the little sea squid that could

Las Vegas, Jen-Luc and I have decided, is a fascinating mix of high and low culture, a city in which seedy shops for tacky souvenirs exist side-by-side with posh Cartier boutiques. Everything's all squished together into one long strip. Our hotel, the Riviera, is in the mid-range of this bizarre continuum: several cuts above, say, a Motel 6, yet nowhere near the ostentatious luxury of the justly famed Bellagio. For one thing, the Riviera doesn't have that incredible fountain. (Jen-Luc Piquant was thrilled to discover, during her Cyber-travels yesterday, that there is a scientific tribute to the Bellagio's one-of-a-kind fountain exploiting the explosion effect of mixing Mentos and Diet Coke.)

The Bellagio has its luxurious charms, but so do some of the other establishments. Circus Circus, across the street from the Riviera, bills itself as a family casino, and has the garish, child-friendly decor to match. But it is also home to one of the best steakhouses in New York. And when Virginia Governor (and presidential hopeful) Mark Warner decided to throw a posh reception in conjunction with the YearlyKos event, he chose to hold it at the top of the Stratosphere. There was a lot of pre-fete buzz before that event, which turned out to be much deserved. It was a catered affair, with live entertainment by a pair of Blues Brothers impersonators, and an open bar where the mixed drinks were poured through gigantic ice sculptures. Lindsey Beyerstein (a.k.a. Majikthise) wondered aloud whether these kinds of events really changed anyone's mind for election purposes. No sooner had she spoken, when an inebriated blogger stumbled up and declared, "Mark Warner rocks! I am SOO voting for him!" So apparently Warner has a lock on the drunken freeloader sector of the blogosphere.

A few of us even managed to snag one of the glowing plastic "ice cubes" festooning the bar as a souvenir. The "glow" comes from a battery-powered LED buried inside the cube. Apart from being a neat little trinket with which to amaze young children, the ice cube offers a convenient segue into the science topic du jour: bioluminescence, the ability of certain living organisms to emit light.

A quick physics review for our non-scientist readership (scientists, feel free to skip down a paragraph): light arises from atomic structure, specifically the electrons that orbit an atom's nucleus (which contains, we all learned in junior high school, protons and neutrons). There are many different energy levels, or orbitals, in which an electron can move, but it has a natural "ground state." Add energy to the electron and it will jump to a higher energy level, but sooner or later, it wants to return to the ground state. To do so, it has to shed the excess energy, which it accomplishes by releasing a particle of light (photon). Only a small part of the excess energy is actually emitted as light; most is released as heat -- which, if you want to get technical is also light/electromagnetic radiation, just not of the visible variety. Bioluminescence is sometimes called "cold light" because there is so little heat lost in the chemical reaction that produces the light. It's not without useful applications: deep sea divers often use "glow sticks," which contain chemical substances that react when the stick is cracked to produce a continuous steady glow for up to 24 hours.

My enthusiasm for this particular subfield dates back several years, when I attended a workshop (sponsored by the American Physical Society) in Boston on opportunities in biology research for physicists. There were lots of excellent cutting-edge talks that weekend, but my favorite was the inspiring story of the Little Sea Squid That Could. The intrepid three-inch creature in question is technically named Euprymna scolopes. His friends just call him Bob -- as in, the Hawaiian bobtail squid.

(When it comes to nomenclature, "Celebrity parents and marine biologists can be so cruel," mourns Jen-Luc, who thinks former Spice Girl Geri Halliwell should be drawn and quartered for naming her daughter Bluebell Madonna. Jen-Luc has also been avidly following the media feeding frenzy concerning Baby Shiloh, a.k.a., the "Brange-Nina." Shiloh is both a place of sanctuary in the Bible to house the Ark of the Covenant, and the name of one of the bloodiest wars in Civil War history, so the Brange-Nina will either be a prophetess/high priestess or a fierce warrior -- possibly both. That's a whole lot better than Bluebell.)

But I digress. We're here to talk about Bob. Bob's a mellow sort of squid. He pretty much hangs out in the shallow waters around the Hawaiian islands, taking in the sun, sand and surf. Well, not so much the sun. He's a nocturnal creature at heart, and doesn't really need the sun, since he has a natural glow about him. Literally. He has a built-in flashlight to help him navigate those murky nighttime waters, hunt for prey, and hide from predators in turn. It's a special organ on his underside, a convenient little cavity that serves a dual purpose as home to colonies of a specific species of bacteria, Vibrio fischeri.

The cavity organ is lined with threadlike cilia that sweep bacteria from the surrounding water into the cavity, and the bacteria, ever adaptable, busily set up their own little colony. Once that colony reaches "critical mass," they emit the telltale glow. The glowing bacteria are surrounded by stacks of reflective plates to focus the light outward. That light helps Bob hunt for prey in dark waters. It also provides camouflage from any organisms trying to eat him, because Bob doesn't cast that telltale shadow on the ocean floor as a result of the moon's rays shining down into the water. Bob can even control the "wattage" of his bio-flashlight, simply by limiting the amount of oxygen that reaches the cavity organ. (The bacteria need lots of oxygen for the chemical reaction that produces the light.)

Bob is not the only sea creature capable of bioluminescence. Certain fish have light organs under their eyes that serve as headlamps so they can hunt for prey in dark ocean waters. The angler has a bioluminescent tip on its nose to attract not just prey, but also a mate. (One shudders at the potential consequences of confusing one for the other, and hopes the glow is color-coded accordingly.) Some species of shrimp, when caught in the jaws of a predator, can vomit up a bioluminescent cloud to distract said predator sufficiently to loosen its hold so the shrimp can escape. And on land, certain insects (the firefly) and plants (mushrooms and other fungus) are also known to emit a glowing light.

Large concentrations of bioluminescent bacteria are also, it seems, behind an ocean phenomenon called the "Milky Seas": glowing white patches of sea water stretching across an expanse as large as Hawaii. It's the stuff of urban legend, a rare occurrence that has mystified mariners for over 400 years. In fact, in his 1870 novel, Twenty Thousand Leagues Under the Sea, Jules Verne's fictional Nautilus submarine travels through a "milky sea" at one point in its journey -- apparently inspired by contemporary accounts from local sailors. The narrator attributes the unusual optical effect to the presence of a vast number of "infusoria, a sort of luminous little worm.... These insects adhere to one another sometimes for several leagues." The narrator goes on to say it is fruitless to try and compute the number of these "infusoria," since ships had been known to float on milky seas for more than 40 miles.

For a 19th century science fiction novel, the explanation offered by Verne's narrator is pretty darn close to what scientists believe is the underlying cause of the milky sea phenomenon. Some 235 documented sightings of milky seas have been recorded since 1915, mostly in the Indian Ocean and near Java, Indonesia, but these are based on eyewitness accounts, not empirical evidence. In 2005, scientists captured the first satellite images of a milky sea, and quite possibly the first image of naturally occurring bioluminescence. (The original data was collected in January 1995.) This enabled them to closely examine the phenomenon for the first time.

Bob relies on vibrio fischeri for his natural glow; the milky seas are due to a cousin of that bacterium, vibrio harveyi (which is also related to vibrio cholerae, the microbe that causes cholera). Okay, they're not exactly luminous worms, but Verne's narrator was on the right track. Certain other marine organisms -- most notably, dinoflagellates -- glow in response to some form of physical stimulation.

But bacteria that cause milky seas seem to glow spontaneously under very rare circumstances. The critical factor is extremely high concentrations: on the order of 40 billion trillion or so bacteria, equivalent to the number of grains of sand it would take to cover the entire earth with a layer 10 centimeters thick. (Incidentally, Jen-Luc points out that while we often perceive the light of the milky sea as white, it is in fact blue. It seems white to us because the rods in our eyes that we use for night vision cannot distinguish colors.) Scientists have yet to figure out what might lead to such unusually high concentrations, but the working hypothesis is that the bioluminescing bacteria are colonizing another kind of organic material, like alga, present in the water.

It remains to be seen what new insights scientists will glean from studying the milky seas, but Bob's built-in bioluminescent flashlight may yield some interesting applications. Recall that the colonies of bacterial in Bob's gullet are surrounded by stacks of reflective plates. It turns out that these aren't made of crystals, as are other similar materials, but of a previously unknown type of protein. (This same protein also makes up the reflective, silvery tissue around the little sea squid's eyes.) Wendy Crookes of the University of Hawaii, Manoa has dubbed these proteins "reflectins." Their unusual amino acid composition is a naturally occurring nanoscale photonic structure, which means it may one day lead to new, self-assembling nanoscale spectroscopic and optic devices.

Dinoflagellates don't cause milky seas, but when physically agitated, they do give rise to such phenomena as red tides, flashing waves, and the telltale sparkling wakes that get churned up behind boats, for instance. No doubt there are plenty of potential real-world applications for those, too, plus a few that might be unintentional.

One of my (many) favorite moments in the film Apollo 13 is when a TV news anchor airs past footage from an interview with astronaut Jim Lovell (played by Hollywood's favorite All-American Everyman, Tom Hanks), in which Lovell recounts his experience as a Navy pilot. His instrument panel went out one night, leaving him with no means of finding his way back to the aircraft carrier. But then he noticed a green glowing trail in the water beneath his airplane: bioluminescing plankton churned up by the aircraft carrier as it moved through the water. Lovell was able to follow that glowing path to safety. I like to think he was saved by the microbe-scale Friends of Bob, the Little Sea Squid that Could.

Comments

[Jennifer Solis]

I just have to say you are atomically marvelous and I love the scientifically inspired alcholic concoctions. I am a micro/marine biology student and your commentary on bioluminisence is refreshing. long live Bob.