacked all pheromones attracted unwelcome attention from other males, who attempted to copulate with their heads. Says lead researcher Joel Levine: “It’s amazing what you see…. There are some pretty crude movies” [Nature News].
To conduct their experiments, the researchers identified the cells on the inside of the fly’s exoskeleton (pictured in glowing green) that produce the pheromones, and inserted a gene into the fly genome to kill all these cells. The manipulated flies provided a sort of blank canvas to allow the scientists to test the role played by each chemical – and how the chemical signals interacted. “We found that one compound – one that males transfer on to females when they copulate – kept other males away,” said Dr Levine. “It’s the male’s way of sort of protecting his investment” [BBC News].
Humans typically feel uneasy when they see a very realistic human-looking robot or computer avatar, a phenomenon called the “uncanny valley” response. According to a new study performed with monkeys, that reaction might have an evolutionary basis.
Researchers hypothesize that the response stems from almost realistic images that signal HUMAN! to us, but then fail to live up to the initial excitement. The uncanny valley response has been documented in humans since the 1970s, and has been blamed for the unpopularity of some CGI films with realistic characters [like The Polar Express and Final Fantasy], and it is touted as the reason Pixar stuck to characters with cartoonish features [New Scientist].
A new surface coating could mean the end of roach traps as we know them. The plastic-like material, called a polyimide resin, is like a Slip ‘n Slide for the normally sure-footed roaches. Insects naturally secrete a fluid that’s an emulsion of oily and watery liquids that helps them stick to almost any surface. The scientists’ polyimide coating absorbs the watery part, cutting bugs’ friction on vertical surfaces by about 40 percent [Popular Science].
In an experiment, a rod with an apple on top was painted with a number of different chemicals, including the polyimide resin. Scientists observed roaches climbing to reach the apple, and measured the friction between the roaches feet and the rod. They found that roaches effortlessly shimmied up rods coated in PTFE, a non-stick coating commonly found on cooking pans. But when the rods were covered in polyimide resin, the creatures lost their grip [New Scientist].
A jumping spider that passes on eating ants in favor of leafy greens has just been described by scientists. The novel arachnid, named Bagheera kiplingi, is exciting because it is the first-known predominantly vegetarian spider; all of the other known 40,000 spider species are thought to be mainly carnivorous [BBC News]. The study was published in the journal Current Biology.
Found in Central America and Mexico, the order-defying jumping spider eats nutrient-rich structures called Beltian bodies, which are found on the tips of Acacia trees. Trees produce the bodies to feed ants that defend them, which is a textbook example of what’s called co-evolutionary mutalism, and one that B. kiplingi has evolved to exploit [Wired.com].Despite a primarily veggie diet, B. kiplingi actively hunts its green prey, which sounds bizarre, since the leaves can’t run away.The spiderfirst sits and stalks its target before it dodges through the ant defenses, snatches a Beltian body, and flees to safety.
The tender interactions between human mothers and their newborn babies may have deep evolutionary roots: a new study found that rhesus macaque monkey mothers engage in strikingly similar behavior with their infants.
The researchers found that the mothers would gaze intently at their newborns, sometimes even taking their baby’s face with their hands and gently pulling it towards them to get an even closer look. They would also engage in “lipsmacking” – an affectionate form of expression, where the macaques rapidly open and close their mouths [BBC News]. Several videos taken by the researchers show that just like human babies, the infant monkeys responded to their mothers by mimicking their facial expressions and returning their stares.
Every year, Nikon's Small World Photomicrography Contest reminds us how much of the world's beauty is hidden to the naked eye. Here we present the judges' top seven picks for photos taken through a light microscope; visit the contest page for a full gallery of winners.
This picture won 7th place for Shirley Owens of Michigan. It shows the fine hairs, or trichomes, on a black-eyed Susan vine, and is magnified 450 times.
Two American men and an Israeli woman have won the Nobel Prize for chemistry for work that probed the structure of the ribosome, the cell’s protein factory. Venkatraman Ramakrishnan, Thomas Steitz, and Ada Yonath worked separately to understand one of life’s core processes: the method by which ribosomes translate genetic code into proteins, the building blocks of all organisms.
Their work revealed what ribosomes, which produce proteins that control the chemistry in all living organisms, look like and how they function at the atomic level. The Laureates also created three-dimensional models that show how different antibiotics bind to the ribosome, research that has been used to develop new anti-infective medicines [Bloomberg].
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Frog tadpoles have a good nose for danger: Scientists know that they go from headlong swimming to total stillness when they smell a predator. Now, researchers have discovered that frogs get that odoriferous training very early on. When they’re still embryos, they can learn to assess the threat level by sniffing for a predator’s pheromones.
Atlantic bluefin tuna populations have 
Some 
The naked mole rat is a species with a long list of peculiarities. The mole rat is about the same size as the more hirsute wild mouse, but lives seven times as long, sometimes reaching the ripe old 
Before one species of jumping 
A new discovery about how 
The chytrid skin fungus is killing 
Surprise, surprise. An independent analysis of the primate fossil that was 
By altering a female fruit fly’s pheromones, researchers have created an 
Humans typically feel uneasy when they see a very realistic human-looking robot or computer avatar, a phenomenon called the “uncanny valley” response. According to a new
The tender interactions between human mothers and their newborn babies may have deep evolutionary roots: a new study found that rhesus macaque 
Two American men and an Israeli woman have won the 
