Left-handed Snails Beat Snail-eating Snakes

Masaki Hoso reported that the snail-eating snake, Pareas iwasakii, has lopsided jaws to better enable it to tug snails out of their shells. Most snails have shells that whirl clockwise (to the right) so P. iwasakii has evolved an upper jaw with more teeth on the right side than the left. In a sample of 28 snakes, the Hoso found each one had an average of 17.5 teeth on its left jaw and 24.9 teeth on the right.
The lack of symmetry helps the snake pry the snails out of their shells with alternate retractions of their left and right jaws, a technique called "mandible walking".

Here's a video of the snake preying upon a "right-handed" snail.

The snail, Satsuma c. caliginosa, has countered the snake's adaptation by evolving a left-handed swirling pattern.

Hoso et al. write in Biology Letters:

In addition, our experiments demonstrate a defensive function of sinistrality for snails against snake predators. Sinistral variants have been generally considered to suffer selective disadvantages on account of the overwhelming predominance of dextrals (Vermeij 1975, 2002; Johnson 1982; Gould et al. 1985; Asami et al. 1998; but see Dietl & Hendricks 2006). However, sinistrals should enjoy a selective advantage over dextrals under chirally biased predation by snakes. The remarkable diversity of sinistral snails in Southeast Asia (Vermeij 1975; Hoso et al. 2006, unpublished data) may be attributable to ‘right-handed predation’ by the snakes.

In the video below, P. iwasakii attacks but fails to consume the lefty snail.

How cool is that?

Hoso, M., Asami, T., & Hori, M. (2007). Right-handed snakes: convergent evolution of asymmetry for functional specialization Biology Letters, 3 (2), 169-172 DOI: 10.1098/rsbl.2006.0600

Evolution 2009 Moscow, ID

I have finally arrived in Moscow, ID for the the joint annual meeting of the Society for the Study of Evolution (SSE), the Society of Systematic Biologists (SSB), and the American Society of Naturalists (ASN). It was a long and enjoyable drive from Salt Lake City where I met up with Weber State evolutionary biologist and fellow blogger Jon Marshall. Along the way we stopped at Waterfall Canyon and the Hot Pots in Ogden, the Craters of the Moon, Ernest Hemingway's grave, and more hot springs in Stanley.

Several other bloggers are participating in the festivities.

I'll be posting about the scientific content as time permits over the weekend, but now it's time for a few beers at the opening reception and Genie Scott's Stephen Jay Gould Award Lecture "The Public Understanding of Evolution and the KISS Principle."

Roald Dahl on Vaccines

When I was younger, my favorite book was James and the Giant Peach by Roald Dahl (also author of Charlie and the Chocolate Factory and Matilda). Turns out that book was dedicated to his daughter Olivia, who tragically died of measles. In this article, Dahl stresses the importance of vaccinations.

Dahl writes "...there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised against measles. I was unable to do that for Olivia in 1962 because in those days a reliable measles vaccine had not been discovered. Today a good and safe vaccine is available to every family and all you have to do is to ask your doctor to administer it. It is not yet generally accepted that measles can be a dangerous illness. Believe me, it is. In my opinion parents who now refuse to have their children immunised are putting the lives of those children at risk.... It really is almost a crime to allow your child to go unimmunised."

Vaccine Wars: The Phantom Menace

It's been 9 months since I read Autism's False Prophets and participated in a discussion over at Science Blogs Book Club. The good news is that there is increased awareness of the overwhelming scientific evidence refutating a link between vaccines and autism. Many organizations including the CDC, the Courts and the National Academy of Science, have all rejected a link between vaccines and autism.

There's even a Jenny McCarthy Body Count. (Former playmate Jenny McCarthy is the most prominent of the anti-vaccine advocates).

So why is the anti-vaccine movement still strong? Oprah has notably given Jenny McCarthy a highly visible platform. Despite overwhelming evidence that vaccines don't cause autism, one in four Americans still think they do. This has led to upsurges in measles, mumps and whooping cough among other easily preventable diseases. Large numbers of unvaccinated kids are dropping the population immunity below the herd immunity threshold for many diseases.

A great article investigating this tragedy is now available at PLoS Biology.

As the article points out, there is a conflict between individual interests and community interests. Pediatrician Jeffrey Baker says that "parents who claim nonmedical exemptions seem to become so focused on their own children that they “lose the bigger picture,” not accepting responsibility for the impacts their actions may have on the health of the community."

Autism's False Prophet's author Paul Offit blames "the media for keeping the myth alive by following the journalistic mantra of ‘balance,’ perpetually presenting two sides of an issue even when only one side is supported by the science. And shows like “Larry King Live” have been “just awful on this issue,” he adds, placing ratings and controversy above public health by repeatedly giving McCarthy and other “true believers” a platform to peddle fear and misinformation."

Medical anthropologist Sharon Kauffman thinks that the easy access to information online has exacerbated the crisis. Kaufman says, “many parents see even the most respected vaccine experts' perspective on the issue as just one more opinion.”

Article author Liza Gross writes, "Scientists on TV and radio are hard-pressed to compete with the emotional appeals of activists....McCarthy emerged as a hero for some parents by telling her story. Personal stories resonate most with those who see trust in experts as a risk in itself—a possibility whenever people must grapple with science-based decisions that affect them, whether they're asked to make sacrifices to help curb global warming or vaccinate their kids for public health. Researchers might consider taking a page out of the hero's handbook by embracing the power of stories—that is, adding a bit of drama—to show that even though scientists can't say just what causes autism or how to prevent it, the evidence tells us not to blame vaccines. As news of epidemics spreads along with newly unfettered infectious diseases, those clinging to doubt about vaccines may come to realize that several potentially deadly diseases are just a plane ride, or playground, away—and that vaccines really do save lives.

"Embracing the power of stories" sounds like framing to me. The notion was abhorrent to me when I first read the Nisbit and Mooney article, but lately I've been feeling less certain regarding the role of scientists in their intersection with the media.

Gross, L. (2009). A Broken Trust: Lessons from the Vaccine–Autism Wars PLoS Biology, 7 (5) DOI: 10.1371/journal.pbio.1000114

Scientia Pro Publica #4 - In Memory of Stephen Jay Gould

Stephen Jay Gould is my homeboy. True story, he grew up in my present hometown of Bayside, NY. I am honored to be included in a blog carnival in his memory: Scientia Pro Publica #4.

I never met SJG, but I did bump into him once. Literally! When I was a junior in college, I visited MCZ at Harvard on my way to the Ernst Mayr Library. (Back in olden days, we didn't have access to "online" articles. If you wanted an article, you had to go to the library and photocopy it from a bound volume.) As I was climbing the stairs to the library, a door swung open and SJG came barreling out, and collided with me. He hardly hesitated save to glance back and scowl at me. Or maybe it was a look of surprise. Hard to say since it happened so fast. I haven't been so thrilled to see a celebrity since the time I sat next to Bobby Orr at a hockey game.

Missing Link Found?

Franzen et al. announced the discovery of the most complete transitional fossil primate ever found. The fossil, described as Darwinius masillae, shows prosimian characteristics (e.g. a grooming claw on the second digit of the foot, and a fused row of teeth in the middle of her lower jaw known as a toothcomb), but has toe and fingernails, opposable thumbs, and a humanlike talus bone.

The Conclusions/Significance section of the abstract tells us,

Darwinius masillae represents the most complete fossil primate ever found, including both skeleton, soft body outline and contents of the digestive tract. Study of all these features allows a fairly complete reconstruction of life history, locomotion, and diet. Any future study of Eocene-Oligocene primates should benefit from information preserved in the Darwinius holotype. Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification.

The announcement accompanies a veritable "media tsunami", including a American Museum of Natural History unveiling, a New York Times article, and a two-hour documentary to be broadcast on the History Channel on Memorial Day (May 25th).

Hype? Uberhype?

Probably, but I am withholding judgment until I find out more about it. Generally speaking, I am in favor greater public awareness of transitional evolutionary fossils. Even if this turns out to be somewhat inaccurate, and the precise phylogenetic position isn't directly linked to man, it will still raise awareness of evolutionary theory among an ill-educated public.

Franzen, J., Gingerich, P., Habersetzer, J., Hurum, J., von Koenigswald, W., & Smith, B. (2009). Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology PLoS ONE, 4 (5) DOI: 10.1371/journal.pone.0005723

The Giant’s Shoulders #11

The Giant's Shoulders #11 is up at Curving Normality. This month's issue has excellent reads from Schrodinger, Faraday, Darwin, et al. I particularly liked the article by Eric Michael Johnson, who blogs at The Primate Diaries. In the article, Rivalry Among the Reefs, Johnson writes about Darwin's little known coral reef work.

Coral reefs hold an important place in the history of evolutionary theory, as they were the subject of Darwin’s first scientific monograph and his official entrance into the scientific community. It was this research, and his eight-year study of barnacles, that led to the Royal Society awarding him the Copley Medal for outstanding achievement in science. Based on depth measurements taken of the coral reefs at Cook, Keeling and Mauritius Islands, Darwin developed his theory of “subsidence” to explain their development. Darwin didn’t know just how coral reefs grew, but he was aware that the living coral formed fringing reefs just below sea level along many coastlines. He was also aware of white strips of limestone that encircled volcanoes throughout the South Pacific. Darwin theorized that these were the remnants of fringing reefs that had been raised above sea level by the rising volcano. The same logic should therefore operate in reverse; if the coast were sinking then the coral would continue to grow upwards in order to remain in the warm, sunlit waters. Eventually, once the coastline was completely submerged, all that would remain would be the coral atoll. After arguing away every problem that had previously plagued coral reef formation, Darwin was left with his triumphant conclusion.

"On this view every difficulty vanishes; fringing-reefs are thus converted into barrier-reefs; and barrier-reefs, when encircling islands, are thus converted into atolls, the instant the last pinnacle of land sinks beneath the surface of the ocean."

Darwin was later shown to be correct by Dr. Harry Ladd, a researcher for the US Geological Survey. Ladd convinced the US War Department to drill holes deep into the Bikini and Eniwetok Atolls just prior to their obliteration in 1952 by hydrogen bombs.

After digging nearly 5,000 feet through the coral of Eniwetok Atoll, the drill finally passed through and hit pay dirt. The atoll had been built up from coral as the land had sunk from view, just as the theory of subsidence had predicted. Tiny organisms, just millimeters across, had pulled themselves up by their own bootstraps to create the largest natural structures ever created by a living being. Just next to the borehole that ended the debate, Ladd erected a small sign that still stands today. It reads, simply “Darwin was right!”

Figure: Darwin's drawing of a reef from Voyage of the Beagle.