Last gasp of my development course

Today, I gave my final lecture in developmental biology this term. We have one more class session which will be a final discussion, but I’m done yapping at them. Since I can’t possibly teach them everything, I offered some suggestions on what to read next, if they’re really interested in developmental biology. They’ve gotten the fundamentals of the dominant way of looking at development now, that good ol’ molecular genetics centered modern field of evo-devo, but I specifically wanted to suggest a few titles to shake them up a little bit and start thinking differently.

  • For the student who is interested in the field, but doesn’t feel that development is necessarily their discipline, I recommended Richard Lewontin’s The Triple Helix: Gene, Organism, and Environment(amzn/b&n/abe/pwll). It’s short, it’s easy, and it’s a good counterweight to the usual gene-happy approach we see in developmental biology.

  • Since we are a liberal arts university, and we value a philosophical approach in addition to the usual bluntly pragmatic tactics we follow in the sciences, I also recommended one work of philosophy: The Ontogeny of Information: Developmental Systems and Evolution(amzn/b&n/abe/pwll), by Susan Oyama. That one is not an easy read, except maybe to the more academically minded. I mentioned that Developmental Systems Theory does not have the powerful research program that is making evo-devo so successful, but it’s still a usefully different way of thinking about the world.

  • If any of my students wanted to go on to grad school in developmental biology, and hoped to make it a profession, I had to tell them that they are required to read D’Arcy Wentworth Thompson’s On Growth and Form(amzn/b&n/abe/pwll). It’s old, it’s a little bit weird, but it’s still a major touchstone in the discipline.

  • Lastly, I told them that there was one more book they had to read if they wanted to consider a career in development: Developmental Plasticity and Evolution(amzn/b&n/abe/pwll), by Mary Jane West-Eberhard. If I were a young graduate student in the field right now, I think I could just open that book to a random page and find an interesting and challenging research problem right there. I might have to flip through a few dozen pages before I found one that wasn’t impossibly hard, but hey, it’s one of those books that fills you in on the array of issues that people are worrying over at the edge of the science.

I don’t think any of these would be a good foundation for an undergraduate course (either Thompson or West-Eberhard or Oyama would probably have a lethal effect on the brain of any unprepared student trying to plow through them), but they’d be great mind-stretchers for any student planning to move on.

So all my lecturing is done for the term, and all that’s left are monstrous piles of grading that will grow ominously in the next week and a half even as I struggle to keep up, and then I can try to polish it all off by Cephalopodmas.

Look out, Phoenix!

In a few weeks, on January 3-7, I’m going to be attending the 2007 Annual Meeting of the Society for Integrative and Comparative Biology in Phoenix. I’m going to be part of a panel in a Media Workshop, along with a few other names you might recognize:

Blogs are online “diaries” that are growing in popularity. Popular political and social commentary blogs are making the news, but is there more out there than chatty gossip and collections of links? How about some science? Can this trendy technology be useful for scientists? Come to the Media Workshop and find out! Experienced science bloggers P.Z. Myers (Pharyngula; http://scienceblogs.com/pharyngula/), Grrl Scientist (Living the Scientific Life; http://scienceblogs.com/grrlscientist/), and John Lynch (Stranger Fruit; http://scienceblogs.com/strangerfruit/) answer your questions about how blogging works, setting one up, finding things to write about, and using the medium for your classes, for research, or for educating the public.

Cool, hey? Even better, afterwards there will be a ten-round boxing match between me and John, with GrrlScientist doing the honors as the card girl (nah, not really…all three of us will probably just buy each other beers and get embarrassingly sloppy.)

The real coolness, though, is in the schedule: there are some great talks and posters going on at this meeting, and once I get the panel out of the way, I am going to thoroughly enjoy myself, learning new stuff. And yes, of course, I will be blogging the SICB meeting.

That’s some tongue

Behold the spectacularly long-tongued glossophagine nectar bat, Anoura fistulata:

i-637ca2695ab40ca81df624a2b3792d1c-anoura.jpg
Anoura fistulata feeding from a test tube filled with sugared water; its tongue (pink) can extend to 150% of body length.

This length of tongue is unusual for the genus, and there is an explanation for how it can fit all of that into its mouth: it doesn’t. The base of the tongue has been carried back deep into the chest in a pocket of epithelium, and is actually rooted in the animal’s chest.

i-2b61d1fb1ab14963a2732fab0816bd67-anoura_anatomy.jpg
Ventral view of A. fistulata, showing tongue (pink), glossal tube and tongue retractor muscle (blue), and skeletal elements (white).

Across the glossophagine nectar bats, maximum tongue extension is tightly correlated with the length of their rostral components, such as the palate and mandible. Although the correlation holds for A. caudifer and A. geoffroyi, A. fistulata falls far outside the 95% confidence interval. Close examination of tongue morphology reveals the basis for this pattern. In other nectar bats, the base of the tongue coincides with the base of the oral cavity (the typical condition for mammals), but in A. fistulata the tongue passes back through the neck and into the thoracic cavity. This portion is surrounded by a sleeve of tissue, or glossal tube, which follows the ventral surface of the trachea back and positions the base of the tongue between the heart and the sternum.

Unsurprisingly, this adaptation co-evolved with the lengthening corolla of a tropical flower, Centropogon nigricans—observations suggest that this bat is the only pollinator of this particular flower.

I’m sure Gene Simmons would be jealous.

Muchhala N (2006) Nectar bat stows huge tongue in its rib cage. Nature 444:701-702.

The science is in: the Tripoli Six are innocent

Go read Effect Measure on the recent events in the case of the Tripoli Six. This is the story of a team of health care workers who were blamed for an outbreak of HIV among young patients at a Libyan hospital—they’ve been tried in a kangaroo court and face very unpleasant prospects.

Now, in a powerful reply to the Libyan accusations, Nature has published the results of a detailed analysis of the viruses afflicting the children, and the story is clear: the cause of the outbreak was the poor hygiene present at the hospital before the six workers arrived. Here are the major conclusions of the paper:

In 1998, outbreaks of human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) infection were reported in children attending Al-Fateh Hospital in Benghazi, Libya. Here we use molecular phylogenetic techniques to analyse new virus sequences from these outbreaks. We find that the HIV-1 and HCV strains were already circulating and prevalent in this hospital and its environs before the arrival in March 1998 of the foreign medical staff (five Bulgarian nurses and a Palestinian doctor) who stand accused of transmitting the HIV strain to the children.

The strains present were also traceable to North Africa and at least one was prevalent in Egypt. They also found that the timing was off: the outbreak had begun before the workers had arrived.

We found that, irrespective of which model was used, the estimated date of the most common recent ancestor for each cluster pre-dated March 1998, sometimes by many years. In most analyses, the probability that the clusters from the Al-Fateh Hospital originated after that time was almost zero. For the three HCV clusters, the percentage of lineages already present before March 1998 was about 70%; the equivalent percentage for the HIV-1 cluster was estimated at about 40%.

Apparently, the scientific evidence which would have exonerated the accused was not allowed in the court. The Gaddafi government continues to live up to its reputation.

Notch

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One of my favorite signal transduction pathways (what? You didn’t know that true nerds had favorite molecular pathways?) is the one mediated by the receptor Notch. Notch is one of those genes in the metazoan toolkit that keeps popping up in all kinds of different contexts—it’s the adjustable wrench of the toolbox, something that handles a general problem very well and therefore gets reused over and over again, and the list of places where it is expressed in Drosophila is impressive.

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Animations of urogenital development

I found these on youtube, a couple of nice cartoony animations of the development of the urogenital system. This is one of the weirder modules in organogenesis, I think; many strange things go on that are relics of ancestral states. We actually build three pairs of kidneys—pronephros, mesonephros, and metanephros—and throw each one away in succession, except the last. Both sexes form paramesonephric (or Müllerian) ducts, in blue in the animation, and these form the core of the female plumbing, but again, males basically throw it away and use a more primitive duct (the mesonephric or Wolffian ducts, in green). It’s a bizarre way to construct an organ, but what’s going on is that we have two systems, excretion and reproduction, tied together in ways that constrain the other’s development, and each is building on elements of the other.

It’s in French, but that shouldn’t slow anyone down. It’s easy to figure out what “paramesonephrique” must refer to, for instance.

Males:

Females:

Neil deGrasse Tyson on ID

Since Nick Matzke has become a fanboy, and Larry Moran has never heard of him, I thought I’d mention that I’ve liked Neil deGrasse Tyson’s column (titled “Universe”) in Natural History for a long time. It is generally on astronomy/astrophysics/cosmology, so it’s far afield from my usual comfort zone, but I don’t mind stretching my brain now and then. I’ve put a few excerpts from one column below the fold here that I thought was particularly good, from the November 2005 issue. It’s titled “The perimeter of ignorance”, and subtitled “a boundary where scientists face a choice: invoke a deity or continue the quest for knowledge.”

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