Monday (today, December 1), I’ll be talking about science writing at a Master’s Tea at Saybrook College at Yale University at 4. It’s open to Yale students and faculty.

On Thursday at 7 pm I’ll be talking at Rockefeller University in Manhattan, as part of the NYC Skeptics Public Lecture Series. The title of the talk is “The Darwin Beat.” Here are more details. Admission is free.

Hope to see some Loom readers there…

Under the magnificent rotunda at Columbia’s Low Library, we sat down to dinner. Michael Purdy, the director of Columbia’s Lamont-Doherty Geological Observatory, kicked off the event by explaining that Alvarez was winning the award because he had changed the way earth scientists view the history of the Earth. Later, Columbia president Lee Bollinger got up to present him with the award, declaring that Alvarez had shown how life was intimately connected to the cosmos. The real highlight of the evening, however, was listening to Alvarez himself.

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Image: The Vetlesen Prize site

Rumpho discovered that the sea slug has incorporated a key gene for photosynthesis from the algae into its own DNA. That means that the slugs don’t just passively let the photosynthesizing structures from the algae (called plastids) harness sunlight. The slugs themselves actually make proteins that are essential for photosynthesis.

I wondered how in the world a gene from algae got into the slug’s own DNA. Rumpho responded (my notes in brackets):

Our thoughts are that the nuclei break open as they go through the guy, releasing their DNA. The DNA is then phagocytosed [eaten] along with the chloroplasts into cells lining the digestive system. The digestive system expands throughout the growing sea slug and interestingly it is found to branch right next to the reproductive organs. In addition, the invertebrate has an open “blood” system, so if the DNA was exchanged from the gut into the blood, it also would come in direct contact with the reproductive organs.

We are doing high-throughput sequencing now on the sea slug transcriptome [the genes expressed in specific cells] and hopefully soon, the genome, so we should learn a lot more about which genes are there.  I will also mention that we frequently/always? find a virus in the sea slug that really takes off as the sea slugs age. We believe it might be a retro-virus, but the support is not strong at this time.  It’s possible the DNA is moving via a viral vector through the blood to the germ line.

Yet another example of a discovery in evolution leading to a new hypothesis, leading in turn to a new experiment. And yet another wrinkle for Hollywood to consider (alien race of plant people who evolved photosynthesis when a deadly virus picked up DNA from their salads inserted it into their DNA…you get the idea…)

The Franklin Institute, Discover Magazine and the National Science Foundation present a fascinating neuroscience symposium.

“Unlocking the Secrets and Powers of the Brain.”
Date: November 19
Time: 7:00pm
Event location: Franklin Theater
Admission: Free with advanced registration, please call 215.448.1254

Moderated by award-winning journalist Carl Zimmer, the discussion features Dan Levitin (best-selling author of This is Your Brain On Music), Michael Gazzaniga (Director for the SAGE Center for the Study of Mind at UC Santa Barbara), Rebecca Saxe (Assistant Professor of Cognitive Neuroscience at MIT), Sam Wang (Welcome to Your Brain) and Ron Mangun (Interim Dean of Social Sciences, a Professor of Psychology and Neurology, and the Director of the Center for Mind and Brain at the UC Davis). A book signing will follow.

Andy writes:

This is all your fault, you know: a bike-riding forum I hang out on had a “check out these science tattoos!” thread, and it got me to thinking: what bicycle science tats are there?  I’d just celebrated my 25th year
in the saddle and was jonesing for some ink.

For ages I struggled to find something that abstracted the kinetics of bikes down to a couple of lines - with no success.

Then I found the power equation in MIT’s _Bicycling Science_ (and Wikipedia).  It describes the power needed to propel a bike against our everyday foes: gravity, weight, friction, wind resistance.  And it describes beautifully the way that the linear components of the resistance give over to the fat slamming wall of wind resistance.

So, of course, I got it tattooed on my calf.  

Thanks for the album.  The passion of nerds is just as intense as the passion of everyday folks, and it’s great to see more of ‘em out there.

Carl: We have crossed a threshold here at the Science Tattoo Emporium. People used to get tattoos, then find out about the Emporium. Now the reverse is happening. So let me take this moment to say that I take no blame if this emporium (and perhaps a glass or two of Frangelico) prompts anyone to get a science-related tattoo they regret the next day. Of course, if you like the results–send them here.

Click here to go to the full Science Tattoo Emporium.

Re: Plant People Concept

Here are the specifics for the aliens in our next movie, VOYAGE TO THE PLANET OF THE PLANT PEOPLE. The people there are vegetarians, eating salads, seaweed drinks, etc. They are green, because when they digest their meals, their bodies move some of the plant matter to their skin. They use it to capture energy from the sun through photosynthesis. So the aliens sit outside in the sun a lot, getting lots of energy and growing to huge sizes, which is why they’re so hard to kill when Earthlings show up. I see the people from Blue Man Group–just add some yellow and we’re set. Or maybe William Dafoe?

Behold, Hollywood, the sea slug Elysia chlorotica. This emerald green slug grazes on algae. As it breaks down the algae, it preserves their photosynthetic structures, called plastids. The plastids are shipped to the surface of its body, where they can continue to photosynthesize. The slug thus makes a living as plants do. And it turns a beautiful shade of green along the way.

Recently, some scientists discovered that the sea slug is even more plantlike than previously thought thought. They wondered if some genes from the algae the slug ate had become incorporated into their own DNA. This movement of genes is called horizontal gene transfer. It’s common among bacteria, which swap genes for antibiotic resistance and such. It’s not as common among multicellular creatures, but it has happened a number of times. For example, our ancestors swallowed up bacteria that eventually became our mitochondria, the structures in our cells that use oxygen to generate energy. Mitochondria still have some of their own bacterial genes, and other bacterial genes have moved into our own DNA. The ancestors of green algae and plants swallowed up photosynthetic bacteria and harnessed their ability to photosynthesize. Those bacteria became plastids. The p of the genes from the plastids are now part of the DNA of plants.

Mary Rumpho of the University of Maine and her colleagues suspected that something like this had happened to the sea slugs. They were struck by the fact that the plastids continue to function in the slugs for months after they’ve been extracted from algae. But plastids normally can’t function on their own. They need help from proteins encoded by genes that are now carried in the algae’s DNA. It was possible that the slugs were making the proteins for their plastids.

So Rumpho’s group gathered up some sea slugs off the coast of Martha’s Vineyard and took a look at their DNA. They also took a look at the DNA of the one species of algae that the slugs put in their skin. As they suspected, the plasmids don’t have all the genes necessary for photosynthesis. The scientists discovered a crucial photosynthesis gene, called psbO, in the DNA of the slug. In fact, the sequence of the slug’s psbO gene is identical to the one in the species of algae that supplies them with their plastids.

Now that scientists can peer into genomes without too much difficulty, they’re probably going to find a lot of these gene transfers, and some of them are going to turn out to be big leaps–like the jump from the plant kingdom to the animal kingdom.  What I want to know is how a photosynthesis gene from the nucleus of algae got integrated into the DNA of the slug that eats it. I also want to know why other plant-eating animals didn’t merge with their food as well. Why aren’t sheep green? And finally, when will Voyage to the Planet of the Plant People wrap up?

Until then, you can enjoy Rumpho’s great web site dedicated to this symbiosis–complete with slug videos.

Organisms send signals to each other, and often those signals are honest–in other words, when another organism receives the signal, it can reliably use it to figure something out about the sender. Male fiddler crabs, like the one shown here, send a big, loud signal with their oversized claw. Often, that signal essentially says, “Do not mess with me.” And in many cases, that’s good advice.

Sometimes, though, it’s a major bluff.

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