BLUE BLOODS
The absence of a skeleton in a marine life form constitutes a form
of perfection.
—JACQUES-YVES COUSTEAU
On the Monterey Bay research boat that November evening, Julie Stewart continued to cradle her research subject. She was waiting for the precise moment to ease her five-foot Humboldt, fins first, into the rough waves. If she made a mistake or just dropped the animal onto the sea surface, the squid might have trouble swimming away. Or, disastrously, the $3,500 satellite tracking tag she had attached to the fin might come off.
She bent down closer to the water. She might have found herself in the water but for John Field, a 6′3″ surfer and research biologist with the National Marine Fisheries Service. John grasped Julie's life vest. From the safety of the boat deck, he braced himself and held tightly, stabilizing Julie so she could concentrate on the task at hand. The mantra at sea is "one hand for yourself, and one for the boat," but she needed two hands to hold the animal.
For an instant the Humboldt, with its strange baseball-size eyes, looked directly at Julie, as though trying to cross the gulf of 700 million years of evolution. The animal flashed red and white, red and white, showing off its chromatophores.
"Kind of like a disco," Gilly commented.
We experience the Humboldt's show of red as a display of anger. Maybe our own brains are hardwired to make the connection between the color red and the flow of blood. But that's not why the Humboldt turns blood-red. In the ocean the color red disappears quite quickly because its long wavelengths cannot easily penetrate water. What appears red above the water appears merely dark below the surface. When the Humboldt turns red below the water surface, it is making itself invisible.
No longer buoyed by salt water, Julie's Humboldt was in fact rather helpless. Its eight arms and two feeding tentacles were pulled down by the full force of the earth's gravity. It was not accustomed to the sensation. Out of its medium, its behavioral choices were limited. A fish out of water flaps on the deck of a boat, trying to escape. A squid, however, lacks the framework of a skeleton. It has no bones or any hard internal structures, other than a flimsy "pen," the evolutionary remnant of the shell that all cephalopods once had. (The pen is so named because it reminded people of ink-filled quill pens.) Made of material somewhat like your fingernails, the pen is easily bent and substitutes for a backbone, and as is the case with our backbone, many of the squid's muscles attach to the pen.
But the flimsy pen can support these muscles only when the squid is in the water. When it's beached or hauled on board a boat, the pen isn't particularly helpful. As a result, the Humboldt cannot flop around like a fish. What it can do is slash with its beak, which is quite sharp. A nasty wound is not uncommon. The animal's arms and tentacles are also dangerous. "The tentacles are their secret weapon, their jack-in-the-box surprise," Gilly said. "If the teeth on the arms get you, it's like getting bitten by fifty garter snakes."
One reason why Julie's squid lay so passive in her arms may have been related to the animal's blood, which supplies oxygen to its cells using chemistry that's quite different from our own. "They have blue blood, ice crystal blue," said Gilly, "as blue as an iceberg."
Blood, of course, flows through an animal's circulatory system, carrying oxygen to all the cells of the animal's body. Oxygen, the third most common element in the universe and essential to life, is produced by land plants, but surprisingly, most of the oxygen in our atmosphere is produced by marine algae.
It's a good thing these algae are around. We owe them our very existence. Were it not for them, we would asphyxiate. Living cells need to have a constant source of oxygen. In vertebrates, oxygen enters the body through lungs and clings to the iron in a hemoglobin molecule. The hemoglobin then travels through our circulatory system, bringing oxygen to cells that need it. If we're running, for example, the hemoglobin drops off extra oxygen to our leg muscles. Not all animals, however, use hemoglobin. Some animals, spiders and lobsters for example, substitute a compound called hemerythrin for hemoglobin.
Mollusks and many other marine animals use hemocyanin—a molecule that may have evolved as long as 1.6 billion years ago, long before the first mollusks and roughly a billion years before the Cambrian Explosion. This seems pretty long ago to me, but scientists interested in molecular evolution believe that hemoglobin, our own oxygen-carrying molecule, may be even older, perhaps even dating back four billion years, to just after the time the earth was formed.
Even if the mollusk's hemocyanin was not the first oxygen-carrying protein to evolve, it must have done its job fairly well. In the Ordovician, the period following the Cambrian, cephalopods proliferated. The Ordovician was a rather eccentric period in earth's history: Most of the Northern Hemisphere was under water and most of the planet's land was gathered into one single supercontinent, Gondwana. This southern supercontinent was slowly drifting over tens of millions of years, inching its way relentlessly south.
For a while, the seas were deliciously warm and the planet seems to have been a kind of Garden of Eden, a time of nirvana that allowed life to flourish in many different forms. A few cephalopod species grew large enough to rank among the largest animals then extant. Protected by long, straight, conical shells, with numerous arms poking out and dangling below their eyes, the larger cephalopods were quite fierce. One group, Cameroceras, lived in shells that may have been as long as 30 feet—the size of a large RV.
Cameroceras, which we would easily recognize today as a cephalopod despite its burdensome shell, was certainly formidable. It may well have been the ocean's top predator. But it would not have been very maneuverable. For most of the Ordovician, this probably wasn't a drawback: Since life proliferated in the warm shallow seas, all Cameroceras had to do was hang out just above the seafloor until some tasty morsel passed by.
During this period, cephalopods ruled. Unfortunately for them, nothing lasts forever. Circumstances were about to change. Gondwana continued its southward journey. As the supercontinent headed nearer the South Pole (eventually North Africa would be directly over the pole), the climate chilled. Gondwana glaciated and the world became cold. This may have happened relatively abruptly, over a period of only several millions of years. Ocean life had little time to adapt and many of the planet's species, including many cephalopod species, died off.
The glaciations themselves may have tripped the climate change, but other explanations have also been offered. One NASA researcher has suggested that a very powerful explosion of a star, a gamma ray burst, may have occurred near enough to earth to destroy the protective ozone layer. Whatever the cause, the cephalopods as a group once again managed to survive. No one knows for sure why cephalopods are so resilient, but their ability to survive might be due in part to their use of hemocyanin in lieu of hemoglobin.
Fast-forward to the Mesozoic era, the era of the dinosaurs and the Triassic, Jurassic, and Cretaceous periods. From about 245 million years ago to 65 million years ago, cephalopods once again ruled the seas. But this time they did not rely on size and power, since they certainly couldn't compete on the same scale as large oceanic predators like the 50-foot Mosasaurs, marine lizards that slithered snakelike through the oceans hunting, among other prey, cephalopods; or like the 500-pound, 10-foot-long sea turtle Protostega that patrolled shallow waters relentlessly in search of luscious squid lunches.
In the face of such enemies, the cephalopods for the most part opted not for size, but for sheer numbers. The predominant cephalopod group, ammonites, spread everywhere throughout the planet's oceans, although they seem to have preferred shallow coastal seas. We know this today because their fossilized shells have turned up in the oddest places—in mile-high mountains in Afghanistan, all over the American Midwest and Southwest, and layered in the southern cliffs of Britain, along the English Channel.
Ammonite fossils were so common around the English town of Whitby that the town's early coat of arms showed three of them. Only these three had been slightly adulterated to meet the needs of the local belief system. Early on, the people of Whitby had decided that the ammonites were the remains of coiled snakes, and a local legend had evolved about a saint named Hilda who rid the town of snakes by turning them to stone.
An ammonite fossil
Of course, the people of Whitby never actually found any ammonites with snakes' heads. So, to validate the legend, they fabricated the evidence: They carved snake heads onto the ammonites, then claimed said heads had always been there.
For a time, Whitby remained fairly committed to the tale of St. Hilda. The town shield featured ammonites with snake heads. But finally science ended the fun by explaining that the coiled fossils were not the remains of snakes, but of animals that had long since disappeared from the earth. The ammonites are still on the town shield, but the snake heads have disappeared.
Of course, ammonite fossils are only the shells in which the animals lived. Science knows almost nothing about the cephalopod that occupied the shells. Curiously, we have more fossilized soft parts from earlier nautilus species than we have for the ammonites, despite their proliferation, so we're not quite sure what the animal inside the shell actually looked like, but scientists extrapolate from modern cephalopods to suggest that ammonites, also, had well-developed eyes, a raspy radula, and many tentacles.
From about 240 million years ago until 65 million years ago, ammonite species were so prolific, and sometimes evolved and disappeared with such rapidity—in the blink of an eye as geologic time goes—that they have become important signposts worldwide for geologists trying to age a particular rock stratum. They are a central pillar of the science of biostratigraphy—the science of correlating ages of rock with the fossils of extinct animals found in those rocks. Some ammonites evolved, proliferated, then disappeared in only one or two million years. If geologists find ammonite fossils in a rock layer, they can age a layer of rock quite accurately to within a million years or so. This can be done worldwide, so a layer of rock in China may be connected to a layer of rock in the American Southwest or in Britain just because the same fossilized ammonite species appears in all three places.
In the eighteenth and nineteenth centuries, ammonites also helped people wrap their minds around the difficult demands of imagining both geological timescales and evolution itself. In Europe in those days, collecting ammonite fossils was a quite respectable outdoor occupation. Even women were allowed to participate. Most ammonites are small and can easily fit into a pocket or purse, although a very few shells may be five or six feet in diameter. Amateur collectors couldn't help but notice that the various ammonite species appeared and then became extinct in correlation with specific geologic layers of rock. Charles Darwin certainly wasn't the first person to notice this, although he was the first to place this interesting little factoid into an overarching theory.
When the dinosaurs died out 65 million years ago, the ammonites also became extinct. But again, the cephalopods as a group survived. We know about the proliferation of ammonites because of their fossilized shells, but we know very little about the early shell-free species. Fossil evidence of their soft bodies is rare, but from time to time, fossilized cephalopod ancestors do turn up. In the summer of 2009, paleontologists discovered a 150-million-year-old squid, an animal that would have shared the seas with the ammonites. Found in Britain, in a region well known for the quality of its fossils, the squid was easily recognizable. Its inch-long ink sac was so well preserved that scientists were able to take a sample of the ink, grind it up, add some liquid, and then use that very ink to sketch the fossilized animal.
Sketch of a 150-million-year-old squid fossil
At about the same time, other scientists reported finding a 95-million-year-old fossil of an octopus in limestone deposits near the present Mediterranean shoreline in Lebanon. This animal, too, lived in the ocean while the dinosaurs still thrived. It also had a distinctly preserved ink sac. Scientists were amazed by the fossil's overall quality, which showed an octopus that looked quite like today's modern octopus. Since not much has changed in the octopus's basic body shape, a few marine biologists believe that the octopus may be an evolutionary dead end and that there aren't going to be many more mega-design changes.
With the satellite tag activated, Julie waited for the waves to settle. At last, after several minutes, the boat rocked into position. She slipped her squid back into the bay, gently, like a mother laying an infant in a cradle. She felt its rough, craggly skin against her fingers. The loose texture made her wonder whether the animal was older than the other two she had already tagged that evening. It certainly was much bigger, almost as long from mantle tip to feeding tentacle tip as Julie was tall. It was many pounds heavier than most of the roughly 50-pound Humboldts that routinely turn up in Monterey Bay.
It was 7 p.m. The cruise had started just after 4, and already Julie had the last of the three research subjects she'd hoped to tag. She and Gilly hoped the expensive computer chips inside the tags attached to the squids' fins would yield some useful information.
The tracking tag
The team wanted to know where the squid traveled. The daily lives of animals—even animals living on land—remain mysterious. We know a tiny bit about charismatic megafauna like whales and elephants and lions, and we're fascinated by the sparks of intelligence shown by dolphins and chimpanzees, but we're pretty ignorant of the habits and preferences of much of the animal life that surrounds us. Learning about animals has been one of humanity's greatest adventures. Each little step we take that advances our knowledge—"Whales sing to communicate with each other" or "Chimpanzees work together and use tools like sticks to acquire food"—feels like the discovery of a new universe to us. Shortly before his death in 1987, sea turtle biologist Archie Carr stood on a Florida beach and spread his arms wide, as if trying to embrace the whole of the Atlantic Ocean. "Where do they go?" he asked about the turtles that had become his life's passion. He wasn't asking for himself. He was leaving a research question for the generations of marine biologists that would follow. Today, in large part because of Carr's passion, we know a great deal about where sea turtles go in the sea, about what they eat, and about how they navigate their way back to the beaches where they hatched.
But our understanding of the behavior of these few sea species is anomalous. Of most sea life, we know nothing. Indeed, much of the life in the ocean has yet to be catalogued. Discovering facts about animals that live in the ocean depths is inordinately difficult—expensive and time-consuming and technology-dependent. Money is tight. We can't afford to spend much on each individual species down there. But, to Julie's good fortune, some money at least is available for studying Humboldts. Commercial fishermen charge the Humboldt squid with the crime of eating salmon and hake and smaller squid, species that commercial fishermen sell at market. This connects the Humboldt to a big-money product and so makes research funding more available than it would be otherwise.
As her third tagged Humboldt swam away, Julie was thrilled. So was Gilly. "We've had hauls like this down in Baja," he said, "but never anything like this up here before."
For a scientist, data is the be-all and end-all, the ultimate goal, the sine qua non of fieldwork. No data, no science. No science, no funding. The goal of an evening cruise like this is to get enough information to keep Gilly's lab humming for months. It doesn't always happen. Fishing for data is as risky as fishing for big-money bluefin. You might hunt and hunt and just as easily come up with nothing as come up with a fortune. The odds are better than wasting your time in Vegas, but not by much.
Julie's tracking tags were fairly large in size, 175 millimeters (a little less than 7 inches in length) and 75 grams (a little less than 3 ounces)—"the size of a karaoke microphone," Gilly mused. You might use something about the same size on a sea turtle or a tuna or a shark. The tags, called Pop-up Archival Transmitting Tags, come with a pair of plastic pins, but it's up to the scientist to figure out how best to attach the tag to the research animal. The scientist can also program the tag to release from the animal in a specified number of days. Stewart had chosen to attach the tag to the fins, using the pins, and to program the tag for release in seventeen days, by which time the data storage chip would be full.
As the squid moves vertically and horizontally through the water, the computer chip in the tag records information, including temperature and light levels, from which depth can be calculated. This information is recorded on the computer chip, but not all of that is sent to the satellite. Instead, because transmitting the data to a satellite is expensive, Julie has opted for the information to be sent to the satellite only periodically. From the satellite, the data is sent to her laptop.
The receiving satellite, one of a six-satellite system called the Argos System, has been providing scientists with important animal behavior data for more than thirty years. Today, well over four thousand tagged animals worldwide provide data via this technology. Much of what we know about sea turtles, for example, comes from Argos technology. By using tracking tags, Barbara Block, a colleague of Gilly at the Hopkins Marine Station who studies sharks, learned that great white sharks migrate far offshore into the Pacific, overturning the belief that the animals stay fairly close to the shoreline. Other tracking tags have shown that dolphins dive much more deeply after prey than hitherto expected. Recently scientists began tracking walrus migrations through the Arctic seas.
The information from the tag that's beamed up to the satellite then down to the scientist is useful, but the information archived in the tag itself, the instant-by-instant story of what the animal's been up to, is the real treasure. When the tag pops up, it transmits its location to the satellite. Scientists will go to great lengths to retrieve that tag, since it has more of what they want. But they also want the instrument itself, since it can be sent back to the manufacturer for reprogramming and reuse. Most marine labs can't afford to waste $3,500.
Unfortunately, looking for a tracking tag about the size of a karaoke microphone bobbing in the waves of the ocean is like looking not just for a needle in a haystack but for a needle in a moving haystack. The task can be both time-consuming and frustrating. You know the item is there, but you just can't see it. Stewart remembers being out on the ocean looking for a tag and knowing from the satellite signal that it was right there, almost beside her. But she just couldn't find it. Eventually she had to give up and accept the financial and scientific loss.
Most tags carry information about a reward if found. Scientists often get them back that way. Fishermen know to pull things like that out of the water. Beachcombers may pick them up. Surfers may find them. Salvador Jorgensen, a great white shark researcher in Barbara Block's lab, once searched high and low for one of his tags. Determined to get his data, he followed the pinpointing signal. It led to a residential neighborhood, then to an individual house. He knocked on the door.
"Do you have my tag?" he asked.
It turned out to be in the wet suit of a surfer who had found it in the water, put it in his pocket, then carried it home and forgot about it.
If following the animal can be expensive, every once in a while, scientists get lucky. The animal comes to them.
