Gator breath...

The little red feathered dinosaur pictured here, and all its feathered relations, have respiratory systems structured very differently from yours and mine. Their lungs are small, but are supplemented by a group of internal air sacs - 7 or 9 of them, depending on the bird. The air sacs are significant for a couple of reasons - they allow a more or less constant supply of air to the lungs, and they also result in the flow of air through the lungs being unidirectional. The lungs of birds don't have alveoli like ours. Instead, they contain large numbers of tiny,highly vascularized tubules known as parabronchi. The unidirectional flow of air through the parabronchi minimizes the mixing of oxygen-rich and oxygen poor air and allows birds to extract oxygen more efficientlly. It has long been thought that this respiratory anatomy was associated with the development of birds and thier aerial lifestyle. New information suggests that it may not be that simple. This new insight comes from those close relatives of birds - alligators.

Nothing startling there. We've long known that alligators are more closely related to birds than they are to the animals in the traditional Class Reptilia. That similarity, indicated by a number of anatomical characteristics such as skull structure and backed up by DNA evidence, has led to the recognition that the Class Reptilia is not a good, monophyletic taxonomic division. Unless birds are included. Tables of contents of zoology text books are about to change.

Still, a study just published in the journal Science provides interesting new insight. Turns out that the american alligator (Alligator mississippiensis) also has a unidirectional flow of blood through its lungs. Of course, alligators are notoriously poor fliers. The fact that this unique respiratory anatomy is shared between alligators and birds pushes the development of it further into the past. Back into the Triassic, some 250 million years ago, prior to the split of the lineage leading to birds and crocodilians. The authors speculate that this remarkable adaptation, rather than being associated with the development of flight, may have given the ancestors of both birds and alligators a competitive advantage in the dryer, less oxygen-rich environment at the time. It's likely that other relatives of birds and alligators breathed in much the same way. That would be the dinosauars.

It's possible that you've run across this rather horrific image recently. It's been showing up in blogs or inboxes for a couple of months now. Most of the times that I've seen it, the suggestion has been that the jig is up for the duck. Teachable moment here. The large bird is a shoebill (Balaeniceps rex), a large, pelican-like bird that lives in the swamps of tropical east Africa. Adults may stand 5 feet tall with a wingspan approaching 10 feet. The common name refers to the distinctive shape of the bird's beak, better seen in an image without an obstructing duck. The beak is well-suited for scooping up prey in aquatic habitats. Like so many of the world's more interesting animals, the shoebill is in trouble. Estimates put the number of surviving shoebills at less than 10,000, and it is considered vulnerable to extinction. As with most threatened species, habitat destruction poses the greatest danger.

Turns out that the story has a happy ending. The photo was actually shot by Mark Kay at the San Diego Zoo. The shoebill was apparently simply moving the duck out of its path. Other photographs taken by Dr. Kay illustrate the outcome.

While perhaps not as exciting, the actual feeding habits of shoebills are fairly interesting. They wade in the east African swamps in search of fish, frogs, small crocodiles, and, yes, sometimes even small waterfowl. One of their preferred items, though, is the African lungfish. Follow the link for some remarkable footage of a shoebill catching and eating a lungfish.

There's absolutely nothing cooler than big fish. Of course, being of the ichthyological persuasion, I might be biased. But I think a lot of people would agree with me. And there's something particularly magical about big FRESHWATER fish. Sure, bluefin tuna, blue marlin, and great white sharks can be huge. But they're way out THERE. A 12 foot fish in your local river is something else entirely.

That's one reason the news reported yesterday at ScientificAmerican.com is especially sad. Two of the world's largest freshwater fish are in danger of extinction. Shocker, right? The Kootenai River population of white sturgeon (Acipenser transmontanus), reported to reach lengths of 18 feet and weigh a half ton, has dwindled from an estimated population of 10,000 in the 1970s to some 500 today. You probably wouldn't be that surprised by the cause of this decline either. Freshwater river living in rivers, declining in numbers in the last century? You can generally bet "dam", and you won't be wrong very often. Libby Dam, built in 1975, impounds the Kootenai and creates Lake Koocanusa, which extends some 90 miles up the river basin behind the dam. The impoundment prevents the periodic flooding, which served as a spawning signal for the river's sturgeon. As a result, the Kootenai white sturgeon have not spawned in the wild for 35 years.
Wildlife biologists are not giving up, and are spearheading a drive to save the sturgeon by opening the floodgates to increase river flow at key times. The Fish and Wildlife Service reports that, thus far, these efforts have been unsuccessful.

The Neotropics have (had?) their own, equally impressive giant, the Amazonian arapaima (Arapaima gigas). The arapaima, also known locally as the piraracu, is the world's largest scaled fish, reaching lengths of over 8 feet (it should be noted that a single, unverified report indicates a maximum size of over 12 feet). Recent museum studies suggest that the arapaima is not a single species, but actually four unique types of fish. This has led to the fear that one or more species may already be gone. The problem for the arapaima is not river impoundment, but overfishing. It is a prized food fish in South America, and its air-breathing habits make it particularly vulnerable to a variety of fishing techniques.
Wanna see the arapaima in action? Sure you do...

He's a semi-aquatic, egg-laying mammal of action....



...and he's got a secret weapon that James Bond would be proud of.

There's no question that the platypus (Ornithorhynchus anatinus) is one of the cooler animals on the planet. It's one of only five surviving species of egg-laying mammals (along with four species of echidnas), it has a tail like a beaver, and a beak like a duck (reflected in both its genus and species names). It is unique enough, and symbolic enough of its homeland, that it's featured on the Australian twenty cent piece. What is less well known about the platypus is that it is also one of very few venomous mammals. Most of the others are shrews, or shrew-like solenodons, which produce venom in modified salivary glands and deliver it through their bite in the same way that venomous snakes do. The platypus is different, in that it has an ankle spur on its hind limb connected to crural gland which produces a pretty impressive witch's brew of proteins. The venom is capable of killing small animals - it's not lethal to humans but, by all accounts, will produce an experience not soon forgotten. The excruciating pain can persist as hyperalgesia that may last for weeks. Both males and females have spurs, but only males produce the venom - that makes it even more interesting from an evolutionary perspective. Throw in the fact that venom production increases in during the mating season and it seems likely that we're looking at an adaptation associated with a dominance heirarchy associated with reproduction.

In a study just published by the American Chemical Society, Misaki Kita and colleagues describe their analyses of the venom of the platypus. Employing a bioassay using nerve cells, they identified eleven novel peptides, with one called heptapeptide-1 playing a particularly significant role. Their studies suggested that the venom might act by affecting the influx of calcium ions in nerve cells. The venom is described as being "like hundreds of hornet stings." So, while he may look cute, step lightly. He's packin'.

It's going to be a long road back for the Haitian people. If you'd like to help out, I'm sure there will be lots of opportunities. Here's one.

Thoughts go out to the good people of Haiti. Enough problems to deal with without this. I know there are many, many causes out there deserving of your charitable dollar. This will certainly be one.

Three species of iguanas in the genus Brachylophus are restricted to the remote Pacific islands of Fiji and Tonga, and represent the most geographically isolated iguanas in the world. For years, they were believed to be the descendants of South American iguanas that had rafted to the islands some 13 million years ago. The prospect of a pregnant iguana, or a boa constrictor for that matter, taking refuge on a mass of floating vegetation and drifting for thousands of miles across the Pacific until it ultimately makes landfall on a desert isle has long been biogeography's ace in the hole. Typically referred to as a "sweepstake" route, this type of somewhat random, long-distance dispersal can certainly be used to explain unusual distribution patterns. Got a group of organisms that are distributed on a continental mainland and on some, but not all, nearby (or not so nearby) islands? Then we can postulate that it rafted from the mainland to those islands where it's found, and not the one's where it's missing. Without question, this is undoubtedly the correct answer to some biogeographical puzzles. However, as with any ace in the hole, you have to be careful how you use it. The probability of such an event, although real, is astronomical. If we have to pull out the sweepstakes dispersal argument too often, it begins to lose its power.

The Fijian iguanas are among the most problematical of such cases - it's a long, long way from South American to Fiji. Even with drifting continents, it's been a long way for a long time. The working hypothesis had the ancestors of the islanders drifting perhaps as much as 5,000 miles. New evidence suggests that it might not have been that difficult - maybe they just walked. Brian Noonan of the University of Mississippi (that's Ole Miss for you SEC fans) and Jack Sites from Brigham Young have published work in The American Naturalist in which they use new molecular data to produce a new estimate regarding the divergence of the island iguanas from their continental relatives. Their analysis suggests a much more ancient divergence of the two lines than had previously been believed. Noonan and Site's data suggests that the Fijian iguanas diverged from their South American cousins over 50 million years ago. This changes the playing field. Literally.

In the Eocene epoch, the position of the continents was dramatically different. There was likely a land bridge (or, at least, an "island-hopping") connection between South America and Antarctica, and between Antarctica and Australia. Throw in the considerably warmer and more homogeneous climate patterns of the Eocene, and we have a much more workable hypothesis to get our iguanas to the isolated islands.

But wait... If we can explain the presence of iguanas on Fiji and Tonga as the result of a widespread distribution across the Southern Hemisphere dating back to the Eocene, then why aren't they found on many other islands in the South Pacific? Noonan and Site have a plausible explanation for that as well. Fossil evidence suggests that iguanas did, in fact, inhabit other South Sea islands, but disappeared. In most cases, that disappearance seems to coincide with the arrival of humans on the islands. And yes, the islanders apparently had a sweet tooth for iguana flesh.

So why haven't the species found on Fiji and Tonga disappeared yet? Well, simply because humans haven't been on those islands as long as an most islands in the region. But give us time...

The last year, of course, has been a big one for evolutionary biologists. We marked Charles Darwin's 200th birthday on February 12 of last year, and on November 24th celebrated the 150th anniversary of the publication of Origin of Species. As a result, we've seen a tremendous outpouring of words regarding the influence of Darwin's work. Still a long way to go, though, to reach the level of awareness that's needed.

We now require a course in evolutionary biology for all of our biology majors. The student reaction varies greatly, typically depending on their field of interest. The field biology types love it, and can't get enough examples and ideas as they try to understand the adaptations they see in their favorite plants and animals. Future educators are a little apprehensive but, for the most part, understand why they need to have some background as they prepare to go out and teach reluctant high schoolers. The toughest group are the premeds. It's not that they're necessarily any more resistant to evolutionary thought than other students; in fact, as a group they are might be a bit more well-read and open-minded than others. It's just that your typical premed is very focused, very driven, and very goal-oriented. A cliche, of course, but not an inaccurate one. At the curriculum level, this translates to, "Don't put me in any class that's not going to help me get into med school." It's sometimes hard for to convince them to how a course dealing with Darwin and speciation and natural selection is beneficial to them.

Wll, our task is getting easier. In a recent paper appearing in the Proceedings of the National Academy of Sciences (available here for free download), Randolph Nesse and his colleagues make a strong argument that evolutionary biology should be considered a basic science for future physicians. Nesse has been a pioneer in this arena - his 1994 book, coauthored with G. C. Williams, Why We Get Sick: The New Science of Darwinian Medicine, is perhaps the best popular exposition of the ideas underlying the new discipline. In the PNAS paper, the authors highlight the key elements making an understanding of evolutionary processes critical for physicians. Doctors must learn to view the human body, not as a machine beset by potential malfunctions, but as a complex system shaped by evolutionary process. Nesse et al. suggest that premedical students should complete evolution courses that emphasize medically pertinent aspects of the field. They go on to recommend that medical schools should teach evolutionary biology as a basic medical science.

We agree, and will try to do our part.

By the way, the American Museum of Natural History maintains an extensive website dealing with Darwin's life and work. It provides the opportunity to view some of the remaining manuscript leaves from Origin of Species. Pretty cool. Check it our here.

As good an opportunity as I can find, I guess, to post this....

The woman who thinks like a cow is Temple Grandin. Dr. Grandin is a professor of animal science at Colorado State University and a leading researcher in the area of animal behavior. She's also the world's most famous autistic person. Autism is a developmental neural disorder, typically manifesting itself before the age of three and usually resulting in an impairment of communciative abilities and social interactions. Autistic individuals often demonstrate restricted and repeated behaviors. Dr. Grandin has shown remarkable insight into animal behavior, and believes that her autism enables her to more fully understand the neural processes of the animals with which she works.

Autism seems to have a genetic basis, although the inheritance of the disorder is not well understood. You've probably heard a little about the controversy surrounding autism and things like pesticides and vaccines. Thus far, though, there is little scientific evidence to suggest a link between autism and environmental agents. There has been some progress, however, in getting at the real causes of the disorder. A new study published in Nature Neuroscience has uncovered evidence that faulty neural connections in the region of the brain functioning in social cognition may lead to autism. The activation of a molecular pathway known as mTOR seems to be involved. This suggests a possible treatment, since drugs inhibiting mTOR are already FDA approved. Keep an eye on this.

By the way, if you think that Temple Grandin sounds like an interesting character, you might be interested in the upcoming movie based on her life. It's set to premiere on HBO on February 6th, with Claire Danes playing Dr. Grandin. Long way from "My So-Called Life."

The most significant driving force behind evolution, of course, is natural selection. But what is it that's being selected? Seems simple enough on the surface. An individual organism - a whitetail deer, an oak tree, a bacterium - has a trait that results in an increased likelihood of survival or reproduction. As a result, it leaves a few more offspring than its neighbors. But it runs deeper than that. Since those beneficial traits are the results of the organism's genetic makeup, it's at the level of the gene that selection typically acts. Certain organisms are fortunate enough to carry, in their genome, copies of genes that produce traits that are, in a relative sense, "better" than the traits displayed by other members of the population.

We know that, over the course of human evolution, a host of mutations have accumulated in our current genome. Until recently, however, it's been difficult to actually put our finger on particular beneficial genes. Our ability to do so has been complicated by the fact that, when a gene is selected and becomes more abundant in the genome, a lot of "junk", neighboring genetic material which is selectively neutral, is carried along. An interesting story at ScientificAmerican.com discusses recent work published by a group led by Pardis Sabeti, an assistant professor in Harvard's Department of Organismal and Evolutionary Biology. Sabeti's research team has used a battery of statistical techniques to identify the particular beneficial gene in blocks of genetic information. Among the strategies employed are an examination of the ancestry of particular genomes. Comparing groups that developed under different environmental pressures helps shed light on the whether genetic variation is a beneficial mutation, or just background noise.

The technique resulted in a hundredfold increase in the ability of the researchers to localize a selected gene, and allowed them to identify a number of beneficial variants. These included a gene affecting pigmentation, one related to sensory perception, and a gene called "large" that may be associated with resistance of some African populations the virus that causes Lassa fever.

As advances in techniques allow us to rapidly accumulate massive amounts of genetic information, our ability to extract some meaning from it becomes critical. Techniques such as those developed by Dr. Sabeti and her team may provide the key.

Oh, and one more thing...



What's the significance of the music video? Well, take a look at the lead singer.

That's Pardis Sabeti - Rhodes scholar, Harvard geneticist, architect of groundbreaking research in human genetics... and lead singer of the alternative rock band Thousand Days.

So, what did you do today?