"He must, so know the starfish and the student biologist who sits at the feet of living things, proliferate in all directions. Having certain tendencies, he must move along their lines to the limit of their potentialities."
Take a look at the two butterflies on the right. Identical, right? Well, not exactly. They're actually two separate species in the genus Heliconia. That's H. melpomene on the top and H. erato on the bottom. They're classic examples of what's known ecologists and evolutionary biologists refer to as Mullerian mimicry, the situation in which two untasty organisms come to resemble one another as a way of reinforcing their evolutionary lesson of unpalatability. The butterflies have long been a rich source of examples of mimicry, from the old story of the monarch and the viceroy (which has turned out not to be as simple as previously believed) to the many examples of mimicry demonstrated by the heliconids, commonly known as the passion-vine butterflies.
Such perfect mimicry has motivated researchers to understand the genetic mechanism by which its produced. Given the large size of the genome, it was considered likely that different genes had to be involved in producing the color patterns observed in the two butterfly species. As it turns out - not the case. Two papers in PLoS Genetics, one examining the population genetics of H. melpomene and another mirroring that work for H. erato, indicate that very small regions of the genomes of both butterflies are involved in determining the color pattern of the wings. Other genes, corresponding to those that affect color pattern of other butterflies, do not play a role in the mimicry.
The researchers now plan to turn their focus to the genetic control of behavior in these species, as preliminary results indicate that the same genes are involved.
Researchers at the University of Minnesota's Institute of Technology have demonstrated that the shapes of fishes are probably influenced by their hydrodynamic environment. Pretty sure we shouldn't be surprised by that. Tuna and flounder, eels and batfish - they've all been pretty specifically to fit into a particular flow (or non-flow) regime. Of course, the toys that these guys employed are pretty cool. The designed two virtual mackerels and two virtual eels. Then, they made one mackerel move like a mackerel and the other one move like an eel. Same with the computerized eels. Then they raced them through a virtual environment. And guess what? The mackerel that was shaped like a mackerel won, as did the eel that was shaped like an eel.
Actually, that's not a trivial as it sounds. Perhaps it's obvious that a fish in a high flow environment should be more streamlined, but it's not as intuitive that a slow swimmer like an eel is actually better suited with an eel-like body - it's certainly possible that other selective pressures could be driving body shape. This work suggests that, for fish, moving through the water efficiently is a huge factor in being successful.
ScientificAmerican.com had an interesting story last month about some fancy detective work investigating the disappearance of North America's megafauna. What we know is that 15,000 years ago, after the last great glaciation, North America was home to an incredibly impressive array of large mammals - one that would rival or exceed that seen on the plains of Africa. American lions, saber-toothed cats, mammoths, mastodons, giant sloths - this list goes on. Even giant birds like the teratorn. We also know that this tremendously diverse group of large animals disappeared rather quickly during the Pleistocene. What we don't know is why. One possible answer is a familiar one - us. A lot of evidence points to the disappearance of North America's large mammals coinciding closely with the appearance of a moderately sized one known as Homo sapiens. In the Late Pleistocene, human hunter-gatherers were migrating from northern Asia into the Americas across the Bering Land Bridge. The guys that usually take the fall are the Clovis people, thought to have made the trek around 13,500 years ago. The southward spread of the Clovis culture, and their distinctive spear points, seems to coincide rather closely with the demise of the the mammoths and their brethren. A lot of healthy debate remains, though.
The Scientific American story details several studies that have investigated the question using dramatically different techniques. In the November 20, 2009 issue of Science, Jacquelyn Gill and coworkers describe their work in which they examine various evidence, including fossil dung. of large herbivores. The dung deposits contain a fungus known as Sporomiella, the amount of which can be used to estimate the density of mammoths and their contemporaries. In addition, pollen and charcoal deposits can be utilized to estimate plant coverage and fire frequencies, both indicators of herbivore densities. From this evidentiary potpourri, Gill and her coworkers deduce that the majority of the big guys disappeared between 14,800 and 13,700 years ago. That would put their downfall well in advance of the arrival of the Clovis culture.
A somewhat more direct line of evidence is discussed in a paper published online by in the Proceedings of the National Academy of Sciences. J. Tyler Faith and Todd Surrovel report their results from carbon-dating of fossil specimens from different genera of North American mammals. They found that, of the 35 general that went extinct during the Pleistocene, 16 could be reliably said to have have vanished between 13,800 and 11,400 years ago - well within the time interval that would allow a Clovis conviction.
But wait... Still another study, this one appearing online at PNAS on December 14, examines DNA extracted from frozen permafrost in Alaska (yes, you read that correctly). Using this pretty sexy technology, Eske Willerslev and his team show the presence of horses and mammoths in Alaska as recently as 10,500 years ago, long after the arrival of human civilization and their supposed decimation of the great North American mammal fauna.
So - three studies, three seemingly contradictory results. But, not necessarily. While it has certainly been suggested that the extermination of the megafauna could have occurred in a geological instant, that doesn't mean that it couldn't have spanned a period of a few thousand years. It's possible that the these studies are painting a portrait of a dramatic extinction event as it started, progressed, and ended.
Considered using some footage from 10,000 B.C. up top. But the cartoon was more believable.
A physiological "law" that many of us learned in college may just be plain wrong. The "3/4 exponent" law relating size to basal metabolic rate probably should be the "2/3 exponent" law.
New paper in Nature identifies a key protein produced by the malarial parasite Plasmodium as part of the process by which it commandeers red blood cells. Understanding the nature of the protein may allow researchers to arrest the infection.
Born ugly, and doomed to extinction. Woe is the blobfish.
New tyrannosaur from New Mexico, the first new one from western North America in over 30 years. Bistahieversor, described by Thomas Carr and Thomas Williamson, was some 9 meters in length and dates to the late Cretaceous.
Some paleontologists go the Gobi Desert and dig up petrified dinosaurs. Some watch lampreys rot. But it's all good.
Our knowledge of the earliest chordates, the ones that showed up in the Cambrian before the evolution of vertebrae and other bones, is sketchy. You'll see images, like the one of Pikaia here, but they're based on the interpretation of a small number of fossils formed when everything fell into place for the preservation of the soft parts remaining after their demise. The picture they paint of our 500 million year old ancestors is nebulous and, perhaps, flawed. And it took rotting lampreys to tell us that.
Researchers at the University of Leicester report in Nature on a study in which they observed the decomposition of the larvae of the modern-day lamprey of genus Lampetra and the lancelet Branchiostoma. These animals are the closest living analogues to the earliest living chordates. What they found may force a rethinking of our interpretation of these earliest chordate fossils?
The research team, led by Mark Purnell of Leicester's Department of Geology, found that the the decomposition process proceeded in a non-random fashion. While some features, like the liver, persisted for months, others, like the heart, were gone within two weeks. Some of the features most important in recognizing advancements in the early chordates are among the most rapid to decay. This raises the real possibility that fossils interpreted as very primitive chordate ancestors may actually be more complex organisms in which key features had simply rotted away prior to preservation. New information such as this may lead to some reevaluation of our ideas about what evolved when. However, caution is in order. The fact that a structure might have been lost to decay doesn't mean it was.
The Monterey Bay Aquarium is one of the world's best. Also one of the more environmentally forward-thinking. Spend a little time checking out their web cams. This is the for the Outer Bay exhibit, but they also have cameras on other exhibits as well (check ou the one overlooking Monterey Bay). The bluefin tuna and pelagic rays are impressive, although there is apparently not a Mola molaon exhibit now.
Invasive species are changing the game all over the world. Pterois volitans, the lionfish, is one of the more dramatic.
Perhaps introduced after Hurricane Andrew in 1992, lionfish are spreading rapidly along the Atlantic coast. The invasion is aided by a lack of predators, an unwillingness of local fisherman to utilize it, and, perhaps most importantly, an apparent ability to resist local parasites. Here's an NPR report from last summer - give it a listen.
Take a look at the two butterflies on the right. Identical, right? Well, not exactly. They're actually two separate species in the genus Heliconia. That's H. melpomene on the top and H. erato on the bottom. They're classic examples of what's known ecologists and evolutionary biologists refer to as Mullerian mimicry, the situation in which two untasty organisms come to resemble one another as a way of reinforcing their evolutionary lesson of unpalatability. The butterflies have long been a rich source of 
examples of mimicry, from the old story of the monarch and the viceroy (which has turned out not to be as simple as previously believed) to the many examples of mimicry demonstrated by the heliconids, commonly known as the passion-vine butterflies.
