Friday, April 22, 2016

Chameleons, Crystals: and Curiosity

Chameleons may be more famous for changing color than for their high-speed tongues: but today I'll be talking about both.
  1. Chameleon Tongues, Mathematically Described
  2. Crystals in Chameleon Skin

Brains, Curiosity, and Being Human


Using our brains is part of being human. So is learning about the universe, and using that knowledge. We're supposed to use our brains. (Catechism of the Catholic Church, 154-159, 2292-2296)

But, particularly if we act without thinking, curiosity can get us killed. I've talked about Georg Wilhelm Richmann before, and why "tickling the dragon's tail" is a bad idea.

Also why Ulysses is in Dante's Malebolge, and it's not because being curious is wrong. (January 23, 2015)

Let's see, what else?

Ethics matter.

'It's for science' isn't an excuse for subjecting humans to lethal experiments: or mistreating animals. I've talked about that before. (March 27, 2015; December 5, 2014)

Basically, science and technology are fine. Ignoring ethics isn't. (Catechism, 159, 2292-2296, 2375-2377, 2414)


1. Chameleon Tongues, Mathematically Described



(From SPL, via BBC News, used w/o permission.)
("The chameleon feeds by snapping out its long tongue"
(BBC News))
"Chameleon's tongue gives up secrets"
Helen Briggs, BBC News (April 20, 2016)

"Scientists have built a mathematical model to explain the secrets of the chameleon's extraordinary tongue.

"It took more than 20 equations to capture mathematically how the reptile's tongue unravels at very high speed to snare insects.

"The model explains the mechanics of the animal's tongue and the inherent energy build-up and rapid release.

"British researchers say the insights will be useful in biomimetics - copying from nature in engineering and design...."
Depending on who you read, chameleons have been around for 60,000,000 years, give or take, or roughly 20,000,000 years. That's how far back we've found various iguana-like fossils.

The odds are good that the critters have been around for a lot longer, and share a common ancestor with iguanids and agamids upwards of 100,000,000 years back.

Somewhere along the line, chameleons acquired their color-changing ability. They're not the only variable-color animals. Quite a few critters go through seasonal color changes, of course; but anoles, squids, octopi, and cuttlefish change quickly.

Back to chameleons: we know of 202 species, not all can change color; they've got zygodactylous feet, which is a fancy way to say two toes point backwards; and they've got weird eyes.

A chameleon eye's lens is convex, not concave like ours. That's not obvious, looking at them, but the way they move their eyes independently of each other is.

Chameleons can swivel their eyes around a whole lot more than we do, which lets them stay still while waiting for their next meal: or avoiding being another critter's food.

Tarsiers have enormous eyes for their size, at least some can turn their heads a full 180 degrees. I'm assuming that's 180 left or right.

Oxford University's professor of mathematical biology Derek Moulton clarified — if that's the right word — what these scientists did:
"...'In mathematical terms, what we've done is we've used the theory of non linear elasticity and captured the energy in these various tongue layers and then passed that potential energy to a model of kinetic energy for the tongue dynamics.'..."
(Helen Briggs, BBC News)
I gather what that means is that the scientists found a set of equations that do a pretty good job of describing what a chameleon's tongue does.

It's a very complicated organ: modified hyoid bones at the core, then about a dozen very thin layers of fibrous material, wrapped in muscles. Energy gets stored in elastic elements — which is what the scientists now understand a bit better.

Heads, Neck Injuries, Getting a Grip, and Designing Robots


We can turn our heads something like 80 degrees left or right: apparently that's about the same for men and women, on average, although men generally have more muscle in our necks.

That may help explain why men aren't quite as likely to have neck injuries. I'd better explain that, considering the preferred reality many folks insist on.

I think humans came in two basic models, male and female: and that this is okay. (May 2, 2012)

That is not even close to yearning for the 'good old days.' I've discussed Addams Family Values, love, and moving forward, before. (January 31, 2016; August 30, 2015; July 12, 2015)

I must believe that we're all created in the image and likeness of God: with free will, masters of our own actions. I must also see all of us as people, with equal dignity: no matter where we are, who we are, or how we act. (Genesis 1:27; Catechism, 360, 1700-1706, 1730-1825, 1932-1933, 1935)

But I don't have to insist that I'm indistinguishable from Elizabeth II, John Krahn, Akihito, or Phumzile Mlambo-Ngcuka. I look a bit like the first two, though: largely because my recent ancestors spent a long time in northwestern Europe.

Less hair and more beard, though, and that's another topic. Topics.

Where was I? Chameleons, eyes, being human. Right.

We've known that chameleons could shoot out their tongues fast and far — and have been learning more about how they manage it. This research could help scientists and technicians design soft, elastic materials for robotics. That's not the scientists' main motive, though. They said their reason for researching was mostly just "scientific curiosity."

More than you probably need (or want) to know about chameleons, tarsiers, and humans:

2. Crystals in Chameleon Skin



(From Alex Hyde/SPL, via BBC News, used w/o permission.)
("The study was conducted on panther chameleons, which are popular pets"
(BBC News))
"Chameleon colours 'switched by crystals' "
Jonathan Webb, BBC News (March 11, 2016)

"Swiss researchers have discovered how chameleons accomplish their vivid colour changes: they rearrange the crystals inside specialised skin cells.

"It was previously suggested that the reptiles' famous ability came from gathering or dispersing coloured pigments inside different cells.

"But the new results put it down to a 'selective mirror' made of crystals.

"They also reveal a second layer of the cells that reflect near-infrared light and might help the animals keep cool...."
Like I said before, (some) chameleons can change color. The real animals are nowhere near as versatile as their cartoon counterparts, though.

Researchers are pretty sure chameleons change color for different reasons: blending in with their surroundings, staying warm or cool, or signalling each other.

Iridophores



(From Teyssier, Saenko, Van Der Marel, Milinkovitch, via BBC News, used w/o permission.)
("A panther chameleon can switch in minutes from camouflage colours to more strident, communicative ones"
(BBC News))
"...Some changes arise from shifting pigments. Tiny packets of the dark dye melanin, for example, can be spread throughout the tendrils of big "melanophore" cells - or gathered into the centre, to lighten the skin again. Many fish and reptiles grow lighter or darker in this way in response to stress, or to match their surroundings.

"Panther chameleons, the subjects of the new study, do this as well. But males can also change between entirely different colours, turning a camouflaged green into a more spectacular yellow, for example, when they see a potential mate or a competitor.

"Until now, many scientists had thought that these changes arose from a similar dispersion trick with yellow or red pigment. The new research suggests this is not the case...."
(Jonathan Webb, BBC News)
Color-changing chameleon skin has a layer of guanine crystals under the outer pigments. The crystals reflect different wavelengths, depending on how they're spaced and arranged: which changes the critters' colors.

Guanine is one of the four main nucleobase in DNA and RNA. We use crystalline guanine as a shampoo additive — for an iridescent look — metallic paints, eye shadow, and nail polish.

The stuff has two tautomeric forms, keto and enol: which matters to folks who make a career or hobby of organic chemistry. My guess is that you're more likely to hear someone mention iambic pentameter: which has more to do with Shakespeare than meters, and that's yet another topic.

Those guanine crystals are in iridophores, a special sort of pigment cell. Here's a photo:


(From M. Milininkovitch, via BBC News, used w/o permission.)
("Inside the 'iridophore' cells of a relaxed chameleon (left) the crystals are tightly packed; excitement causes them to loosen (right)"
(BBC News))

Cool Chameleons



(From M. Milinkovitch, Lanevol.org, via BBC News, used w/o permission.)
("An extra layer of cells that reflect near-infrared wavelengths may help chameleons stay cool in the sun"
(BBC News))
"...Beneath the layer of iridophores that contained a nice, regular lattice of crystals, the team also spotted an additional layer, where the cells were much bigger and more chaotically organised.

"Because that higgledy-piggledy structure reflects near-infrared light particularly well, they believe it might serve to reflect the sun's warming rays and keep the chameleons cool.

"This split appears to be unique to chameleons; other lizards tend to have their crystals arranged in a regular way to give bright colours, or a disorganised way that reflects the heat. With their added layer, chameleons manage to combine the two extremes...."
(Jonathan Webb, BBC News)
Merriam-Webster says "higgledy-piggledy" first showed up in 1598, means "in a confused, disordered, or random manner," and that we don't know its etymology.

Etymology is a word's derivation, entomology is the scientific study of insects, and chameleons eat insect. Insects have compound eyes, some critters with compound eyes living near hydrothermal vents can see infrared.

Quite a few insects can see ultraviolet colors. So could we, at least the wavelengths close to 'visible' light, but the lens of our eye is opaque to ultraviolet. And that's — you guessed it — still another topic.

Posts I remembered while writing this one:

3 comments:

Brigid said...

Number agreement or missing article: "scientists found set of equations that"

The Friendly Neighborhood Proofreader

Brian Gill said...

Right you are. Thanks, Brigid!

Paul Smith said...

Our Mother Nature is rich with its secrets and mysterious creatures! It is an interesting fact that a panther chameleon can switch in minutes from camouflage colors to more strident... Amazing! Nice sharing! Best regards, http://proofreading-services.org/proofreader.php

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