Birds of a feather...: This avian gynandromorph exhibits hen traits on its right side, and rooster traits on its left side, and is giving scientists insight into sex development in birds and other animals.
Courtesy Roslin Institute, University of EdinburghI must not have been paying attention lately because it appears there are some real bizarre chickens out there that are half rooster and half hen. I don't mean a jumbled mix where a bird exhibits some hen characteristics here and a couple rooster traits there – no, these are barnyard oddballs where one side is a female, and the other side is a male. It’s as if someone sliced a bird of each sex smack dab down the middle and sewed the two different halves together. A real, feathered chimerical freak show. These natural anomalies (known as gynandromorphs) appear in other life forms and have apparently been around for centuries.
Anyway, new research out of the University of Edinburgh’s Roslin Institute indicates that differences in male and female chicken cells - rather than hormones triggering genes – play a major role in determining sexual development in birds.
“This research has completely overturned what we previously thought about how sexual characteristics were determined in birds. We now believe that the major factors determining sexual development are built into male and female cells and derive from basic differences in how sex chromosome genes are expressed. Our study opens a new avenue for our understanding of sexual development in birds.” - Dr Michael Clinton
With mammalian development – including humans – after the two gamete cells (sperm and ova) fuse, the zygote’s somatic cells begin to grow and develop into whatever body plan it’s forming. The embryo remains sexually indifferent until certain genes switch on and sex-determining hormones are secreted. And for a long time it was thought all vertebrates developed in this same manner. But it looks like birds follow a completely different plan of action. Avian somatic cells don’t wait to get their cue from the gonads, and seem to already “know” their own sexual identity before any sex-determining hormones are secreted.
Named cell autonomous sex identity (CASI), the phenomenon runs counter to the prevailing ideas of development of sexual traits in birds, and explains why a gynandromorph can display female traits on one side and rooster traits on the other in the same bird. The male or female cells are dominant on the respective sides.
“It also means we must now reassess how this developmental process occurs in other organisms. There is already some evidence that organs such as the heart and brain are intrinsically different in males and females and birds may provide a model for understanding the molecular basis for these gender differences.” – Dr. Michael Clinton
The findings which appeared in the journal Nature, could also lead to answering why one gender is predisposed to certain diseases while the other isn’t. But whether they’ll be able to explain why gynandromorph chickens make the best fighting birds in cockfights is another question.
SOURCES and LINKS
Roslin Institute release
More about gynandromorphs
More about gonads
Sciencemag.org story
Old school way of thinking: This idea of man as the be-all, end-all of evolution- the unchanging, final edit of nature- is exactly what the Smithsonian's new exhibition hall is trying to negate.
Courtesy wikimediaThe Smithsonian Institute will open a new exhibition hall tomorrow (March 17, 2010), the David H. Koch Hall of Human Origins (this opening coincides with the institute’s 100-year anniversary). The 15,000-square-foot hall will focus on what it means to be human, examining how our defining characteristics emerged over time. One cool thing about the new exhibition (in addition to…everything) is the highlight (in the form of bronze statues) of a-typical hominid species. There’s a statue of Homo heidelbergensis, Paranthropus boisei, and even Homo floresiensis (the “hobbit” species). Now, I know what you’re thinking, “What?! Where’s the Australopithecus africanus?!!” Well, it’s not in this exhibition (at least not in the form of a shiny effigy). The reason for this is to emphasize that our ancestry is not a straight line (as A. africanus might imply because it is a possible direct ancestor of Homo sapiens). Instead, our lineage is much less tidy; there’s species overlap, some species die off… the diagrams are messy. The David H. Koch Hall of Human Origins is trying to get at the fact that we Homo sapiens are just another iteration in our branch-laden tree, not the pinnacle of evolutionary development. I think that’s a great point to remind people of.
Other features of the exhibition include forensically reconstructed life-sized faces of some of our ancestors, 75 skull reproductions, key events in humanity’s evolution (environmental changes, behavioral innovations, etc.), a human family tree, and virtual tours of important research sites. I haven’t had the chance to visit it yet, but the American Museum of Natural History in New York also has a relatively new human origins exhibition. I think it’s exciting that more and more museums are taking on this topic. In the past museums have shied away from it for fear of stirring up controversy. The Milwaukee Public Museum, for example has an exhibit about evolution- it’s on a tiny wall in a dark corner…but at least they have one. It’s important for museums to present scientific research, and the exciting exploration of human evolution is no exception. So if you’re in the D.C. area, be sure to check out the new Smithsonian Hall of Human Origins.
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Cool, it is a baby mammoth: A new traveling museum exhibit features a frozen baby mammoth, found in the ice of Siberia in 2007.
Courtesy Field MuseumA few years ago, I posted a story about the find of a frozen baby mammoth in Siberia. You can refresh your memory of that discovery here.
Now, an exhibit on mammoths and mastodons has opened at the Field Museum of Chicago and visitors have the chance to see the frozen mammoth baby up close and in person (and right now you can look at the photo of it on exhibit right next to this paragraph). The Field Museum hosts the exhibit through Sept. 5 and then an international tour begins, running through 2014.
Here's an interesting story about what researchers have been able to learn about mammoths based on their findings from the mammoth baby, as well.
Don't Leaf Me Behind!
in Diversity of Organisms and Biological Populations Change Over Time
An Instant Classic: Hey, Aesop, what if I told you Mr. Hare won the race?
Courtesy Milo Winter
You’re probably familiar with Aesop’s classic fable The Tortoise and the Hare: Mr. Hare challenges Mr. Tortoise to a foot race. Mr. Tortoise accepts. Mr. Hare dashes from the start line, but stops just before the finish line to take a nap. In the meantime, Mr. Tortoise plods along to win the race!! The moral of the story? University of Minnesota professor and Institute on the Environment resident fellow, Dr. Peter Reich’s award-winning take on the fable may surprise you.
Dr. Peter Reich: This guy studies leaves for a living.
Courtesy Regents of the University of Minnesota
Dr. Reich studies leaves. In particular, Dr. Reich has discovered three characteristics of leaves that allow researchers to identify where and how plants live: longevity, productivity, and nitrogen content. Longevity measures how old a leaf lives. Did you know leaves in the tropics live only 5-6 weeks whereas Canadian spruce leaves can live up to 18 years old? Productivity measures how much sugar the leaf makes (yes, leaves make sugar called “glucose,” which nearly every animal uses to fuel their body – that’s why your momma tells you to eat your vegetables!). Finally, nitrogen is like a vitamin for plants: they need it to grow big and strong. How much nitrogen a leaf has is important because it determines how much energy a plant can make.
Canadian Spruce: If these leaves were human, they could be legal adults!
Courtesy Steven J. Baskauf
Tropical Leaves: These guys may look BIG, but they are not going to be around for long.
Courtesy Flickr
What about the moral of The Tortoise and the Hare? Dr. Reich’s research says there are basically two types of leaves: ones that are like Mr. Tortoise and ones like Mr. Hare. Tortoise-like leaves work slowly, but steadily. They’re the marathon runners of the leaf world. Hare-like leaves work really fast! But they can’t keep it up for long. They’re sprinters. Could you run a marathon at your top sprinting speed? Probably not, and neither can leaves be both ultra-fast and long-lasting at the same time. Instead, leaves “tradeoff” speed for endurance. Like human runners, leaves don’t have to be all fast and short-lived or all slow and long-lived; they can fall somewhere inbetween and be medium speed and medium-lived.
So who cares about marathon and sprinting leaves anyway? Lots of people! Dr. Reich just won the BBVA Frontiers of Knowledge Award in recognition of this important research. Being able to group the thousands of plants out in the world into a handful of groups is allowing scientists to do incredible research that can be used around the world.
For example, Dr. Reich’s newest research is looking at the different responses of tortoise-leaves versus hare-leaves to changing environments, such as higher levels of carbon dioxide in the air caused by climate change. As each generation of leaves reproduces, new genetic combinations are created. New genetic traits that are helpful to the plant’s survival are passed on to the next generation. The more genetic combinations created, the better chance a species has of “finding” the right traits in a changing environment. This is where Dr. Reich’s interpretation of the moral of The Tortoise and the Hare may surprise you: because hare-leaves have fast, short lives, they reproduce more genetic combinations and are better able to deal with change. Tortoise-leaves will struggle more to adapt. That is, for leaves, slow and steady does not always win the race!
Want to know more?? Dr. Reich recently gave a lecture as part of the Institute on the Environment’s Frontiers on the Environment series. You can hear it here.
Rex in the hen house
Courtesy Mark RyanA new study came out last week that appeared destined to shake up the current line of thought that birds descended from dinosaurs. Birds share common traits with some dinosaurs, including furculas (wishbones), hollow bones, and other skeletal features, which scientists have interpreted to mean the former descended from the latter. But now a new study by researchers at Oregon State University, it may have happened just the opposite way.
"We think the evidence is finally showing that these animals which are usually considered dinosaurs were actually descended from birds, not the other way around," said John Ruben, a professor of zoology at OSU, and the study’s lead author.
The study involved the fossil of a Microraptor, a dromaeosaurid dinosaur with evidence of feathers on both its arms and legs. Studying the skeletal remains, Ruben and his colleagues constructed 3-dimensional models that they tested for flight capabilities. Their study showed Microraptor’s structure better suited to be glider rather than a flyer. From this Ruben extrapolated that it made more sense that Microraptor descendents came down from the trees and eventually evolved into flightless birds we call dromaeosaurs or raptors.
"Raptors look quite a bit like dinosaurs but they have much more in common with birds than they do with other theropod dinosaurs such as Tyrannosaurus," he said. The study appears in the journal for the Proceedings of the National Academy of Science (PNAS).
Sounds good at first, and I have to admit I was smitten with the idea. But not everyone feels the same way.
Over at the Smithsonian’s Dinosaur Tracking blog, freelance science writer Brian Switek has pointed out that Ruben’s proclamation is “actually only a commentary, or the equivalent of an opinion piece.”
He then goes on to point out some of the flaws in Ruben’s argument, particularly the uncertainty surrounding Microraptor’s place in the evolution of flight, and the lack of reasonable evidence that Velociraptor wasn’t a dinosaur. Switek doesn’t think Ruben’s claim stands up to scrutiny.
But what annoys Switek most is how the media inundates the various outlets with this kind of science news, giving it wide distribution and often, undeserved credibility.
“In this increasingly fragmented media landscape, knowledgeable science writers who recognize a fishy story when they see one are getting outnumbered. More often, websites and newspapers simply reprint press releases issued by universities and museums (science writers call this “churnalism”), and this policy sometimes lets questionable science slip through the cracks.” – Brian Switek
One of the reasons for this is the internet. There's just a huge amount of time and space that requires constant feedings of content now. It does make things difficult to sort through. There have been times I’ve begun researching some new science story to post on Science Buzz only to become frustrated with details that don’t seem to add up, confusing statements, info that counters other info, and outright misinformation. Some of it may be due to the writer(s) not being able to properly articulate or distill a particular idea or hypothesis for the general reader (I know I suffer from this occasionally). Sometimes it’s due to the fact that many science writers lack access to the papers themselves (most science journals require paid subscriptions to access anything beyond an abstract of the story), so writers are left with relying on press releases and abstracts or another writer’s thoughts on the subject (like I’m doing here). But other times it ends up being that there’s no real story at all, just a rehash of something from months or years ago that somebody figures needed to be in the headlines again.
To this end, paleontologist Dave Hone over at his Archosaur Musings blog recently posted “A guide for journalists reporting on dinosaur stories” that deals with some of issues raised here. It’s worth reading.
Science Buzz has also covered science writing issues in previous posts.
How to read/write science news
Bad Science Journalism
SOURCE and MORE INFO
ScienceDaily.com story
Microraptor gui: Bird or Dinosaur
Origin and Evolution of Birds
Ibex: Capra ibex
Courtesy Nino BarbieriA recent article in the Journal of Archaeological Science reminded me of the importance of the Scientific Method Often we hear new and exciting scientific theories that seem plausible, especially if these ideas are presented in prestigious journals. However, the beauty of the Scientific Method is its verifiability, whether or not the data can be recreated through repetitive testing (If we truly believed everything the first time, our budding young scientists would have nothing to do!)
Michael Campana from the University of Cambridge and colleagues from across the UK and Ireland recently ran a sequence of DNA tests on 18th and 19th century parchments made from animal skins in order to reveal the complexities of ancient parchment analysis. Parchment is one of the most valuable archaeological and historical artifacts that can be used to understand not only language and history, but DNA testing on it can reveal clues to animal population studies, animal husbandry, different historical animal breeds, and provenance (where the animal or skins originated from). In the case of the Dead Sea Scrolls, DNA testing on the parchment could reveal what type of animal was used and possibly where it came from, providing additional data for questions regarding who wrote the scrolls.
Campana and colleagues analyzed both mitochondrial and autosomal genetic data using stable isotope, genetic, phylogenetic and ion beam analysis. All samples were considered to be well preserved and ideal samples for accurate testing. All but one parchment produced multiple DNA sequences that matched several different species including cow, goat, sheep, and even human. In other words, a parchment assumed to be made from one individual of one species, gave conflicting results as more than one species or more than one individual. Of course it can be assumed the parchment was not made of human skin and therefore human genetic data must have came from handling and processing of the parchment, but parchments can also be contaminated in long-term storage or contact with each other. Testing results can also be skewed by glues and inks or other preparatory treatments used to improve the surface. All of these factors need to be considered when testing truly ancient parchment like the Dead Sea Scrolls.
Previous DNA test results from 2001 and 1996 on the Dead Sea Scrolls produced results pointing to a single species, either ibex (Capra ibex) or domestic goat. While these results may indeed be correct, the likelihood that the results were so exact, when testing such as Campana's and colleagues on better preserved and more recent parchment were so complex, questions the accuracy of the earlier DNA testing. Of course we must not forget, precious artifacts like the Dead Sea Scrolls can not be needlessly dissected to offer unlimited samples for DNA testing labs. But as, Campana states, “Improving our understanding of parchment's DNA content would allow us to develop a predictive model for sampling of historic manuscripts.”
So the messages for today, bravo for the Scientific Method and go see the Dead Sea Scrolls at the Science Museum! Learn the science, archaeology, history and more that surround these amazing artifacts. Ask questions like: did the scroll writers choose ibex for some scrolls over goat because they thought these documents were so special or was ibex as readily available as any other animal species? Did the handling of the scrolls by shepherds who supposedly found them contaminate the actual scroll DNA with sheep, human or goat DNA? What can DNA testing tell us about other ancient artifacts? As long as there are unanswered questions, no matter how small, there will be a need for scientific investigation; which is good news for our future scientists!
Naked Mole Rat: a mighty survivor both hairless and nearly blind
Courtesy MissTessmacherThe naked mole rat (Heterocephalus glaber) is truly one of the most remarkable animals on this earth. On average 3 inches long and weighing just over an ounce, one would not think this creature so high and mighty. However, its unusual traits have brought it under more medical scrutiny and established an ever increasing presence in research laboratories. Stories have rung for years about how the only species to survive a world Armageddon would be cockroaches and rats. My money is on the naked mole rat.
While called a rat, they are one of 37 species of mole rats globally and are more closely related to guinea pigs and porcupines than other Rodentia. Limited to parts of East Africa, they spend their lives under ground in a highly social commune of individuals, all governed by a queen. This is very similar to the eusociality seen in bees and ants. The queen is the only female to breed, with all other individuals serving as guards or workers. This unusual social life for a mammal in a colony can lead to fierce competitions among females when the old queen dies. It may take days or weeks of power struggle before life in the colony returns to normal.
In search of plant tubers for sustenance, they dig through the dirt with their teeth, developing a system of burrows that can carry on for miles. One of the naked mole rats remarkable features is its ability to survive in the high carbon dioxide environments of these tunnels. Their extremely low metabolic rate and high absorption of oxygen allow them to overcome the limitations of the cramped and congested space. Research has found that these mole rats are void of a pain transmitter called Substance P found in other mammals, and have an uncanny resistance to the oxidative stress of daily metabolism.
Researchers hope this could lead to new insights into the process of aging. Captive research colonies have had individuals live as long as 28 years. That is more than nine times as long as a research mouse! This longevity and unique durability lead even more scientists to consider the naked mole rat for captive study populations in the fight against other afflictions like stroke and cancer. If these superman-like traits haven’t given you a deeper appreciation for such a tiny hairless creature, perhaps you just need a clever ditty to sing their praises. Oh! …you so UGLY!
The Open Dinosaur Project
in Earth and Space Science, Life Science, Diversity of Organisms, Scientific Inquiry, and Biological Populations Change Over Time
Measuring the SMM camptosaurus: SMM paleo lab volunteers Becky Huset (left) and Neva Key consult over their ornithischian limb bone measurements for the Open Dinosaur Project.
Courtesy Mark RyanThe Open Dinosaur Project (ODP) allows anyone with an interest in paleontology, and access to skeletal information, scientific publications, or museum skeletons themselves the opportunity to be part of the compilation of an actual scientific paper. Paleontologists Andy Farke, Matt Wedel, and Mike Taylor make up the core ODP team, but only the core. The rest of the team is made up of individuals around the world. The hope is to put together a comprehensive database of information about the dimensions of limb bones (legs, arms, hands, and feet) of ornithischian (bird-hipped) dinosaurs in museums around the world with a goal of “investigating the evolution of locomotion and limb proportions in this group.”
“The Open Dinosaur Project fits very comfortably into that loose coalition of ideas: we’re trying to democratize science, open up data, blog the process, and make sure that the final publications are freely available to the world,” Mike Taylor said during a recent interview with the Brazilian science publication Ciência Hoje On-line.
Putting tape to toe: SMM volunteer Becky Huset measures the metatarsals and phalanx of the musuem's camptosaurus for the Open Dinosaur Project.
Courtesy Mark RyanTwo volunteers here at the Science Museum of Minnesota got themselves involved with this unique study. Becky Huset and Neva Key both work in the SMM paleo lab, usually hunched over fossils extracting them from rocks or preparing them for display. But recently, the two have spent time out on gallery floor measuring the limbs of some of the museum’s mounted ornithischian dinosaurs.
“We did the Camptosaurus and some cast bones from Stegosaurus from the collections,” Becky said. She added that measurements of the SMM Triceratops were already listed.
Why only ornithischian dinosaurs? Part of the reason was to keep the study somewhat manageable. But ornithischian dinosaurs also have an interesting evolution of locomotion that to date hasn’t been studied in depth. The dinosaur order radiated from a two-legged (biped) form into at least three different four-legged (quadruped) forms including armored dinosaurs (e.g. stegosaurs and ankylosaurs), ceratopsians (e.g. triceratops and chasmosaurus), and various ornithopod types, (e.g. camptosaurs, hadrosaurs, and iguanodontids).
.thumbnail.jpg "How to measure a scapcoracoid: One of several measuring aids available to project volunteers from the Open Dinosaur Project website.")
How to measure a scapcoracoid: One of several measuring aids available to project volunteers from the Open Dinosaur Project website.
Courtesy Open Dinosaur ProjectIn order to aid team members in gathering the proper information, instructions, templates, and other documents are available on the Open Dinosaur Project website. Diagrams explaining ornithischian limb osteology – including each bone’s proper name - are also on the site, as are illustrations showing exactly how to properly measure the dimensions of different bones. For those involved who don’t have access to museum specimens or material in other collections, the team leaders provide lists where prior publications with skeletal information can be accessed and mined for the study.
By last week, the Open Dinosaur Project had acquired nearly 1600 entries, but the results of all this work remain to be seen. The compiled data will be analyzed over the next couple months, and Farke, Wedel, and Taylor plan to begin writing the paper this spring. When completed the study will be submitted for publication in a peer-reviewed journal. If all goes as planned, after publication, the lead researchers will make all the data available online for future studies.
Now that their data has been entered on the ODP site, SMM volunteers Huset and Key will have their names included as contributors, and eligible to be included in the resulting paper.
"We wanted to get the general public excited about and involved in doing “real” science, working in cooperation with paleontologists. There is a great interest out there in paleontology, particularly dinosaurs. It’s amazing how many non-paleontologists read the technical literature! I thought, “Why not harness this enthusiasm?” There have been many people waiting for this sort of opportunity (even if they didn’t know it), and I think the response speaks for itself." – Andy Farke in Ciência Hoje On-line
Becky Huset enjoyed being involved with the project. “[It] sounded like a good idea,” she said. “I like having knowledge that is freely available to everyone, and it was a good way to contribute to a paper. Do some "real" work."
LINKS
Open Dinosaur Project website
Wedel’s & Taylor’s dino-related blog
More about Ornithischian dinosaurs
Osteology (the scientific study of bones)
Sinosauropteryx
Courtesy Chuang Zhao and Lida XingScientists from China and the United Kingdom say they have found hints of color present in the fossils of both an ancient bird called Confuciusornis and a non-avian dinosaur called Sinosauropteryx. Using an electron microscope the researchers detected differently-shaped organelles called melanosomes in the feathers of each creature. Melanosomes contain melanin which determines color in human hair, animal fur, and feathers, but it's the shape of the melanosomes that determine the shade.
"A ginger-haired person would have more spherical melanosomes, and a black-haired or grey-haired person would have more of the sausage-shaped structures," said Mike Benton, professor of paleontology at the University of Bristol, and leader of the study.
Both shapes were found in the remains of Confuciusornis, which lived during the Early Cretaceous period. In the Sinosauropteryx fossil, which dates back to the same time, light and dark bands visible along its tail were determined to be white and ginger in color when its fossilized melanosomes were viewed under the microscope. The presence of melanosomes also confirms that the turkey-sized dinosaur had actual feathers rather than just shredded connective tissue as some scientists have suggested. The research appears in the latest issue of Nature.
Watch an interview with Professor Benton.
SOURCES
University of Bristol page
BBC story
Elysia chlorotica: You think you're so special, don't you?
Courtesy lauredhelSome of you may already know my feelings on mollusks. In short, I’m against them.
It’s not that I necessarily want them all exterminated, or anything. It’s just that mollusks, with their tentacles and beaks and pseudopodia and large brains, freak my Schmidt out. And I tend to live under a “you’re either with us or against us” credo, and mollusks obviously aren’t “with us.” (They aren’t with me, anyway. Frankly, most things aren’t.)
But I get by. I know that there are mollusks out there, doing… I don’t know what. Probably something utterly horrible. But we leave each other alone, and more or less leave it at that. It’s a workable arrangement.
Now and again, however, a mollusk stretches its squishy neck out and, by its very existence, makes cracks in the already fragile JGordon/Mollusca peace. It’s like the cold war, really—if one side does something strange, or develops a fantastic new piece of technology, the other side gets a little nervous. So, naturally, I’m a little cagey about this news:
There’s a marine slug (a mollusk, of course, that feeds itself through photosynthesis.
Are you kidding me? I’m all, “I think I’ve got chronic anxiety!” and this lousy slug is like, “That’s too bad. Also, I feed myself with sunlight.” I can’t even get groceries because my car battery died (there’s a very scary tree near my bus stop, so that’s out), and this little jerk is a phototroph. If I had laser eyes, or something, the situation would be a little more balanced, but last time I checked I didn’t have laser eyes.
I have to give it to the slug, though—it’s a pretty neat trick. Early in its approximately one-year-long lifecycle, the slug eats some photosynthetic algae. From that point on, the slug is photosynthetic; it feeds itself by using sunlight to convert CO2 and water into sugar, just like plants do. What’s more, the photosynthesis isn’t being performed by algae inside the slug (some organisms, like lichen contain algae, which feeds them). The slug itself has genes for photosynthesis, and the photosynthesizing genes from the algae are just required to kick-start the slug’s own abilities. And then, BAM, a photosynthetic animal.
The leaf-shaped slug, which lives in salty swamps in Eastern Canada and grows to be about an inch long, is remarkable not only for its photosynthetic abilities, but also for something unique in the process written above. Getting those kick-starting genes from the algae requires gene transfer. Passing genes from one species to another is a rare and complicated thing, but some microscopic, single-celled organisms have been known to do it. This is the first time gene transfer has been observed between two multi-cellular organisms (the slug and the algae, of course).
Aside from being, well, just sort of weird, the slug’s gene transferring abilities might turn out to be useful in the future of gene therapy, where new genes are inserted into cells to combat diseases. A practical application whatever transferring mechanism the slug and algae use is a long way off, though. And, anyway, I’ll be damned if I ever use anything that came from a mollusk.
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