Evolution of direct development in echinoderms

In chapter 14 of the Origin of Species, Darwin wondered about the whole process of metamorphosis. Some species undergo radical transformations from embryo to adult, passing through larval stages that are very different from the adult, while others proceed directly to the adult form. This process of metamorphosis is of great interest to both developmental and evolutionary biologists, because what we see are major transitions in form not over long periods of time, but within a single generation.

We are so much accustomed to see a difference in structure between
the embryo and the adult, that we are tempted to look at this
difference as in some necessary manner contingent on growth. But there
is no reason why, for instance, the wing of a bat, or the fin of a
porpoise, should not have been sketched out with all their parts in
proper proportion, as soon as any part became visible. In some whole
groups of animals and in certain members of other groups this is the
case, and the embryo does not at any period differ widely from the
adult: thus Owen has remarked in regard to cuttlefish, “There is no
metamorphosis; the cephalopodic character is manifested long before
the parts of the embryo are completed.” Landshells and fresh-water
crustaceans are born having their proper forms, whilst the marine
members of the same two great classes pass through considerable and
often great changes during their development. Spiders, again, barely
undergo any metamorphosis. The larvae of most insects pass through a
worm-like stage, whether they are active and adapted to diversified
habits, or are inactive from being placed in the midst of proper
nutriment or from being fed by their parents; but in some few cases,
as in that of Aphis, if we look to the admirable drawings of the
development of this insect, by Professor Huxley, we see hardly any
trace of the vermiform stage.

Why do some lineages undergo amazing processes of morphological change over their life histories, while others quickly settle on a single form and stick with it through their entire life? In some cases, we can even find closely related species where one goes through metamorphosis, and another doesn’t; this is clearly a relatively labile character in evolution. And one of the sharpest, clearest examples of this fascinating flexibility is found in the sea urchins.

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Outrageous!

How dare cartoonists make fun of atheists? We are not to be mocked!

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You know what this demands, right? Rioting in the streets! That’s right — all you True Atheists will get off your butts right now and go set an embassy or a cartoonist, whichever is handiest, on fire.

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Or not.

Scienceblogs doesn’t want to hear from you

It’s nothing personal. For much of this morning, they’re going to be moving the database to a new server, and they’re going to shut off write access to it. That means you won’t be able to write comments on any of the articles on scienceblogs for about 3 hours, from 9-12ET today.

Don’t panic.

This is one step they’re taking to improve performance and make those annoying “internal server errors” and double-posts a thing of the past.

D’oh! Coturnix, who must be more aware of the time than I am, tells me that comments will be off from 9-12pm today. Never underestimate how late a programmer will sleep in; I just assumed 9am was plenty late for someone to get up, have coffee, read the newspaper, write a couple of pages, make a trip to the grocery store, and go in and take care of the lab animals—which was what I got done before 9—and that all that stuff would have been gotten out of the way by lunchtime.

Telegraphic kookiness

Time for another edition of “I get email”! Below the fold you’ll find a comprehensive example of the kind of exhortation I get all the time—this one is a long list of assertions that god is right, science is wrong, all transmitted in short sentences that aren’t in any particular order.

No, I didn’t reply to this one. He’s got 41 numbered points that he claims refute evolution, everything from “male nipples arouse women” to claims that Jupiter couldn’t form because gasses expand, and then there’s Pascal’s wager and lots of bible quotes. It’s a very silly list, don’t strain yourself over it.

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Town on stilts

Worried that global warming will submerge your real estate? Here’s the solution the town of Galveston hit upon after they were devastated by a hurricane in 1900: the entire town was hoisted up on stilts, and new fill placed underneath. The photographs are amazing—it was an impressive engineering project, and it was all done with manual labor.

It’s also a little bit familiar. In my old home town, you could date the houses by their construction: the older ones were all built up on foundations that raised the floor a couple of feet off the ground, because the town was on a flood plain—my parents had photos of people canoeing down the streets when the Green River rose above its banks. There the solution was to build a dam on the river and control it that way, and that’s when the newer houses could have these peculiar things called basements.

Damming the ocean is a rather bigger problem.

Et tu, New Zealand?

They’re popping up everywhere, and now in
New Zealand:

A Trust which teaches schoolchildren about evolutionary and creationist views of the universe wants to build a $30 million dinosaur park and museum, probably on the Coromandel Peninsula.

The Dinosaurs Aotearoa Museum Trust is working with Wellington’s Weta Workshop, which created characters for Peter Jackson’s Lord of the Rings trilogy, to create life-sized dinosaurs in a 40ha theme park.

Founders Darren and Jackie Bush run a Wellington business called Dinosaurs Rock which runs programmes about dinosaurs and geology for schools, giving children both the scientific theory of evolution and the biblical view that the world was created by God in seven days about 6000 years ago.

May they all go bankrupt.

Return of the Son of the Bride of Haeckel

The Discovery Institute is so relieved — they finally found a textbook that includes a reworked version of Haeckel’s figure. Casey Luskin is very excited. I’m a little disappointed, though: apparently, nobody at the Discovery Institute reads Pharyngula. I posted a quick summary in September of 2003 that went through several textbooks, and showed a couple of examples where redrawn versions of Haeckel’s diagram were used. More recently, I posted a fairly exhaustive survey by Patrick Frank of the use of that diagram since 1923, which showed that it was rare, and that the concept of recapitulation was uniformly criticized. Really, guys, the horse of recapitulationism is dead. Biologists riddled it with bullets in the 19th century, and have periodically kicked it a few times to be sure. For Intelligent Design creationists to show up over a century later and flog the crumbling bones of a long extinguished horse and crow victory is awfully silly.

So how can you still find any vestiges of Haeckel’s work in textbooks?

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