Archive for February, 2010

Blind Cousins to the Arthropod Superstars

By Carl Zimmer | February 10, 2010 4:31 pm

Speleonectes tulumensis600

Suddenly this obscure, blind cave dweller has become extremely interesting. It turns out to be a close cousin of the most diverse group of animals on Earth, the insects.

Insects–all one-million-plus-species of them–belong to a lineage of animals called arthropods. The arthropods emerged early in the history of animals, and while many of the early arthropods such as trilobites disappeared long ago, a vast diversity thrive on Earth today. Living arthropods share a number of traits in common, such as a hardened, segmented exoskeleton and compound eyes. But they’ve evolved into lots of different forms, ranging from scorpions to horseshoe crabs to centipedes to daddy longlegs to butterflies. They fly through the sky, plunge to the bottom of the sea, thrive in scorching deserts, and hang out in your kitchen.

In order to understand how the arthropods evolved into all this diversity, scientists have labored for many decades to figure out how they are related to one another. It has been a tricky undertaking for many reasons. For one thing, different lineages of arthropods have frequently evolved the same traits independently. So just because two species have long stalk-shaped eyes doesn’t mean that they share a close stalk-shaped ancestor. It’s possible they might have each evolved from two separate ancestors with ordinary eyes.

When scientists started to sequence DNA from arthropods, they hoped that they would be able to get a sharper picture of arthropod evolution. It has helped clear up some things. For example, for a long time scientists believed that insects were closely related to centipedes and millipedes. Along with their anatomical similarities, these two groups are also both mainly land-dwellers. But studies on DNA have pretty clearly demonstrated that, in fact, insects are closer to crustaceans like lobsters and shrimp than they are to centipedes and millipedes. So the two groups descend from two separate invasions of land.

However, studies on DNA did not immediately make all the uncertainties about arthropods disappear. And there’s no reason to have expected it would. DNA is not magic. It’s a great repository of information about the history of life, but it’s not perfect. For example, just as two insects may independently evolve stalk eyes, two lineages may evolve a similar sequence in a particular stretch of DNA. Another problem arises with groups like arthropods that blossomed very quickly into many lineages a long time ago. It’s hard to tease apart the ordering of the branches, just as it’s hard to tease apart distant galaxies in a telescope.

So scientists have been gathering more arthropod DNA and analyzing it in new ways, in order to find strong evidence for kinships. In Nature today, a team of scientists at the University of Maryland, Duke University, and the Natural History of Museum in LA have presented a particularly massive analysis. They lined up 41,000 bases of DNA from 62 genes in 75 species spanning the diversity of arthropods. They found that a number of the branches of the tree held up under a number of different statistical tests. The tree, in all its full glory, is reproduced at the bottom of this post.

In some respects, it supports a lot of traditional taxonomy. For example, everything we call an insect are closer to each other than to any arthropod not considered an insect. But there are also some intriguing surprises.

The one I’ll mention here is the cave-dwelling critter I mentioned at the top of the post. It’s called Speleonectes tulumensis. It lives only in the pitch-black, oxygen-free waters at the bottom of deep caves in the Bahamas. It belongs to a group of arthropods, which the authors of the new study dub Xenocarida, that have mystified scientists ever since they were discovered in the 1980s. Some researchers argued that they were the most primitive of all crustaceans. Yet some xenocarids have remarkably elaborate brains. Thanks to the fact that they live at the bottom of deep caves, scientists haven’t given them quite the attention they’ve lavished on fruit flies and honeybees and other arthropods in easier reach.

According to the new study, however, they deserve the attention of anyone interested in where insects came from. That’s because they are the closest living relative to the insects (along with springtails and other six-legged arthropods, the hexapods).  They can therefore offer clues to what the forerunners of insects were like. Insects may not have evolved out of deep caves–it’s possible that xenocarids lived in other parts of the ocean in the past but have only survived in one extreme habitat. But before there were insects, this new study suggests, the proto-insects may have looked like this. It’s yet another demonstration of the knowledge that we can get even from rare, obscure species. If we had accidentally wiped out the xenocarids, no one would have ever known the important place they have in the history of this arthropod-dominated world.

Fig2_Nature_1Dec09_v2

CATEGORIZED UNDER: Evolution, The Tangled Bank

Oh–And One Other Piece of Advice: That Way Madness Lies

By Carl Zimmer | February 10, 2010 1:37 pm

Nature’s Nicola Jones interviewed me about the art and business of writing books, and you can read it in this week’s issue. It’s part of a series of interviews about books that will be appearing this month.

CATEGORIZED UNDER: Meta

Science and the Media: Blizzard Edition

By Carl Zimmer | February 10, 2010 1:13 pm

Here at Fortress Zimmer, we’re gradually getting buried under the latest Snowmageddon, Blizzaster, SnOMG, or whatever you want to call it. The real spectacle so far has been the giddiness of local meteorologists on television and on weather blogs. My wife Grace reminded me of this excellent 1954 essay by E.B. White, in which he described listening to the radio about Hurrican Edna. Suddenly, I feel linked to history.

It became evident to me after a few fast rounds with the radio that the broadcasters had opened up on Edna awfully far in advance, before she had come out of her corner, and were spending themselves at a reckless rate. During the morning hours, they were having a tough time keeping Edna going at the velocity demanded of emergency broadcasting. I heard one fellow from, I think, Riverhead, Long Island, interviewing his out-of-doors man, who had been sent abroad in a car to look over conditions on the eastern end of the island.

“How would you say the roads were?” asked the tense voice.

“They were wet,” replied the reporter, who seemed to be in a sulk.

“Would you say the spray from the puddles was dashing up around the mudguards?” inquired the desperate radioman.

“Yeah,” replied the reporter.

It was one of those confused moments, emotionally, when the listener could not be quite sure what position radio was taking–for hurricanes or against them.

CATEGORIZED UNDER: Meta

Happy 100, Jacques Monod

By Carl Zimmer | February 9, 2010 4:14 pm

The great French biologist Jacques Monod would have turned 100 today. I am personally fond of him for having said, “What is true for E. coli is true for the elephant,” but he did much more than coin lovely phrases about microbes. His work on how genes switch on and off earned him a Nobel in 1965, and he also gave deep thought to the philosophy of biology, seeing it as the interplay of chance and necessity. Here’s a blog post from Larry Moran with more, and here’s Monod’s 1971 book, Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology

[Thanks to Jim Hu for pointing out this auspicious day!]

CATEGORIZED UNDER: Microcosm: The Book

Darwin Out of Africa

By Carl Zimmer | February 8, 2010 6:00 am

DarwinHere’s the course of Charles Darwin’s ancestors out of Africa over the past 50,000 years or so. It’s based on an analysis of the Y chromosome belonging to his great-great grandson. Details here.

CATEGORIZED UNDER: Evolution, The Tangled Bank

How Do *You* Spell Brain? [Science Tattoo]

By Carl Zimmer | February 6, 2010 11:36 am

brain tattoo400Tim writes,

I’m a post-doctoral cognitive neuroscientist working in MR research at the University of Pittsburgh.  I stumbled across the Science Tattoo Emporium and wanted to share my own science based ink.

The attached image shows my second tattoo and the most directly science-themed ink (although the others are also peripherally linked to the career I love so dear).  The four hieroglyphic characters are the earliest written form of the word “brain” and are found in the Edwin Smith Surgical Papyrus.  Dating back to seventeenth century BC Egypt, the papyrus is perhaps the first neurological case study describing the symptoms of head injuries and the odd fleshy matter that was often visible in the most gruesome of head wounds.  These symbols and the story of the papyrus are the opening to the classic textbook “Principles of Neuroscience”, which I first came across when taking an undergraduate course in 2000.  In honor of starting my graduate research career in studying the brain, I got this tattoo while attending a neuroscience conference in NYC in 2002.

Anyway, hope you enjoy.  Thanks for putting together the gallery that lets me know I’m not the only geek crazy enough to make his passion a permanent part of his body.

Click here to go to the full Science Tattoo Emporium.

CATEGORIZED UNDER: Science Tattoo Emporium

Is Telephony Making Us Stupid?

By Carl Zimmer | February 5, 2010 9:14 am

Twain by Brady 200The more people yell about Facebook, Google, and Twitter, the more I think back to Mark Twain, and his 1880 sketch, “A Telephonic Conversation.”

I consider that a conversation by telephone—when you are simply sitting by and not taking any part in that conversation—is one of the solemnest curiosities of this modern life. Yesterday I was writing a deep article on a sublime philosophical subject while such a conversation was going on in the room. I notice that one can always write best when somebody is talking through a telephone close by. Well, the thing began in this way. A member of our household came in and asked me to have our house put into communication with Mr. Bagley’s, down town. I have observed, in many cities, that the gentle sex always shrink from calling up the central office themselves. I don’t know why, but they do. So I touched the bell, and this talk ensued:—

Central Office. [Gruffly.] Hello!

I. Is it the Central Office?

C. 0. Of course it is. What do you want ?

I. Will you switch me on to the Bagleys, please ?

C. 0. All right. Just keep your ear to the telephone.

Then I heard, k-look, k-look, k’look— klook-klook-klook-look-look! then a horrible “gritting” of teeth, and finally a piping female voice: Y-e-s? [Rising inflection.] Did you wish to speak to me?”

Without answering, I handed the telephone to the applicant, and sat down. Then followed that queerest of all the queer things in this world,—a conversation with only one end to it. You hear questions asked; you don’t hear the answer. You hear invitations given; you hear no thanks in return. You have listening pauses of dead silence, followed by apparently irrelevant and unjustifiable exclamations of glad surprise, or sorrow, or dismay. You can’t make head or tail of the talk, because you never hear anything that the person at the other end of the wire says. Well, I heard the following remarkable series of observations, all from the one tongue, and all shouted,—for you can’t ever persuade the gentle sex to speak gently into a telephone:—

Yes? Why, how did that happen?

Pause.

What did you say?

Pause.

Oh, no, I don’t think it was.

Pause.

No! Oh, no, I didn’t mean that. I meant, put it in while it is still boiling,—or just before it comes to a boil.

Pause.

WHAT?

Pause.

I turned it over with a back stitch on the selvage edge.

Pause.

Yes, I like that way, too; but I think it ‘s better to baste it on with Valenciennes or bombazine, or something of that sort. It gives it such an air,—and attracts so much notice.

Pause.

It ‘s forty-ninth Deuteronomy, sixty-fourth to ninety-seventh inclusive. I think we ought all to read it often.

Pause.

Perhaps so; I generally use a hair-pin…

You can read the rest of sketch online (horrors!) in the archives of the Atlantic.

[Image: Wikipedia]

CATEGORIZED UNDER: Meta

Dinosaur Colors: Now Officially Redonkulous

By Carl Zimmer | February 4, 2010 2:05 pm

anchiornis illustrationI seem to have ended up as the Dinosaur Feather Color Bureau Chief at the New York Times. After discovering colors in fossil bird feathers, scientists found colors in dinosaurs last week. But this week another group of scientists has got the color pattern across a dinosaur’s entire body.

Imagine: Silver Spangled Hamburgs of the Jurassic!

Image courtesy of National Geographic. Check out their 3-D version.

National Academies Communication Award: Nominations Open

By Carl Zimmer | February 3, 2010 2:13 pm

nas600I’ll be a judge again this year for the National Academies Communication Award, a $20,000 prize for excellence in reporting on science. The prize is awarded in four categories:

  • Book
  • Magazine/Newspaper
  • Film/Radio/TV
  • Online

The nominations are now open. More information can be found here.

CATEGORIZED UNDER: General

Your Inner Amazon

By Carl Zimmer | February 3, 2010 12:03 pm

mtsitunes220One of the most mind-blowing things I learned about while writing my book Microcosm: E. coli and the New Science of Life was the incredibly diversity of microbes that call our bodies home. These microbes outnumber our cells by about ten to one, and collectively they have thousands times more genes than found in the human genome. E. coli may be the most familiar of these lodgers, but it is just small player in an inconceivably complex ecosystem on which our health depends.

So I was very excited to interview Rob Knight of the University of Colorado, a biologist who’s been co-authoring a string of stunning papers recently on the thousands of species that live on our skin, in our mouths, in our guts, and elsewhere on or in our bodies. Our conversation is now available on the latest “Meet the Scientist” podcast. We talk about how microbes help each other thrive in our bodies, the way bacteria in our guts release neurotransmitters, how microbes may regulate your weight, and much more. Check it out.

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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.
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