Iturria:  Science Daily

Fossils of First Feathered Dinosaurs from North America Discovered: Clues On Early Wing Uses

ScienceDaily (Oct. 25, 2012) — The ostrich-like dinosaurs in the original Jurassic Park movie were portrayed as a herd of scaly, fleet-footed animals being chased by a ferocious Tyrannosaurus rex. New research published in the journal Science reveals this depiction of these bird-mimic dinosaurs is not entirely accurate -- the ornithomimids, as they are scientifically known, should have had feathers and wings.

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This is an artistic reconstruction of feathered ornithomimid dinosaurs found in Alberta. (Credit: Julius Csotonyi)

The new study, led by paleontologists Darla Zelenitsky from the University of Calgary and François Therrien from the Royal Tyrrell Museum of Palaeontology, describes the first ornithomimid specimens preserved with feathers, recovered from 75 million-year-old rocks in the badlands of Alberta, Canada.
"This is a really exciting discovery as it represents the first feathered dinosaur specimens found in the Western Hemisphere," says Zelenitsky, assistant professor at the University of Calgary and lead author of the study. "Furthermore, despite the many ornithomimid skeletons known, these specimens are also the first to reveal that ornithomimids were covered in feathers, like several other groups of theropod dinosaurs."
The researchers found evidence of feathers preserved with a juvenile and two adults skeletons of Ornithomimus, a dinosaur that belongs to the group known as ornithomimids. This discovery suggests that all ornithomimid dinosaurs would have had feathers.
The specimens reveal an interesting pattern of change in feathery plumage during the life of Ornithomimus. "This dinosaur was covered in down-like feathers throughout life, but only older individuals developed larger feathers on the arms, forming wing-like structures," says Zelenitsky. "This pattern differs from that seen in birds, where the wings generally develop very young, soon after hatching."
This discovery of early wings in dinosaurs too big to fly indicates the initial use of these structures was not for flight.
"The fact that wing-like forelimbs developed in more mature individuals suggests they were used only later in life, perhaps associated with reproductive behaviors like display or egg brooding," says Therrien, curator at the Royal Tyrrell Museum and co-author of the study.
Until now feathered dinosaur skeletons had been recovered almost exclusively from fine-grained rocks in China and Germany. "It was previously thought that feathered dinosaurs could only fossilize in muddy sediment deposited in quiet waters, such as the bottom of lakes and lagoons," says Therrien. "But the discovery of these ornithomimids in sandstone shows that feathered dinosaurs can also be preserved in rocks deposited by ancient flowing rivers."
Because sandstone is the type of rock that most commonly preserves dinosaur skeletons, the Canadian discoveries reveal great new potential for the recovery of feathered dinosaurs worldwide.
The fossils will be on display this fall at the Royal Tyrrell Museum in Drumheller, Alberta.

Genomic Hitchhikers in Birds Shed Light On Evolution of Viruses

Iturria: Science Daily

ScienceDaily (Oct. 16, 2012) — The genomes of birds are riddled with DNA sequences from viruses, according to a study to be published on Oct. 16 in mBio®, the online open-access journal of the American Society for Microbiology. Analysis of these viral sequences, known as endogenous retroviruses (ERVs), can provide insights into how both hosts and viruses have evolved over the eons.

"We examined the evolution of avian retroviruses on the basis of their fossil remnants in the three avian genomes that have been completely sequenced," write the authors from Johns Hopkins University and Uppsala University, Sweden. The authors go on to say their analyses of ERVs in chicken, turkey, and zebra finch genomes reveal that birds were a hotbed of viral evolution early in their history.
All genomes are cobbled together works-in-progress. Scientists have long known that the human genome, for example, is not all human: like most every other genome studied to date, a good chunk of the DNA we call "human" is actually made up of proviruses, sequences that retroviruses have deposited there to take advantage of the cell's ability to copy DNA and translate that DNA into working proteins. These proviruses can either be inherited in the DNA we get from our parents (endogenous retroviruses), or they can be picked up during our lifetime (exogenous retroviruses).
The study reveals that millions of years ago birds were host to many different kinds of ERVs, serving as a kind of melting pot: a meeting and mingling place where viruses recombined and shared genetic information.
Unlike early studies of ERVs in chickens, which studied selected segments of the genome and uncovered only alpha-retroviruses, this study used complete genome sequences and found a great diversity of viral sequences in bird genomes, representing the same major groups as those of mammals, but exhibiting more diversity. Most of the ERVs in birds were distinct from those found in other animals, probably indicating that the viruses did not move much between different kinds of hosts.
"We conclude that avian retroviral evolution differs from that of other vertebrates," write the researchers. "Avian retroviruses seem to have evolved rather independently from the rest of the retroviruses over the last 150 million years."
Stepher Goff of Columbia University, who was not involved in the research but edited the article for mBio®, says genome-level studies like this are a boon to virologists.
"This paper is filling a big gap in our understanding of these viruses," says Goff. "This is something that needed to be done, and advancing sequencing technology made it easy to do."

Crows Don't Digest Prions, May Transport Them to Other Locations

Iturria: Science Daily

ScienceDaily (Oct. 17, 2012) — Crows fed on prion-infected brains from mice can transmit these infectious agents in their feces and may play a role in the geographic spread of diseases caused by prions, such as chronic wasting disease or scrapie.

The new research published Oct. 17 in the open access journal PLOS ONE by Kurt VerCauteren from the US Department of Agriculture (USDA) and other colleagues, shows that prions can pass through crows' digestive systems without being destroyed, and may be excreted intact after ingestion by the birds. According to the authors, their results demonstrate a potential role for the common crow in the spread of infectious diseases caused by prions.
Prions are infectious proteins that cause diseases in humans and other animals. Studies so far have suggested that insects, poultry and scavengers like crows may be passive carriers of infectious prions, but this is the first demonstration that prions can retain their ability to cause disease after passing through the avian digestive system.
The authors fed crows with brain samples from mice infected with prions, and found that the crows passed infectious prions up to 4 hours after eating the infected samples. When healthy mice were injected with the infected crow excretions, all the mice showed signs of prion disease. The authors state that their results support the possibility that crows that encounter infected carcasses or consume infected tissue may have the capacity to transport infectious prions to new locations.

Migratory Birds’ Ticks Can Spread Viral Haemorrhagic Fever

Iturria: Science Daily

ScienceDaily (Oct. 22, 2012) — A type of haemorrhagic fever (Crimean-Congo) that is prevalent in Africa, Asia, and the Balkans has begun to spread to new areas in southern Europe. Now Swedish researchers have shown that migratory birds carrying ticks are the possible source of contagion.

The discovery is being published in the US Centers for Disease Control and Prevention journal Emerging Infectious Diseases.
Crimean-Congo Haemorrhagic fever is a serious disease that begins with influenza-like symptoms but can develop into a very serious condition with high mortality (30%). The disease occurs in Africa, Asia, and the Balkans but it has recently started to spread to new areas in southern Europe. It is caused by a virus that is spread by tick bites and common host animals are various small mammals and ungulates. Humans are infected by tick bites or close contact with contagious mammals.
Researchers have now studied the dissemination mechanisms of this potentially fatal disease. The study is multidisciplinary, with bird experts, tick experts, molecular biologists, virologists, and infectious disease physicians from Uppsala University and Uppsala University Hospital in collaboration with colleagues from the Swedish Institute for Communicable Disease Control, Kalmar and Linköping. Ornithologists and volunteers also helped gather birds.
During two spring seasons in 2009-2010, a total of 14 824 birds were captured at the two ornithological stations Capri (Italy) and Anticythera (Greece), on their way from Africa to Europe. A total of 747 ticks were gathered and analysed for the virus.
Some 30 different bird species were examined, and one species, the woodchat shrike, which winters in southern Africa and nests in Central Europe, proved to be a carrier of virus-infected ticks.
"This is the first time ticks infected with this virus have been found on migratory birds. This provides us with an entirely new explanation of how this disease, as well as other tick-borne diseases, has spread to new areas, where new mammal populations can be infected by the infected ticks," says Erik Salaneck, one of the authors of the study.
The Hyalomma tick, which spreads the disease, does not thrive in northern Europe, preferring warmer latitudes. But with a warmer climate, the boundary for both the tick species and the disease could move northward with the help of migratory birds.

Researchers Find Our Inner Reptile Hearts

Iturria: Science Daily

ScienceDaily (Sep. 14, 2012) — The genetic building blocks behind the human heart's subtle control system have finally been identified.

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The reptilian heart has a thin wall surrounding a spongy inner part. In many ways, this resembles the embryonic state in birds, humans and other mammals. The anatomy of their hearts is subsequently completely different from reptiles, but studies of the genetic building blocks now show that all the hearts have a common molecular structure. The reptilian heart can thus provide us with insight into how the heart works in a human. (Credit: Figure by Bjarke Jensen)

An elaborate system of leads spreads across our hearts. These leads -- the heart's electrical system -- control our pulse and coordinate contraction of the heart chambers. While the structure of the human heart has been known for a long time, the evolutionary origin of our conduction system has nevertheless remained a mystery. Researchers have finally succeeded in showing that the spongy tissue in reptile hearts is the forerunner of the complex hearts of both birds and mammals. The new knowledge provides a deeper understanding of the complex conductive tissue of the human heart, which is of key importance in many heart conditions.
Forerunner of conductive tissue
"The heart of a bird or a mammal -- for example a human -- pumps frequently and rapidly. This is only possible because it has electrically conductive tissue that controls the heart. Until now, however, we haven't been able to find conductive tissue in our common reptilian ancestors, which means we haven't been able to understand how this enormously important system emerged," says Bjarke Jensen, Department of Bioscience, Aarhus University. Along with Danish colleagues and colleagues from the University of Amsterdam, he can now reveal that the genetic building blocks for highly developed conductive tissue are actually hidden behind the thin wall in the spongy hearts of reptiles. The new results have just been published in the journal PLoS ONE.
Different anatomy conceals similarity
"We studied the hearts of cold-blooded animals like lizards, frogs and zebrafish, and we investigated the gene that determines which parts of the heart are responsible for conducting the activating current. By comparing adult hearts from reptiles with embryonic hearts from birds and mammals, we discovered a common molecular structure that's hidden by the anatomical differences," explains Dr Jensen. Since the early 1900s, scientists have been wondering how birds and mammals could have developed almost identical conduction systems independently of each other when their common ancestor was a cold-blooded reptile with a sponge-like inner heart that has virtually no conduction bundles.
Human fetal hearts
The studies show that it is simply the spongy inner tissue in the fetal heart that gets stretched out to become a fine network of conductive tissue in adult birds and mammals. And this knowledge can be put to use in the future. "Our knowledge about the reptilian heart and the evolutionary background to our conductive tissue can provide us with a better understanding of how the heart works in the early months of fetal life in humans, when many women miscarry, and where heart disorders are thought to be the leading cause of spontaneous abortion," says Professor Tobias Wang.
Fact box: Why did we not keep reptilian hearts?

• Reptiles are cold-blooded animals and therefore have the same temperature as their surroundings. Their spongy hearts are efficient enough to maintain their low metabolism.
• Birds and mammals -- including humans -- have independently of each other developed a high body temperature (warm-bloodedness) and spend enormous amounts of energy maintaining it. Their pulse has to increase to pump all the blood needed for high metabolism. This means they require efficient conductive tissue in the heart.

Climate Change to Fuel Northern Spread of Avian Malaria: Malaria Already Found in Birds in Alaska

Iturria: Science Daily

ScienceDaily (Sep. 19, 2012) — Malaria has been found in birds in parts of Alaska, and global climate change will drive it even farther north, according to a new study published September 19 in the journal PLoS ONE.

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Researchers at SF State have discovered malaria in birds in Alaska, including the Common Redpoll, above. (Credit: Jenny Carlson, SF State)

The spread could prove devastating to arctic bird species that have never encountered the disease and thus have no resistance to it, said San Francisco State University Associate Professor of Biology Ravinder Sehgal, one of the study's co-authors. It may also help scientists understand the effects of climate change on the spread of human malaria, which is caused by a similar parasite.
Researchers examined blood samples from birds collected at four sites of varying latitude, with Anchorage as a southern point, Denali and Fairbanks as middle points and Coldfoot as a northern point, roughly 600 miles north of Anchorage. They found infected birds in Anchorage and Fairbanks but not in Coldfoot.
Using satellite imagery and other data, researchers were able to predict how environments will change due to global warming -- and where malaria parasites will be able to survive in the future. They found that by 2080, the disease will have spread north to Coldfoot and beyond.
"Right now, there's no avian malaria above latitude 64 degrees, but in the future, with global warming, that will certainly change," Sehgal said. The northerly spread is alarming, he added, because there are species in the North American arctic that have never been exposed to the disease and may be highly susceptible to it.
"For example, penguins in zoos die when they get malaria, because far southern birds have not been exposed to malaria and thus have not developed any resistance to it," he said. "There are birds in the north, such as snowy owls or gyrfalcons, that could experience the same thing."
The study's lead author is Claire Loiseau, a former postdoctoral fellow in Sehgal's laboratory at SF State. Ryan Harrigan, a postdoctoral scholar at the University of California, Los Angeles, provided data modeling for the project. The research was funded by grants from the AXA Foundation and National Geographic.
Researchers are still unsure how the disease is being spread in Alaska and are currently collecting additional data to determine which mosquito species are transmitting the Plasmodium parasites that cause malaria.
The data may also indicate if and how malaria in humans will spread northward. Modern medicine makes it difficult to track the natural spread of the disease, Sehgal said, but monitoring birds may provide clues as to how global climate change may effect the spread of human malaria.