There will be no NORMAL Friday Weird Science this week. Sci's got something special coming at ya! Keep your eyes peeled.
But of course, I couldn't just do a week without doing my NORMAL weird science, right?? Ok, I'll be honest, nothing else really appealed to me and...it's SNAILS IN SPACE. You know what? I don't NEED a reason.
SEND IN THE SNAILS.
Balaban et al. "Functional changes in the snail statocyst system elicited by microgravity" PLoS ONE, 2011.
Animals on this planet have been under the influence of almost every environment imaginable (ok, not liquid hot magma, but everything else). Caves, oceans, saltwater, freshwater, sand, ROCK, you name it, there's probably something living in or near or on it. But there's one thing that's been completely constant during the entire development of life on earth:
It holds us down, and it's what we fight when we have to hold our heads up. And it's been around for as long as life on earth has been around. Even protozoans respond to gravity. And when evolution develops a good system, if it's not broke, don't fix it. Therefore, the way that we and other vertebrates orient ourselves in response to gravity uses a system that has been remarkably conserved all over the family tree.
And this means that when we want to study the effects of gravity on some animal systems, we can use animals that you might not think about when you think of gravity. Like snails!
Snails and SPACE. Snails are great for space. The authors go into some detail on how great snails are for space. They don't eat much, they take up very little space so you'll still be under your weight limit, they can easily stay active (well, "active" is relative for snails) in fairly small confines. They don't get bored and tear up the joint (the authors don't mention this, but I have to imagine its a consideration). Snails make great little astronauts. They even come with their own little suits! And when they come back down to earth, postflight snails taste lovely in a saute with some garlic and butter...
Anyway. When it comes to gravity, snails are more similar to humans than you might think. They, like us, have a little balance organ called the scatocyst (in humans its in the ear and is known as the vestibular system) which responds to gravity in a similar way. Like vertebrates, there is a little weighted mass inside (in this case made of calcium carbonate) which moves around with gravity as the snail is tilted. The motions of the calcium carbonate get detected with little epithelial cells and giant hair cells, which have lots of hairs (called setae). As the calcium carbonate moves around the setae bend where the calcium carbonate hits. The bend of the setae sends signals to the brain, allowing the snail to orient itself with respect the gravity. The system is really very similar in humans, with crystals resting on a membrane, though we have extra bits for sensation of rotation (snails don't really get spun around so much).
And the question is, how does the function of this system respond to exposure to microgravity (like, you know, space). So the scientists sent the snails to space. After 2-3 of space flight, the snails returned to earth, and the scientists began to check their balance. They had a separate group of snails that stayed home.
It is time...TO TIP THE SNAILS.
You see what I did there.
I can't help it, everything is funnier when you use the word snails. Hehehehehehe (need more coffee...).
But yes, they DID tip the snails. They put the snails on a fine wire mesh, and carefully tilted them 180 degrees so their heads were pointing down. This is actually a condition that snails will experience in normal life. Say a snail is going along its merry way on a leaf. It gets toward the end of the leaf and the leaf will start to bend down. The snail's statocyst will detect this and the snail will pull a (slow) about face and begin to go back the way it came (slowly). Like this:
The scientists took home bound snails and space snails (hehehe, space snails. I can't get over it!), and tilted them. They then measured the amount of time it took the snail to turn register that it was falling and turn around. And the space snails were FASTER at this than the earth bound snails, suggesting that their gravireceptor (gravity sensing) system is more sensitive after being in space.
They then inserted electrodes into the snails (you can do this with invertebrates without disturbing them, for a really awesome example of this, see SFN 2009 coverage of crayfish recording), and tilted this again, this time looking at how fast the hair receptors and setae in the statocyst responded to tilt. Again, the space snails were more sensitive to tilt after having spent time in microgravity. You can see below that their cells responded with more signal strength to tilt than did the cells of earth bound snails.
Next up, directional sensitivity. Most snails on earth respond with a turn around when only their HEAD is facing down. After all, that's what you've got to be worried about, right? But the space snails didn't seem to care which end was facing down, they reoriented themselves when their head was facing down, AND when their tail was facing down. Those snails wanted to be on the FLAT, thank you.
And finally, of course, scientists want to know the MECHANISM. WHY are snails from space more sensitive to changes in direction than earth snails? And for this...they centrifuged the snails.
Snails. In a centrifuge. I LOVE IT.
So they centrifuged earth and space snails, which will allow them to see how their systems respond to changes in gravity. When they looked at gene expression, the space snails had more hPEP in their statocyst receptors, which is a protein that is stimulated under "load", meaning when the cells are stimulated by the calcium carbonate falling against them, indicating the tilt of the snail. The space snails had more staining, indicating they had undergone a lot of "tilt" in space. And thus might be more sensitive to further tilt.
In humans, the adaptation to space and microgravity results in something called Space Adaptation Syndrome, which looks a lot like motion sickness. Only in space. When they come back to earth, they have to readapt to gravity, and undergo another adaptation, readjusting to the constant feeling of their feet being down. It appears that snails do this too, though there's no record of whether or not the snails got the nauseated side effects of their adaptations (snails can't hurl, so I guess it's a moot point). It looks like exposure to microgravity in snails makes their statocysts (their gravireceptors) more sensitive to changes in direction. An important thing to have when you're constantly having to reassess which way is up.
Balaban, P., Malyshev, A., Ierusalimsky, V., Aseyev, N., Korshunova, T., Bravarenko, N., Lemak, M., Roshchin, M., Zakharov, I., Popova, Y., & Boyle, R. (2011). Functional Changes in the Snail Statocyst System Elicited by Microgravity PLoS ONE, 6 (3) DOI: 10.1371/journal.pone.0017710