Today is my second synchro-blogging of the week! When Laelaps showed me the video that went with this paper, and explained the concept...I was HOOKED. We had to blog it. It's too good. It's too GROSS. Just you wait. So we HAVE blogged it, and when you're done reading this, go over to Laelaps and read his take on this...this grossness.
We've all got different ways of tracking down our food and making sure it sits in one place while we eat it. Some take the slightly easier route and eat plants (only slightly, they may not be able to move, but they've got other methods to make sure you don't eat them). Some species run their food down, some bite and poison, some descend on it from above. Some snag it in a web. And then there are those that use their glue guns.
May I introduce you to the VELVET WORM.
Sci has to say those things give me the crawling heebie-jeebies. All those little LEGS, and the crawling, and...ewwwww.
Velvet worms (Onychophora) are OLD. They were one of the first groups of animals to come on land, and have been crawling in that super creepy way over the ground for the past 500 MILLION YEARS. Must be a pretty effective model. They're not insects, really, when they are placed in evolutionary trees, they are often wedged between the arthopods (insects), and the annelids (worms). And well, that's basically what they look like, right?
But what's really interesting about these dudes is that they are carnivores. And they have a REALLY weird way of capturing prey.
Haritos et al "Harnessing disorder: onychophorans use highly unstructured proteins, not silks, for prey capture" Proceedings of the royal society B, 2010.
Observe the video
And a brief transcript of Sci watching the video:
"whoa. uuuughhhh...ew...It's all crawly...heh. No matter how mysterious David Attenborough tries to sound, there's nothing making the 'velvet worm' sound spooky. But...ewwwww...ok it looks a little better at night...that cricket's all like "what did I see? what? I feel confused..." EWWWW!!!!!! What did that velvet worm DO?!?! OMG that looks like...ugh, that does not look like spider silk, I think we all know what that really looks like...GROOOOOSSSSSSS. Let's watch it again!!!"
Yeah, I bet you all thought almost the exact same thing.
Anyway, the velvet worm captures its prey by using two squirt guns on either side of its head to squirt sticky stuff onto the prey object. The object is immobilized and the velvet worm digs in. But what IS the stuff that comes out from the slime glands (yes, "slime glands" really IS the technical term)? It's not SILK like comes out of spiders (and I should hope not, cause those slime shots would make Spiderman a LOT less romantic). The protein content of the slime is known, but what this paper was investigating was how the slime formed up. Was it in strands like silk? Or was it...something else?
Whatever it is, it'd better be good at its job. Slime methods of capture NEED to be effective, because producing slime is expensive. It takes a lot of energy and a lot of resources. And as you can see from the video, that's a LOT of slime. This stuff better do the trick EVERY TIME.
The methods of the paper are only really funny because they contain headings like "slime collection", "slime treatments", and "slime analysis". Always be gentle with your slime and make sure it undergoes the best and more careful treatments. OH OH!! And don't forget "Effect of additives on the gelling mechanism of slime". Extremely important stuff.
The velvet worm's goop is made mostly of 99% water, but when dried it's full of protein, with little bits of sugar, lipids, and a surfactant to act as a wetting or foaming agent. The slime is some powerful stuff, when forcibly ejected (not sure how they got the velvet worm to eject the stuff, maybe they just grabbed and squeezed?) onto a glass surface, it becomes a clear solid within just a few seconds. The stuff is composed mostly of proline, a common amino acid. What's more interesting about proline is the ring structure:
This ring structure makes proline a particularly interesting amino acid, because it makes it a very bad team player. Other amino acids link together, and can then form secondary structures like helices and beta sheets, but proline is too structurally constrained to help out with that, and thus, if you've got a lot of proline, you've going to end up with few beta sheets and alpha helices. This means that you end up with...a pile of disordered protein, which is very different from the highly ordered strands seen in spiders. It means that your ending protein is going to end up flopped open and with everything hanging out, and unable to form a hydrophobic core like you'd see with more structured proteins.
So you've got all this protein, letting it all hang out. It's in a solution when the worm squirts. But how does it harden from a liquid to a sticky mass? The scientists think it's all about the interaction between the protein and WATER. When the goo is squirted into a tube, it stays liquid for a while, but when you spread it out in the environment over a large surface area (like a cricket), the proteins spread out, and regions of hydrophobic animo acids allow the goo to repel the water its in very quickly. This means you get rapid DRYING. With the water gone, hydrophobic proteins in the solution can start forming bonds, and you go from slime to sticky strands to full on glue in less than a minute. The poor cricket never had a chance.
Finally, I just have to point out one VERY important point. This worm and those glue guns. See this?
Now see THIS.
Thus the clever Katy Perry immobilizes
Snoop Dogg her prey! Velvet Worms. Showing Katy Perry how it's done since 2010.
Haritos, V., Niranjane, A., Weisman, S., Trueman, H., Sriskantha, A., & Sutherland, T. (2010). Harnessing disorder: onychophorans use highly unstructured proteins, not silks, for prey capture Proceedings of the Royal Society B: Biological Sciences, 277 (1698), 3255-3263 DOI: 10.1098/rspb.2010.0604