mucus, slime and killer snot monsters

VampJenLuc Dragon*Con is nigh, and I'll be heading out to Atlanta next Thursday to participate in several panels over that weekend, including one on "The Science of the Whedonverse," wherein I will join fine folks like JPL's Kevin Grazier (tech consultant for Eureka) analyzing the science behind Joss Whedon's most beloved series: Firefly/Serenity, Dollhouse, and of course, Buffy the Vampire Slayer and Angel.(I'll also be on a few panels on the Skeptic track, and talking about The Calculus Diaries, given that the book's release is — yikes! — this Tuesday.)

There's far too much to discuss in one hour (I wrote an entire book on Buffyverse physics, and you could easily do the same for Firefly and the neuroscience of Dollhouse), but I hope we'll touch on some of my favorite topics: the Gentlemen's exploding heads in the Emmy-nominated episode "Hush"; the time-tinkering physicist in "Happy Anniversary" (Angel, Season 2); the thermodynamics of magic in the Buffyverse; and some of the real-world biological counterparts to demons and monsters, like the Queller demon in "Listening to Fear" (Buffy, Season 5). 211px-Queller As the episode opens, Willow and Tara are gazing at the constellations when they a meteor streaking across the sky. It’s not an ordinary meteor: this one has a soft chewy demon center, unleashing an overgrown, slimy lizard-like creature onto a community already overrun with demons. The Queller demon vomits a sticky, odiferous substance onto its victim’s face, which then hardens, suffocating said victim. Xander resents being forced to spend his weekend researching a killer snot monster, and an exasperated Giles upbraids him that it's important because "it's a killer snot monster from outer space!" I'm still waiting for the SyFy original movie on that one: Killer Snot Monsters from Outer Space would give Sharktopus a run for its money.

I was reminded of all things slimy and snot-like this past week, upon reading a short post by Brian of Laelaps about a new method for extracting DNA-rich tissue from dolphins. In the past, the standard techique has been dart biopsies: you shoot the creature with a small harpoon-like device and when you pull it out, there's a bit of tissue attached, ideal for genetic analysis. Jen-Luc Piquant sniffs that if she were a dolphin, she would find this very irritating, if not outright painful. And indeed, dart biopsies can't be used on very young dolphins for fear of injury.

Get a dolphin to blow in a tube, however — the dolphin equivalent of a breathlayzer — and you collect a sample of "dolphin blow" (oh, stop sniggering!): air infused with a mix of proteins and liquids to comprise a sort of "lung surfactant." Per Brian, prior work showed that dolphin blow contains traces of reproductive hormones, so why not  genetic material? To find out, the University of Queensland researchers held polyproplene tubes — which look disturbingly akin to a solidified condom in the photo below — over the dolphins' blowholes and collected enough genetic material to produce DNA profiles that closely matched that obtained by analyzing the dolphins' blood. One more challenge remains: the dolphins used in the study were from the National Aquarium in Baltimore, who are far more likely to cooperate with such procedures than dophins reared in the wild. But I'm sure if we just explained to them that they can either be pinged with sharp darts and lose a bit of tissue, or breathe into a tube for a few minutes, they'll see reason. Collecting-dolphin-blow

From Brian's description, dolphin blow seems quite similar to what a materials scientist might term a "viscous colloid," a class of materials that includes mucus, a substance with which we all have had firsthand experience. When the Spousal Unit appeared on The Colbert Report this past March, I went with him to NYC, only to be felled by a nasy cold virus during our stay. For three days, my morning ritual included the ceremonial Clearing of the Mucus — undertaken while the Spousal Unit was off getting his morning coffee to spare him the horror of witnessing something akin to a scene from The Exorcist. (A good marriage needs a bit of mystery.) Having witnessed what was expelled form my nasal passages, I can readily believe Wikipedia's assertion that "the average human body produces about a liter of mucus per day."

Usually, though, mucus is beneficial, helping ward off infection by trapping nasty paticles that enter through the nose (or mouth) before they can get down into the respiratory tract. It's a bit sensitive to temperature: in cold weather, for instance, our mucus can thicken, only to "melt" when we come in from the cold for a nice hot bowl of soup, thereby causing one's nose to run at the table in a most unappetizing fashion. I hate being "that person" at the dinner table. We have all been that person at some point.

Elsewhere in Nature, mucus and other slimy substances have some very desirable properties of great interest to scientists – not to mention celebrities of advancing years. Slug mucus is enjoying a renaissance of sorts as an anti-aging compound in high-end cosmetics. Beyond the pursuit of vanity, it also provides a useful model in the development of new synthetic lubricants, which could one day be used to combat friction in molecular-scale nanomachines. And then there's the lowly hagfish, a pretty darn ugly eel-like creature that excretes copious amounts of slime from pores all along its body when it feels threatened in any way. That slime mixes with saltwater to transform into a sticky goo.

The hagfish puts the human mucus production system to shame: it can churn out 1 liter of mucus in less than a second, according to hagfish guru Douglas Fudge, a marine biologist at the University if Guelph in Canada. Hence the creature's Latin name, Myxine glutinosa, from the Greek myxa ("mucus") and the Latin gluten ("glue"). The resulting slime bonds to the gills of an attacking fish and blocks respiratory flow: the victim perishes by choking on snot. Should the victim attempt to chew its way through the slime to escape, the stuff will just expand further, and the victim will suffocate that much faster. The hagfish gets out of its own mess by tying itself into a knot, then pushing the knot down the length of its body to scrape off the slime.

And that brings me to another gratuitious Buffyverse reference! The long-suffering Giles turns into a Fyarl demon in “A New Man” (Buffy, Season 4), gaining the ability to shoot a sticky mucus through his nostrils that hardens into a solid and immobilizes an opponent. Excreting large globules of snot it not as showy as, say, shooting searing laser beams from his eyes, but Spike declares the ability dead useful in a fight. Just ask the hagfish. Or Peter Venkman in Ghostbusters.



Mucus is what’s known as a “phase-change” material because it moves from liquid to solid. The change is usually triggered by temperature (hot to cold, or vice versa) or environmental factors (wet to dry, dry to wet). Mucus is made up of protein-and-sugar molecules (mucin), as well as lots of water, which gives the material its slippery texture. As the substance loses moisture, it becomes more rigid, undergoing a sort of phase transition, although scientists who study these strange materials prefer to describe the process in more vague terms: the substance goes from a “fluid-like” to a “solid-like” state. Once ejected, the substance rapidly cools down and begins losing moisture. As it dries out, it forms a hard shell.

Unlike other forms of mucus, hagfish slime doesn’t harden. It stays slimy even in very chilly water, in part because both the hagfish and its victim are immersed in salty seawater, so it never has a chance to dry out. But hagfish slime has a secret ingredient:  the usual protein-and-sugar concoction also contains long threadlike fibers. The technical term is "intermediate filaments," and these fibers are finer than spider's silk, and as strong. The fibers form protein strands that expand rapidly once the mucins comes into contact with seawater, causing the substance to “blow up” into a sticky gel. The consistency is a bit like half-solidified Jell-O, or watered-down hair gel. The fibers are so stretcy, they can enlongate like taffy to three times their length before finally snapping. Fudhe designed his own apparatus to stretch the filaments: something akin to a ping pong paddle, except with a filament where the paddle part should be. (Diagnostic electronics are embedded in the handle.)

Intermediate filaments can be found in most animal cells, creating a kind of scaffolding so that the cells are rigid enough to maintain their shape, yet still flexible enough to have a bit of give and take. That's an interesting finding, because until quite recently, most biologists had assumed cell structure was rigidly inflexible. So they were initially skeptical of Fudge's model, until French researchers traced a 3D contour of the fibers using an atomic force microscope, and also found them to be stretchy rather than inflexible.

Fudge is one of the leading experts on hagfish, which might be a dubious distinction if the creature weren't so fascinating… and if its slime weren't so complex. There's still a lot to learn about hagfish slime. For instance, the goo is ejected as a mix of disc-shaped vesciles and wound-up protein fibers (just like balls of yarn), and the vesicles burst when they come into contact with sea water, and the fibers unwind. The resulting mixture traps sea water, and that's what causes it to swell. But what keeps those vesicles from bursting prematurely? There has to be a stabilizaing compound among the ingredients.

In 2003, Fudge thought he'd found the answer when an analysis revealed very high concentrations of methylamines, notably trimethylamine oxide. That's a compound often found in shark tissue, for instance, to keep salt water from leaching bodily fluids out of the shark through osmosis. But it turned out to be something of a red herring. His team actually "milked" the glands of drugged-up hagfish, releasing the substance into air instead of salt water — and still there was an explosion of slime. The hagfish is full of surprises. Fudge surmises that the gland might be pressurized — kind of like how Reddi-Wip doesn't foam up until it's released from the can.

All promising materials have potential applications and hagfish slime is no exception. Its unique properties could help save human lives by curtailing bleeding in an accident victim during surgery, for example. The mucus would expand upon contact with the blood (which is mostly water and salt), staunching blood flow. That stretchy property is another bonus for potential applications. Fudge compares them to the plastic rings tha hold together a six-pack of beer: pull them apart and they syart to loosen and deform; in the case of the fibers, they actually rearrange into new molecular formations, eerily similar to spider silk. So those amazing fibers could be used — or synthesized — to make ultra-light yet super-strong textiles ("bio-steel"), as well as biomedical devices, tissue engineering and biosensors. And as any hagfish could attest, mucus is a terrific defense mechanism, which is one reason why the U.S. military is investigating its properties for military applications.

More frivolously, a group of students in British Columbia figured out how to use hagfish slime as an egg substitute in scones; they believe it could also serve as a thickening agent in eggnog. They failed to include the recipe in their report, but an interpid blogger at the Museum of Awful Food adapted a recipe for just that purpose, which we reproduce here (duly credited) for those in need of some fresh-baked hagfish slime scones for Sunday morning. If you make them, be sure to let us know how they taste; we share the blogger's skepticism that hagfish slime will be an effective substitute, given that egg yolk plays a big role in emulsification and texture….

Hagfish-Slime Cheddar-Gruyere Scones

4 cups all-purpose flour
2 tablespoons baking powder
4 teaspoons sugar
1/2 teaspoon salt
1 cup (two sticks) chilled unsalted butter, cut into 1/2-inch cubes
2 cups (packed) coarsely grated extra-sharp yellow cheddar cheese (about 9 ounces), or a mix of 6 ounces cheddar and 3 ounces gruyere.
1-1/2 cups chilled heavy whipping cream
6 tablespoons hagfish slime

Preheat oven to 375F

In a food processor, blend flour, baking powder, sugar, and salt. Cut in the butter using quick pulses until the mixture resembles coarse meal. Add cheese and cut in using quick pulses. In a small bowl, whisk together the cream and hagfish slime. With the food processor running, add cream mixture through feed tube. Process until dough just holds together – don’t overmix!

Turn dough out onto a lightly floured work surface. Gather the dough together and divide into quarters. Pat each quarter into a round just short of 1 inch high (it should be about 6-7 inches in diameter). Using a clean, sharp knife, cut each round into six wedges. Transfer half the wedges to ungreased baking sheets lined with parchment paper, spacing them about 2 inches apart.

Bake the first batch of scones until the edges just start to brown and a toothpick comes out clean, about 20 minutes. Transfer them, still on their parchment paper, to a wire rack to cool at least 10 minutes, during which time put in the second batch of scones.

Serve warm or at room temperature. The scones will stand for about 8 hours. Do not refrigerate. If you want to reheat them, warm them in a 350F oven for about 5 minutes.


5 thoughts on “mucus, slime and killer snot monsters”

  1. This is fascinating and, you know, kinda gross. It seems like once any bodily fluid (or phase-change material) sees the light of day we tend to find it unsettling. Except, I guess, for tears.

  2. Partially Deflected

    So in the world of serious Buffy discussions, is the original movie with Kristy Swanson considered part of the canon, or is Ms Gellar the only true Buffy?

  3. Thank you for your blog. I really liked your mucus coverage, I liked it even better once I saw this video of an anesthetized hagfish’s slime in action:
    Thanks for sending me searching for video and for stimulating my brain. Do you ever feel really lucky to have ended up liking science? So many people miss out. How do you feel about phase-change material being unsettling? I’m not a big fan of injury or disease, but once it happens it’s somewhat akin to a visit to an “inside the body zoo”. I often find the sensation similar to “wow, there really are giraffes and tapirs!”
    Thanks again,

  4. i’m curious if you’ve tried that recipe yourself, or you are just giving the “tips” for the others..:) it should be delicious, i bet.

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