'Singing' Mice: The Ongoing Debate of Nature Vs. Nurture

ScienceDaily (Mar. 9, 2011) — What happened to being "quiet as a mouse"? Researchers have recently shown that, rather than being the silent creatures of popular belief, mice emit ultrasonic calls in a variety of social contexts, and these calls have song-like characteristics. So if mice sing, where do they get their music? Are they born with the songs fully formed in their heads, or do they learn them from their peers?

These questions are of great interest to scientists as, while many organisms produce genetically regulated vocalizations, only a select few species (such as ourselves) can actually learn these vocalizations. If it turns out that mice can indeed learn new songs, it would provide a very convenient mammalian model of vocal learning.

Whether or not mouse song involves learning either through auditory imitation or behavioral feedback (e.g., from the mother), however, is a subject of hot debate, and the answer is proving elusive. To highlight the difficulties facing researchers, two studies published on March 9, 2011 in the open-access journal PLoS ONE have come to differing conclusions about whether mouse vocalization patterns are innate or learned.

In the first study, researchers from Northeastern Ohio Universities Colleges of Medicine and Pharmacy and the MRC Institute of Hearing Research conducted a study to understand developmental changes in mouse song that would allow parents to distinguish older mice from younger mice. They found that many features of mouse song changed with age. For example, the pattern of syllables within songs became more complex.

According to lead author Jasmine Grimsley, "We concluded that the increased complexity of song suggests that mice may be capable of vocal learning, but we also recognized that other factors besides learning, such as genetically controlled neuromuscular development, might explain the increased complexity. We conducted our study in normal hearing, CBA/CaJ mice, and we intend to use the results to understand how the brain codes the meaning of these sounds."

The second study, a collaboration among Azabu University, the RIKEN Brain Science Institute, and the Okanoya Emotional Information Project used a cross-fostering experiment to test whether the vocalization patterns were more strongly influenced by genetics or environment. The researchers used males from two mouse strains, C57BL/6 and BALB/c, which emit different vocalizations. Males from each strain were raised in litters of the opposite strain until weaning. Vocalization patterns were recorded at 10-20 weeks of age, and the researchers compared vocalizations of cross-fostered mice to control mice reared by genetic parents.

According to first author Takefumi Kikusui, "We first showed that two strains of mice, BALB and B6, sing strain-unique song types. We then showed that rearing BALB by B6 parents do not change the BALB characteristics of the song, and vise-versa. The fact that the cross-fostered animals sang songs similar to those of their genetic parents suggests that the structure of this courtship sound is under strong genetic control."

When asked about the results from the other study, corresponding author Dr. Kazuo Okanoya noted that, "they demonstrate substantial developmental changes in social vocalizations with age. They also characterized complex behavioral phenotypes of mice vocalizations. However, in our opinion, developmental and phonotypical complexities of mice vocalizations are not related with whether or not the vocalizations are learned."

Dr Grimsley said of the Japanese research, "while we believe that the study by Kikusui et al. indicates that some aspects of mouse songs are genetically driven, the conclusion that vocal learning does not occur in mice is too strong for the experiments that they performed. In our opinion, the jury is still out regarding whether mice do, or do not, exhibit vocal learning."

Which is it then, nature or nurture? It appears that it is still too early to say for sure, and we do not yet know whether the mating songs of mice are genetically determined or learned from their parents. What is certain, however, is that even carefully performed scientific research does not always produce straight-forward answers.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/03/110309182656.htm

New Wintering Grounds for Humpback Whales Discovered Using Sound

ScienceDaily (Mar. 9, 2011) — Researchers have made a remarkable new discovery regarding humpback whale wintering grounds.

In the thick of whale season, researchers from Hawai'i Institute of Marine Biology (HIMB) and the National Oceanic and Atmospheric Administration (NOAA) shed new light on the wintering grounds of the humpback whale. The primary breeding ground for the North Pacific was always thought to be the main Hawaiian Islands (MHI). However, a new study has shown that these grounds extend all the way throughout the Hawaiian Archipelago and into the Northwestern Hawaiian Islands (NWHI), also known as Papahānaumokuākea Marine National Monument (PMNM).

Humpback whales, an endangered species, were once on the brink of extinction due to commercial whaling practices of the last century. Today, thanks to international protection, their numbers have dramatically increased, resulting in a greater presence of these singing mammals during the winter months. Song is produced by male humpback whales during the winter breeding season. All males on a wintering ground sing roughly the same song any given year, but the song changes from year to year. No one is exactly sure why the whales sing but some researchers believe it could be a display to other males. Between 8,500 and 10,000 whales migrate to Hawai'i each winter; while the rest of the population can be found in places like Taiwan, the Philippines, the Mariana Islands, Baja California, Mexico, amongst other Pacific locations (Calambokidis et al. 2008).

Over the past three decades, population recovery has resulted in a steady increase in the number of whales and a geographic expansion of their distribution in the MHI. Until recently, however, no empirical evidence existed that this expansion included the Northwestern Hawaiian Islands. This changed recently when scientists from HIMB and NOAA published their findings in the current issue of the journal Marine Ecology Progress Series, detailing the presence of humpback whale song in the Northwestern Hawaiian Archipelago. These researchers deployed instruments known as Ecological Acoustic Recorders (EARs) in both the NWHI and MHI to record the occurrence of humpback whale song, as an indicator of winter breeding activity. Humpback whale song was found to be prevalent throughout the NWHI and demonstrated trends very similar to those observed in the MHI.

Dr. Marc Lammers, a researcher at HIMB and the lead scientist of the project explains "these findings are exciting because they force us to re-evaluate what we know about humpback whale migration and the importance of the NWHI to the population." The results are also of particular relevance in light of recent suggestions that an undocumented wintering area for humpback whales exists somewhere in the central North Pacific. Dr. Lammers and his colleagues believe that the NWHI could be that area.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/03/110308172840.htm

Blue Whale-Sized Mouthfuls Make Foraging Super Efficient

ScienceDaily (Dec. 12, 2010) — How much can a blue whale eat in a single mouthful and how much energy do they burn while foraging? These are the questions that Bob Shadwick from the University of British Columbia, Canada, and his colleagues have asked. They discovered that blue whales can swallow almost 2,000,000kJ (almost 480,000kcalories) in a single mouthful of krill, and eat 90 times as much energy as they burn during a dive.

Diving blue whales can dive for anything up to 15 minutes. However, Bob Shadwick from the University of British Columbia, Canada, explains that blue whales may be able to dive for longer, because of the colossal oxygen supplies they could carry in their blood and muscles, so why don't they?

'The theory was that what they are doing under water must use a lot of energy,' says Shadwick. Explaining that the whales feed by lunging repeatedly through deep shoals of krill, engulfing their own body weight in water before filtering out the nutritious crustaceans, Shadwick says, 'It was thought that the huge drag effect when they feed and reaccelerate this gigantic body must be the cost'. However, measuring the energetics of blue whale lunges at depth seemed almost impossible until Shadwick and his student Jeremy Goldbogen got chatting to John Hildebrand, John Calambokidis, Erin Oleson and Greg Schorr who were skilfully attaching hydrophones, pressure sensors and two-axis accelerometers to the elusive animals. Shadwick and Goldbogen realised that they could use Calambokidis's measurements to calculate the energetic cost of blue whale lunges. They publish their discovery that blue whales swallow almost 2,000,000kJ (almost 480,000kcalories) in a mouthful of krill, and take in 90 times as much energy as they burn during a single dive in The Journal of Experimental Biology.

Analysing the behaviour of each whale, Goldbogen saw that dives lasted between 3.1 and 15.2 minutes and a whale could lunge as many as 6 times during a single dive. Having found previously that he could correlate the acoustic noise of the water swishing past the hydrophone with the speed at which a whale was moving, Goldbogen calculated the blue whales' speeds as they lunged repeatedly during each dive. Next the team had to calculate the forces exerted on the whales as they accelerated their colossal mouthful of water. Noticing that the whales' mouths inflated almost like a parachute as they engulfed the krill, Goldbogen tracked down parachute aerodynamics expert Jean Potvin to help them build a mathematical model to calculate the forces acting on the whales as they lunged. With Potvin on the team, they were able to calculate that the whales used between 3226 kJ of energy during each lunge. But how did this compare with the amount of energy that the whales could extract from each gigantic mouthful of krill?

Goldbogen estimated the volume of the whales' mouths by searching the whaling literature for morphological data and teamed up with paleontologist Nick Pyenson to measure the size of blue whale jaw bones in several natural history museums. He also obtained krill density values from the literature -- which are probably on the low side. Then he calculated the volume of water and amount of krill that a whale could engulf and found that the whales could consume anything from 34,776kJ up to an unprecedented 1,912,680kJ from a single mouthful of krill, providing as much as 240 times as much energy as the animals used in a single lunge. And when the team calculated the amount of energy that a whale could take on board during a dive, they found that each foraging dive could provide 90 times as much energy as they used.

Shadwick admits that he was initially surprised that the whales' foraging dives were so efficient. 'We went over the numbers a lot,' he remembers, but then he and Goldbogen realised that the whales' immense efficiency makes sense. 'The key to this is the size factor because they can engulf such a large volume with so much food in it that it really pays off,' says Shadwick.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2010/12/101209074356.htm

Primates Are More Resilient Than Other Animals to Environmental Ups and Downs

ScienceDaily (Dec. 2, 2010) — What sets humankind's closest relatives -- monkeys, apes, and other primates -- apart from other animals? According to a new study, one answer is that primates are less susceptible to the seasonal ups and downs -- particularly rainfall -- that take their toll on other animals. The findings may also help explain the evolutionary success of early humans, scientists say.

The study appeared online in the Nov. 30 issue of American Naturalist.

"Wild animals deal with a world that's unpredictable from year to year," said study lead author Bill Morris, a biologist at Duke University. "The weather can change a lot; there can be years with plenty of food and years of famine," he explained.

To find out how well primates cope with this unpredictability compared with other animals, researchers working at the National Evolutionary Synthesis Center (NESCent) in Durham, N.C. analyzed decades of birth and survival data for seven species of wild primates: muriqui monkeys and capuchin monkeys in Central and South America, yellow baboons, blue monkeys, chimpanzees and gorillas in Africa, and sifakas (lemurs) in Madagascar.

Collecting this data was no small effort. Nearly every day for more than 25 years, seven research teams working around the world have monitored the births, lives, and deaths of thousands of individual primates.

Thanks to a new database developed at NESCent, the scientists were able to pool their painstakingly-collected data and look for similarities across species.

When they compared year-to-year fluctuations in primate survival to similar data for other animals -- namely, two dozen species of birds, reptiles, and mammals -- they found that primate survival remained more stable despite seasonal variation in rainfall.

"Primates appear to be well buffered against fluctuations in weather and food availability relative to a lot of other animals," said co-author Susan Alberts, a biologist at Duke University and associate director at NESCent.

A number of traits may help shield primates from seasonal ups and downs. "For one thing, they're social," said co-author Karen Strier, an anthropologist at the University of Wisconsin-Madison. Primates live in groups and share information with each other, so they're better able to find food and water in times of scarcity, Strier explained.

Primates also owe their adaptability to broad, flexible diets that enable them to adjust to seasonal shortages of their favorite foods. "Primates will eat leaves, grasses, fruits, flowers, bark, and seeds. They're generalists," said Alberts.

In the distant past, similar traits may have also buffered other primates -- namely, humans -- against environmental ebbs and flows, scientists say.

"Modern humans have all the same traits these primate species have: we're smart, we have social networks, and we have a broad diet," said Morris. "Modern humans also arose during a period when Africa's climate was changing," Morris added. "So the same traits that allow non-human primates to deal with unpredictable environments today may have contributed to the success of early humans as well."

If primates are good at coping with environmental ups and downs, then why are so many of them now endangered? Despite being well buffered from changing weather, human activities still take their toll, the scientists say. With nearly half of the world's primates now in danger of becoming extinct due to hunting and habitat loss, continued monitoring will be key, Strier addded.

"Everything we can learn about them now will help prevent their extinction in the future."

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2010/12/101201124347.htm

Do Chimpanzees Mourn Their Dead Infants?

ScienceDaily (Feb. 2, 2011) — For the first time, researchers of the Max Planck Institute for Psycholinguistics in the Netherlands report in detail how a chimpanzee mother responds to the death of her infant. The chimpanzee mother shows behaviours not typically seen directed toward live infants, such as placing her fingers against the neck and laying the infant's body on the ground to watch it from a distance. The observations of Katherine Cronin and her team provide unique insights into how chimpanzees, one of humans' closest primate relatives, learn about death.

Their commentary appears online in the American Journal of Primatology.

The research team conducted their observations at Chimfunshi Wildlife Orphanage Trust in Zambia, where wild-born chimpanzees who have been rescued from illegal trade live in the largest social groups and enclosures in the world. Dr. Katherine Cronin and Edwin Van Leeuwen of the Max Planck Institute for Psycholinguistics collaborated with Innocent Chitalu Mulenga of Chimfunshi and Dr. Mark Bodamer, a professor of Psychology at Gonzaga University in Washington State, USA.

Close relationship

Chimpanzee mothers typically are in close contact with their offspring for several years, carrying them almost continuously for two years and nursing until they are four to six years old. The close relationship between the mother and offspring continues for several years after weaning, and is one of the most important relationships in chimpanzee life.

Premature death

Cronin and her colleagues observed the behaviour that a female chimpanzee expressed toward her 16-month-old infant who had recently died. After carrying the infant's dead body for more than a day, the mother laid the body out on the ground in a clearing and repeatedly approached the body and held her fingers against the infant's face and neck for multiple seconds. She remained near the body for nearly an hour, then carried it over to a group of chimpanzees and watched them investigate the body. The next day, the mother was no longer carrying the body of the infant.

Nearly nothing is known about how primates react to death of close individuals, what they understand about death, and whether they mourn. The MPI researchers therefore believe to have reported a unique transitional period as the mother learned about the death of her infant, a process never before reported in detail. But they largely refrain from interpretation, while providing extensive video to allow viewers the opportunity to judge for themselves what chimpanzees understand about death.

'The videos are extremely valuable, because they force one to stop and think about what might be happening in the minds of other primates', Cronin says. 'Whether a viewer ultimately decides that the chimpanzee is mourning, or simply curious about the corpse, is not nearly as important as people taking a moment to consider the possibilities.'

Mother-infant bond

Previous reports have documented chimpanzee mothers carrying their deceased young for days or weeks, demonstrating that the severing of the mother-infant bond is incredibly difficult for chimpanzees. The current research complements these observations and sheds new light on how chimpanzees might learn about death.

'These data contribute to a small but growing body of data on how nonhuman primates respond to death. We hope these objective accounts will continue to accumulate and eventually allow researchers to take a comprehensive look at the extent to which nonhuman primate understand death, and how they respond to it.'

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/01/110127160441.htm

Clam Cleanup, Biologists Clam Up Waterways To Determine Sources Of Pollution

January 1, 2009 — Biologists are able to determine the sources of toxins in water by using clams as pollutant traps. Clams naturally clean water by feeding absorbing toxins in their tissues as they draw in water. By placing the clams downstream of industrial parks and highways, they can be analyzed for pollutants. Biologists open the clams after exposure to these waters and detach them from their shells-- various lab tests reveal contaminants in the waterway.

Many of our streams and rivers are contaminated with pollutants like pesticides, lead, arsenic and PCBs. It's a problem that's costly to clean up. Scientists are using a new, inexpensive way to fix the problem.

Lurking in many rivers and streams are contaminants. Some you can see, and some you can't. Hidden chemicals ruin waterways and everything in it. To clean things up, biologists are teaming up with local high school students to dredge up clams to use as tiny detectives. They help by finding the source of toxic leaks.

"We're using them as pollutant traps," said Harriette Phelps, Ph.D., a biologist at the University of the District of Columbia in Washington, D.C.

Students put the clams in streams that lead to rivers. Clams then suck in water swept down from industrial parks and highways.

"It's been a great experience to actually come and see them and be the ones to pick them up out of the water," student Caitlin Virta said.

Clams clean the water as they feed, absorbing toxins in their tissues. The clams are collected back from streams. Then, scientists pry open the clams and detach them from their shell. Later, lab tests reveals the clam's secret -- the kinds and quantities of pollutants in the water.

"We can trace them back to sources, and then hopefully we can go from there and get rid of the sources," Dr. Phelps said.

The clams detected a banned pesticide in Maryland, believed buried years ago and now slowly leaking. "I thought it was really cool how you could tell the health of a stream from analyzing clam leftovers," Virta said.

It's a cool way to clean up the environment.

BIOACCUMULATION AND CLAMS: Clams are filter-feeders, meaning they draw water into their shells, remove the food they find, and then draw in more food-rich water to continue feeding. This means that lots of water works its way through their shells. The muscle of the clam gathers not only food, but other material suspended in water during this process, which can lead to the accumulation of toxins and pollutants. Bioaccumulation is the term for toxins and pollutants that collect in the tissue of an organism. Biomagnification is a related term, referring to the transfer of such substances from prey to predator. If a prey animal bioaccumulates toxins in its body, then its predator, after consuming many of the smaller animals will accumulate many, many times the amount of the toxin in any one of their prey.

SECONDARY STANDARDS: Even if your tap water meets the EPA's basic requirement for safe drinking water, some people still object to the taste, smell or appearance of their water. These are aesthetic concerns, however, and therefore fall under the EPA's voluntary secondary standards. Some tap water is drinkable, but may be temporarily clouded because of air bubbles, or have a chlorine taste. A bleach-like taste can be improved by letting the water stand exposed to the air for a while.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/videos/2009/0110-clam_cleanup.htm

Primates' Unique Gene Regulation Mechanism: Little-Understood DNA Elements Serve Important Purpose

ScienceDaily (Feb. 9, 2011) — Scientists have discovered a new way genes are regulated that is unique to primates, including humans and monkeys. Though the human genome -- all the genes that an individual possesses -- was sequenced 10 years ago, greater understanding of how genes function and are regulated is needed to make advances in medicine, including changing the way we diagnose, treat and prevent a wide range of diseases.

"It's extremely valuable that we've sequenced a large bulk of the human genome, but sequence without function doesn't get us very far, which is why our finding is so important," said Lynne E. Maquat, Ph.D., lead author of the new study published February 9 in the journalNature.

When our genes go awry, many diseases, such as cancer, Alzheimer's and cystic fibrosis can result. The study introduces a unique regulatory mechanism that could prove to be a valuable treatment target as researchers seek to manipulate gene expression -- the conversion of genetic information into proteins that make up the body and perform most life functions -- to improve human health.

The newly identified mechanism involves Alu elements, repetitive DNA elements that spread throughout the genome as primates evolved. While scientists have known about the existence of Alu elements for many years, their function, if any, was largely unknown.

Maquat discovered that Alu elements team up with molecules called long noncoding RNAs (lncRNAs) to regulate protein production. They do this by ensuring messenger RNAs (mRNAs), which take genetic instructions from DNA and use it to create proteins, stay on track and create the right number of proteins. If left unchecked, protein production can spiral out of control, leading to the proliferation or multiplication of cells, which is characteristic of diseases such as cancer.

"Previously, no one knew what Alu elements and long noncoding RNAs did, whether they were junk or if they had any purpose. Now, we've shown that they actually have important roles in regulating protein production," said Maquat, the J. Lowell Orbison Chair, professor of Biochemistry and Biophysics and director of the Center for RNA Biology at the University of Rochester Medical Center.

The expression of genes that call for the development of proteins involves numerous steps, all of which are required to occur in a precise order to achieve the appropriate timing and amount of protein production. Each of these steps is regulated, and the pathway discovered is one of only a few pathways known to regulate mRNAs directly in the midst of the protein production process.

Regulating mRNAs is one of several ways cells control gene expression, and researchers from institutions and companies around the world are honing in on this regulatory landscape in search of new ways to manage and treat disease.

According to Maquat, "This new mechanism is really a surprise. We continue to be amazed by all the different ways mRNAs can be regulated."

Maquat and the study's first author, Chenguang Gong, a graduate student in the Department of Biochemistry and Biophysics at the Medical Center, found that long noncoding RNAs and Alu elements work together to trigger a process known as SMD (Staufen 1-mediated mRNA decay). SMD conditionally destroys mRNAs after they orchestrate the production of a certain amount of proteins, preventing the creation of excessive, unwanted proteins in the body that can disrupt normal processes and initiate disease.

Specifically, long noncoding RNAs and Alu elements recruit the protein Staufen-1 to bind to numerous mRNAs. Once an mRNA finishes directing a round of protein production, Staufen-1 works with another regulatory protein previously identified by Maquat, UPF1, to initiate the degradation or decay of the mRNA so that it cannot create any more proteins.

While the research fills in a piece of the puzzle as to how our genes operate, it also accentuates the overwhelming complexity of how our DNA shapes us and the many known and unknown players involved. Maquat and Gong plan on exploring the newly identified pathway in future research.

This research was supported by a grant from the General Medical Sciences Division of the National Institutes of Health and an Elon Huntington Hooker Graduate Student Fellowship.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/02/110209131828.htm

Snails' Complex Muscle Movements, Rather Than Mucus, Key to Locomotion

ScienceDaily (Mar. 11, 2011) — New evidence suggests that the key to locomotion in snails stems from the animal's complex muscle movements, and not from its mucus, as had been previously thought. This finding could open the door to the construction of robots which could imitate this form of propulsion.

The main aim of this study, carried out in collaboration with the University of California at San Diego (UCSD) and Stanford University (both in the US) is to characterize some aspects of gastropod (snails and slugs) locomotion to basically respond to one question: To what extent do they depend on the physical properties of their mucus to propel themselves forward? This question is fundamental when applying the studied mechanism to the construction of biomimetic robots. "The aim is for the robot to be able to propel itself in any fluid mucus without having to carry its own reserve of mucus along," explained one of the authors of the research study, Javier Rodríguez, Professor at the UC3M Department of Thermal and Fluids Engineering. "Bear in mind," he stated, "that snail mucus has a very particular behaviour because it is a specific type of fluid with complex physical characteristics called non-Newtonian fluid."

Until now, it was known that snails and slugs move by propagating their body in a series of muscular wave motions to advance from their tail to their head, but the importance of their mucus in this process was not known. The conclusion obtained by these scientists is that this fluid's properties are not essential for propulsion. "Without a doubt, it could have other uses, such as climbing walls, moving upside down, or preserving moisture in the body when on a dry surface, but if we want to construct a robot that emulates a snail, the latter could move over fluid mucus with ordinary properties" pointed out Professor Rodríguez, who has recently published an article on this matter, together with his colleagues from the North American universities, in the scientific review, Journal of Experimental Biology.

To carry out this study, the researchers have characterized the propagation of these muscular waves which occur along the body of gastropods. For this purpose, they place the snails and slugs so that they move on transparent surfaces, illuminating their undersides in different ways so as to record images through digital cameras, subsequently analyzing this data by computer. "The ways to illuminate the body vary depending on what is being measured," stated María Vázquez, research fellow from the UC3M Fluid Mechanics Group where she has collaborated in experiments carried out in Spain and in the US. "For example," she explained further, "to measure the speed of the wave, we placed a light on the underneath part of the snail, while to measure the vertical deformation of the body we used a low power flat laser (so as not to harm the animal) projected at a given angle." Together, all of these measures have allowed the 3D reconstruction of the snail's underside during propulsion.

Very diverse applications

The most surprising thing about snail movement is summed up very well in a phrase from a biology professor from Stanford University, Mark W. Denny, written in the 1980's: "How can an animal with just one leg walk on glue?" And the mucus is highly adhesive, which offers some advantages such as walking on walls and moving on the ceiling. Furthermore, as anyone who has ever held a snail in their hand can testify, when snails move, they do not use force over specific points, as animals with legs do, but rather they distribute a relatively low force over a relatively large area. "What also happens," Professor Rodríguez pointed out, "is that it is difficult to move over glue without exerting quite a bit of force while dragging fluid along." Snails, after millions of years of evolution, have succeeded in being able to move on a highly adhesive surface, avoiding these inconveniences "which is without a doubt of interest and worthy of study," he added

This type of research can help in the design of biomimetic robots that carry out functions which conventional devices cannot do. Some Japanese researchers, for example, propose using the snail propulsion mechanism to move an endoscope though a human body (the trachea, intestines, etc), taking advantage of the mucus film that usually covers these ducts. "This mechanism," Javier Rodríguez remarked, "generates a smooth distribution of force instead of supporting itself in concrete points, which would reduce the irritation caused by the movement of an endoscope, in this case."

At the moment, the results published by the UC3M, UCSD and Stanford scientists only deal with the experimental part of study carried out, although they are working on a second article that includes a simple theoretical model which explains these animals' movement. The preliminary results were presented last November at the Annual Conference of The American Physical Society. In addition, these researchers are interested in extending their analysis to situations in which the animal moves up slopes of varying angles.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/03/110307101442.htm

Monitoring the Health of Endangered, Wild Chimpanzees

ScienceDaily (Nov. 29, 2010) — Siv Aina Jensen Leendertz has studied wild chimpanzees living in the tropical rain forest in Ivory Coast at close quarters for a year, and her doctoral thesis describes the health monitoring of this endangered species. Her thesis focuses on the risk of retroviral infection in these chimpanzees due to their hunting of monkeys.

Infectious diseases represent a growing threat to wild chimpanzees and other endangered species of apes. There is therefore a great need to monitor the health of these animals and to map sources of infection in their habitat.

Siv Aina Jensen Leendertz' research has shown a high incidence of the retroviruses simian immunodeficiency virus (SIV), simian T-cell leukemia virus (STLV- type1) and simian foamy virus (SFV) in red colubus monkeys, which are the main prey of chimpanzees. Furthermore, she shows that the chimpanzees become infected with SFV due to their habit of hunting these monkeys.

However, infection by SIV was not detected in the chimpanzees, even though they are highly exposed to this virus. This apparent resistance poses interesting questions about the host-parasite relationship between SIV in red colobus monkeys and wild chimpanzees in their natural habitat. Retroviral infections in primates are precursors of, for instance, the human immunodeficiency virus HIV and Leendertz' doctoral research can therefore contribute towards research into retroviral infections in humans.

The thesis also describes general principles for health monitoring. The health of wild chimpanzees often has to be monitored from a distance and samples for analysis consist for the most part of faeces and urine. Leendertz has therefore developed and refined methods that are particularly apt for this kind of fieldwork.

Her research has been carried out in collaboration with The Robert Koch Institute in Berlin, The Taï Chimpanzee Project at the Department of Primatology at The Max Planck Institute for Evolutionary Anthropology in Leipzig and The Epidemiology and Biostatistics Centre at The Norwegian School of Veterinary Science.

Siv Aina J. Leendertz presented her doctoral thesis on 29^thOctober 2010 at The Norwegian School of Veterinary Science (NVH). The thesis is entitled: "Investigation of wild chimpanzee health and risk of retroviral infection through hunting of red colobus monkeys."

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2010/11/101118084048.htm

Weed-Eating Fish 'Key to Reef Survival'

ScienceDaily (Mar. 11, 2011) — Preserving an intact population of weed-eating fish may be vital to saving the world's coral reefs from being engulfed by weed as human and climate impacts grow.

A new study by researchers at the ARC Centre of Excellence for Coral Reef Studies has found weed-eaters like parrotfish and surgeonfish can only keep coral reefs clear of weed up to a point. After the weeds reach a certain density, they take over entirely and the coral is lost.

For some years researchers have pinned their hopes on the ability of weed-eating fish to keep the weeds at bay while the corals recover following a major setback like bleaching, a dump of sediment from the land, or a violent cyclone.

However the latest work by Dr Andrew Hoey and Professor David Bellwood at CoECRS and James Cook University shows that once the weeds reach a certain density, the fish no longer control them, and prefer to graze less weedy areas. "As a result, the whole system tips from being coral-dominated to weed-dominated," Andrew says.

"And our work shows that it doesn't take a very high density of the fleshy seaweeds like Sargassum to discourage the fish, a patch of weed the size of a back garden could be enough to trigger a change. The fishes show a clear preference for grazing more open areas."

Coral reefs are in decline worldwide, with many of them -- especially in the Asia-Pacific region -- showing 'phase shifts' from being coral-dominated to degraded states dominated by large fleshy seaweeds.

"In countries where people harvest the weed-eating fishes with spearguns, nets and so on, like Fiji, we are seeing a fundamental change in the nature of reefs from coral to weeds," Andrew says. "In Australia where there is much less harvesting of herbivorous fishes, the corals are in better shape and bounce back more readily from setbacks."

The new insight into how well or poorly fish control weeds was gained by transplanting different densities of sargassum weed on a reef off Orpheus Island -- and then using remote video cameras to record what the fish did.

"My wife and I must have watched hours and hours of video of fish feeding on weeds and counting the number of bites they took. It's one of the less glamorous aspects of doing marine science," he admits with a laugh.

In all they counted 28 species of fish taking 70,685 separate bites of weed and removing an average of 10 kilos of weed a day. In the more open areas this was enough to control the weed.

But Andrew also noticed the fish avoided the densely-weeded areas, perhaps for fear of predators lurking in the weed or because mature weeds are less palatable.

"This suggested to us there is a critical weed density, beyond which fish no longer control the weeds and they then take over the reef system. This in turn implies a need to keep the herbivore population as healthy as possible to avoid the reef reaching that tipping point."

Fortunately, in Australia's Great Barrier Reef Marine Park the harvesting of herbivorous fish is limited to a few recreational fishers. However Andy says it is his view that herbivorous fish ought to be carefully protected in order to give the Reef's corals their best chance of making a rapid recovery from impacts like mass bleaching, the mud dumped by recent floods, and cyclones like Yasi.

"We should also bear in mind that this study was conducted in an area of the Great Barrier Reef Marine Park that has been protected from all commercial and recreational fishing for over 20 years and so is likely to have intact fish communities.

"How herbivores respond in areas of the world where they are still heavily fished may be absolutely critical to the survival of large areas of reef in Asia and the Pacific -- and hence to the human communities who depend on them for food, tourism and other resources."

The paper appears in the latest issue of Ecology Letters.

Diego Efrain Quintero Gámez C.I. v.-18.879.989

Asignatura: Electrónica del Estado Sólido

Fuente:http://www.sciencedaily.com/releases/2011/03/110310093802.htm