That zebrafish movie annotated and explained, a little

By popular request, here’s a roughly annotated version of that zebrafish development movie.

Stuff to watch for:

  • This movie starts at the 8-16 cell stage. The cells of the embryo proper (blastomeres) are at the top, sitting on a large yolk cell.

  • The pulsing is caused by the synchronous early divisions of all the cells. They lose synchrony at the mid-blastula transition.

  • Epiboly is the process by which the cells migrate downward over the yolk. An arrow will briefly flash, pointing to about 11:00, in the direction of the animal pole (where the future nose will form, sorta). That happens just before the whole animal begins to rotate within the chorion, just to make following everything more difficult.

  • After the animal rolls over, the animal pole is pointing straight up at you, and the migrating cells will form the germ ring, a thickening around the equator of the embryo. Cells will also migrate towards one point along the ring, forming a thickening called the keel. This is where the embryonic axis is forming; cells are migrating into the interior at this point in the process called gastrulation, and this region is roughly equivalent to the dorsal lip of a frog.

  • The whole animal is going to roll over again, this time to its side. The keel is thickening and lengthening towards the animal pole. The body of the fish is going to form along the right side of spherical embryo in this view.

  • While the keel is extending anteriorly, cells are still also migrating to surround the yolk—epiboly continues, with the yolk bulging out a bit until it is finally surrounded and closed off at the blastopore.

  • The head and tail extend. You’ll see the eye forming, so you’ll be able to tell which end is the head end.

  • Along the right side, you’ll also see the tissue form regular little blocks: these are the somites, or body segments.

  • The tail continues to extend and lifts off the surface of the yolk. When there are about 18 somites (the resolution is too low, so don’t try to count them), the animal will begin to twitch.

I’ll load up another one in a bit that will show a hint of the horrible stuff we do to them in the lab: we get the babies drunk and watch deformities develop.

How would ID have contributed?

Carl Zimmer brings up another essential point about the HAR1F study: it was work that was guided by evolutionary theory. The sequence would not have been recognized in the billions of nucleotides in the genome if it hadn’t been for an analysis directed by the principles of evolution.

Wells’ diatribe was amazingly wrong. I looked at it again and there could be another half-dozen essays in just picking up apart the stupidity in it.

Dawkins and Paxman

Hey, this is a pretty good interview of Richard Dawkins by Jeremy Paxman. I don’t know much about this Paxman fellow, but he asks hard, sharp questions, yet still gives Dawkins plenty of time to answer them. That’s good interviewing technique, I think.

I’m not too impressed with the spartan set, putting them both in plain uncomfortable-looking chairs set all alone in an empty, echoing room…but it does put the focus on the words. They should have saved a few more pennies and just done audio.

(via Father Dan)

A zebrafish timelapse recording

At my talk on Tuesday, the centerpiece was a short movie of zebrafish development—I was trying to show just how amazingly cool the process was. People seemed to like that part of the show, at least, so I thought I’d try to figure out this YouTube doohickey and upload it for general viewing. So here it is, a timelapse recording of about 18 hours of zebrafish embryology compressed into 48 seconds:

I’ve got more, and my students will be making videos of their own soon enough, so maybe I’ll try uploading some other stuff soon. I’m discovering that YouTube is a little tricky about the aspect ratio, and the conversions do add some distracting compression artifacts to the movie…I may have to tinker quite a bit to get a more satisfactory image.

Note to self: set aside time for jail, September 2008

The odious Ken Mehlman has announced that that mob of pigs, scoundrels, and theocrats will be slouching into Minneapolis on September 1-4, 2008. Anyone else care to join me in the protest lines that week?

When we get tired of yelling obscenities and imprecations at the parasites, we can always duck into the Science Museum of Minnesota, just down the street, for revitalization. Or we could just hang out in the SMM the whole time and take visiting Rethuglicans on tours of the dinosaur exhibit, and watch them stroke out and gasp for breath.

Wells: “Darwinism is Doomed” because we keep making progress

There are days when I simply cannot believe how dishonest the scoundrels at the Discovery Institute can be. This is one of them. I just read an essay by Jonathan Wells that is an appalling piece of anti-scientific propaganda, an extremely squirrely twisting of some science news. It’s called “Why Darwinism is doomed”, and trust me, if you read it, your opinion of Wells will drop another notch. And here you thought it was already in the gutter!

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I consider myself an adventurous eater, BUT…

I have to draw the line somewhere.

The dish in front of me is grey and shiny.

“Russian dog,” says my waitress Nancy.

“Big dog,” I reply.

“Yes,” she says. “Big dog’s penis…”

We are in a cosy restaurant in a dark street in Beijing but my appetite seems to have gone for a stroll outside.

Nancy has brought out a whole selection of delicacies.

They are draped awkwardly across a huge platter, with a crocodile carved out of a carrot as the centrepiece.

Nestling beside the dog’s penis are its clammy testicles, and beside that a giant salami-shaped object.

“Donkey,” says Nancy. “Good for the skin…”

I’m sorry, but butchering random animals, sometimes endangered animals, for the purpose of consuming arbitrary small bits of their anatomy because of a perceived magical benefit…no, thanks. Besides, if driving a big car is a sign of a tiny penis, I suspect anyone caught needing to consume a tiger’s erectile organ is deeply inadequate, not just in the crotch, but the brain as well.

A devil’s catechism

My review of Dawkins’ The God Delusion(amzn/b&n/abe/pwll) (currently at #4 on Amazon’s bestseller list!) is in the latest issue of Seed, which showed up at my door while I was flying out East. They changed my suggested title, which I’ve at least used on this article, in favor of the simpler “Bad Religion”. You could always buy the magazine to read it, but I’ll give you a little taste of what I thought.

Oh, yeah…Seed does that nice plus of having an artist render a portrait of the author, so there’s also a picture, artfully ruggedized and made much more attractive than I am in reality. Not that I’m complaining.

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