Tuesday, September 15, 2009
The green mussel is known for being a notoriously invasive fouling species, but scientists have just discovered that it also has a very powerful form of adhesion in its foot, according to a recent article in the Journal of Biological Chemistry. The stickiness of the mussel's foot could possibly be copied to form new man-made adhesives.
Other mussels have inspired synthetic polymers that have been made into versatile adhesives and coatings, explained J. Herbert Waite, senior author and a professor in UC Santa Barbara's Marine Science Institute. They all rely on proteins that contain an amino acid called "Dopa," (identical to the Dopa used to treat Parkinson's disease) and have been studied extensively by Waite and his research group.
Waite learned that the green mussel, Perna viridis, relies on an alternative to the common "Dopa" chemistry, based on an elaborate modification of the amino acid tryptophan in the green mussel's adhesive protein. Its adhesive chemistry is much more complicated than that of mussels previously studied. It took Waite and his team six years to unravel the story.
The green mussel's sticky adhesiveness has the potential to help form strong bonds in wet surfaces, including teeth and bones. In addition, the adhesive could be used to repair ships that have developed cracks while at sea and must be repaired in a wet environment.
Waite was first alerted to the complicated adhesive of the green mussel when a Japanese group contacted him to comment on their research on the animal. He then learned of an infestation of green mussels in Tampa Bay, Fla.
On further study, he learned that the aggressive green mussel had moved from India's Sea of Bengal to many locations around the world, including the coasts of Japan, Australia, Korea, China, the Philippines, and Indonesia. Additionally, many Pacific Islands and the coasts of some countries surrounding the Gulf of Mexico have been invaded. "People are interested in how they invade, adapt, and spread so easily," said Waite.
Waite asked the U.S. Geological Survey and Florida Sea Grant to send him frozen specimens from Tampa Bay, as this is the only way that California would allow the green mussel to be shipped into the state. The feet were severed from about 100 freshly shucked mussels. After thawing, they were placed in a tissue grinder and then centrifuged for study.
"One aspect that is kind of scary is that the green mussel is more successful than other kinds of mussels at living in polluted water," said Waite. Coastal power plants that flush warm seawater into the ocean provide an ideal environment for the mussels. "Once they get a foothold, they stay."
The other authors on the paper are Hua Zhao and Jason Sagert of the Institute of Chemical and Engineering Sciences in Singapore, and Dong Soo Hwang of the Marine Science Institute at UCSB.
(Photo: Rod Rolle)
UC Santa Barbara
A team of researchers recovered 25 marine shell beads dating back to around 70,000 to 85,000 years ago from sites in Morocco, as part of the European Science Foundation EUROCORES programme ‘Origin of Man, Language and Languages’. The shells have man-made holes through the centre and some show signs of pigment and prolonged wear, suggesting they were worn as jewellery.
Across all the locations shells were found from a similar time period from the Nassarius genus. That these shells were used similarly across so many sites suggests this was a cultural phenomenon, a shared tradition passed along through cultures over thousands of years. Several of the locations where shells have been found are so far inland that the shells must have been intentionally brought there.
“Either people went to sea and collected them, or more likely marine shell beads helped create and maintain exchange networks between coastal and inland peoples. This shows well-structured human culture that attributed meaning to these things,” said Francesco d’Errico, lead author and director of research at the French National Centre for Scientific Research (CNRS). “Organised networks would also assist trading of other items, as well as genetic and cultural exchange – so these shells help reveal the connections between cognition and culture.”
For scientists, beadworks are not simply decoration, they also represent a specific technology that conveys information through a shared coded language. It indicates more advanced thinking and the development of modern cultural traits, giving clues to how such innovative behaviours might link to the spread of humans out of Africa.
“The early invention of the personal ornament is one of the most fascinating cultural experiments in human history,” d’Errico continued. “The common element among such ornaments is that they transmit meaning to others. They convey an image of you that is not just your biological self.”
Until recently the invention of personal ornaments was thought to coincide with the colonisation of Europe some 40,000 years ago, linking advanced cognitive capacity to early human dispersal. Yet this changed with the 2006 discovery of shell beads in Africa and the Near East dating back 35,000 years earlier, showing that symbolic thinking emerged more gradually through human evolution.
Curiously, shell beads disappear from the archaeological record in Africa and the Near East 70,000 years ago, along with other cultural innovations such as engravings on ochre slabs, and refined bone tools and projectile points. They reappear in different forms up to 30,000 years later, with personal ornaments simultaneously re-emerging in Africa and the Near East, and for the first time in Europe and Asia. This may reflect an entirely new and independent phase of population growth with previously unseen innovations allowing a more efficient exploitation of a wider variety of environments.
The temporary disappearance of cultural innovations could well be linked to population decreases during a long period of harsher climate conditions 60,000 to 73,000 years ago. This would have isolated populations, disrupting social and exchange networks.
This study was part of a broad network of 21 research projects and 44 individual research teams from 12 European countries forming the European Science Foundation EUROCORES programme ‘Origin of Man, Language and Languages’(OMLL). This highly interdisciplinary collaborative action brought together scientists from a wide range of disciplines including genetics, linguistics, anthropology, archaeology, neurophysiology or cognitive sciences.
Dr Eva Hoogland, EUROCORES coordinator for the cognitive sciences at the European Science Foundation said: “This study presents a very good example of the groundbreaking results that can be gained from an interdisciplinary environment. Some questions, such as those concerning the interconnections between human cognition and culture, can only be addressed if scientists of varying backgrounds join forces. As witnessed by this study, this opens up new avenues for research when it happens on a structural basis, by leading scientists from across Europe.”
(Photo: Copyright d'Errico/Vanhaeren)
European Science Foundation
A new study finds that large-scale farming projects can erode the Earth’s surface at rates comparable to those of the world’s largest rivers and glaciers.
Published online in the journal Nature Geosciences, the research offers stark evidence of how humans are reshaping the planet. It also finds that – contrary to previous scholarship – rivers are as powerful as glaciers at eroding landscapes.
“Our initial goal was to investigate the scientific claim that rivers are less erosive than glaciers,” says Michele Koppes, a professor of geography at the University of British Columbia (UBC) and lead author of the study.
“But while exploring that, we found that many of the areas currently experiencing the highest rates of erosion are being caused by climate change and human activity such as modern agriculture,” says Koppes, who conducted the study with David Montgomery of the University of Washington.
In some cases, the researchers found large-scale farming eroded lowland agricultural fields at rates comparable to glaciers and rivers in the most tectonically active mountain belts.
“This study shows that humans are playing a significant role in speeding erosion in low lying areas,” says Koppes. “These low-altitude areas do not have the same rate of tectonic uplift, so the land is being denuded at an unsustainable rate.”
Koppes says other significant causes of low-altitude erosion include glacier melting caused by climate change and volcanic eruptions.
The highest erosion rates have typically been seen at high altitudes where tectonic forces pit rising rock against rivers and glaciers, says Koppes, who with Montgomery created with an updated database of erosion rates for more than 900 rivers and glaciers worldwide, documented over the past decade with new geologic measuring techniques.
Contrary to previous scholarship, they found that rivers and glaciers in active mountain ranges are both capable of eroding landscapes by more than one centimetre per year. Studies had previously indicated that glaciers could erode landscapes as much as 10 times faster than rivers, Koppes says.
Incorporating geologic records, biologic records and computer simulations, the study reconstructed Arctic summer temperatures at a resolution down to decades, and thereby extends the climate record a full 1,600 years beyond the 400 year-long record that was previously available at that resolution. This newly lengthened record shows that recent warming was preceded by a cooling trend that lasted at least 1,900 years and should have continued throughout the 20th Century. These results indicate that recent warming is more anomalous than previously documented, says Darrell Kaufman of Northern Arizona University--the lead author of the study.
Conducted by an international team of scientists and primarily funded by the National Science Foundation (NSF), the study is described in the September 4, 2009, issue of Science.
Kaufman says that the results of his team's study are significant not only because of their implications for our understanding of human influences on climate change, but also because they agree with the National Center for Atmospheric Research's (NCAR) climate model, which is used for predicting future climate change; this agreement increases confidence in the model's simulations of future climate change.
Specifically, the Kaufman et al. study is the first to quantify at a decadal resolution a pervasive cooling across the Arctic from the early part of the first millennium AD to the industrial revolution, according to Kaufman. During this period, summer temperatures in the Arctic cooled at a rate of about 0.2 degrees Celsius per millennium, leading to the 'Little Ice Age', a period of sustained cold that ended around 1850.
"Scientists have known for a while that the current period of warming was preceded by a long-term cooling trend," says Kaufman. "But our reconstruction quantifies the cooling with greater certainty than before."
The researchers believe that the long cooling trend was caused by a previously recognized wobble in the Earth's axis of rotation that slowly increased the distance between the Earth and the Sun during the Arctic summer, and thereby reduced summer sunshine in the Arctic. (See figure.) But even though this cooling wobble persisted throughout the 20th Century, by the middle of the 20th Century, summer temperatures in the Arctic were about 0.7 degrees Celsius (33.3 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued. This incongruity provides evidence of human influences on climate change, says Kaufman.
What's more, the results of the Kaufman et al. study together with recent records of thermometer readings indicate that the last decade was the warmest of the last two millennia--with Arctic temperatures averaging about 1.4 degrees Celsius (34.5 degrees Fahrenheit) higher than would have been expected if the cooling trend had continued, according to Kaufman.
Kaufman says that his team's study agrees with previous studies that have shown that Arctic temperatures increased during the 20th Century almost three times faster than temperatures increased throughout the rest of the Northern Hemisphere. Called arctic amplification, this phenomenon is caused by increases in the Arctic's absorption of the sun's heat by dark land and exposed ocean as Arctic ice and snow melt away. "The ability of such a slight wobble in the Earth's axis to cause a significant temperature change over the 1,900 year period preceding the onset of recent warming provides further evidence of the sensitivity of the Arctic's climate system," says Kaufman.
"Because we know that the processes responsible for past arctic amplification are still operating, we can anticipate that it will continue into the next century," says Gifford Miller of the University of Colorado, Boulder, a member of the study team. "Consequently, Arctic warming will continue to exceed temperature increases in the rest of the Northern Hemisphere, resulting in accelerated loss of land ice and an increased rate of sea-level rise, with global consequences."
Real-world records of climate change
The 2000-year reconstruction of Arctic temperatures provided by the Kaufman et al. study incorporated three types of field-based data--each of which captured the response of a different component of the Arctic's climate system to changes in temperature.
These field-based data included temperature reconstructions that were published by the Kaufman et al. team earlier this year. These reconstructions were based on evidence provided by sediments from Arctic lakes, including algal abundance, which reflects the length of the growing season, and the thickness of annually deposited sediment layers, which increases during warmer summers when deposits from glacial melt-water increase. The Kaufman et al. study also incorporated previously published data from glacial ice and tree rings that was calibrated against the instrumental temperature record.
The Kaufman et al. study also included a 2,000 year-long computer simulation of climate change that incorporated the Earth's slow rotational wobble and resulting reduction in seasonal sunlight in the Arctic. Because the model's estimate of the amount of cooling resulting from the wobble effect matched the cooling reflected in the long record of climate change provided by lake sediments and other natural archives, this analysis increased confidence in the model's ability to accurately predict temperature responses in the Arctic to factors that influence climate change. "This result is particularly important because the Arctic is perhaps the most sensitive area of the Earth to the human factors that influence climate change," says David Schneider of NCAR, who is a member of the research team.
"As we are confronted with evidence of global warming, it is extremely helpful to be able to use paleoclimate data to provide context for today's climate relative to the range and trajectory of recent climate regimes," says Neil Swanberg, director of NSF's Arctic System Science Program. "This reconstruction uses a variety of data sources to extend high resolution records back in time sufficiently long to compare reconstructed temperatures to those from models that include changes in insolation due to changes in the Earth's orbital patterns. That the results appear to match so well increases our confidence in our understanding of the processes that are impacting the global Earth system."
(Photo: Darrell Kaufman, Northern Arizona University)
National Science Foundation
The researchers analyzed DNA from hunter-gatherer and early farmer burials, and compared those to each other and to the DNA of modern Europeans. They conclude that there is little evidence of a direct genetic link between the hunter-gatherers and the early farmers, and 82 percent of the types of mtDNA found in the hunter-gatherers are relatively rare in central Europeans today.
For more than a century archaeologists, anthropologists, linguists, and more recently, geneticists, have argued about who the ancestors of Europeans living today were. We know that people lived in Europe before and after the last big ice age and managed to survive by hunting and gathering. We also know that farming spread into Europe from the Near East over the last 9,000 years, thereby increasing the amount of food that can be produced by as much as 100-fold. But the extent to which modern Europeans are descended from either of those two groups has eluded scientists despite many attempts to answer this question.
Now, a team from Mainz University in Germany, together with researchers from UCL (University College London) and Cambridge, have found that the first farmers in central and northern Europe could not have been the descendents of the hunter-gatherers that came before them. But what is even more surprising, they also found that modern Europeans couldn't solely be the descendents of either the hunter-gatherer alone, or the first farmers alone, and are unlikely to be a mixture of just those two groups. "This is really odd", said Professor Mark Thomas, a population geneticist at UCL and co-author of the study. "For more than a century the debate has centered around how much we are the descendents of European hunter-gatherers and how much we are the descendents of Europe's early farmers. For the first time we are now able to directly compare the genes of these Stone Age Europeans, and what we find is that some DNA types just aren't there - despite being common in Europeans today."
Humans arrived in Europe 45,000 years ago and replaced the Neandertals. From that period on, European hunter-gatherers experienced lots of climatic changes, including the last Ice Age. After the end of the Ice Age, some 11,000 years ago, the hunter-gatherer lifestyle survived for a couple of thousand years but was then gradually replaced by agriculture. The question was whether this change in lifestyle from hunter-gatherer to farmer was brought to Europe by new people, or whether only the idea of farming spread. The new results from the Mainz-led team seems to solve much of this long standing debate.
"Our analysis shows that there is no direct continuity between hunter-gatherers and farmers in Central Europe," says Prof Joachim Burger. "As the hunter-gatherers were there first, the farmers must have immigrated into the area."
The study identifies the Carpathian Basin as the origin for early Central European farmers. "It seems that farmers of the Linearbandkeramik culture immigrated from what is modern day Hungary around 7,500 years ago into Central Europe, initially without mixing with local hunter gatherers," says Barbara Bramanti, first author of the study. "This is surprising, because there were cultural contacts between the locals and the immigrants, but, it appears, no genetic exchange of women."
The new study confirms what Joachim Burger´s team showed in 2005; that the first farmers were not the direct ancestors of modern European. Burger says "We are still searching for those remaining components of modern European ancestry. European hunter-gatherers and early farmers alone are not enough. But new ancient DNA data from later periods in European prehistory may shed also light on this in the future."
University College London
"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," said Fred Turek, professor of neurobiology and physiology in the Weinberg College of Arts and Sciences and director of the Center for Sleep and Circadian Biology. "We think some factors are under circadian control. Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity."
The findings could have implications for developing strategies to combat obesity in humans, as the United States and the world battle what has been called an "obesity epidemic." More than 300 million adults worldwide are obese, including more than a third of American adults.
Details of the obesity study, which was led by Turek, were published online Sept. 3 by the journal Obesity.
"One of our research interests is shift workers, who tend to be overweight," said lead author Deanna M. Arble, a doctoral student in Turek's lab. "Their schedules force them to eat at times that conflict with their natural body rhythms. This was one piece of evidence that got us thinking -- eating at the wrong time of day might be contributing to weight gain. So we started our investigation with this experiment."
Simply modifying the time of feeding alone can greatly affect body weight, the researchers found. Mice that were fed a high-fat diet during normal sleeping hours gained significantly more weight (a 48 percent weight increase over their baseline) than mice eating the same type and amount of food during naturally wakeful hours (a 20 percent increase over their baseline). There was no statistical difference between the two groups regarding caloric intake or the amount of activity.
Over a period of six weeks, both groups of mice were allowed to eat as much high-fat diet as they wanted during their daily 12-hour feeding phase. (Much like many humans, mice have a preference for high-fat food.) Since mice are nocturnal, the 12-hour feeding phase was during the day for those fed during normal sleeping hours and during the night for those fed during naturally wakeful hours. Food was not provided during the other 12 hours of their day.
Our circadian clock, or biological timing system, governs our daily cycles of feeding, activity and sleep, with respect to external dark and light cycles. Recent studies have found the body's internal clock also regulates energy use, suggesting the timing of meals may matter in the balance between caloric intake and expenditure.
The researchers next plan to investigate the molecular mechanisms behind their observation that eating at the "wrong" time can lead to weight gain.
The new images, captured by an international team of astronomers including the University of Bristol, are from the largest panoramic survey of Andromeda ever made. The survey covers a region nearly a million light years across.
It charted Andromeda’s unexplored outskirts for the first time and detected faint stars and giant structures that are almost certainly remnants of smaller galaxies, cannibalised by Andromeda as part of its ongoing expansion.
At 2.5 million light years from our own galaxy – the Milky Way Galaxy – the Andromeda Galaxy (M31) is our closest giant neighbour. It is so large it is visible to the naked eye from the Northern Hemisphere.
Another nearby galaxy, the Triangulum Galaxy (M33), was seen to be surrounded by a giant stellar ‘halo’ that the team believes provides persuasive evidence for its recent encounter with Andromeda. Stars are pulled from Triangulum as it orbits Andromeda due to the strong gravity of this massive galaxy. These stars are then consumed by Andromeda and contribute to its unstoppable expansion.
Dr Avon Huxor, from the University of Bristol’s Physics Department and an author on the paper, said: “Galaxies are large collections of stars and other matter that are held together by gravity. Theory holds that they evolve and grow by absorbing smaller galaxies over time. One way to test this idea is to find the left-overs from this process.
“But finding these faint structures is difficult, since it involves looking over an area hundreds of times larger than the main disk of the galaxy. The really exciting thing about this study is that we can see this merging of galaxies in real detail for the first time. Oddly enough, it is hard to do this with our own Galaxy, as we sit within it, which makes it difficult to disentangle what the data is telling us.”
Dr. Alan McConnachie, from the NRC Herzberg Institute of Astrophysics in Canada, who led the survey team, said: “That we are finding streams and structures over the entire survey area is a startling demonstration of the vast size of this ‘typical’ galaxy. Until a few years ago, no-one expected to find anything this far from the centre of a galaxy. But Andromeda is showing us that galaxies are much bigger than we originally thought.”
The results published set the stage for a more detailed reconstruction of the formation of Andromeda, a process that appears to be continuing to this day.
(Photo: John Dubinski and Larry Widrow)
University of Bristol
But behind the artwork's precision is a mystery: How did illustrators refine the details, which rival the precision of engravings on a modern dollar bill, centuries before microscope lenses were invented?
The answer, says Cornell paleontologist John Cisne, may be in the eyes of the creators. The Celtic monks evidently trained their eyes to cross above the plane of the manuscript so they could visually superimpose side-by-side elements of a replicated pattern, and thereby, create 3-D images that magnified differences between the patterns up to 30 times.
The monks could then refine any disparities by minimizing the apparent vertical depth of the images -- ultimately replicating the design element to submillimeter precision. Cisne proposed the idea in the July 17 issue of the journal Perception (Vol. 38, No. 7).
The paper suggests that the technique, called free-fusion stereocomparison, which takes advantage of the brain's ability to perceive depth by integrating the slightly different views from each eye, was known nearly a thousand years before it was articulated by stereoscope inventor Sir George Wheatstone in the 19th century.
Cisne analyzed the most detailed illuminated manuscripts of the Middle Ages, created between 670 and 800 A.D., including the Book of Kells (circa 800 A.D.); some have as many as 30 lines per centimeter.
The artists stayed mum about their techniques, possibly because their talent gave their Celtic church an edge over the Roman church in the competition for disciples. "If you're in the middle of a propaganda war, [it helps] if the angels are clearly on your side," Cisne said.
But they left a few clues, he said, including the high degree of symmetry and repetition among many of the most intricate patterns and the elements' spacing, which is usually at about the distance between an average person's pupils.
"It turns out that if you can draw accurately enough, you can easily get a magnification of the lateral [horizontal] distance something like 10, 20 or 30 times -- about the magnification you could get under a dissecting microscope," Cisne said.
The monks likely created a highly accurate template for the design elements by drawing the same element repeatedly, comparing versions and modifying to create a standardized model. From there, they could replicate it into complex designs, using free-fusion stereoscopic comparison and minimizing errors along the way.
Many of the design elements contain minute imperfections that are consistent throughout rows or columns, supporting the idea that the monks worked from templates. And depictions of scribes from the era often show the monks holding pen in one hand and erasing knife in the other -- another clue that they made modifications along the way.
"The idea is that these guys did it just the same way I do when I use a drawing tube and a microscope -- lay down a reference grid, fill in the details, and then compare the details with your template," Cisne said.
Their knowledge of stereoscopic imagery likely died with the monasteries, which were later decimated by the Vikings, Cisne said. The original manuscripts are in Dublin and London; Cisne worked from high-quality reproductions in Cornell's Division of Rare and Manuscript Collections in Kroch Library. They're a reminder, Cisne said, that ingenuity can sometimes trump technology.
"Most people don't appreciate what a fine instrument they have in their eyes," he said, "and how their visual system can be used in other than the obvious ways."
(Photo: Lindsay France/Cornell University)
Rice is classified into two major varietal groups: Japonica and Indica, both of which were grown in China some 8,000 years ago and are believed to have originated from there. The new study, published Aug. 25 in the Proceedings of the National Academy of Sciences, confirms that basmati rice, long assumed to be an Indica variety, is actually more closely related genetically to Japonica rice.
Basmati, which is endemic to northern India, Pakistan and Iran, has been falsely assumed to be in the Indica group due to its characteristic long, thin grains and because it is grown in India, where Indica varieties are widespread. Japonica varieties, which include sushi rice, are widely grown in East and Southeast Asia and tend to have shorter, stickier grains.
When the gene, called BADH2, loses its function through the natural process of mutation, rice becomes fragrant. This study reports eight novel mutations in BADH2 associated with fragrance and found that a previously discovered mutation, or allele, is shared by the vast majority of fragrant rice varieties today, including the fragrant Japonica varieties known as basmati and the fragrant Indica variety known as Thai jasmine.
Through genetic analysis of the DNA flanking BADH2, the researchers determined that the major fragrance allele originated in a Japonica-ancestor of basmati rice and was later transferred to Indica varieties, including Thai jasmine rice.
"People think that all rice [varieties] in India are from the Indica varietal group, but that's not true," said Susan McCouch, professor of plant breeding and genetics and the paper's senior author. Michael Kovach, a doctoral student in McCouch's lab, is the paper's first author.
The new study supports findings from a 2005 paper by McCouch that showed the close genetic relationship of basmati rice to the Japonica varietal group.
"India has both Indica and Japonica rice," McCouch added. "Basmati is a unique type of rice but it is genetically more closely related to sushi rice from Japan than to many of the long grained Indica rices grown elsewhere in India. It is intriguing to think about what these relationships tell us about human migration and cultural exchange."
The findings have important implications for claims of ownership of rice varieties and traits, said Kovach. Rice fragrance is one of the most highly valued traits of rice, and it can command higher prices on the global market.
Thai scientists recently patented the use of a genetic engineering strategy to knock out the BADH2 gene while claiming the fragrance trait was part of their national heritage -- through Thai jasmine rice -- and "belonged to the Thai people," Kovach said.
"They would like to use this approach to impart this characteristic fragrance on other crops like wheat and maize," Kovach added. "There was no proof that the common BADH2 allele causing fragrance in Thai jasmine rice actually did not originate in jasmine varieties, until this study."
"The results suggest something profound and interesting about human culture, and that is, we are all hybrids," said McCouch. "Claims of ownership of rice are important for national identity, but people's concepts of national identity are often over-simplified. Humans continuously exchange ideas, technology and everything that is valuable, and in the exchange, they become something new. The lesson is that while each culture and each rice variety represents something unique, much of what we value most is shared by all."
(Photo: Cornell U.)