Octopus (29 page)

The deep ocean seems like a harsh place to live. There is unimaginably high pressure: if you dangle an empty coke can to the bottom of the ocean and then bring it up, you'll get a small crumpled ball of metal. Living in that pressure may be less challenging for soft animals than for armored ones, since pressure changes could crumple skeletons. And high pressure may interfere with metabolism in unknown ways. Then there's the water quality: plants in the deep do not use sunlight to help make food and give off oxygen, so the water contains a low percentage of oxygen. It's also cold, a constant few degrees above freezing. Fewer species can survive in this inhospitable environment, and finding prey may be very difficult. And there is little to no light available.

Deep-sea and cave animals adapt to the lack of light in two different ways. One way is to evolve into not using light as a sensory cue at all. Like the cave crayfish in Florida, some species have reduced eyes or none, having gone completely blind. The deep-sea blind cirrate octopus (Cirrothauma murrayi) has done just this: the eyes are tiny, pigmented cups and there's no lens or any other focusing device. They can detect light but that's about all—no visual shapes, no object recognition. To compensate for the lack of light for vision, they use other information sources. Cephalopods already have the ability to use and learn from touch information, and no
doubt the cirri on the arms of vampire squid are very sensitive to touch. This ability is shared among the true squid, which have a row of pits along the edge of the body, each containing a mechanically sensitive receptor. But the vampire squid's filaments extend the range of touch many body lengths, and anything triggering one of these feelers can be attacked by the squid. Probably the vampire squid have excellent chemical sensitivity, but we don't know that yet, because we've never been able to keep an animal of this species alive in the lab.

A second way to deal with the lack of light is to make one's own light by creating bioluminescence. This feature is common in many shallow-water, night-active animals, like the sea pen and the lanternfish, which have to cope with darkness. Vampire squid have also adapted to the dark: they have wide-pupil blue eyes that pick up the maximum amount of light. They have a variety of devices to make their own light and the techniques to manipulate them. First, although they do not have an ink sac, vampire squid have a bioluminescent mucus that they can jet out, presumably at the approach of a potential predator, likely distracting it in the same way as a black ink jet for a shallow-water octopus or squid. Second, they have a pair of light organs at the base of the fins with a moveable flap that could be used as a shutter. These could act as a searchlight, turning a beam of light onto a potential prey species that tactile sensing from the filaments has picked up. And third, they have a huge number of tiny photophores all over the body and the arms. These could work two ways: they might give a general dim lighting as visual counter-shading. With even a little light from above, a dark animal would stand out in silhouette from below. With low-level light giving just enough illumination, it could blend in. And the second function of these lights has been seen by ROV viewers: a disturbed vampire squid threw its arms back over its body and flashed the lights on the arms, which should startle any creature.

Vampire squid deal with the cold, dark, oxygen-poor water around them by slowing down their metabolism. They glide through the water, flapping their peglike fins and maybe contracting their arm webs as jellyfish do their bell, though they can make bursts of speed. Slow movement would mean they could live with less oxygen—back to the basic molluscan model—which allows them to live in places where fast but oxygen-demanding predators can't live. Cold would also slow down vampire squid. We don't know whether cold would also lengthen their lifespan, but it's a good bet,
since James found that the deep-sea spoon-arm octopus lives at least six years. By the way, for those imagining that vampire squid are monsters of the deep, they are tiny—only up to 5 in. (13 cm) long.

A disadvantage of the sparsely inhabited deep is that when it comes time to reproduce, vampire squid may have trouble finding a mate. Perhaps vampire squid use chemical cues, or they may flash coded messages to each other with their photophores. One possible clue comes from the size of the vertical lobe in their brain, which is the learning and storage center for visual information in octopuses. The vertical lobe in vampire squid is a huge percentage of the brain size, a whopping 28 percent, compared to the common octopus's 13 percent. What is that large lobe needed for? This vertical lobe is the learning area in octopuses. The bigger a brain area, the more important the function that's controlled by that area. It's not surprising, for example, that octopuses have a large brachial lobe devoted to control of all its arms, and the true squid have a smaller one.

The deep sea is such a difficult environment to live in that extreme adaptations have to be made to the basic coleoid plan. That is a lot of evolutionary pressure, though. The many octopuses without cirri, true squid and sepiolids, thrive in shallow water and among fierce competition. Of the huge number of species in the Octopodidae, only a few species—the vampire squid, the finned deep-sea octopuses, and the glass octopus—have managed what must have been a difficult transition to this demanding habitat.

This glimpse into cephalopod variations leaves us with a lot of questions. Why is the pygmy squid so small and giant squid so big? Which are better at camouflage, cuttlefish or octopuses? Which cephalopod is likely to become social, and will that take its intelligence in a whole new direction? Why does the vampire squid have such a huge vertical lobe in its brain, and does brain lobe size indicate the amount of information processing that a particular brain area handles? Why are most cephalopods semelparous—having one reproduction at the end of their lifespan—and others like pygmy squid and nautilus are quite different, continuously laying eggs once mature. How does the octopus control all those arms and coordinate all those suckers, and will learning about squid arm actions help us understand octopus arm movement? It will take a new generation of octopus and squid researchers to investigate these questions.

Still, the three of us have helped lay the foundation for the recent study of octopuses. In our work, we have combined three aspects of science—basic
research, practical applications, and communicating discoveries to the public. All dimensions are important, and interweaving them is the way to do science. Jennifer's observational field research from the 1980s is still being cited. Her comparative work, often with Roland, on personality, play, and tool use challenges conventional thinking about invertebrates. Roland has decades of experience with captive octopuses, and with James is an author on one of the world's first papers to propose applying the concept of enrichment to all animals: giant Pacific octopuses were used as model organisms in that publication. In 1995, James embraced the World-Wide Web as a forum for sharing research on the behavior, life history, husbandry, and physiology of cephalopods with an appreciative, varied public.

Maybe our most important accomplishment is two-fold. We have shown what many suggested for years, that the octopus is a very smart animal. Then, we've moved forward in examining the ethics of treatment of this invertebrate and in developing practical ways to assure that octopuses are well cared for. And we are still having a great time doing it.

Postscript

Keeping a Captive Octopus

O
ctopuses can be kept as pets. They are occasionally sold at aquarium shops, for this reason. With a few exceptions, related to laws in particular states and a few rare species (which don't live off North America), collecting a local octopus from the ocean to keep in an aquarium is sustainable. The effort required to catch a single local octopus helps to prohibit unsustainable exploitation. With proper knowledge and equipment, advanced aquarists can successfully keep healthy octopuses in captivity. But these remarkable animals have some special needs. We only recommend keeping octopuses to those who are already familiar with maintaining marine (saltwater) aquariums and have knowledge of the octopus's ecology, life history, evolution, and behavior.

Octopuses watch us as much as we watch them. It is sometimes hard for us to remember that these invertebrates are mollusks, with relatives such as slugs, snails, clams, and oysters. After all, clams and oysters don't have a brain or even a head; they simply have a hard shell to hide within. Cephalopods—octopuses, squid, cuttlefish—are often compared with fish, the dominant group of large vertebrates in the ocean. Like fish, they have well-developed senses and brains, are active, and are found in all oceans of the world. A wonder of the natural world is how similar the eyes of an octopus and a fish are, even though they are two unrelated groups of animals. But in other ways, cephalopods are very different from fish. Most fish, with some exceptions like salmon, live many years and reproduce multiple times. If the reproductive output in one year is low, the population of mature fish will be around the following year to reproduce again. Because most octopus species only reproduce once, they literally put all their eggs in one basket. The combined effect of this with their short life span of only one year or so makes octopus populations incredibly sensitive to small environmental changes. In tough years, populations can crash.

The Challenge

The short natural lifespan of most octopuses doesn't change, even under the best care in captivity. Animals collected in the wild have already lived a large part of their short lifespan. It is difficult to know how old an octopus collected in the wild is; even size is a poor indicator. In the laboratory, octopuses the same age, with the same genes (siblings), raised at the same temperature, and fed the same food can easily differ in weight by a factor of ten or more. In the wild, where genetic composition, access to food, and temperatures differ, one could expect even greater size variability at the same age. Anyone considering keeping an octopus in captivity needs to understand that with care, octopuses are not likely to live much more than a year, often less, before dying from natural causes. Giant Pacific octopuses live for about three years, but you'll need a swimming pool–sized tank to keep them in. Those who choose to keep these animals must do everything they can to ensure that proper care is given during this brief period, so that the octopus survives to its natural old age.