Kraken

by Wendy Williams

  The bobtail squid and its bacteria must begin a kind of holding of hands on a cellular level. This brings the squid’s light-organ cells to maturation. Unless these squid cells change, the animal’s light organ will not function, the squid will not be protected, and it will likely become somebody else’s dinner.

  Still, the squid is a hard taskmaster: Once the squid has the bacteria, and the bacteria are living and multiplying in the light organ, the squid doesn’t keep the same specific living bacteria from one day to the next. Each morning, at just about dawn, when it is done hunting and is preparing for its rest period snuggled in the sand, the bobtail squid expels almost all the bacteria from the day before. Over the next hours, the bacteria remaining in the squid’s light organ multiply and multiply until the necessary number are present when the squid goes out to hunt again that night.

  But here’s the really intriguing point: The bobtail squid doesn’t acquire just any bacteria. Only one particular kind will do, the luminous and ubiquitous Vibrio fischeri, the same species used by the French inventor in 1900 to make lights for people. If the wrong kind of bacteria try to enter the squid, the squid rejects them. The squid has no choice in this matter. Its very health and survival depends on its finding and nurturing the right bacteria. Hardworking Vibrio fischeri are so essential to the bobtail squid that the animal constantly monitors the light productivity of the bacteria. If the little organisms are not doing their job well enough, the squid evicts them.

  The squid is not born with these bacteria. Just as a human baby develops in the uterus free of any and all bacteria, the bobtail squid develops in the egg in a sterile environment. When it hatches, one of its absolutely essential tasks is to find and nurture the rod-shaped Vibrio. The human baby must also acquire the correct bacteria.

  The parallels between squid and human go even further. When the squid finds and nurtures the right bacteria, the bacteria interact with the developing animal and aid the animal in its ongoing maturation. The first batch of Vibrio taken in interacts with the squid’s cells so that both squid cells and Vibrio develop in tandem. Because of similar basic cell interactions, human babies also need the right bacteria to interact with the newborn’s stomach and intestinal cells. For example, we need specific bacteria in our gut to manufacture vitamin K, important for blood coagulation, and vitamin B12.

  Like the squid, the human baby develops in the uterus in a sterile environment. But unlike the squid, which must go out and hunt for the bacteria after emerging from the egg, the human baby receives the first dose of necessary bacteria in the mother’s birth canal. Without the process of a natural birth, the baby may not encounter these bacterial helpers at the appropriate time, and some of the infant’s post-birth development may be at risk.

  “During passage through the birth canal,” explains McFall-Ngai, “we begin to pick up our bacterial partners, which are essential for our health. The squid research, which is far easier than research on mammals, investigates the ‘molecular language’ that occurs between host and symbiont.” Some researchers connect the increase in human bowel disease in the developed world with the increase in C-sections. “We are 90 percent bacteria,” McFall-Ngai explained. In mathematical terms, humans have 1014 bacterial cells, but only 1013 human cells. That is, if you’re just counting cells, there are a lot more of them than of us.

  Bobtail squid are aiding research in the field of human medicine in another way, too. After the squid acquires the right kind of bacteria, the bacteria do not bioluminesce immediately. Their light does not shine until they have achieved high enough population levels. When the critical level has been reached, the glow begins. Other researchers are studying this phenomenon, called “quorum sensing,” in order to develop a new and better kind of antibiotic for human use. If scientists can better understand the interaction of the bobtail squid and Vibrio fischeri, and understand how Vibrio bacteria communicate with each other in the squid’s light organ, they may be able to find a way to interrupt that communication. By preventing the communication, they may be able to prevent the bacteria from reproducing. And this ability might eventually be the foundation for the development of a whole new line of antibiotics, of medications that don’t destroy a bacterial infection but instead prevent the infection from overwhelming the host organism in the first place. The key to developing this new line of drugs, researchers say, is understanding the fundamental relationship between the squid and the bacteria throughout the squid’s lifetime.

  One of the biggest problems cephalopods face is how to live safely in a 3-D world. When you imagine swimming in the deep ocean, you have to rethink human-oriented concepts of “up” and “down.” As rather large surface animals who live on the continental crust, we usually need only be aware of animals living on the same plane that we do: Will we be attacked by a lion? Trampled by an elephant? Usually, “up” and “down” are not words that hold terror for us. We don’t fear giant birds swooping down from above to scoop us up and carry us away, and we don’t fear giant worms bursting out of the earth’s crust to grab us and drag us underground. For the most part, we only need to be aware of enemies that, like us, are firmly rooted to life atop the soil.

  But surviving in the ocean is more complex. An animal living in the sea needs to have the responses and defenses of a fighter pilot. The enemy can come from anywhere, from the left or from the right, but also from above or from below. It’s a three-dimensional world down there. Skeleton-free cephalopods are particularly at risk, since predators don’t need to worry about the bones. “The creatures are really just rump steaks swimming around,” Australian Mark Norman once quipped. They need special protection.

  In response, the animals have evolved an impressive tool kit of tricks. The bathyscaphoid squid, named in honor of a self-powered sea exploration vehicle that was developed after Beebe’s bathysphere, comprise a family of squid that spends its early life, when it is most vulnerable and most likely to turn into someone else’s dinner, at the ocean’s surface, where there are plenty of small tidbits for a tiny animal to eat. As bathyscaphoid squid develop, they descend deeper and deeper into the water. These squid have evolved a body that’s translucent and almost completely invisible. At the top level of the ocean, the water is rich with nutrients. It’s easy for the squid, as predators, to find food. Unfortunately, it is also easy in the sunlight to become prey to other predators. But with a body that’s almost transparent, these young squid are ghostlike, nearly invisible. Being nearly invisible when tiny is quite convenient. The young squid at the sea surface can easily sneak up on its even tinier prey without being noticed. A prey animal might perceive what seems to be a twinkle of sunlight at the sea surface, only to find itself enveloped in a mass of squid arms and tentacles.

  Locating your enemy in the ocean is a 24/7 task. Color and luminosity are both armor and weaponry. Many animals developed the ability to change shape and color to blend in with their surroundings. Some fish can do this, as can some frogs and, of course, chameleons, but no group of animals is as sophisticated in this strategy as are the cephalopods. When we watch these animals zip through a myriad of psychedelic displays in only seconds, we stare, transfixed. But the basic organization of this magic show is simpler than you might think: It’s done with three layers of three different types of cells near the skin surface—a layer of chromatophores, a layer of iridophores, and a layer of leucophores.

  The top layer of cells, the chromatophores, contains the colors yellow, red, black, or brown. The colors present are species-dependent. The color in a chromatophore cell sits near the cell’s center in a tight little ball with a highly elastic cover. When the muscles controlling the chromatophore are at rest, this ball of color is covered over and can’t be seen. When a chromatophore is showing, what you’re seeing is this little ball, stretched out into a disk roughly seven times the diameter of the at-rest ball.

  To operate properly, one chromatophore cell has a number of support cells, including muscle cells and nerve cells. The ar
rangement is cunningly elaborate. Anywhere from four to twenty-four muscle cells might attach to only one chromatophore. When these muscles contract, pulling on the chromatophore cell, the elastic sac is stretched out, revealing the color inside. When the muscles relax, the ball returns to normal size and the color disappears.

  There’s a simple way to envision this: Imagine a small, circular sheet of red paper. Crumple it into a tiny, tight ball. The color red is now only a pinpoint. Using your hands—and the hands of up to eleven other people if they’re around to simulate the twenty-four muscle cells—stretch the paper out so that it’s flattened to its full size. Then crinkle the paper into a tiny ball again. Do that umpteen times a second to simulate flashing. On an infinitely smaller scale, that’s how a cephalopod operates one individual chromatophore.

  This is enormously elaborate engineering requiring a considerable amount of coordination and support. The muscles surrounding the color-containing cells are controlled by nerves that interact with other nerves. Some scientists think that this complicated system requiring massive amounts of computing power may be one explanation for cephalopod intelligence.

  Just below the layer of chromatophores is another layer of cells, the iridophores. This layer of cells shows a different array of colors—metallic blues, greens, and golds. The iridophores do not open and close. Instead, they reflect light. They are sometimes used to camouflage an animal’s organs, such as eyes, by shimmering and drawing attention away from the organ. Some scientists have studied this strategy of distraction-by-light-show as a way to improve camouflage for soldiers on the battlefield.

  Underneath this layer is the final layer, a layer of leucophores, flattened cells that passively reflect the color of background light, increasing the animal’s camouflage.

  When I first watched cephalopods showing off their artistic genius, some of their techniques seemed familiar. I knew I had seen this use of color and light somewhere else. Then I remembered Claude Monet’s many paintings of water lilies, of haystacks, and of a cathedral at Rouen. Monet painted the same scene many times, but each painting is different because the master could so expertly show the differences created by only slight shifts of light.

  Cephalopods are the original Impressionists. I often wonder if the French painters didn’t quietly study the cephalopods’ techniques. Both the Impressionists’ and the cephalopods’ light shows provide the illusion of great depth by using luminosity—the reflection of light. Both skillfully use thousands of points of light and color to trick the observer.

  But not all cephalopods enjoy equal artistic talent. Cuttlefish, which live nearer the ocean’s surface where light still penetrates, are outstanding in their Impressionistic skills. Humboldts, on the other hand, are quite limited. With their highly honed predatory abilities and their large size, they don’t need to devote so much energy to disguising themselves. Moreover, since so much of their lives is spent in dark ocean depths, all the Humboldt needs is red chromatophores, which allow it to disappear quickly.

  The giant Pacific octopus, probably the largest of the octopuses, also has red chromatophores. Its size and its ability to hide in crevasses lessens its need for color disguises. Since the production of so many dramatic color options is energy-intensive, it’s not surprising that the ability disappears in those species that have better survival strategies.

  Some octopus species not lucky enough to be large do have entrancing color choices. The tiny blue-ringed octopus of Australia has lots of color options from which to choose and also has various clever camouflaging strategies. It may vanish in plain sight by taking on different colors and forms, but when it’s challenged, it quickly rematerializes and shows startling, almost repulsive blue rings. The unusual tone warns predators of its deadly poison. Most octopuses are venomous (the poison is delivered via the saliva), but the toxins are rarely harmful to humans. In fact, medical researchers are studying some of the proteins in octopus toxins in the hopes of improving current cancer treatments. But a bite from the blue-ringed octopus can kill a human by paralyzing muscles and making it impossible for the victim to breathe.

  Most cuttlefish are not that poisonous. Instead, they rely on their artistic expertise, which researchers suspect is so finely honed because cuttlefish are such easy prey. Cuttlefish, apparently for eons, have made choice delicacies for all kinds of predators. Dolphins find cuttlefish delicious, but they like neither the cuttlebone nor cuttlefish ink, which upsets the dolphin’s digestive system. Australian scientists recently found that dolphins adept at “butchering” cuttlefish gather in the Upper Spencer Gulf. They gorge on an annual holiday treat—the massive die-off of thousands of cuttlefish that have finished mating. The dolphins herd the dying cuttlefish onto sand plains and kill them. Then the dolphins cleverly get rid of both the cuttlebone and the ink. Once the cuttlefish is properly prepared, the dolphins eat the meal.

  Unlike other species, cuttlefish cannot escape predators by swimming deeper, because the cuttlebone will disintegrate under pressure. Instead, cuttlefish hide by pretending to be something else. Roger Hanlon, a cephalopod researcher at Woods Hole’s Marine Biological Laboratory, is studying cephalopod camouflage abilities that may have military applications, as is the Air Force Research Laboratory in Dayton, Ohio. Recently, the Department of Defense awarded the MBL scientist $1.2 million for a study of “Proteinaceous Light Diffusers and Dynamic 3-D Skin Texture in Cephalopods.” The Ohio lab is studying some of the proteins involved in cephalopod camouflage to see if some of those proteins might somehow be used to help soldiers become less visible on the battlefield.

  When I visited the Hanlon lab, I watched as a cuttlefish rested on the bottom of a tank covered in small bits of sandy-colored gravel. The animal’s body and some of its arms took on the color of the sand, but two of its arms waved languidly in the water. Next to the animal was a plant with dark-colored fronds. The cuttlefish’s two waving arms took on the same dark color and looked just like the plant fronds.

  The effect was spectral. It was also dismaying to realize that my own eyes were so easily fooled. We humans are supposed to enjoy the advantage of terrific eyesight and a brain smart enough to perceive what it is we’re looking at. Now it turns out that our eyes are not quite as special as we once believed.

  In fact, some scientists suggest, the cephalopod eye may actually be superior in many ways to our own.

  Rob Yeomans holds out some Humboldt eyes

  The urbilateria, the hypothetical last common ancestor shared by humans and cephalopods, probably had the ability to respond to light in some way. These early “eyes” were probably very simple—maybe little more than small indented cups in the animal’s outer surface. The cups wouldn’t have “seen” in the sense that we understand the meaning of the word. Instead, the indentations would have contained compounds capable of responding to light, an ability that would have provided some kind of evolutionary advantage. When other species evolved a method of counteracting this simple eye, more complicated eyes would have appeared. Eventually, the complicated camera eye—the eye we possess—evolved. Some scientists believe that the development of our sophisticated eye was the result of an ongoing evolutionary arms race.

  We consider our eye, the camera eye with its marvelous lens and cornea, to be the best available. In fact, when Charles Darwin thought about the human eye, he wrote that it caused him to doubt his own theory. How could natural selection, with its seeming randomness, account for such a complicated and finely tuned organ?

  When scientists began studying the cephalopod eye, they found that it, too, was quite complicated. Despite our evolutionary distance from each other, the cephalopod eye and the human eye are strikingly similar in that we both possess nature’s most complex style of eye, the camera eye. This similarity turned out to be one clue that helped scientists better understand the eye’s evolution, and evolution in general.

  But there are important differences. For example, the lens of the cephalopod eye is proportionately much large
r than the lens of the human eye. Moreover, our eye has a blind spot in the middle of the image. The cephalopod eye has no such spot. These and other differences all add up to a cephalopod eye that might perceive the world with a bit more clarity—with the ability to perceive only slight differences in brightness. In the deep sea, where color is less important than light and where animals use light as camouflage, this ability can confer a significant advantage.

  Clarity, however, is not to be confused with color. In our environment, the ability to see color is advantageous. Some scientists believe we evolved the ability to see red (most mammals cannot see red) because young red leaves on trees are more nutritious and because red fruits are better to eat.

  We humans see color because different wavelengths of light hit three different types of cones in each of our eyes. (Some people, almost always men, are color-blind because they have only two types of cones.) This means that we can see a range of colors that we arrogantly call “visible light.” I write “arrogantly” because the term is a little human-centric. Other animals can see much more of the light spectrum. Some, like goldfish and birds, have four types of cones, and a few have even more. Included among this fortunate list are butterflies and, possibly, your basic, everyday, park-loitering, bread-begging pigeon. These animals experience many more colors than we do. Some fish have cones that specialize in paying attention to a deeper, richer red than the red that we see. This means that the fish’s ultimate experience of “red” is quite different from ours.

  I’m jealous. Imagine the beauty of the Impressionist paintings created by an artist with five types of color cones instead of only our meager three. It’s as though we’re stuck with watching the world using mid-twentieth-century Technicolor when pigeons, goldfish, and butterflies get to enjoy twenty-first-century digital technology.