by Edith Widder
Color has all kinds of interesting stories to tell when viewed with spectrometers, which are not subject to the kinds of deceptions to which our eyes may succumb. As I had experienced with those yellow roses in the hospital, the brain cannot be trusted to report colors accurately. When the light is too dim for the red, green, and blue cones that are the basis for our color vision, then our more sensitive rods take over, reporting light but not discriminating color. Nonetheless, the brain may supply the sensation of a particular color, informed by expectations rather than actual data.*1
Even when the color is bright enough for the cones to detect, they can be fooled, since pure green light can look the same to our eyes as a mixture of blue and yellow light; and what we call white light can be any of a wide variety of color combinations that stimulate our three different cone types equally. Color in the ocean carries important information about how animals are seen (or not seen) and what their light-emitting abilities may have evolved to communicate. Details related to the relative contributions of specific colors, plotted as spectra, can also provide hints about the chemicals responsible for producing the light. The OMA promised exciting new discoveries, if only there were some way to gain access to living deep-sea light emitters so we could measure their bioluminescent emission spectra.
As chance would have it, there was, because just down the hall from Jim Case’s lab was Jim Childress’s. Childress, a pioneer in the study of metabolism in deep-sea animals, had perfected methods of bringing the animals up alive. Despite a common misperception that deep-sea dwellers die from extreme changes in pressure when brought to the surface, changes in temperature are far more damaging. Deep ocean water, which constitutes about 90 percent of the volume of the ocean, is very cold, averaging between thirty-two and thirty-seven degrees Fahrenheit. If you capture deep-sea animals in a net and drag them up through warm surface waters, they are basically cooked and consequently either dead or dying by the time they reach the surface. Pressure changes are less damaging for many of these animals because they don’t have air-filled spaces, like air bladders, and thus don’t experience explosive changes in volume. Childress was able to keep animals alive by capturing them with nets that directed the catch into thermally insulated capture devices of his own design.
Usually, at the end of the net there is just a mesh bag, called the cod end,*2 that holds the catch. Childress replaced that bag with a large-diameter PVC tube that contained a mesh bag inside to retain the catch, and ball valves at either end of the tube that could be closed at depth, sealing the catch in the ambient cold water. In this way, animals could be brought up alive, and if they were kept cold aboard the ship, they could usually be maintained long enough for Childress and his team of grad students to make critical measurements related to their metabolism and, Case reasoned, long enough for us to study their bioluminescence.
Thus it came to pass that I went on my first ocean expedition in 1982, aboard the 110-foot research vessel Velero IV. One hundred and ten feet is one and three-quarters bowling alleys long, which is not a lot. One bowling alley length housed the bridge, the mess, the lab, and the sleeping quarters for eleven scientists, seven crew members, and one ship’s cat, Buffy, while the remaining three-quarters was the fantail or back deck. The dry lab*3 was in the bowels of the ship and required maneuvering all the scientific gear down a steep ladder and then strapping absolutely everything down so it wouldn’t go flying the first time we hit rough seas. The mess was tiny, the food terrible. The four-person cabin I was in was cramped and musty. Opportunities for sleep were rare and usually uncomfortable. I had a top bunk that was crosswise to the ship’s main axis, so when the ship rolled side-on to the waves, I slid up and down the length of the bed. In rough seas, the porthole at the foot of the bunk leaked and the mattress grew soggy. Nine scientists shared one head with sketchy plumbing. Those in the know maneuvered to be between third and fifth in line for the shower—the sweet spot between when the hot water first surfaced and when there was no more. For anything other than liquid, the toilet required four or more flushes—a common source of aggravation. I once saw the head door slammed open in a fit of pique as one of my fellow grad students emerged, holding a turd in his bare hand. He flung it over the side of the ship and then, seeing me, muttered, “Fucking floaters!”
Going to sea on research expeditions is not for everyone, but I loved it. This was the kind of swashbuckling adventure I had dreamed about as a kid. A two a.m. shout into the cabin of “Net’s up!” would send us all scrambling out of our bunks and into our wet-weather gear. Out on deck, we each took up our assigned position or task, working the hydraulic A-frame, crewing the capstans used to haul in the tag lines, schlepping five-gallon plastic carboys of seawater from the chiller to set at the ready next to the trawl bucket. We each had a vital role to play, and we depended on and looked out for one another. If you screwed up and weren’t paying attention as the heavily weighted net appeared over the transom and went sliding across the deck, somebody could get seriously injured. It was a brief period of high stress, rewarded by the extraordinary payout of whatever came whooshing out of the cod end as it was held over a large metal washtub and the ball valves were cracked open.
During night recoveries, the contents of the trawl bucket glowed with streamers of liquid blue light: scintillating plankton, glowing krill, and mangled but occasionally still-pulsating jellyfish. When the trawl bucket was carried into the wet lab, everyone congregated around it, plunging bare hands into the bone-chilling water to haul out one animal after another. I joined in, pulling out a bright red shrimp*4 the size of a hamster. It had long red antennae, a beautifully sculpted carapace with elegant curved spines, and a multitude of feathery legs, and when I lifted it out of the water it spewed brilliant streams of sapphire-blue light from nozzles on either side of its mouth. The light pooled in my palm and spilled between my fingers, dripping back into the bucket, where it continued to glow. Also in the bucket were lanternfish, each sporting light organs called photophores that looked like jeweled studs adorning their sides. There were hatchetfish, so named because their body shape is like a hatchet; its tail forms the handle and its silver-sided body the blade, and along the bottom edge of that blade are two rows of light organs that look like two-toned fingernails painted mostly silver with magenta lunules.
Besides these more common species, it seemed like every haul held at least one special surprise. There was a velvet-black dragonfish, slender and long, like an eel with a whiplike bioluminescent fishing lure protruding from its chin. There was a vampire squid, an inky black, gothlike creature with eight arms connected to one another by a web of skin and each lined with fleshy spikes. It had two enormous eyes at the base of the arms and two large, lidded light organs that looked like a second set of eyes at the base of two big flapping fins. There was even a stoplight fish, a midnight-black beauty with a big red light organ under each eye and a smaller blue one right behind it.
As it turns out, bioluminescence comes in all colors: red, orange, yellow, green, blue, and violet. In the open ocean, blue dominates. This makes sense if you think in terms of efficient visual communication. The reason everything looks blue underwater is that blue is the color that travels farthest through water. The other colors are scattered and absorbed to varying degrees and gradually disappear. You may notice the very weak penetration of red light if your scuba buddy is wearing something red. Above water, a red Speedo appears red because it absorbs all colors except red light, which reflects off the bathing suit and back to your eyes. Deep enough below the surface, however, where there are no more red photons, the suit absorbs all available light and appears black.*5
It seems wrong that the color of a thing is defined by a negative—in other words, what it doesn’t absorb. Chlorophyll appears green because it absorbs red and blue, using the energy from these colors to make photosynthesis possible. The green that reflects back to our eyes is the unuseful stuff—basically discarded p
hotons. Most of the visual information we take in is in the form of rejected photons—that is, reflected light. Bioluminescence is an exception to this general rule because it is emitted photons. That so much of this bioluminescence is blue helps explain why so many deep-sea animals are red: If the only light to see with is blue, being red is akin to being black. Red pigments absorb blue photons, reflecting nothing back to the eyes of predators.
Since downwelling sunlight filtered through seawater is blue and the majority of bioluminescence is blue, most deep-sea animals have evolved eyes that see only blue light. The stoplight fish is different from most of its kind. It sees blue light, but it can also see red light, which means it’s got sniper-scope vision! To be able to see and sneak up on prey undetected is a superpower with the added benefit that red light helps break the camouflage of one of the stoplight fish’s common prey items, red shrimp. While a red shrimp in blue light appears black and well camouflaged, under red light it will stand out like a beacon in the darkness. And there is potentially still one more benefit: This remarkable fish can use its red light at close range to communicate with a prospective mate over a private wave band without fear of attracting the attention of visual predators.
I had read about many of these animals. I had seen pictures of specimens preserved in formalin and pencil drawings of what they were supposed to look like. I had read statistics on how the vast majority of animals brought up in trawl nets are bioluminescent. But I was still gobsmacked by the reality of so many fantastically strange creatures with multiplicities of light-producing means and methods.
In every trawl, there were examples of the different proposed functions of bioluminescence that I had been reading about. There were lights for finding food, either in the form of bioluminescent fishing lures used to attract prey or built-in flashlights for locating prey in the dark. There were lights for attracting mates with different-shaped light organs or different flash patterns, used as species and sex identifiers. And there were bioluminescent defense strategies, like spewing luminescence into the water to distract a predator, or very bright light organs on the tails of some lanternfish that could be used to temporarily blind a pursuer. And virtually all the fish, shrimp, and squid sported belly lights, used to eliminate the silhouette that is the search image of so many open-ocean predators. This form of camouflage is so commonplace in the ocean that it’s the equivalent of color-matching camouflage on land.
One of the fish I pulled out of the trawl bucket was a saber-toothed viperfish, its awesome name a consequence of the fearsome curved fangs that protrude from its lower jaw. These teeth are so long and so sharp that if they closed inside the mouth, they would impale the fish’s own brain. Instead, they slide into grooves in the upper lip, and when the mouth is closed they extend to a point just above the eye. That should be more than enough badassery for any one creature, but this fish piles on with a panoply of light organs that stretch the imagination in terms of possible functions. An elegant long fin ray grows out of its back and arches forward, dangling a luminescent lure in front of its fearsome maw. Clearly, this must be used for fishing. Two rows of prominent photophores along the belly certainly serve to camouflage the fish’s silhouette, hiding it from the eyes of upward-looking predators. A flashlight under each eye might aid in finding food or attracting a mate. But what of the photophores inside the mouth? Are they another means of attracting prey, or do they illuminate the long, lucent fangs, perhaps as a threat? Even more bizarre are the tiny, inconspicuous light organs embedded in a mucous layer that covers the back, belly, and fins. When these organs light up, the fish strobes an outline of its body—for what? Defense? Sex? Disco dancing?
Another unexpected prize from the trawl was an exceptionally large anglerfish. Most deep-sea fish are small—an adaptation to living in a food-poor environment. Hatchetfish are the size of a silver dollar. Lanternfish are no bigger than a pocketknife. Even the fearsome viperfish is generally less than a foot long. The apparent ferocity of anglerfish is often much diminished in viewers’ eyes when they learn that gruesome countenance is associated with a fish the size of a plum, or in some cases a plum pit. But this anglerfish was the size of an eggplant—a big one. Like most anglers, she had an enormous mouth filled with needle-sharp teeth and a bioluminescent lure called an esca. But this lure looked like it was designed by Dr. Seuss. It consisted of a short, stout rod protruding from her upper lip and crowned by a tulip-shaped light organ, festooned with two bundles of long, delicate translucent threads. Was this elaborate structure an adaptation for attracting prey or mates? Both are possible; some lures seem to mimic small prey, while the ornateness of others is believed to aid a male in identifying a female of his own species.
The male anglerfish is much smaller than his female counterpart. He lacks a lure and has no teeth for consuming prey. For many anglerfish species, the male’s only hope for continued existence is as a gigolo. In the unimaginably immense black void of the deep sea, he must somehow locate a potential mate, either visually or by smell, and, upon finding her, seal the relationship with an eternal kiss by latching on to her flank, where his flesh fuses with hers. Her bloodstream then grows into his body, providing him with sustenance, in return for which he provides sperm upon demand. This lifetime commitment may sound romantic, but it’s not all hearts, flowers, and pillow talk. He’s a bloodsucker and a sperm bag, and she’s ugly and weighs half a million times more than he does.*6
And she has a nasty temper to boot. I witnessed her vicious streak when I had her in an aquarium and tried to photograph her head-on to capture the full measure of her stunning unattractiveness. I was using a long-handled paintbrush to occasionally nudge her back end around so she would face the front of the aquarium. Every time I touched her side, no matter how gently, she would twist around and snap at the point of contact. I presume a male might expect the same reception, which suggests he may need to execute great caution in selecting his method of approach and point of attachment.*7
When the expedition was over, I had a hard time readjusting to life on land. It wasn’t obvious why. I was pretty sure I wasn’t missing the sleep deprivation, bad food, or lousy plumbing. Eventually, though, I realized that what I did miss was the excitement and camaraderie of being at sea. Still jacked up on adrenaline, I felt the world was off kilter. All the students roaming around campus seemed alien and clueless, nothing like the members of the tight little team I had been part of at sea, and I was dismayed by their obliviousness to the secret world revealed by our net hauls. How was it possible that they didn’t know that just a hop, skip, and deep dive offshore there are outlandish life-forms festooned with headlights, taillights, belly lights, mouth lights, fishing lures, and light-spewing nozzles? That should be front-page news—right? That nasty-tempered angler we brought up turned out to be a species never seen before! Why was that not a banner headline? It was incomprehensible to me that the world held such wonders, about which most people knew almost nothing.
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While many may claim that getting a Ph.D. is as easy as riding a bike…through a desert, with no sleep, while people in black robes try to distract you by setting your hair on fire…that was not my experience. I loved the five years I spent completing my degree. It was without question the best academic experience of my life. Which is why, when I graduated in 1982 and it came time to move on, I was finding it difficult to get excited about what should have been a great opportunity.
A couple of months after passing my orals, I flew from sunny Santa Barbara to cold and sunless Madison, Wisconsin,*8 to interview for a postdoc position in the laboratory of a scientist on the leading edge of research in excitable membranes. The interview went well, and I was offered the position. I tried to feel enthusiastic, but the truth was, I was disheartened by the idea of moving so far from the ocean. I believed I belonged on a ship, and leaving just felt wrong. Jacques Cousteau claimed, “The sea, once it casts its spell
, holds one in its net of wonder forever.” I was in the sea’s thrall. At least I had one more research expedition to look forward to before my departure, and it promised to be especially exciting, because it involved a new approach to deep-sea exploration.
Bruce Robison, at that time an associate research scientist at UCSB, had spent years going to sea to study midwater fish on the kinds of expeditions I had just experienced. Then, one fateful day, he and Jim Childress were walking across campus and spotted a sign for FREE DONUTS AND COFFEE attached to an announcement for an ocean engineering seminar. They figured they’d check it out. In addition to the caffeine-and-sugar rush, they were treated to a movie about the Wasp deep-sea diving suit and a post-film discussion of its engineering functions. Robison, known as Robi to his friends, wondered about possible science applications. He was frustrated by the limitations imposed by net sampling and wanted more direct access to what constituted the most unexplored frontier on our planet, the midwater.
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The first submersible to carry humans into the deep sea did so in the early 1930s, when William Beebe, a scientist with the New York Zoological Society, and Otis Barton, an engineer, made a series of thirty-five deep dives (maximum depth, 3,028 feet) off Bermuda in a steel sphere of Barton’s design. Dangling from a steel cable, the 5,400-pound sphere and its two occupants were hoisted up and down through the water by a steam-powered winch while Beebe, peering out through a six-inch porthole, made observations that he later included in a series of articles for National Geographic and in a book entitled Half Mile Down.
Beebe was a gifted raconteur, and his words opened a portal to a heretofore alien world. Besides inspiring future explorers and environmentalists, including E. O. Wilson, Rachel Carson, Jane Goodall, and Sylvia Earle, he is also credited with helping to pioneer the field of ecology, championing the need to study animals in their native habitats.
