Morris has very hard water, so we’re familiar with loading up the water softener in the basement with bags and bags of potassium chloride pellets. I didn’t realize (but I should have) that the water softener is mildly radioactive. Cool! Nuclear physics is real!
I know most of you have already read it with your print subscription to Seed, but I’ll mention it anyway: my last column can now be read on the web. This one is all about the weird, accidental, clumsy way segmentation patterns in flies are set up.
Neurulation is a series of cell movements and shape changes, inductive interactions, and changes in gene expression that partitions tissues into a discrete neural tube. It is one of those early and significant morphogenetic events that define an important tissue, in this case the nervous system, and it’s also an event that can easily go wrong, producing relatively common birth defects like holoprosencephaly and spina bifida. Neurulation has been a somewhat messy phenomenon for comparative embryology, too, because there are not only subtle differences between different vertebrate lineages in precisely how they segregate the neural tissue, but there are also differences along the rostrocaudal axis of an individual organism. A recent review by Lowery and Sive, though, tidies up the confusion and pulls disparate stories together.
A while back, I summarized a review of the evolution of eyes across the whole of the metazoa — it doesn’t matter whether we’re looking at flies or jellyfish or salmon or shrimp, when you get right down to the biochemistry and cell biology of photoreception, the common ancestry of the visual system is apparent. Vision evolved in the pre-Cambrian, and we have all inherited the same basic machinery — since then, we’ve mainly been elaborating, refining, and randomly varying the structures that add functionality to the eye.
Now there’s a new and wonderfully comprehensive review of the evolution of eyes in one specific lineage, the vertebrates. The message is that, once again, all the heavy lifting, the evolution of a muscled eyeball with a lens and retinal circuitry, was accomplished early, between 550 and 500 million years ago. Most of what biology has been doing since is tweaking — significant tweaking, I’m sure, but the differences between a lamprey eye and our eyes are in the details, not the overall structure.
We’ve got a splendid new analysis of a southeast Asian artiodactyl from the Thewissen lab that reveals that these little deer-like animals are a sister taxon to whales — so this pushes our understanding of the ancestry of whales yet further back. Carl Zimmer has already described the essentials — I’ll just show a few pictures of the fossils.
Here’s an interesting question: “if you could take a pill which enhanced attention and cognition with few or no side effects, would you?”
Shelley says yes. Janet says no. I say it depends on that qualifier, “few or no side effects” — if that were true, I’d say “Yes! Gimme more!” This is no dilemma at all.
Of course, that’s cheating. There’s no such thing as a drug that has no side effects. The real dilemma would crop up if a cognitive enhancer were available that did have problematic side effects — then my worry would be that pressure to succeed in my classes would be driving students to harm themselves in substantial ways. That happens already. Students take no-doz or skimp on sleep to do well, so there is some unavoidable harm from the stress of learning.
So that’s the information I need before I can make any decision — this is an issue that requires weighing costs and benefits, and telling me there is no cost simplifies it too much. For instance, caffeine has costs, but they’re low enough that my choice is to drink in moderation, but not to give it up altogether.
Those of you who have been pregnant, or have been a partner to someone who has been pregnant, are familiar with one among many common consequences: lower back pain. It’s not surprising—pregnant women are carrying this low-slung 7kg (15lb) weight, and the closest we males can come to the experience would be pressing a bowling ball to our bellybutton and hauling it around with us everywhere we go. This is the kind of load that can put someone seriously out of balance, and one way we compensate for a forward-projecting load is to increase the curvature of our spines (especially the lumbar spine, or lower back), and throw our shoulders back to move our center of mass (COM) back.
Here’s the interesting part: women have changed the shape of individual vertebrae to better enable maintenance of this increased curvature, called lordosis, and fossil australopithecines show a similar variation.
On the one hand, this is a strange tale of mutant, bisexual, necrophiliac flies, and you’ve got to love it for the titillating nature of the experiments. But on the other, much more interesting hand, it’s a story about drilling down deeply into the causes of a complex behavior, and tracing it to a single gene product — and it also reveals much about the way the chemicals sloshing about in the brain can modulate responses to stimuli. Work by Grosjean and others on a simple Drosophila mutant, genderblind, which causes flies to be indiscriminate about gender in their courtship, opens up a window into how sexual responses are shaped and specified.
Think about human sexual responses. Some of us, when we see an attractive woman, are at least mildly aroused; others are have their sexual interest picqued when they see an attractive man; still others might feel sexual urges when they see a shoe, or a plush animal, or a pot of baked beans. No matter what the stimulus, these are all biological responses, with something in the environment matching some trigger in our brains and initiating a cascade of neural, neurochemical, and hormonal activity that leads to sexual behaviors. The question we want to address is what every step in the biology is doing; unfortunately, human behaviors are both too complex and not amenable to ethical experimentation, so we turn instead to simpler organisms that allow us to find simpler causes and carry out thorough experiments to probe the behavior.
I’ve known that scorpions have fluorescent cuticles — if you go out into the desert with a black light and shine it on the ground, the scorpions will often glow green and blue and be easy to spot. I had no idea that many spiders exhibit the same phenomenon, but there they are, glowing away. I may have to visit my local head shop (in Morris? Hah!) and get some black light bulbs to see what the fauna in my living room is up to.
Fluorescence is actually a fairly common property: all it requires is a molecule called a fluorophore that can absorb and capture transiently photons of a particular wavelength, or energy, and release them at a lower energy. What this means is that a fluorescent substance absorbs light at one range of wavelengths, and then re-emits those photons at a longer wavelength; there is a color shift. In the case of black light posters and spiders and scorpions, they are absorbing light at wavelengths our eyes can’t detect (wavelengths below about 400nm, or ultraviolet light) and shifting it to a wavelength we can see, for instance to a nice blue at 450nm, cyan at around 500nm, or green at about 550nm. So to test this, all you need is a dark room, a spider, and a light source that glows at the wavelength that is absorbed by the fluorophore, and a detector (like, say, your eyes) that can collect light at the emission wavelength.
As Sheril hinted earlier, there is now a formal call for a science debate by the presidential candidates.
A CALL FOR A PRESIDENTIAL DEBATE ON SCIENCE AND TECHNOLOGY
Given the many urgent scientific and technological challenges facing America and the rest of the world, the increasing need for accurate scientific information in political decision making, and the vital role scientific innovation plays in spurring economic growth and competitiveness, we, the undersigned, call for a public debate in which the U.S. presidential candidates share their views on the issues of The Environment, Medicine and Health, and Science and Technology Policy.
I’ve expressed my opinion of such an effort before — I think it’s an excellent idea, but suspect that most of the candidates would refuse to submit to it. Not only is there the science test factor, in which we’re asking them to get evaluated on something most know nothing about, but the Republican slate in particular is full of astonishing idiots who hold beliefs contradicted by science. I just can’t believe they’ll step up on the podium for this one, unless they perhaps see an opportunity to hijack the discussion to promote their personal piety.
I still want it to happen: this is an opportunity to apply pressure to our candidates to have some minimal, basic science literacy. As I previously mentioned, though, those airheads with nice hairdos that populate the television media are even more dim than the candidates themselves, and must not be allowed anywhere near the event — I want wildlife biologists armed with tranquilizer guns at the doors, with orders to shoot Russert and Blitzer and anyone from Fox News on sight. How about if we put Natalie Angier, Carl Zimmer, John Horgan, Ira Flatow, John Tierney, and Cornelia Dean on a panel asking questions? How about if we ask Science and Nature to send representatives with questions? I would dearly love to see a debate on any subject where the candidates had to deal with issues of some substance.
So let’s all make a noise about this one, OK? Rattle the cages, and tell the candidates we want to hear opinions on topics that matter for the leader of a technological, 21st century society, rather than the usual tripe.
