Axis formation in spider embryos

Blogging on Peer-Reviewed Research

Some of you may have never seen an arthropod embryo (or any embryo, for that matter). You’re missing something: embryos are gorgeous and dynamic and just all around wonderful, so let’s correct that lack. Here are two photographs of an insect and a spider embryo. The one on the left is a grasshopper, Schistocerca nitens at about a third of the way through development; the one on the right is Achaearanea tepidariorum. Both are lying on their backs, or dorsal side, with their legs wiggling up towards you.

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There are differences in the photographic technique — one is an SEM, the other is a DAPI-stained fluorescence photograph — and the spider embryo has had yolk removed and been flattened (it’s usually curled backward to wrap around a ball of yolk), and you can probably see the expected difference in limb number, but the cool thing is that they look so much alike. The affinities in the body plans just leap out at you. (You may also notice that it doesn’t seem to resemble a certain other rendition of spider development).

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Clearly, bloggers need to take over science journalism

Aaargh. When will the media learn? National Geographic is running this ridiculous headline right now: New Fossil Ape May Shatter Human Evolution Theory, in which the reporter claims a discovery of some teeth could “demolish a working theory of human evolution.” It’s not true. Where is this nonsense coming from?

I read the article. It’s titled “A new species of great ape from the late Miocene epoch in Ethiopia.” The exciting news is that the “combined evidence suggests that Chororapithecus may be a basal member of the gorilla clade, and that the latter exhibited some amount of adaptive and phyletic diversity at around 10-11 Myr ago.” It concludes with a suggestion that we need to do more research in sediments appropriate to Miocene apes. There aren’t an exploding paradigms or revolutions suggested.

I read the associated news article in Nature. It’s titled “Oldest gorilla ages our joint ancestor.” It says that this discovery pushes back the time of divergence of the gorilla lineage from our own. This is just ordinary science.

Now read the blogs — they’re doing a much better job of evaluating this work than the traditional media. For one thing, they’re actually looking at it critically. Afarensis points out that these are only a few teeth, and it’s awfully thin grounds for a substantial revision of the timeline. John Hawks makes a similar point, but also highlights the fact that there is an unresolved problem — we need to reconcile paleontological and molecular dates. Even John Wilkins, a “mere” philosopher, weighs in sensibly that teeth are plastic characters in phylogeny, and deplores this peculiar media habit of taking a recalibration of a historical detail as a major reformulation of theory. All these discussions are sober and interested and most important of all, accurate.

The lesson is clear: when you see some wild and crazy claim of scientific revolutions and the demolition of long-held theories, go immediately to the science blogs for some clear-eyed sanity and informed evaluation from experts.

Male pregnancy?

Yesterday’s discussion of future biological advances that will piss off the religious right had me thinking about other innovations that I expect will happen within a few decades that might just cause wingnuts to freak out. First thing to come to mind is that it will be something to do with reproduction, of course, and it will scramble gender roles and expectations…so, how about modifying men to bear children? It sounds feasible to me. Zygotes are aggressive little parasites that will implant just about anywhere in the coelom — it’s why ectopic pregnancies are a serious problem — so all we need to do there is culture a bit of highly vascularized tissue in the male abdomen that will serve as a secure home for a few months. We’ll have to play some endocrine games, too, which may effect his love life but will also prepare him to lactate post-partum. There’s the minor anatomical problem that the vagina is a unique tissue, and no, the urethra is not homologous or analogous (fortunately; we wouldn’t want to have to push an 8 pound baby through the penis, even if female hyenas can manage it) — but that’s what c-sections are for. Given money, time, and a few weird volunteers, it could be done.

The next question is, has it been done? Are there any other vertebrates that have males doing the hard work of pregnancy? There were the gastric brooding frogs, which one would think could have made the leap easily — the eggs were just swallowed and developed in the stomach — but only the mothers seemed to have done the job. They’re all extinct, anyway. Male frogs of the genus Rhinoderma brood their young in their mouths, but this is after external fertilization and development, so they’re actually simply holding larvae in a safe place — and they’re also endangered. The precedents aren’t promising.

There is an extremely interesting and successful example, though: the syngnathid fishes, sea horses and pipefish. In all 232 species, the female lays her eggs in a specialized male structure called the brood pouch, where they are fertilized and develop. It’s a true male pregnancy!

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My plan to become a household name continues apace!

It’s nice to see these casual references to PZ Myers, as if anyone would have heard of me:

The lab is at 101 Theory Drive, a developer’s idea of a scientific street name that Lynch found presumptuous.

It is a mark of the difficulty of life sciences — biology and its many descendants — that to call something a theory is to honor, not slight it. Theory, evolutionary biologist P.Z. Myers has written, is what scientists aspire to. Lynch, for all of his bombast, was respectful of the intellectual protocols of his science.

“I would have called it Hypothesis Drive,” he said.

The article is part of an interesting series on research into learning and memory, that is also unfortunately marred by some casual sexism on the part of its subject. See, Zuska, you just had to ruin it for me!

P.S. I think of myself as more of a developmental biologist than evolutionary biologist, but OK, I am very interested in evolutionary issues.

Wait until the creationists try to wrap their little minds around artificial life … oops, too late

Here’s some exciting news: Artificial life likely in 3 to 10 years. It is exciting but not surprising at all — but of course we’re going to be able to assemble entirely artificial life forms soon. It’s just a particularly complicated kind of chemistry, and it’s more of a deep technical problem than anything else. I wouldn’t be quite so specific about the date — there are also all kinds of surprises that could pop up — but I’m optimistic, and I think the overall assertion is supported by the increasing rate of accomplishment in the field.

But of course, in addition to the usual suggestions from interested followers of science that I should mention this cool article on the blog, I’ve gotten a few from creationist complainers (Already! See what my email is like?) Expect to hear more outrage from the religious right as this story develops in the coming years, which might be a good thing … they’re going to have to spread themselves thin to fight all the interesting work coming out of biology, and evolution won’t be the only target anymore. Anyway, here’s one of my creationists, expressing his unhappiness in odd directions.

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Your mama’s soul doesn’t love you

If it existed, it might also be profoundly autistic and … diabetic? So science cannot disprove the existence of a soul, but one thing we’re learning is how much valued human properties such as love and attachment and awareness of others are a product of our biology — emotions like love are an outcome of chemistry, and can’t be separated from our meaty natures.

The latest issue of BioEssays has an excellent review of the role of the hormone oxytocin in regulating behaviors. It highlights how much biochemistry is a determinant of what we regard as virtues.

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Endless Forms Most Beautiful

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I just finished Sean B. Carroll’s Endless Forms Most Beautiful: The New Science of Evo-Devo the other day, and I must confess: I was initially a bit disappointed. It has a few weaknesses. For one, I didn’t learn anything new from it; I had already read just about everything mentioned in the book in the original papers. It also takes a very conservative view of evolutionary theory, and doesn’t mention any of the more radical ideas that you find bubbling up on just about every page of Mary Jane West-Eberhard’s big book. One chapter, the tenth, really didn’t fit in well with the rest—the whole book is about pattern, and that chapter is suddenly talking about a few details in the evolution and development of the human brain.

So I read the whole thing with a bit of exasperation, waiting for him to get to the good stuff, and he never did. But then after thinking about it for a while, I realized what the real problem was: he didn’t write book for me, the inconsiderate bastard, he wrote it for all those people who maybe haven’t taken a single course or read any other books in the subject of developmental biology. I skimmed through it again without my prior biases, and realized that it’s actually a darned good survey of basic concepts, and that I’m going to find it very useful.

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Trying too hard

Jonathan Eisen dresses down university press departments that oversell science, and also hits on one of my pet peeves: the attempt to portray all scientific research as addressing human ills. In this case, it’s claiming that research on shark gene expression will help treat birth defects.

In my own research, I look at the effects of alcohol (among other things) on embryonic development in zebrafish, and it is a kind of animal model of Fetal Alcohol Syndrome. People always jump to the assumption that I’m trying to find a cure for FAS, and I have to correct them: I definitely am not. FAS is a developmental disorder, and is not curable … and we already have a solution in the form of public policy and maternal education that can prevent the problem. I use teratogens as a simple tool to perturb the process of development so I can view the interactions involved; I also see development as an event involving both genes and the environment, and just about everyone mucks around with genes, so I’m looking at it from the other side.

So my work with teratogens is much more directly applicable to research on birth defects, and I deny the association; most of the work out there on gene expression in fins is going to even more remote from applied medical uses, not that that will stop PR departments.