Tag: Reptiles

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Crocodile tears please thirsty butterflies and bees

The butterfly (Dryas iulia) and the bee (Centris sp.) were most likely seeking scarce minerals and an extra boost of protein. On a beautiful December day in 2013, they found the precious nutrients in the tears of a spectacled caiman (Caiman crocodilus), relaxing on the banks of the Río Puerto Viejo in northeastern Costa Rica. A boat carrying students, photographers, and aquatic ecologist Carlos de la Rosa was passing slowing and quietly by, and caught the moment on film. They watched and photographed in barely suppressed excitement for a quarter of an hour while the caiman basked placidly and the insects fluttered about the corners of its eyes. De la Rosa reported the encounter in a peer-reviewed letter in the May 2014 issue of the Ecological Society of America’s journal Frontiers in Ecology and the Environment. “It was one of those natural history moments that you long to see up close,” said de la Rosa, the director of the La Selva Biological Station for the Organization for Tropical Field Studies in San Pedro, Costa Rica. “But then the question becomes, what’s going on in here? Why are these insects tapping into this resource?” Though bountiful in the ocean, salt is often a rare and valuable resource on land, especially for vegetarians. It is not uncommon to see butterflies sipping mineral-laden water from mud puddles. When minerals are rare in the soil, animals sometimes gather salt and other rare minerals and proteins from sweat, tears, urine, and even blood. De la Rosa had seen butterflies and moths in the Amazon feeding on the tears of turtles and a few caimans. Tear-drinking “lachryphagous” behavior in bees had only recently been observed by biologists. He remembered a 2012 report of a solitary bee sipping the tears of a yellow-spotted river turtle in Ecuador’s Yasuní National Park. But how common is this behavior? Back at the field station, he did a little research. He was surprised to find more evidence of tear-drinking than he expected in the collective online record of wilderness enthusiasts, casual tourists, professional photographers, and scientists. He now thinks the phenomenon may not be as rare as biologists had assumed — just hard to witness.

“I did a Google search for images and I found out that it is quite common! A lot of people have recorded butterflies, and some bees, doing this,” said de la Rosa. A search of the scientific literature produced a detailed study of bees drinking human tears in Thailand, as well as the remembered October 2012 “Trails and Tribulations” story about the Ecuadorian bee and the river turtle by Olivier Dangles and Jérôme Casas in ESA’s Frontiers. This experience reminds us that the world still has many surprises for ecologists, de la Rosa said. There so much still to be studied. De la Rosa is a specialist in the biology of non-biting midges, and a natural historian, with his eyes always open to new discoveries. Scientists at La Selva have discovered hundreds of species of aquatic insects that are still unnamed and undescribed. “I have over 450 undescribed species from Costa Rica in my laboratory. If I did nothing for the rest of my life but collaborate with taxonomists and try to describe those, I would never get done,” he said. De la Rosa’s job as director of La Selva Biological Station brings him an unusual number of serendipitous encounters with wildlife. He lives on site in the lowland rainforest, and he never needs an alarm clock. Howler monkeys wake him every morning. “I learned I have to carry a camera with me 24/7, because you never know what you’re going to find when you’re walking to the office or the dining hall,” he said. One day, he spied a new species of dragonfly on his way to breakfast. It had emerged from its larval form in the small pool of water caught in the cupped leaves of a bromeliad plant. He did a double-take. Dragonflies don’t live on bromeliads. Or do they? “Those are the kinds of things that, you know, you don’t plan for them, you can’t plan for them,” de la Rosa said. There was only one known species of dragonfly in the world that lives in bromeliads. Now there will be two.

http://www.sciencedaily.com/  Science Daily

May 27, 2014

http://www.sciencedaily.com/releases/2014/05/140501075941.htm  Original web page at Science Daily

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Blood test developed for devastating disease of boas, pythons

University of Florida researchers have developed a simple immune-based screening test to identify the presence of a debilitating and usually fatal disease that strikes boas and pythons in captivity as well as those sold to the pet trade worldwide. Known as inclusion body disease, or IBD, the highly infectious disease most commonly affects boa constrictors but pythons and other snake species in the boid family are also occasionally infected with the virus that causes the disease. IBD was first seen in snakes in the late 1970s, said Elliott Jacobson, D.V.M., Ph.D., a professor emeritus of zoological medicine at the UF College of Veterinary Medicine and co-author of a study that appeared in December in PLOS ONE. “We don’t know the prevalence, but we see more of IBD in the United States because there are some 2 million boas being kept as pets in this country,” Jacobson said. “This simple blood test will help determine whether or not an animal has this disease and potentially will help clean up colonies of snakes that will ultimately be disease-free.” Although snakes infected with IBD may display neurological signs, such as head-tilting, chronic regurgitation or disequilibrium, there is also a population of snakes that are subclinical, meaning they are infected but otherwise appear healthy.

“That’s a big problem, because healthy-seeming animals that are affected with IBD are being sold and sent around the world,” he said. “However, they may develop the disease sometime later and may be the source of infection for other snakes.” On Jacobson’s research team at the UF veterinary college were his former graduate student, Li-Wen Chang, B.V.M., Ph.D., the principal investigator in the study, and Jorge Hernandez, D.V.M., Ph.D., a veterinary epidemiologist. To develop the test, the researchers studied a monoclonal antibody produced in response to a unique protein that accumulates in cells of snakes having IBD. They then sequenced the protein in an effort to further understand the nature and cause of the disease. Although the cause of IBD is unclear, the UF team found genetic links of this unique protein are associated with a family of viruses that primarily infect rodents but may infect humans. However, there is no evidence to indicate that the virus that causes IBD can infect people. When Chang joined the study in 2008, she realized the limited availability of snake databases and potential causative agents of the disease presented additional challenges.

“It took us almost a year to finally produce this antibody, and three more years to validate its performance for immuno-based diagnostic tests,” Chang said. University of California-San Francisco researchers identified the Golden Gate virus in 2012 and scientists now consider it to be a potential cause of IBD. UF’s findings supplement that theory, although more studies of disease transmission need to be conducted to confirm the role of Golden Gate virus in the development of IBD, Jacobson said. The research was performed at the UF’s Interdisciplinary Center for Biotechnology Research through the university’s veterinary diagnostic laboratories, where the new test is now offered. It will supplement existing molecular and histological tests, which are more widely available but also more expensive, Jacobson added. In addition, the test’s ease of use and simplicity will offer veterinary practitioners a good first-line diagnostic tool to screen for IBD in snake species that show signs of the disease, or even before these signs occur. We know now that this disease exists in multiple collections and populations,” Jacobson said. “It is important to determine why some snakes are not showing clinical signs of the disease. Could there be another agent operating synergistically? Perhaps one virus needs to be present but another virus needs to be present also, or perhaps the subclinical cases only have one of those agents, not both.” Only strict quarantine of new arrivals to snake populations and the culling of infected snakes, as well as mite control, can mitigate the spread of the disease, according to a 2013 fact sheet prepared by the American Association of Zoo Veterinarians’ infectious disease committee. “It’s a situation of management,” Jacobson said. “You’ll never completely eradicate this disease.”

http://www.sciencedaily.com/ Science Daily
February 18, 2014

http://www.sciencedaily.com/releases/2014/01/140129135002.htm Original web page at Science Daily

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Living on islands makes animals tamer

Most of us have seen pictures and probably YouTube videos of “tame” animals on the Galapagos Islands, the biological paradise that was Charles Darwin’s major source of inspiration as he observed nature and gradually developed his ideas about the importance of natural selection as a mechanism by which populations of organisms would change — evolve genetically — across generations, eventually becoming better and better suited to life in their current conditions. A corollary of Darwin’s revolutionary idea was that organisms would also evolve to lose structures, functions, and behaviors they no longer needed when environmental circumstances changed. He noted that island animals often acted tame, and presumed that they had evolved to be so after coming to inhabit islands that lacked most predators. But more than 150 years later that almost casual observation remained to come under scientific scrutiny. A team of researchers from the University of California, Riverside, Indiana University Purdue University Fort Wayne and George Washington University published a study showing that island lizards are indeed “tame” as compared with their mainland relatives. The researchers were able to approach island lizards more closely than they could approach mainland lizards.

“Our study confirms Darwin’s observations and numerous anecdotal reports of island tameness,” said Theodore Garland, a professor of biology at UC Riverside and one of the paper’s coauthors. “His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists.” Study results appear online in the Proceedings of the Royal Society B. They will appear in the journal in print on Feb. 22. The researchers conducted analyses of relationships of flight initiation distance (the predator-prey distance when the prey starts to flee) to distance to mainland, island area, and occupation of an island for 66 lizard species, taking into account differences in prey size and predator approach speed. They analyzed island and mainland lizard species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas. Their results showed that island tameness exists and that flight initiation distance decreases as distance from mainland increases. In other words, island lizards were more accessible the farther the islands were from the mainland. “The suggestion by Darwin and others that prey on oceanic islands have diminished escape behavior is supported for lizards, which are distributed widely on both continents and islands,” Garland said.

He explained that escape responses are reduced on remote islands, because predators are scarce or absent there, and natural selection under reduced predation favors prey that do not waste time and energy developing and performing needless escape. The research team also found that prey size is an important factor that affects escape behavior. “When prey are very small relative to predators, predators do not attack isolated individual prey,” Garland said. “This results in the absence of fleeing or very short flight initiation distance.” The researchers found no conclusive evidence showing that flight initiation distance is related to island area. They found, however, that predator approach speed is an important factor in lizards. “It is possible that other factors favor island tameness. For example, if food is scarce on islands, the cost of leaving food to flee would favor shortened flight initiation distance,” Garland said.

http://www.sciencedaily.com/  Science Daily February 4, 2014

http://www.sciencedaily.com/releases/2014/01/140110103720.htm  Original web page at Science Daily

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Why lizards may inherit the Earth

Monitor lizards extract oxygen both when they inhale and exhale, perhaps explaining why they are so successful. A lizard captures oxygen from air both when inhaling and exhaling — a feat normally associated with birds. Many scientists believe birds developed the adaptation to cope with the enormous requirements of energy needed to take flight, and the discovery of so-called unidirectional breathing in the savannah monitor lizard raises questions about when and why the trait first evolved. “To go and find a similar air-flow pattern in animals as distantly related to birds as monitor lizards is mind blowing,” says Mathew Wedel, an evolutionary biologist at Western University of Health Sciences in Pomona, California, who was not involved in the discovery. Mammals and many other vertebrates breathe tidally, which means that air travels into the lung to gas-exchanging cavities called alveoli and then back out via the same path. Not birds, which store some of the air they inhale in specialized sacs. When they exhale oxygen is extracted from this air. In 2010, a team led by Colleen Farmer at the University of Utah in Salt Lake City reported that alligators and other crocodile-like animals, too, practice unidirectional breathing. The discovery hinted that dinosaurs might have also breathed the same way. But Wedel says that “it wasn’t super surprising that crocs might be a bit bird like,” because their lungs resemble those of birds.

Now a team led by Farmer and colleague Emma Schachner, an evolutionary biologist at the same institution, report in Nature that savannah monitor lizards (Varanus exanthematicus) employ the same breathing mechanism. Monitor lizards are a group of 70 or so species that includes komodo dragons, the largest lizards on Earth. On the surface, their lungs look like they would employ tidal breathing, Schachner says. “When you pull the lungs out it just looks like a bag with chambers. It doesn’t look anything like the bird lung.” But computed tomography (CT) scans revealed a large chamber, with a series of up to 11 brachial tubes branching off in parallel and linked to one another via perforations — a set-up that could enable one-way flow. To test this possibility, the researchers dissected the lizards’ lungs and filled them with water containing suspended spheres, to better track how the water flowed. The water flowed tidally through the large chamber, but unidirectionally in the smaller brachial tubes. Schachner’s team confirmed that air followed these patterns during breathing as well by implanting sensors in the lungs of five lizards and measuring air flow as the animals breathed. The discovery of unidirectional breathing in monitor lizards could either mean that the trait evolved in the common ancestor of birds, crocodiles and lizards — an animal that lived roughly 270 million years ago and resembled an iguana — or that the feature evolved independently in each evolutionary branch, Schachner says. To determine which scenario is correct, Schachner’s team plans to study the breathing patterns of still more reptiles, such as iguanas, geckoes and bearded dragons.

Her team’s study also raises questions about why unidirectional breathing developed in the first place. Farmer has hypothesized that it helps animals obtain oxygen while they’re holding their breath because unidirectional breathing allows more oxygen to be extracted from air — something that many lizards do when startled. Crocodiles can hold their breath for upwards of 20 minutes, and ancient marine reptiles may have found the trait useful for long dives, Schachner says. The trait could have also been an adaptation to lower oxygen levels on Earth, she says. During the early Triassic era 250 million years ago, oxygen made up 12% of air, compared to 21% today. “It might explain something about why monitor lizards are so successful,” says Wedel. These lizards get more oxygen from air than any other reptile and they live in environments ranging from parched desert to tropical forest. “Who knows when the next asteroid hits, maybe monitor lizards will inherit the Earth,” Wedel says. Schachner believes that no one found unidirectional breathing in lizards because the trait is so hard to measure, especially in wild animals. Wedel hopes the discovery by Schachner’s team will inspire others to eschew conventional wisdom. “Now everybody who wakes up tomorrow and reads this paper will look at familiar organisms with a bit of curiosity and mistrust.” Measurements in live lizards, as well as in the lungs of dissected animals, showed that air flows out of the lungs through special sacs, rather than backtracking on the path it took on its way in.

Nature
January 7, 2014

Original web page at Nature

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Snakes control blood flow to aid vision

A new study from the University of Waterloo shows that snakes can optimize their vision by controlling the blood flow in their eyes when they perceive a threat. Kevin van Doorn, PhD, and Professor Jacob Sivak, from the Faculty of Science, discovered that the coachwhip snake’s visual blood flow patterns change depending on what’s in its environment. The findings appear in the most recent issue of the Journal of Experimental Biology. “Each species’ perception of the world is unique due to differences in sensory systems,” said van Doorn, from the School of Optometry & Vision Science. Instead of eyelids, snakes have a clear scale called a spectacle. It works like a window, covering and protecting their eyes. Spectacles are the result of eyelids that fuse together and become transparent during embryonic development. When van Doorn was examining a different part of the eye, the illumination from his instrument detected something unusual. Surprisingly, these spectacles contained a network of blood vessels, much like a blind on a window. To see if this feature obscured the snake’s vision, van Doorn examined if the pattern of blood flow changed under different conditions. When the snake was resting, the blood vessels in the spectacle constricted and dilated in a regular cycle. This rhythmic pattern repeated several times over the span of several minutes. But when researchers presented the snake with stimuli it perceived as threatening, the fight-or-flight response changed the spectacle’s blood flow pattern. The blood vessel constricted, reducing blood flow for longer periods than at rest, up to several minutes. The absence of blood cells within the vasculature guarantees the best possible visual capacity in times of greatest need.

“This work shows that the blood flow pattern in the snake spectacle is not static but rather dynamic,” said van Doorn. Next, the research team examined the blood flow pattern of the snake spectacle when the snake shed its skin. They found a third pattern. During this time, the vessels remained dilated and the blood flow stayed strong and continuous, unlike the cyclical pattern seen during resting. Together, these experiments show the relationship between environmental stimuli and vision, as well as highlight the interesting and complex effect blood flow patterns have on visual clarity. Future research will investigate the mechanism underlying this relationship. “This research is the perfect example of how a fortuitous discovery can redefine our understanding of the world around us,” said van Doorn.

Science Daily
November 26, 2013

Original web page at Science Daily

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New approach to treating venomous snakebites could reduce global fatalities

A team of researchers led by Dr. Matt Lewin of the California Academy of Sciences, in collaboration with the Department of Anesthesia at the University of California, San Francisco, has pioneered a novel approach to treating venomous snakebites — administering antiparalytics topically via a nasal spray. This new, needle-free treatment may dramatically reduce the number of global snakebite fatalities, currently estimated to be as high as 125,000 per year. The team demonstrated the success of the new treatment during a recent experiment conducted at UCSF; their results have been published in the medical journal Clinical Case Reports. Snakebite is one of the most neglected of tropical diseases — the number of fatalities is comparable to that of AIDS in some developing countries. It has been estimated that 75% of snakebite victims who die do so before they ever reach the hospital, predominantly because there is no easy way to treat them in the field. Antivenoms provide an imperfect solution for a number of reasons — even if the snake has been identified and the corresponding antivenom exists, venomous bites often occur in remote locations far from population centers, and antivenoms are expensive, require refrigeration, and demand significant expertise to administer and manage.

“In addition to being an occupational hazard for field scientists, snakebite is a leading cause of accidental death in the developing world, especially among otherwise healthy young people,” says Lewin, the Director of the Center for Exploration and Travel Health at the California Academy of Sciences. “We are trying to change the way people think about this ancient scourge and persistent modern tragedy by developing an inexpensive, heat-stable, easy-to-use treatment that will at least buy people enough time to get to the hospital for further treatment.” In his role as Director of the Academy’s Center for Exploration and Travel Health, Lewin prepares field medicine kits for the museum’s scientific expeditions around the world and often accompanies scientists as the expedition doctor. In 2011, Lewin put together snakebite treatment kits for the Academy’s Hearst Philippine Biodiversity Expedition, which would have required scientists to inject themselves if they needed treatment. When he saw their apprehension about the protocol, Lewin began to wonder if there might be an easier way to treat snakebite in the field. In some fatal snakebites, victims are paralyzed by the snake’s neurotoxins, resulting in death by respiratory failure. A group of common drugs called anticholinesterases have been used for decades to reverse chemically-induced paralysis in operating rooms and, in intravenous form, to treat snakebite when antivenoms are not available or not effective. However, it is difficult to administer intravenous drugs to treat snakebite outside of a hospital, so Lewin began to explore the idea of a different delivery vehicle for these antiparalytics — a nasal spray.

In early April of 2013, Lewin and a team of anesthesiologists, led by Dr. Philip Bickler at UCSF Medical Center, designed and completed a complex experiment that took place at the medical center. During the experiment, a healthy human volunteer was paralyzed, while awake, using a toxin that mimics that of cobras and other snakes that disable their victims by paralysis. The experimental paralysis mimicked the effects of neurotoxic snakebite, progressing from eye muscle weakness all the way to respiratory difficulty, in the same order as is usually seen in envenomation. The team then administered the nasal spray and within 20 minutes the patient had recovered. The results of this experiment were published online in the medical journal, Clinical Case Reports. Later in April, Lewin delivered one of the keynote addresses, titled “How Expeditions Drive Clinical Research,” at the American Society for Clinical Investigation/Association of American Physicians joint meeting in Chicago, during which he talked about this experiment and its origins. As a result, he met Dr. Stephen Samuel, an Indian physician and scientist from Trinity College Dublin who was interested in collaborating in India, where an estimated 1 million people are bitten by snakes every year, resulting in tens of thousands of deaths. Lewin flew to India to help Samuel set up treatment protocols at a rural hospital in Krishnagiri.

In late June, Samuel, Dr. CS Soundara Raj and colleagues at TCR Multispecialty Hospital in Krishnagiri, Tamil Nadu, India treated a snakebite victim using this method. The patient was suffering from persistent facial paralysis from a krait bite, despite having undergone a full course of antivenom treatment. Upon treatment with the antiparalytic nasal spray, the facial paralysis was reversed within 30 minutes. Two weeks after being treated, the patient reported having returned to her daily activities. Lewin and his colleagues in the United States are now conducting additional studies on mice to develop new methods and drug combinations, as there are many combinations of anticholinesterases and anticholinergic agents that could be tried to make delivery of the drugs more predictable through the mucous membranes in the nose or eyes. He is also working to set up future clinical studies with Samuel, Soundara Raj and their colleagues in India. While there is much work in front of them, they have already taken important steps toward addressing a major global need. The entire team has embraced the TCR Multispeciality Hospital motto that “no patient should die from snakebite.”

Science Daily
August 20, 2013

Original web page at Science Daily

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The origin of the turtle shell: Mystery solved

A team of researchers from Japan has finally solved the riddle of the origin of the turtle shell. By observing the development of different animal species and confirming their results with fossil analysis and genomic data, researchers from the RIKEN Center for Developmental Biology show that the shell on the turtle’s back derives only from its ancestors’ ribcage and not from a combination of internal and external bone structures as is often thought. Their study is published today in the journal Nature Communications. The skeleton of vertebrates has evolved throughout history from two different structures, called the endo- and exoskeleton. In the human skeleton, the backbone and bones of the limbs evolved from the endoskeleton, whereas most of the skull elements derive from the exoskeleton. Fish scales and the alligator’s bony skin nodules are other examples of exoskeletons. The origin of the shell on the turtle’s back, or carapace, was unclear until now because it comprises parts of obvious endoskeletal origin and others that look more like the exoskeleton of alligators and fish. The outer part of the turtle carapace was thought to have derived from exoskeletal bones, while the internal part has been shown to originate from ribs and vertebrae and to be connected to the internal skeleton of the animal. However, no direct evidence has been obtained to show that the bony structures developing outside the ribcage in turtles derived from the exoskeleton.

To investigate whether the turtle carapace evolved with any contribution from its ancestors’ exoskeleton, Dr. Tatsuya Hirasawa and his team carefully observed developing embryos of Chinese soft-shell turtles, chickens and alligators. In their analysis, they compared the development of the turtle carapace, the chick’s ribs and the alligator’s bony skin nodules. The researchers found that the major part of the turtle’s carapace is made from hypertrophied ribs and vertebrae and therefore derives solely from endoskeletal tissue. This finding was confirmed by the observation of fossils of the ancient turtle Odontochelys and the ancient reptile Sinosaurosphargis, that both exhibit shells of endoskeletal origin. Odontochelys has a rigid shell instead of a flexible ribcage. And Sinosaurosphargis possesses an endoskeletal shell similar to the turtle’s under, and separate from, a layer of exoskeletal bones. Taken together these results show that the turtle carapace has evolved independently from the exoskeleton. This scenario is also consistent with the recent phylogenetic analyses based on genomic data that have placed turtles in the same group as birds, crocodiles and marine reptiles like Sinosaurophargis, contradicting recent studies based solely on fossil record. “Recently, genomic analyses had given us evidence that turtles evolved from reptiles closely related to alligators and dinosaurs, not from primitive reptiles as once thought. Our findings match the evolutionary history revealed by the genomic analyses, and we are about to unravel the mystery of when and how the turtle shell evolved,” explains Dr. Tatsuya Hirasawa who led the research. “Our aim is to one day understand it as well as we understand the evolution of birds from dinosaurs,” he concludes.

Science Daily
July 23, 2013

Original web page at Science Daily

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Multi-sensory organs in crocodylian skin sensitive to touch, heat, cold, environment

Previously misunderstood multi-sensory organs in the skin of crocodylians are sensitive to touch, heat, cold, and the chemicals in their environment, finds research in BioMed Central’s open access journal EvoDevo. These sensors have no equivalent in any other vertebrate. Crocodylians, the group that includes crocodiles, gharials, alligators and caimans, have particularly tough epidermal scales consisting of keratin and bony plates for added protection. On the head, these scales are unusual because they result from cracking of the hardened skin, rather than their shape being genetically determined. The scales have sensors known as dome pressure receptors (DPR) or Integumentary Sensory organs (ISOs) with fingertip sensitivity. Researchers from the University of Geneva investigated ISOs in Nile crocodiles (Crocodylus niloticus) and the spectacled caiman (Caiman crocodilus) to find out exactly what these micro-organs can ‘see and how they are formed.’. ISOs appear on the head of the developing caiman and crocodile embryos before the skin starts to crack and form scales. Nile crocodiles additionally develop ISOs all over their body. In both animals the ISOs contain mechano-, thermo-, and chemo-sensory receptor-channels giving them the combined ability to detect touch, heat/cold and chemical stimuli, but not salinity. Nile crocodiles have separate salt glands on their tongues which help regulate osmolarity in hyper-saline environments.

This means that they can detect surface pressure waves allowing them to quickly find prey even in the dark. The thermal sensitivity help them to maintain body temperature by moving between basking in the sun and cooling in the water, and the chemical sensors may help them to detect suitable habitats. Prof Michel Milinkovitch, who led this study explained, “ISO sensors are remarkable because not only are they able to detect many different types of physical and chemical stimuli, but because there is no equivalent in any other vertebrates. It is this transformation of a diffuse sensory system, such as we have in our own skin, into ISO which has allowed crocodilians to evolve a highly armored yet very sensitive skin.”

Science Daily
July 23, 2013

Original web page at Science Daily

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Genetic factors shaping salamander tails determine regeneration pace

Salamanders’ capacity to regrow lost limbs may seem infinite when compared with that of humans, but even amongst salamanders, some species regenerate body parts very slowly, while others lose this capacity as they age. Now, researchers have found that salamanders’ capacity to regrow a cut tail depends on several small regions of DNA in their genome that impact how wide the tail grows. The results are published July 3 in the open access journal PLOS ONE by Randal Voss and colleagues from the University of Kentucky. In the study, approximately 66-68% of the differences in regeneration among animals correlated with the width of their tails at the site of amputation. Molecular analysis revealed several genetic markers that had small, additive effects on the width of the tail, and thus contributed to the animals’ regenerative capacity. Voss adds, “Our results show that regenerative outgrowth is regulated locally by factors at the site of injury. Although we do not know the nature of these local factors yet, our findings suggest they are distributed quantitatively along the length of the tail.”

Science Daily
July 23, 2013

Original web page at Science Daily

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Turtle genome analysis sheds light on turtle ancestry and shell evolution

From which ancestors have turtles evolved? How did they get their shell? New data provided by the Joint International Turtle Genome Consortium, led by researchers from RIKEN in Japan, BGI in China, and the Wellcome Trust Sanger Institute in the UK provides evidence that turtles are not primitive reptiles but belong to a sister group of birds and crocodiles. The work also sheds light on the evolution of the turtle’s intriguing morphology and reveals that the turtle’s shell evolved by recruiting genetic information encoding for the limbs. Turtles are often described as evolutionary monsters, with a unique body plan and a shell that is considered to be one of the most intriguing structures in the animal kingdom. “Turtles are interesting because they offer an exceptional case to understand the big evolutionary changes that occurred in vertebrate history,” explains Dr. Naoki Irie, from the RIKEN Center for Developmental Biology, who led the study. Using next-generation DNA sequencers, the researchers from 9 international institutions have decoded the genome of the green sea turtle and Chinese soft-shell turtle and studied the expression of genetic information in the developing turtle. Their results published in Nature Genetics show that turtles are not primitive reptiles as previously thought, but are related to the group comprising birds and crocodilians, which also includes extinct dinosaurs. Based on genomic information, the researchers predict that turtles must have split from this group around 250 million years ago, during one of the largest extinction events ever to take place on this planet.

“We expect that this research will motivate further work to elucidate the possible causal connection between these events,” says Dr. Irie. The study also reveals that despite their unique anatomy, turtles follow the basic embryonic pattern during development. Rather than developing directly into a turtle-specific body shape with a shell, they first establish the vertebrates’ basic body plan and then enter a turtle-specific development phase. During this late specialization phase, the group found traces of limb-related gene expression in the embryonic shell, which indicates that the turtle shell evolved by recruiting part of the genetic program used for the limbs. “The work not only provides insight into how turtles evolved, but also gives hints as to how the vertebrate developmental programs can be changed to produce major evolutionary novelties.” explains Dr. Irie. Another unexpected finding of the study was that turtles possess a large number of olfactory receptors and must therefore have the ability to smell a wide variety of substances. The researchers identified more than 1000 olfactory receptors in the soft-shell turtle, which is one of the largest numbers ever to be found in a non-mammalian vertebrate.

Science Daily
May 14, 2013

Original web page at Science Daily

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An emergency hatch for baby lizards

Talk about hatching an escape plan. Unborn lizards can erupt from their eggs days early if vibrations hint at a threat from a hungry predator, new research shows. The premature hatchlings literally “hit the ground running—they hatch and launch into a sprint at the same time,” says behavioral ecologist J. Sean Doody, who is now at the University of Tennessee, Knoxville. Researchers have long known that an array of factors can affect when eggs laid by all kinds of creatures finally hatch. Some fish eggs, for instance, hatch only at certain light or temperature levels, while fungal infections can prompt lizard eggs to crack open early. Chemical or physical signals sent by predators can prompt some frog embryos to speed up their breakouts, while others delay hatching in a bid to stay safe. In lizards and other reptiles, however, such “environmentally cued hatching” strategies aren’t well understood. That curtain began to lift a bit a few years ago, when Doody and student Philip Paull of Monash University in Australia began studying a population of delicate skinks (Lampropholis delicata) in a park near Sydney. There, the common lizards laid white, leathery eggs the size of aspirin capsules in rock crevices. The eggs generally incubate for 4 to 8 weeks before hatching, but Doody got a surprise in 2010, when he and Paull were plucking eggs from the crevices to make measurements. “They started hatching in our hands, at just a touch—it shocked us,” Doody recalls. “It turned into a real mess, they were just hatching everywhere.”

Soon, Doody launched a more systematic study of the phenomenon. In two lab experiments, the researchers compared the hatching dates for skink eggs exposed to vibrations with those of eggs that weren’t shaken. And in three field experiments, they poked and prodded eggs with a small stick, or squeezed them gently with their fingers to measure how sensitive the eggs were to the kinds of disturbances a predator, such as a snake, might cause. They also measured how far the premature hatchlings could dash. Delicate skinks aren’t the only reptiles that hatch in response to an environmental cue; here, a lizard known as a Tegu (in the genus Tupinambis) breaks out after a bit of “egg tickling.” Together, the experiments offer “compelling evidence” that embryonic skinks can detect and respond to predator-like signals, the authors write in the March 2013 issue of Copeia. The vibrated laboratory eggs, for instance, hatched an average of 3.4 days earlier than the unshaken controls. And in the field, the hatching of disturbed eggs was “explosive,” they note; the newborns often broke out of the egg and then sprinted more than one-half meter to nearby cover in just a few seconds. “It’s amazing,” Doody says. “It can be hard to see because it happens so quick.”

There may be a downside to such emergency exits, however. “Early hatching skinks were significantly smaller and left behind larger residual yolks in their eggs than spontaneously hatching skinks,” the authors write, potentially reducing the chances of survival. Still, it is probably better to be stunted than eaten, Doody says. The skink study is “very cool” and “very clear—we really don’t have well documented examples like this in reptiles,” says biologist Karen Warkentin of Boston University. In the 1990s, she discovered a tropical frog that can hatch early in response to vibrations from predators, and has since become a prominent scholar of hatching cues. There’s growing evidence, she says, that embryos are much more sensitive to the world outside their eggs than once believed. “This is not just happening in delicate skinks—I’m thinking that environmentally cued hatching is very widespread, in many groups.” But exactly how embryos make the decision to stay put or bail out, she says, “is something we’re still trying to understand.”

Science Daily
April 29, 2013

Original web page at ScienceNow

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New measurement of crocodilian nerves could help scientists understand ancient animals

Crocodilians have nerves on their faces that are so sensitive, they can detect a change in a pond when a single drop hits the water surface several feet away. Alligators and crocodiles use these “invisible whiskers” to detect prey when hunting. Now, a new study from the University of Missouri has measured the nerves responsible for this function, which will help biologists understand how today’s animals, as well as dinosaurs and crocodiles that lived millions of years ago, interact with the environment around them. The trigeminal nerve is the nerve responsible for detection of sensations of the face,” said Casey Holliday, assistant professor of anatomy in the MU School of Medicine. “While we’ve known about these sensitive nerves in crocodiles, we’ve never measured the size of the nerve bundle, or ganglion, in their skulls, until now. When compared to humans, this trigeminal nerve in crocodiles is huge.” The key to this measurement is a specific hole in the skull. The trigeminal nerve is rooted inside the skull, but must travel through a large hole before it branches out to reach the crocodile’s skin on its face. By examining how the skull size, brain size and ganglion size relate to each other, scientists can estimate how sensitive the face is. Eventually, Holliday hopes to measure this nerve in other ancient and contemporary species to learn more about animal behavior.

“Currently, we rely on alligators, crocodiles and birds to provide us with information about how ancient reptiles, such as pre-historic crocodiles and dinosaurs, functioned,” said Holliday, who co-authored the study with doctoral student Ian George. “However, the first thing we have to do is to understand how the living animals function.” When comparing the size of the hole for the trigeminal nerve found in alligators to that of certain dinosaurs, George says that the hole in the much-larger dinosaur skull is very similar in size or even smaller, which could give scientists more information about how well dinosaurs could detect small sensations on the face. From there, the scientists can start to trace the evolution of this nerve and the mechanism used by crocodiles. “Some species of ancient crocodiles lived on land and they probably wouldn’t have a use for a sensitive face that can detect disturbances in the water,” George said. “So our next step is to trace back and determine when the nerve got bigger and see how that might have paralleled the animals’ ecology.” Holliday says that this information will aid future research, including when his team will examine skulls of ancient crocodiles. Understanding this nerve and its functions could also lead to better understanding of the anatomical basis for behavior in many living animals, including fish, electric eels, platypi and humans. “The same way that we would look at the size of the visual cortex in the brain to understand how well an animal might see, we can now look at the trigeminal nerve in animals to determine how sensitive their skin on their faces is,” Holliday said.

Science Daily
April 29, 2013

Original web page at Science Daily

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Getting under the shell of the turtle genome

The genome of the western painted turtle (Chrysemys picta bellii) one of the most widespread, abundant and well-studied turtles in the world, is published this week in Genome Biology. The data show that, like turtles themselves, the rate of genome evolution is extremely slow; turtle genomes evolve at a rate that is about a third that of the human genome and a fifth that of the python, the fastest lineage analyzed. As a group, turtles are long-lived, can withstand low temperatures including freezing solid, can survive for long periods with no oxygen, and their sex is usually determined by the temperature at which their eggs develop rather than genetically. The painted turtle is most anoxia-tolerant vertebrate and can survive up to four months under water depending on the temperature. Turtles and tortoises are also the most endangered major vertebrate group on earth, with half of all species listed as endangered. This is the first turtle, and only the second non-avian reptile genome to be sequenced, and the analysis reveals some interesting insights about these bizarre features and adaptations, many of which are only known in turtles.

The western painted turtle is a freshwater species, and the most widespread turtle native to North America. Bradley Shaffer and colleagues place the western painted turtle genome into a comparative evolutionary context, showing that turtles are more closely related to birds and crocodilians than to any other vertebrates. They also find 19 genes in the brain and 23 in the heart whose expression is increased in low oxygen conditions — including one whose expression changes nearly 130 fold. Further experiments on turtle hatchlings indicated that common microRNA was involved in freeze tolerance adaptation. This work consistently indicates that common vertebrate regulatory networks, some of which have analogs in human diseases, are often involved in the western painted turtle achieving its extraordinary physiological capacities. The authors argue that the painted turtle may offer important insights into the management of a number of human health disorders, particularly those involved with anoxia and hypothermia.

Science Daily
April 16, 2013

Original web page at Science Daily

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DNA reveals mating patterns of critically endangered sea turtle

New University of East Anglia research into the mating habits of a critically endangered sea turtle will help conservationists understand more about its mating patterns. Research published February 3 in Molecular Ecology shows that female hawksbill turtles mate at the beginning of the season and store sperm for up to 75 days to use when laying multiple nests on the beach. It also reveals that these turtles are mainly monogamous and don’t tend to re-mate during the season. Because the turtles live underwater, and often far out to sea, little has been understood about their breeding habits until now. The breakthrough was made by studying DNA samples taken from turtles on Cousine Island in the Seychelles. The hawksbill turtle (Eretmochelys imbricata) was listed as critically endangered in 1996 by the International Union for Conservation of Nature (IUCN), largely due to a dramatic reduction in their numbers driven by the international trade in tortoiseshell as a decorative material — an activity which was banned in the same year. The Seychelles are home to the largest remaining population of hawksbill turtles in the western Indian Ocean. Cousine Island is an important nesting ground for the hawksbill and has a long running turtle monitoring program. It is hoped that the research will help focus conservation efforts in future.

Lead researcher Dr David Richardson, from UEA’s school of Biological Sciences, said: “We now know much more about the mating system of this critically endangered species. By looking at DNA samples from female turtles and their offspring, we can identify and count the number of breeding males involved. This would otherwise be impossible from observation alone because they live and mate in the water, often far out to sea. “We now know that female turtles mate at the beginning of the season — probably before migrating to the nesting beaches. They then store sperm from that mating to use over the next couple of months when laying multiple nests. “Our research also shows that, unlike in many other species, the females normally mate with just one male, they rarely re-mate within a season and they do not seem to be selecting specific ‘better quality’ males to mate with. “Understanding more about when and where they are mating is important because it will help conservationists target areas to focus their efforts on. “It also lets us calculate how many different males contribute to the next generation of turtles, as well as giving an idea of how many adult males are out there, which we never see because they live out in the ocean. “Perhaps most importantly, it gives us a measure of how genetically viable the population is — despite all the hunting of this beautiful and enigmatic species over the last 100 years.

“The good news is that each female is pairing up with a different male — which suggests that there are plenty of males out there. This may be why we still see high levels of genetic variation in the population, which is crucial for its long term survival .This endangered species does seem to be doing well in the Seychelles at least.” Lead author Karl Phillips, a PhD student in UEA’s school of Biological Sciences, added: “This is an excellent example of how studying DNA can reveal previously unknown aspects of species’ life histories.”

Science Daily
February 19, 2013

Original web page at Science Daily

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Extreme ‘housework’ cuts the life span of female Komodo Dragons

An international team of researchers has found that female Komodo Dragons live half as long as males on average, seemingly due to their physically demanding ‘housework’ such as building huge nests and guarding eggs for up to six months. The results provide important information on the endangered lizards’ growth rate, lifestyle and population differences, which may help plan conservation efforts. The Komodo dragon is the world’s largest lizard. Their formidable body size enables them to serve as top predators killing water buffalo, deer and wild boar and they have also been known to kill humans. A research team which included scientists from the University of Melbourne, Australia, Indonesia and Italy studied 400 individual Komodo Dragons for 10 years in eastern Indonesia, their only native habitat. The team then produced a model of the Dragon’s growth rate, with results published in the current issue of international journal PLoS One. Males live to around 60 years of age, reaching an average 160 centimetres in length and 65 kg at adulthood. However their female counterparts were estimated to live an average of 32 years and reach only 120 cm in length, and 22kg.

Dr Tim Jessop from the Department of Zoology at the University of Melbourne was a co-author on the study and said that the team were surprised by the significantly shorter lifespan of the female Komodo Dragon. “The sex-based difference in size appears to be linked to the enormous amounts of energy females invest in producing eggs, building and guarding their nests. The process can take up to six months during which they essentially fast, losing a lot of weight and body condition, he said. “Males and females start off at the same size until they reach sexual maturity at around seven years of age. From then on females grow slower, shorter and die younger.” The research team was keen to understand the growth rate of the Komodo Dragons as this critical process can indicate how the species prioritises its energy use in lifestyle and reproductive strategies. The results suggest that females have high energy ‘costs’ for reproduction resulting in their smaller size, whereas to reproduce successfully, males must keep increasing in size. The results could have dramatic consequences for the endangered species as early female deaths may be exacerbating competition between males over the remaining females, possibly explaining why males are the world’s largest lizards. “These results may seem odd to humans when the life span between Australian men and women differ by five years. But each species has different strategies to pass on their genes. For example humans invest a lot of energy in few children as raising them is very energy intensive, whereas insects will have hundreds of offspring with no input into their rearing.”

Science Daily
October 30, 2012

Original web page at Science Daily

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Understanding how salamanders grow new limbs provides insights into potential of human regenerative medicine

Based on two new studies by researchers at the Salk Institute for Biological Studies, regeneration of a new limb or organ in a human will be much more difficult than the mad scientist and supervillain, Dr. Curt Connors, made it seem in the Amazing Spider-man comics and films. As those who saw the recent “The Amazing Spiderman” movie will know, Dr. Connors injected himself with a serum made from lizard DNA to successfully regrow his missing lower right arm — that is, before the formula transformed him into a reptilian humanoid. But by studying a real lizard-like amphibian, which can regenerate missing limbs, the Salk researchers discovered that it isn’t enough to activate genes that kick start the regenerative process. In fact, one of the first steps is to halt the activity of so-called jumping genes. In research published August 23 in Development, Growth & Differentiation, and July 27 in Developmental Biology, the researchers show that in the Mexican axolotl, jumping genes have to be shackled or they might move around in the genomes of cells in the tissue destined to become a new limb, and disrupt the process of regeneration.

They found that two proteins, piwi-like 1 (PL1) and piwi-like 2 (PL2), perform the job of quieting down jumping genes in this immature tadpole-like form of a salamander, known as an axolotl — a creature whose name means water monster and who can regenerate everything from parts of its brain to eyes, spinal cord, and tail. “What our work suggests is that jumping genes would be an issue in any situation where you wanted to turn on regeneration,” says the studies’ senior author, Tony Hunter, a professor in the Molecular and Cell Biology Laboratory and director of the Salk Institute Cancer Center. “As complex as it already seems, it might seem a hopeless task to try to regenerate a limb or body part in humans, especially since we don’t know if humans even have all the genes necessary for regeneration,” says Hunter. “For this reason, it is important to understand how regeneration works at a molecular level in a vertebrate that can regenerate as a first step. What we learn may eventually lead to new methods for treating human conditions, such as wound healing and regeneration of simple tissues.”

The research team, which included investigators from other universities around the country, sought to characterize the transcriptional fingerprint emerging from the early phase of axolotl regeneration. They specifically looked at the blastema, a structure that forms at a limb’s stump. There the scientists found transcriptional activation of some genes, usually found only in germline cells, which indicated cellular reprogramming of differentiated cells into a germline state. In the Development, Growth & Differentiation study, the research team, led by Wei Zhu, then a postdoctoral researcher in Hunter’s laboratory, focused on one of these genes, the long interspersed nucleotide element-1 (LINE-1) retrotransposon. LINE-1 elements are jumping genes that arose early in vertebrate evolution. They are pieces of DNA that copy themselves in two stages — first from DNA to RNA by transcription, and then from RNA to DNA by reverse transcription. These DNA copies can then insert themselves into the cell’s genome at new positions. A few years ago, Fred Gage, professor in the Laboratory of Genetics at the Salk Institute, discovered that LINE-1 elements move around during neuronal development, and may program the identities of individual neurons. “Most of these copies appear to be ‘junk’ DNA, because they are defective and can never jump again,” says Hunter. But all mammals, including humans, still have active LINE-1 genes, and the salamander, whose genome is 10 times larger than a human’s, contains many more.

Active LINE-1 retrotransposons can keep jumping, and that was true in the developing blastema where LINE-1 jumping was dramatically switched on. But in the researchers’ companion study, in Developmental Biology, they found that PL1 and PL2 switch off transcription of repeat elements, such as LINE-1. “The idea is that in the development of germ cells, you definitely don’t want these things hopping around,” says Hunter. “The mobilization of these jumping genes can introduce harmful genomic rearrangements or even abort the regeneration process.” In fact, when the researchers inhibited PL1 and PL2 activity in the axolotl limb blastema, regeneration was significantly slowed down. “The need to switch on one set of genes to stop other genes from jumping just illustrates how amazingly difficult it would be to regenerate something as complex as a limb in humans,” Hunter says. “But that doesn’t mean we won’t learn valuable lessons about how to treat degenerative diseases.”

Science Daily
October 16, 2012

Original web page at Science Daily

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Evolutionary history of lizards and snakes reconstructed using massive molecular dataset

A new study, published online in Biology Letters on Sept. 19, has utilized a massive molecular dataset to reconstruct the evolutionary history of lizards and snakes. The results reveal a surprising finding about the evolution of snakes: that most snakes we see living on the surface today arose from ancestors that lived underground. The article, entitled “Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species,” describes research led by John J. Wiens, an Associate Professor in the Department of Ecology and Evolution at Stony Brook University. The study was based on 44 genes and 161 species of lizards and snakes, one of the largest genetic datasets assembled for reptiles. The results show that almost all groups of snakes arose from within a bizarre group of burrowing blind snakes called scolecophidians. This finding implies that snakes ancestrally lived underground, and that the thousands of snake species living today on the surface evolved from these subterranean ancestors. The authors suggest that there are still traces of this subterranean ancestry in the anatomy of surface-dwelling snakes. “For example, no matter where they live, snakes have an elongate body and a relatively short tail, and outside of snakes, this body shape is only found in lizards that live underground,” said Professor Wiens. “Snakes have kept this same basic body shape as they have evolved to invade nearly every habitat on the planet — from rainforest canopies to deserts and even the oceans.”

Science Daily
October 2, 2012

Original web page at Science Daily

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Sick snakes lead scientists to virus discovery

By investigating the cause of a fatal snake disease, scientists have found a virus that shares characteristics with two known virus families that can cause fatal hemorrhagic fevers in humans. Filoviruses and arenaviruses are genetically distinct and have previously been found only in mammals, but the newly identified virus hints at an evolutionary relationship between them. Howard Hughes Medical Institute investigator Joseph DeRisi and his colleagues published their findings, which they say underscore the genetic diversity of infectious viruses, in the open-access online journal mBio on August 14, 2012. “We know very little about the natural ecology of many of the viruses that might impact human health.” DeRisi, who studies parasitic and viral infections at the University of California, San Francisco, notes that almost all recent diseases in humans have origins in viruses from animal populations. “But we know very little about the natural ecology of many of the viruses that might impact human health,” DeRisi says. “One of the main goals of my lab is to investigate the source of infectious disease where the etiology—the cause—is not known.”

That’s why when DeRisi found a letter on his desk asking him to help uncover the cause of an infectious disease in snakes, he took a second look. The letter was from a concerned snake-owner who was worried about her boa constrictor, Larry. Larry’s veterinarian had heard of DeRisi’s research on bird viruses and suggested his owner see if she could interest him in inclusion body disease. The highly contagious disease is well-known at zoos and by exotic pet owners for the brain damage, behavioral changes, and wasting that it causes, for which there is no treatment. “There was a veterinarian’s phone number at the bottom of the letter,” recalls DeRisi. “I called the vet, Chris Sanders, who said, ‘this is a probably the most important disease we’re worried about in domestic snakes in zoos and aquariums.” DeRisi learned that the tell-tale sign of the disease is the accumulation of proteins inside the snake’s cells. “Every cell in almost every tissue of the body is basically filling up with junk,” DeRisi says. “The origin of that junk was thought to be an unidentified virus replicating in the cells and putting itself together in these giant protein aggregates.”

When DeRisi decided to search for that virus, the California Academy of Sciences had recently reported an outbreak of inclusion body disease in their boa constrictors. Collaborating with Freeland Dunker, a veterinarian at the museum, DeRisi obtained samples of snake tissue from five boa constrictors that had suffered from the disease. To identify the virus, Mark Stenglein, a postdoctoral researcher in the DeRisi lab, with the help of Jessica Franco, an undergraduate working in DeRisi’s lab through HHMI’s Exceptional Research Opportunity Program, used high-throughput sequencing methods to rapidly sequence all of the RNA in the cells of the sick snakes. “In an infected cell, most of the RNA is from the snake,” says Stenglein. “About 95 percent of the sequences are snake RNA—but what is left over is viral RNA. That’s what we’re looking for.” The trick was to separate the snake RNA from the virus RNA by comparing sequences from the infected snake to the RNA sequences of a healthy snake. “Here we had a bit of a problem,” DeRisi explains. “No boa constrictor genome had been sequenced.” Fortuitously, DeRisi was in the process of organizing a contest, initiated by HHMI investigator David Haussler, in which teams compete to develop a computer program that assembles genetic sequences into a previously unknown animal genome. DeRisi suggested the “Assemblathon” competitors try assembling the boa constrictor genome. By the end of the competition, Stenglein had exactly what he needed to identify which of the genetic sequences from the diseased snakes were foreign and might belong to the virus.

When Stenglein studied the RNA sequences that were not present in the boa constrictor genome, he noticed several similarities to arenavirus genes. “Arenaviruses had only ever been found in mammals, so to find them in a reptile and potentially associated with this disease in snakes was immediately very interesting,” says Stenglein. “If you had asked me to predict what type of virus we would find, this is not what I would have predicted. Next, using open-source software developed by Graham Ruby, another scientist in DeRisi’s lab, Stenglein assembled the genome of the virus from the viral RNA sequences. He found that the sequences from the snake virus belonged to four genes—one of which was most similar to genes found in filoviruses. The scientists found genetic material from their newly identified virus in six of nine snakes with inclusion body disease. Those sequences were not present in any of the seventeen healthy snakes whose samples he tested. And when Stenglein introduced the virus into healthy boa constrictor cells, the virus replicated and the cells became clogged with protein aggregates just like those in snakes with inclusion body disease. Understanding the link between the virus and disease should help improve diagnostics and slow the spread of inclusion body disease, DeRisi says, although it’s too soon to know for sure whether the newly identified virus is its direct cause. Further, he says, by showing that arenavirus infections are not limited to mammals and finding evidence that arenaviruses and filoviruses likely share a common ancestor, his team has learned some important biology about infectious disease.

Howard Hughes Medical Institute
September 4, 2012

Original web page at Howard Hughes Medical Institute

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Lizard’s future hinges on voluntary measures

Finger-sized and sand-coloured, the dunes sagebrush lizard (Sceloporus arenicolus) blends into the scenery in the small pockets of the American southwest that it calls home. But with controversy swirling around a US government decision last week to not list it as ‘endangered’, the diminutive reptile has become a high-profile symbol of a larger question: can voluntary measures save a threatened species? A specialist in extreme habitats, the lizard lives only in sand-dune depressions and the groves of three-foot-tall shin oaks (Quercus havardii) in western Texas and south eastern New Mexico. Land-use changes have contributed to fragmentation and loss of this habitat; ranchers use herbicides to remove shin oaks from grazing areas, and in western Texas the lizard’s range falls within one of the most productive oil and gas regions in the continental United States.

The Center for Biological Diversity, a non-profit conservation organization based in Tucson, Arizona, petitioned the US Fish and Wildlife Service (FWS) in Washington DC to list the lizard under the Endangered Species Act (ESA) in 2002, and later included it in a lawsuit to list several hundred species. The FWS proposed listing the lizard in 2010, outlining scientific evidence showing that the species faced “immediate and significant threats due to oil and gas activities, and herbicides” throughout its range. The proposal then went through peer review and public comment. However, on 13 June, the FWS decided not to list the reptile after all, citing “unprecedented commitments to voluntary conservation agreements” in place in both New Mexico and Texas. Texas comptroller Susan Combs has hailed the decision as a “major victory for Texas jobs and our energy economy”. Opponents say that the decision is a political one, made by an administration that is anxious to avoid election-year threats from the oil industry and members of Congress. State politicians have long opposed an endangered listing for the lizard, saying that the science to support such a designation is lacking. But herpetologist Lee Fitzgerald from Texas A&M University in College Station has studied the lizard for 19 years and says that “more is known about this species than many that are listed”.

In 2010, the state and the oil and gas industry funded Fitzgerald to update a survey he had done in 2007. The survey identified 28 previously undocumented lizard locations. Texas officials called the revelation an important step in developing their conservation plans, and the oil-and-gas industry said that it “drove home the point” that the lizard is not threatened by energy production. However, Fitzgerald points out, those 28 sites were on private land that had not been accessed at the time of his initial survey. “We weren’t surprised where we found or didn’t find the lizard,” he says. “We identified suitable habitat, and if you go to those places, there’s a good chance you’ll find one.” The problem, he says, is that such habitats are being chopped up or are disappearing due to human activity. Although voluntary conservation plans are not new, the dunes sagebrush lizard is the first species to be targeted in Texas. In New Mexico, which contains 73% of the lizard’s habitat, such voluntary agreements have been in place since 2008, but McKinnon contends that they have failed to effectively reduce threats to the lizard. In Texas, property owners who agree to participate in the state’s conservation plan can sign a Certificate of Inclusion, which designates activities that are allowed to continue, as well as specific conservation measures that need to be done. The motivation is to avert an endangered species designation.

“A lot of landowners feel they don’t want someone in Washington, a 1,000 miles and a time zone away, telling them what they can and can’t do,” says Jason Brooks, executive director of the Texas Habitat Conservation Foundation, a non-profit organization in Austin created to implement the plan. The federal government will still play a role in the lizard’s protection, says Michelle Shaughnessy, the southwest region’s assistant director for ecological services at the FWS. “We have legal responsibility to make sure that things go how they are supposed to go,” she says. “It’s a workable alternative to listing.” Shaughnessy says that the FWS will also will be watching whether lizard habitat is stabilizing, increasing or decreasing, and has the option to reconsider listing. The voluntary approach is also being emulated elsewhere in the state. A conservation plan is under way for the prairie chicken, and officials in Williamson County hope that the county’s conservation foundation will prevent listing of four salamander species. But many fear that voluntary plans lack the teeth to ensure species protection. “While policies are similar under ESA listing or the Texas plan, listing would have enforcement,” says Fitzgerald. “Science doesn’t care what policy mechanism is put in place, and it’s going to let you know whether what you decided to do works. But by the time the science lets us know if this doesn’t work, it may be too late.”

Nature
July 2012

Original web page at Nature

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Lonesome George dies but his subspecies genes survive

The rarest animal in the world is no more. Lonesome George, the last of the Pinta Island tortoises, was found dead on Sunday. But a small hope remains for his subspecies, as its genes have survived. “He was an iconic animal for the Galápagos,” says Robert Silbermann, chief executive of the Galapagos Conservation Trust. “It’s devastating to me,” says Gisella Caccone of Yale University in New Haven, Connecticut, who has studied Galápagos giant tortoises for 20 years. “You develop a special bond.” According to the Galápagos National Park, an autopsy will try to determine why George died. He is thought to have been about 100 years old, but Galápagos giant tortoises can live twice that long. “I thought we had more time,” Caccone says. About 14 subspecies of Galápagos giant tortoise (Chelonoidis nigra) once lived on the islands. The differences between them were one of the inspirations for Charles Darwin’s theory of evolution. With the loss of Lonesome George, four of those subspecies have now died out. Thanks to a major conservation programme, the overall population of Galápagos giant tortoises has swelled to around 20,000, from a low in the 1970s of a few thousand. The Hood Island subspecies has recovered from a low of 15 to more than 1200. Nevertheless, the species is still classed as “Vulnerable” by the International Union for Conservation of Nature.

Lonesome George’s subspecies lived on Pinta Island until humans introduced goats that devastated the vegetation and deprived them of food. George was found living alone in 1972 and taken into captivity for his own safety. Conservationists tried and failed to find a female of his subspecies, and attempts to mate him with females of other subspecies didn’t work out. Lonesome George was the last purebred Pinta Island tortoise. A tortoise from Prague Zoo was claimed to be a Pinta Island tortoise, but genetic tests showed otherwise (Animal Conservation, DOI: 10.1111/j.1469-1795.2007.00113.x). But many of the subspecies’ genes live on. Tortoises living around Wolf Volcano on the Galápagos island of Isabela combine the genes from several subspecies. The interbreeding was caused by whalers and pirates, who dumped tortoises on Isabela. These hybrid tortoises preserve genes from several subspecies thought to be extinct, including Pinta Island tortoises. Following that discovery, Caccone led an expedition to the area and collected 1667 DNA samples from the tortoises. Her team is now combing through them, looking for more animals that carry Pinta DNA. The hope was to breed these animals with Lonesome George, but that cannot happen now. However, if there are enough animals of Pinta descent, it should be possible to breed the species back into existence. “By doing selective breeding, you can bring back some of the genetic makeup,” Caccone says.

New Scientist
July 10, 2012

Original web page at New Scientist

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Turtles more closely related to birds than lizards and snakes, genetic evidence shows

The evolutionary origin of turtles is one of the last unanswered questions in vertebrate evolution. Paleontological and morphological studies place turtles as either evolving from the ancestor of all reptiles or as evolving from the ancestor of snakes, lizards, and tuataras. Conflictingly, genetic studies place turtles as evolving from the ancestor of crocodilians and birds. Having recently looked at more than a thousand of the least-changed regions in the genomes of turtles and their closest relatives, a team of Boston University researchers has confirmed that turtles are most closely related to crocodilians and birds rather than to lizards, snakes, and tuataras. The researchers published their findings in the Royal Society journal Biology Letters. By showing that turtles are closer relatives to crocodiles and birds (archosaurs) than lizards, snakes and tuatara (lepidosaurs), the study challenges previous anatomical and paleontological assessments. Nick Crawford, a post-graduate researcher in biology in BU’s Graduate School of Arts & Sciences and lead author of the study, achieved these findings by using computational analysis to examine regions of the different animals’ genomes. “Turtles have been an enigmatic vertebrate group for a long time and morphological studies placed them as either most closely related to the ancestral reptiles, that diverged early in the reptile evolutionary tree, or as closer to lizards, snakes, and tuataras,” says Crawford.

The study is the first genomic-scale analysis addressing the phylogenetic position of turtles, using over 1000 loci from representatives of all major reptile lineages including tuatara (lizard-like reptiles found only in New Zealand). Earlier studies of morphological traits positioned turtles at the base of the reptile tree with lizards, snakes and tuatara (lepidosaurs), whereas molecular analyses typically allied turtles with crocodiles and birds (archosaurs). The BU researchers challenged a recent analysis of shared microRNA families that suggested turtles are more closely related to lepidosaurs. They did this with data from many single-copy nuclear loci dispersed throughout the genome, using sequence capture, high-throughput sequencing and published genomes to obtain sequences from 1145 ultraconserved elements (UCEs) and their variable flanking DNA. The resulting phylogeny provides overwhelming support for the hypothesis that turtles evolved from a common ancestor of birds and crocodilians, rejecting the hypothesized relationship between turtles and lepidosaurs.

The researchers used UCEs because they are easily aligned portions of extremely divergent genomes, allowing many loci to be interrogated across evolutionary timescales, and because sequence variability within UCEs increases with distance from the core of the targeted UCE, suggesting that phylogenetically informative content in flanking regions can inform hypotheses spanning different evolutionary timescales. The combination of taxonomic sampling, the genome-wide scale of the sampling and the robust results obtained, regardless of analytical method, indicates that the turtle-archosaur relationship is unlikely to be caused by long-branch attraction or other analytical artefacts. The BU study is the first to produce a well-resolved reptile tree that includes the tuatara and multiple loci, and also is the first to investigate the placement of turtles within reptiles using a genomic-scale analysis of single-copy DNA sequences and a complete sampling of the major relevant evolutionary lineages. Because UCEs are conserved across most vertebrate groups and found in groups including yeast and insects, this framework is generalizable beyond this study and relevant to resolving ancient phylogenetic enigmas throughout the tree of life. This approach to high throughput phylogenomics — based on thousands of loci — is likely to fundamentally change the way that systematists gather and analyse data.

Science Daily
June 12, 2012

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Ancient giant turtle fossil was size of Smart Car

Picture a turtle the size of a Smart car, with a shell large enough to double as a kiddie pool. Paleontologists from North Carolina State University have found just such a specimen — the fossilized remains of a 60-million-year-old South American giant that lived in what is now Colombia. he turtle in question is Carbonemys cofrinii, which means “coal turtle,” and is part of a group of side-necked turtles known as pelomedusoides. The fossil was named Carbonemys because it was discovered in 2005 in a coal mine that was part of northern Colombia’s Cerrejon formation. The specimen’s skull measures 24 centimeters, roughly the size of a regulation NFL football. The shell which was recovered nearby — and is believed to belong to the same species — measures 172 centimeters, or about 5 feet 7 inches, long. That’s the same height as Edwin Cadena, the NC State doctoral student who discovered the fossil. “We had recovered smaller turtle specimens from the site. But after spending about four days working on uncovering the shell, I realized that this particular turtle was the biggest anyone had found in this area for this time period — and it gave us the first evidence of giantism in freshwater turtles,” Cadena says.

Smaller relatives of Carbonemys existed alongside dinosaurs. But the giant version appeared five million years after the dinosaurs vanished, during a period when giant varieties of many different reptiles — including Titanoboa cerrejonensis, the largest snake ever discovered — lived in this part of South America. Researchers believe that a combination of changes in the ecosystem, including fewer predators, a larger habitat area, plentiful food supply and climate changes, worked together to allow these giant species to survive. Carbonemys’ habitat would have resembled a much warmer modern-day Orinoco or Amazon River delta. In addition to the turtle’s huge size, the fossil also shows that this particular turtle had massive, powerful jaws that would have enabled the omnivore to eat anything nearby — from mollusks to smaller turtles or even crocodiles. Thus far, only one specimen of this size has been recovered. Dr. Dan Ksepka, NC State paleontologist and research associate at the North Carolina Museum of Natural Sciences, believes that this is because a turtle of this size would need a large territory in order to obtain enough food to survive. “It’s like having one big snapping turtle living in the middle of a lake,” says Ksepka, co-author of the paper describing the find. “That turtle survives because it has eaten all of the major competitors for resources. We found many bite-marked shells at this site that show crocodilians preyed on side-necked turtles. None would have bothered an adult Carbonemys, though — in fact smaller crocs would have been easy prey for this behemoth.”

Science Daily
May 29, 2012

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Australian saltwater crocodiles are world’s most powerful biters

In Greg Erickson’s lab at Florida State University, crocodiles and alligators rule. Skeletal snouts and toothy grins adorn window ledges and tables — all donated specimens that are scrutinized by researchers and students alike. Lately, Erickson, a Florida State biology professor, and his colleagues have been pondering a particularly painful-sounding question: How hard do alligators and crocodiles bite? The answer is a bite force value of 3,700 pounds for a 17-foot saltwater crocodile (as well as tooth pressures of 350,000 pounds per square inch). That’s the highest bite force ever recorded — beating a 2,980-pound value for a 13-foot wild American alligator Erickson’s lab measured in 2005. They estimate that the largest extinct crocodilians, 35- to 40-foot animals, bit at forces as high as 23,100 pounds. Erickson, along with several colleagues, including Florida State biology professors Scott Steppan and Brian Inouye, and graduate student Paul Gignac, reported their findings in the journal PLoS One. Their study looks at the bite force and tooth pressure of every single species of crocodilian. It took more than a decade to complete and required a wily team of croc handlers and statisticians, as well as an army of undergraduate and graduate students. Erickson describes crocodilian bite-force testing as being a bit like dragon slaying by committee.

As a result of the study, Erickson and his team have a new understanding on how these animals became so successful and a better understanding about the remarkable biology of living crocodiles and alligators. They’ve also developed new methods for testing bite forces. The data contributes to analyzing performance in animals from the past and provides unprecedented insights on evolution and statistically informed models about other reptiles such as dinosaurs. The study’s findings are so unique that Erickson’s team has been contacted by editors at the “Guinness Book of World Records” inquiring about the data. Over the 11 years that his current study took place in both the United States and Australia, Erickson and his team roped 83 adult alligators and crocodiles, strapped them down, placed a bite-force device between their back teeth and recorded the bite force. An engineering calculation was then used to estimate the force generated simultaneously by the teeth nearest the front of the jaws. The team moulded the teeth with dentist’s dental putty, made casts and figured out the contact areas. As Erickson describes it: “I have to admit, the first time I placed our meter into the maw of an adult crocodile, I was nervous. It was all over in the blink of an eye. When it struck, it nearly wrested my grip from the handle. The noise of the jaws coming together was like a gunshot. The power of the animal was astounding, and the violence of the event frightening.”

Overall, the researchers looked at crocodilians both mundane and exotic, from American alligators to 17-foot Australian saltwater crocodiles and the Indian gharial. Among the world’s most successful predatory reptiles, these creatures have been “guardians of the water-land interface for over 85 million years,” Erickson said. But just how they were able to occupy and dominate ecological niches for so long is a mystery. Erickson and his team knew that the reptiles evolved into different sizes, from 3-footers to 40-footers, and they showed concurrent major changes in their jaw shape and tooth form, while their body form remained largely unchanged. “We set out to answer how this anatomical variance related to their ability to generate bite force and pressures for feeding in the different forms and thus how they have been so successful,” Erickson said. “The bite force over the contact area is the pressure, which is more pertinent to feeding performance than bite force. Ultimately, it tells us just what they were doing with those prodigious bite forces.” And, he added, gators and crocs have comparable maximal bite-force capacity when measured pound for pound. They basically all have the same musculoskeletal design, just different snouts and teeth.

“It is analogous to putting different attachments on a weed eater — grass cutter, brush cutter, tree trimmer, they all have the same type of engine,” Erickson said. “There are bigger and smaller engines, with higher and lower horsepower, but they have the same attachments.” His research team is already using the study’s data to explore bite-force and tooth-pressure performance in fossil forms. The team is building the world’s most sophisticated models for extinct crocodiles and dinosaurs based on the findings, as well as continuing to study the significance of croc snout form. As for modern-day crocs and gators, well, there’s little doubt that they are truly the world’s bone-crushing champions. Just remember that old Floridian maxim: Always maintain a healthy distance between yourself and the nearest gator. “If you can bench-press a pickup truck, then you can escape a croc’s jaws,” Erickson warned. “It is a one-way street between the teeth and stomach of a large croc.”

Science Daily
April 17, 2012

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Unlocking the secrets of sea turtle migration

Sea turtles have long and complex lives; they can live into their 70s or 80s and they famously return to their birthplace to nest. But new research suggests this isn’t the only big migration in a sea turtle’s life. We’re starting to realize that developmental migrations — ones that sea turtles make before they mature — are even more amazing,” says Dr. Peter Meylan, professor of natural sciences at Eckerd College in St. Petersburg, Florida. “They only do it one time, but it can be much longer than the reproductive migrations they do as adults and may involve tens of thousands of kilometers.” Meylan has been tagging and tracking sea turtles with his wife, Anne Meylan of the Florida Fish & Wildlife Research Institute, and Jennifer Gray and other colleagues from the Bermuda Aquarium. They have compiled the results of long-term capture programs in Caribbean Panama (17 years) and Bermuda (37 years) in a summary paper, “The Ecology and Migrations of Sea Turtles: Tests of the Developmental Habitat Hypothesis,” in the Bulletin of the American Museum of Natural History. “Bermuda is a place where young turtles go to grow up,” Meylan says. “They arrive there after living out in the ocean. In Bermuda waters they grow from about the size of a dinner plate to the size of a wash tub, and then move on to different, adult habitats.”

For example, some green turtles hatched in Costa Rica were spending their “growing up” years thousands of kilometers away in Barbados, North Carolina and Bermuda before heading off to spend their adulthoods near Nicaragua. Young turtles have already survived hatching from their untended eggs, escaped hungry predators on their rush to the ocean, and have avoided marine predators once there. This research points to developmental migrations as another vulnerable time for sea turtles. “Tag-return data from this study suggest that this may be another dangerous time for these turtles, and protection as they move into their adult foraging ranges could be a productive objective of policy change for effective marine turtle conservation,” says Meylan.

Science Daily
April 3, 2011

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Vibrating skulls help snakes hear

When a rattlesnake shakes its tail, does it hear the rattling? Scientists have long struggled to understand how snakes, which lack external ears, sense sounds. Now, a new study shows that sound waves cause vibrations in a snake’s skull that are then “heard” by the inner ear. “There’s been this enduring myth that snakes are deaf,” says neurobiologist Bruce Young of the University of Massachusetts, Lowell, who was not involved in the new research. “Behavioral studies have suggested that snakes can in fact hear, and now this work has gone one step further and explained how.” In humans, sound waves traveling through the air hit the eardrum, causing the movement of tiny bones and vibrations of tiny hair cells in the inner ear. These vibrations are then translated into nerve impulses that travel to the brain. Snakes have fully formed inner ear structures but no eardrum. Instead, their inner ear is connected directly to their jawbone, which rests on the ground as they slither. Previous studies have shown that vibrations traveling through the ground—such as the footsteps of predators or prey—cause vibrations in a snake’s jawbone, relaying a signal to the brain via that inner ear.

It was still unclear, however, whether snakes could hear sounds traveling through the air. So Biologist Christian Christensen of Aarhus University in Denmark took a closer look at one particular type of snake, the ball python (Python regius). Studying them wasn’t easy. “You can’t train snakes to respond to sounds with certain behaviors, like you might be able to do with mice,” says Christensen. Instead, he and his colleagues used electrodes attached to the reptiles’ heads to monitor the activity of neurons connecting the snakes’ inner ears to their brains. Each time a sound was played through a speaker suspended above the snake’s cage, the researchers measured whether the nerve relayed an electrical pulse (the snakes showed no outward response to the sounds). The nerve pulses were strongest, the researchers found, with frequencies between 80 and 160 hertz—around the frequency for the lowest notes of a cello, though not necessarily sounds that snakes encounter often in the wild. The snakes don’t seem to be responding to vibrations that these sounds cause in the ground, since these vibrations were too weak to cause nerve activity when they weren’t accompanied by sound in the air, Christensen and his colleagues found. However, when the researchers attached a sensor to the snake’s skull, they discovered that the sound waves were causing enough vibration in the bone—directly through the air—for the snakes to sense it. The results appear online today in The Journal of Experimental Biology.

ScienceNow
February 21, 2012

Original web page at ScienceNow

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Vibrating skulls help snakes hear

When a rattlesnake shakes its tail, does it hear the rattling? Scientists have long struggled to understand how snakes, which lack external ears, sense sounds. Now, a new study shows that sound waves cause vibrations in a snake’s skull that are then “heard” by the inner ear. “There’s been this enduring myth that snakes are deaf,” says neurobiologist Bruce Young of the University of Massachusetts, Lowell, who was not involved in the new research. “Behavioral studies have suggested that snakes can in fact hear, and now this work has gone one step further and explained how.” In humans, sound waves traveling through the air hit the eardrum, causing the movement of tiny bones and vibrations of tiny hair cells in the inner ear. These vibrations are then translated into nerve impulses that travel to the brain. Snakes have fully formed inner ear structures but no eardrum. Instead, their inner ear is connected directly to their jawbone, which rests on the ground as they slither. Previous studies have shown that vibrations traveling through the ground—such as the footsteps of predators or prey—cause vibrations in a snake’s jawbone, relaying a signal to the brain via that inner ear.

It was still unclear, however, whether snakes could hear sounds traveling through the air. So Biologist Christian Christensen of Aarhus University in Denmark took a closer look at one particular type of snake, the ball python (Python regius). Studying them wasn’t easy. “You can’t train snakes to respond to sounds with certain behaviors, like you might be able to do with mice,” says Christensen. Instead, he and his colleagues used electrodes attached to the reptiles’ heads to monitor the activity of neurons connecting the snakes’ inner ears to their brains. Each time a sound was played through a speaker suspended above the snake’s cage, the researchers measured whether the nerve relayed an electrical pulse (the snakes showed no outward response to the sounds). The nerve pulses were strongest, the researchers found, with frequencies between 80 and 160 hertz—around the frequency for the lowest notes of a cello, though not necessarily sounds that snakes encounter often in the wild.

The snakes don’t seem to be responding to vibrations that these sounds cause in the ground, since these vibrations were too weak to cause nerve activity when they weren’t accompanied by sound in the air, Christensen and his colleagues found. However, when the researchers attached a sensor to the snake’s skull, they discovered that the sound waves were causing enough vibration in the bone—directly through the air—for the snakes to sense it. The results appear online today in The Journal of Experimental Biology.

ScienceNow
January 10, 2012

Original web page at ScienceNow

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Whiskers marked milestone in evolution of mammals from reptiles

Research from the University of Sheffield comparing rats and mice with their distance relatives the marsupial, suggests that moveable whiskers were an important milestone in the evolution of mammals from reptiles. Using high-speed digital video recording and automatic tracking, the research team, which was led by Professor Tony Prescott from the University Department of Psychology, have shed light on how rodents such as mice and rats move their whiskers back-and-forth at high speed and in varying ways to actively sense the environment around them in a behaviour known as whisking. Whisking allows mice or rats to accurately determine the position, shape and texture of objects, make rapid and accurate decisions about objects, and then use the information to build environmental maps. When running in a straight line, rats and mice move their whiskers back-and-forth the same amount on both sides. However when turning, they bias their whisker movements in the direction of the turn, and when the whiskers on one side of the head contact an object, those on the opposite side sweep round to gather more information. These active sensing strategies boost the information gained by the whiskers helping the animals to better understand their world through touch.

In their latest research, the team have shown that whisking like that of rodents, using these active sensing strategies, is also seen in a small South American marsupial — the grey short-tailed opossum. This animal has many similarities to an early mammal that would have lived more than 125 million years ago; that is, around the same time that the evolutionary lines leading to modern rodents and marsupials diverged. This evidence suggests that some of the first mammals may also have whisked like a modern mouse or rat, and that the appearance of moveable whiskers was pivotal in the evolution of mammals from reptiles. The research is published in Philosophical Transactions of the Royal Society B on 12 November 2011 and will also be presented on the same day at the Society for Neuroscience conference. The earliest mammals were nocturnal, and tree-living. In order to successfully move around and thrive in this challenging environment these animals needed to effectively integrate information from multiple senses — sight, sound, smell, and touch. Facial whiskers provided mammals with a new tactile sense not available to reptiles that could help them to get around in the dark.

In addition to continuing to investigate the similarities and differences between rodents and marsupials, the team is also using these insights from biological whisker sensing to develop animal-like robots that can use artificial whiskers to navigate without vision. These robots could have applications in search-and-rescue, particularly in environments, such as disaster sites, where vision is compromised by smoke or dust. Professor Tony Prescott said: “This latest research suggests that alongside becoming warm-blooded, giving birth to live young, and having an enlarged brain, the emergence of a new tactile sense based on moveable facial whiskers was an important step along the evolutionary path to modern mammals. Although humans no longer have moveable whiskers they were a critical feature of our early mammalian ancestors.”

Science Daily
November 27, 2011

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Python study may have implications for human heart health

A surprising new University of Colorado Boulder study shows that huge amounts of fatty acids circulating in the bloodstreams of feeding pythons promote healthy heart growth, results that may have implications for treating human heart disease. CU-Boulder Professor Leslie Leinwand and her research team found the amount of triglycerides — the main constituent of natural fats and oils — in the blood of Burmese pythons one day after eating increased by more than fiftyfold. Despite the massive amount of fatty acids in the python bloodstream there was no evidence of fat deposition in the heart, and the researchers also saw an increase in the activity of a key enzyme known to protect the heart from damage. After identifying the chemical make-up of blood plasma in fed pythons, the CU-Boulder researchers injected fasting pythons with either “fed python” blood plasma or a reconstituted fatty acid mixture they developed to mimic such plasma. In both cases, the pythons showed increased heart growth and indicators of cardiac health. The team took the experiments a step further by injecting mice with either fed python plasma or the fatty acid mixture, with the same results.

“We found that a combination of fatty acids can induce beneficial heart growth in living organisms,” said CU-Boulder postdoctoral researcher Cecilia Riquelme, first author on the Science paper. “Now we are trying to understand the molecular mechanisms behind the process in hopes that the results might lead to new therapies to improve heart disease conditions in humans.” The paper is being published in the Oct. 28 issue of the journal Science. In addition to Leinwand and Riquelme, the authors include CU postdoctoral researcher Brooke Harrison, CU graduate student Jason Magida, CU undergraduate Christopher Wall, Hiberna Corp. researcher Thomas Marr and University of Alabama Tuscaloosa Professor Stephen Secor. Previous studies have shown that the hearts of Burmese pythons can grow in mass by 40 percent within 24 to 72 hours after a large meal, and that metabolism immediately after swallowing prey can shoot up by fortyfold. As big around as telephone poles, adult Burmese pythons can swallow prey as large as deer, have been known to reach a length of 27 feet and are able to fast for up to a year with few ill effects.

There are good and bad types of heart growth, said Leinwand, who is an expert in genetic heart diseases including hypertrophic cardiomyopathy, the leading cause of sudden death in young athletes. While cardiac diseases can cause human heart muscle to thicken and decrease the size of heart chambers and heart function because the organ is working harder to pump blood, heart enlargement from exercise is beneficial. “Well-conditioned athletes like Olympic swimmer Michael Phelps and cyclist Lance Armstrong have huge hearts,” said Leinwand, a professor in the molecular, cellular and developmental biology department and chief scientific officer of CU’s Biofrontiers Institute. “But there are many people who are unable to exercise because of existing heart disease, so it would be nice to develop some kind of a treatment to promote the beneficial growth of heart cells.” Riquelme said once the CU team confirmed that something in the blood plasma of pythons was inducing positive cardiac growth, they began looking for the right “signal” by analyzing proteins, lipids, nucleic acids and peptides present in the fed plasma. The team used a technique known as gas chromatography to analyze both fasted and fed python plasma blood, eventually identifying a highly complex composition of circulating fatty acids with distinct patterns of abundance over the course of the digestive process.

In the mouse experiments led by Harrison, the animals were hooked up to “mini-pumps” that delivered low doses of the fatty acid mixture over a period of a week. Not only did the mouse hearts show significant growth in the major part of the heart that pumps blood, the heart muscle cell size increased, there was no increase in heart fibrosis — which makes the heart muscle more stiff and can be a sign of disease — and there were no alterations in the liver or in the skeletal muscles, he said. “It was remarkable that the fatty acids identified in the plasma-fed pythons could actually stimulate healthy heart growth in mice,” said Harrison. The team also tested the fed python plasma and the fatty acid mixture on cultured rat heart cells, with the same positive results, Harrison said. The CU-led team also identified the activation of signaling pathways in the cells of fed python plasma, which serve as traffic lights of sorts, said Leinwand. “We are trying to understand how to make those signals tell individual heart cells whether they are going down a road that has pathological consequences, like disease, or beneficial consequences, like exercise,” she said.

The prey of Burmese pythons can be up to 100 percent of the constricting snake’s body mass, said Leinwand, who holds a Marsico Endowed Chair of Excellence at CU-Boulder. “When a python eats, something extraordinary happens. Its metabolism increases by more than fortyfold and the size of its organs increase significantly in mass by building new tissue, which is broken back down during the digestion process.” The three key fatty acids in the fed python plasma turned out to be myristic acid, palmitic acid and palmitoleic acid. The enzyme that showed increased activity in the python hearts during feeding episodes, known as superoxide dismutase, is a well-known “cardio-protective” enzyme in many organisms, including humans, said Leinwand.

Science Daily
November 15, 2011

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Most vertebrates — including humans — descended from ancestor with sixth sense

People experience the world through five senses but sharks, paddlefishes and certain other aquatic vertebrates have a sixth sense: They can detect weak electrical fields in the water and use this information to detect prey, communicate and orient themselves. A study in the Oct. 11 issue of Nature Communications that caps more than 25 years of work finds that the vast majority of vertebrates – some 30,000 species of land animals (including humans) and a roughly equal number of ray-finned fishes – descended from a common ancestor that had a well-developed electroreceptive system. This ancestor was probably a predatory marine fish with good eyesight, jaws and teeth and a lateral line system for detecting water movements, visible as a stripe along the flank of most fishes. It lived around 500 million years ago. The vast majority of the approximately 65,000 living vertebrate species are its descendants. “This study caps questions in developmental and evolutionary biology, popularly called ‘evo-devo,’ that I’ve been interested in for 35 years,” said Willy Bemis, Cornell professor of ecology and evolutionary biology and a senior author of the paper. Melinda Modrell, a neuroscientist at the University of Cambridge who did the molecular analysis, is the paper’s lead author.

Hundreds of millions of years ago, there was a major split in the evolutionary tree of vertebrates. One lineage led to the ray-finned fishes, or actinopterygians, and the other to lobe-finned fishes, or sarcopterygians; the latter gave rise to land vertebrates, Bemis explained. Some land vertebrates, including such salamanders as the Mexican axolotl, have electroreception and, until now, offered the best-studied model for early development of this sensory system. As part of changes related to terrestrial life, the lineage leading to reptiles, birds and mammals lost electrosense as well as the lateral line. Some ray-finned fishes – including paddlefishes and sturgeons – retained these receptors in the skin of their heads. With as many as 70,000 electroreceptors in its paddle-shaped snout and skin of the head, the North American paddlefish has the most extensive electrosensory array of any living animal, Bemis said. Until now, it was unclear whether these organs in different groups were evolutionarily and developmentally the same.

Using the Mexican axolotl as a model to represent the evolutionary lineage leading to land animals, and paddlefish as a model for the branch leading to ray-finned fishes, the researchers found that electrosensors develop in precisely the same pattern from the same embryonic tissue in the developing skin, confirming that this is an ancient sensory system. The researchers also found that the electrosensory organs develop immediately adjacent to the lateral line, providing compelling evidence “that these two sensory systems share a common evolutionary heritage,” said Bemis. Researchers can now build a picture of what the common ancestor of these two lineages looked like and better link the sensory worlds of living and fossil animals, Bemis said.

PhysOrg.com
November 1, 2011

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Lizard genome unveiled

Publication of the genome of the North American green anole lizard has filled a yawning genome-sequence gap in the animal lineage. The paper, which appeared in Nature, is the first to sequence the genome of a non-avian reptile. “This fills out a clade that has been completely ignored before,” says lead author Jessica Alföldi of the Broad Institute of MIT and Harvard in Cambridge, Massachusetts. Amniotes, the first truly terrestrial vertebrates, diverged from other animals some 320 million years ago to form the mammalian and reptilian lineages. Until now, however, the only representatives of the reptile branch to be sequenced were birds — the chicken, the turkey and the zebra finch. But “birds have rather odd genomes that may not be totally representative”, says Alföldi, who collaborated with more than 20 different groups on the project. Molecular ecologist Anita Malhotra of Bangor University, UK, who was not involved in the study, agrees. “One can’t possibly expect to comprehend the whole of amniote biology by comparison to the chicken,” she says. The genome of the green anole, Anolis carolinensis, has already offered up evidence to support this point, including the revelation — through the sequence of a previously unknown X chromosome — of a sex-determination system similar to that of humans. This finding makes birds, with their ‘reverse’ ZW system — in which females, not males, have two different sex chromosomes — the odd ones out among the amniotes.

The A. carolinensis sequence also provides clues about the development of the amniotic egg, a major evolutionary innovation that allowed animals to breed out of water by protecting the developing embryo from drying out. Using proteomics — large-scale identification of proteins by mass spectrometry — facilitated by the genome sequence, the researchers were able to hunt down and investigate egg-protein genes in the lizard. They found that, among amniotes, egg proteins seem to have evolved more rapidly than other proteins. The high mutation rate that this would have entailed may have been instrumental in the evolution of the egg. The Anolis genus is considered a textbook example of evolutionary adaptation, owing to the independent evolution of hundreds of sister species on islands throughout the Caribbean. Alföldi and her colleagues knew that the lizards offered “a rather neat system to study evolution”, but until now, “we didn’t really know how they all fitted together”. By comparing the A. carolinensis genome to shorter sequences from 92 other Anolis species, the authors uncovered evidence that similar features seen in different species resulted from convergent evolution rather than inter-island migration.

Their work underscores the importance of learning as much about related species’ genomes as possible. “To me, this paper highlights the fact that just taking one representative of a major lineage is not enough,” says Malhotra. Vertebrate biologist and palaeontologist Susan Evans at University College London agrees, but thinks that even more amniote sequences are needed. “It is worth bearing in mind that the very reasons that made Anolis an obvious choice may also make it atypical,” she says. “It will be illuminating to compare it with more conservative lizards – not to mention representatives of a wider range of reptiles such as snakes, tuatara, crocodiles and turtles.”

Nature
September 20, 2011

Original web page at Nature