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Corante Blogs examine, through the eyes of leading observers, analysts, thinkers, and doers, critical themes and memes in technology, business, law, science, and culture.

The Press Will Be Outsourced Before Stopped

Vin Crosbie, on the challenges, financial and otherwise, that newspaper publishers are facing: "The real problem, Mr. Newspaperman, isn't that your content isn't online or isn't online with multimedia. It's your content. Specifically, it's what you report, which stories you publish, and how you publish them to people, who, by the way, have very different individual interests. The problem is the content you're giving them, stupid; not the platform its on."
by Vin Crosbie in Rebuilding Media

Travels In Numerica Deserta

There's a problem in the drug industry that people have recognized for some years, but we're not that much closer to dealing with it than we were then. We keep coming up with these technologies and techniques which seem as if they might be able to help us with some of our nastiest problems - I'm talking about genomics in all its guises, and metabolic profiling, and naturally the various high-throughput screening platforms, and others. But whether these are helping or not (and opinions sure do vary), one thing that they all have in common is that they generate enormous heaps of data.
by Derek Lowe in In the Pipeline

Disrobing the Emperor: The online “user experience” isn't much of one

Now that the Web labor market is saturated and Web design a static profession, it's not surprising that 'user experience' designers and researchers who've spent their careers online are looking for new worlds to conquer. Some are returning to the “old media” as directors and producers. More are now doing offline consulting (service experience design, social policy design, exhibition design, and so on) under the 'user experience' aegis. They argue that the lessons they've learned on the Web can be applied to phenomena in the physical and social worlds. But there are enormous differences...
by Bob Jacobson in Total Experience

Second Life: What are the real numbers?

Clay Shirky, in deconstructing Second Life hype: "Second Life is heading towards two million users. Except it isn’t, really... I suspect Second Life is largely a 'Try Me' virus, where reports of a strange and wonderful new thing draw the masses to log in and try it, but whose ability to retain anything but a fraction of those users is limited. The pattern of a Try Me virus is a rapid spread of first time users, most of whom drop out quickly, with most of the dropouts becoming immune to later use."
by Clay Shirky in Many-to-Many

The democratisation of everything

Over the last few years we've seen old barriers to creativity coming down, one after the other. New technologies and services makes it trivial to publish text, whether by blog or by print-on-demand. Digital photography has democratised a previously expensive hobby. And we're seeing the barriers to movie-making crumble, with affordable high-quality cameras and video hosting provided by YouTube or Google Video and their ilk... Music making has long been easy for anyone to engage in, but technology has made high-quality recording possible without specialised equipment, and the internet has revolutionised distribution, drastically disintermediating the music industry... What's left? Software maybe? Or maybe not."
by Suw Charman in Strange Attractor

RNA Interference: Film at Eleven

Derek Lowe on the news that the Nobel Prize for medicine has gone to Craig Mello and Andrew Fire for their breakthrough work: "RNA interference is probably going to have a long climb before it starts curing many diseases, because many of those problems are even tougher than usual in its case. That doesn't take away from the discovery, though, any more than the complications of off-target effects take away from it when you talk about RNAi's research uses in cell culture. The fact that RNA interference is trickier than it first looked, in vivo or in vitro, is only to be expected. What breakthrough isn't?"
by Derek Lowe in In the Pipeline

PVP and the Honorable Enemy

Andrew Phelps: "Recently my WoW guild has been having a bit of a debate on the merits of Player-vs.-Player (PvP) within Azeroth. My personal opinion on this is that PvP has its merits, and can be incredible fun, but the system within WoW is horridly, horribly broken. It takes into account the concept of the battle, but battle without consequence, without emotive context, and most importantly, without honor..."

From later in the piece: "When I talk about this with people (thus far anyway) I typically get one of two responses, either 'yeah, right on!' or 'hey, it’s war, and war isn’t honorable – grow the hell up'. There is a lot to be said for that argument – but the problem is that war in the real historical world has very different constraints that are utterly absent from fantasized worlds..."
by Andrew Phelps in Got Game

Rats Rule, Right?

Derek Lowe: "So, you're developing a drug candidate. You've settled on what looks like a good compound - it has the activity you want in your mouse model of the disease, it's not too hard to make, and it's not toxic. Everything looks fine. Except. . .one slight problem. Although the compound has good blood levels in the mouse and in the dog, in rats it's terrible. For some reason, it just doesn't get up there. Probably some foul metabolic pathway peculiar to rats (whose innards are adapted, after all, for dealing with every kind of garbage that comes along). So, is this a problem?.."
by Derek Lowe in In the Pipeline

Really BAD customer experience at Albertsons Market

Bob Jacobson, on shopping at his local Albertsons supermarket where he had "one of the worst customer experiences" of his life: "Say what you will about the Safeway chain or the Birkenstock billionaires who charge through the roof for Whole Foods' organic fare, they know how to create shopping environments that create a more pleasurable experience, at its best (as at Whole Foods) quite enjoyable. Even the warehouses like Costco and its smaller counterpart, Smart & Final, do just fine: they have no pretentions, but neither do they dump virtual garbage on the consumer merely to create another trivial revenue stream, all for the sake of promotions in the marketing department..."
by Strange Attractor in Total Experience

The Guardian's "Comment is Free"

Kevin Anderson: "First off, I want to say that I really admire the ambition of the Guardian Unlimited’s Comment is Free. It is one of the boldest statements made by any media company that participation needs to be central to a radical revamp of traditional content strategies... It is, therfore, not hugely surprising to find that Comment is Free is having a few teething troubles..."
by Kevin Anderson in strange
In the Pipeline: Don't miss Derek Lowe's excellent commentary on drug discovery and the pharma industry in general at In the Pipeline

The Loom

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March 30, 2005

Love Darts in the Backyard

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Posted by Carl Zimmer

love dart.gifSpring is finally slinking into the northeast, and the backyard wildlife here is shaking off the winter torpor. Our oldest daughter, Charlotte, is now old enough to be curious about this biological exuberence. She likes to tell stories about little subterranean families of earthworm mommies and grub daddies, cram grapes in her cheeks in imitation of the chipmunks, and ask again and again about where the birds spend Christmas. This is, of course, hog heaven for a geeky science-writer father like myself, but there is one subject that I hope she doesn't ask me about: how the garden snails have babies. Because then I would have to explain about the love darts.

Garden snails, and many other related species of snails, are hermaphrodites, equipped both with a penis that can deliver sperm to other males and with eggs that can be fertilized by the sperm of others. Two hermaphroditic snails can fertilize each other, or just play the role of male or female. Snail mating is a slow, languorous process, but it also involves some heavy weaponry. Before delivering their sperm, many species (including garden snails) fire nasty-looking darts made of calcium carbonate into the flesh of their mate. In the 1970s, scientists sugested that this was a gift to help the recipient raise its fertilized eggs. But it turns out that snails don't incorporate the calcium in the dart into their bodies. Instead, love darts turn out to deliver hormones that manipulate a snail's reproductive organs.

Evolutionary biologists have hypothesized that this love dart evolved due to a sexual arms race. When a snail receives some sperm, it can gain some evolutionary advantage if it can choose whether to use it or not. By choosing the best sperm, a snail can produce the best offspring. But it might be in the evolutionary interest of sperm-delivering snails to rob their mates of their ability to choose. And love darts appear to do just that. Their hormones prevent a snail from destroying sperm with digestive enzymes, so that firing a love dart leads to more eggs being fertilized.

Recently Joris Koene of Vrije University in the Netherlands Hinrich Schulenberg of Tuebingen University in Germany set out to see how this evolutionary arms race has played out over millions of years. They analyzed DNA from 51 different snail species that produce love darts, which allowed them to work out how the snails are related to one another. They then compared the darts produced by each species, along with other aspects of their reproduction, such as how fast the sperm could swim and the shape of the pocket that receives the sperm.

Koene and Schulenberg found that love darts are indeed part of a grand sexual arms race. Love darts have evolved many times, initially as simple cones but then turning into elaborate harpoons in some lineages. (The picture at the end of this post shows eight love darts, in side view and cross section.) In the same species in which these ornate weapons have evolved, snails have also evolved more powerful tactics for delivering their sperm, including increasingly complex glands where the darts and hormones are produced. These aggressive tactics have evolved, it seems, in response to the evolution of female choice. Species with elaborate love darts also have spermatophore-receving organs that have long, maze-like tunnels through which the sperm have to travel. By forcing sperm to travel further, the snails can cut down the increased survival of the sperm thanks to the dart-delivered hormones.

Sexual conflict has been proposed as a driving force in the evolution of many species, and this new research (which is published free online today at BMC Evolutionary Biology) supports the idea that hermaphrodites are not immune to it. What's particularly cool about the paper is that all these attacks and counter-attacks co-vary. That is, species with more blades on their love darts tend to have longer rerpoductive tracts and more elaborate hormone-producing glands and so on. Only by comparing dozens of species were they able to find this sort of a relationship.

My wife always tells me that as a science writer, I ought to be well-prepared to give our children the talk about the birds and the bees. But I'm not sure the love darts would send quite the right message.

love dart gallery.gif

Comments (4) + TrackBacks (0) | Category: Evolution


1. Nick on March 30, 2005 12:40 PM writes...

There's a delightful bit about love darts in one of Gerald Durrell's books about his childhood in Corfu. It think it's Birds, Beasts, and Relatives. Gerald's observation of snails mating leads to a discussion between Dr. Theodore Stephanides and Gerald's brother Lawrence (author of The Alexandria Quartet) about the advantages of being a hermaphrodite.

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2. ACW on March 31, 2005 04:00 PM writes...

As I read this account, the old song "Cupid, draw back your bow" kept running through my mind.

In a couple of places you used the words "male" and "female"; for example, you say "deliver sperm to other males" and "female choice". I found those places a little confusing and would appreciate some clarification. Also: how are the darts delivered? Are they thrown somehow, or does one snail simply push the dart into its mate? Dartguns, or harpoons?

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3. W. W. Matera on April 1, 2005 10:33 AM writes...

I've always sworn that snails had more fun than anybody. They're both with each other at once together! What more could a true Libidian want?

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4. linus on April 8, 2005 11:27 AM writes...

Hermaphrodites, Love Darts - just 2 more examples that are pushing me towards accepting intelligent design. ;)

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