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Octopus live in all the worlds oceans. They can survive the frigid oceans around Antarctica and have been found at depths of 17,000 feet. The Minoans painted octopuses on vases 3,500 years ago and the Beatles sang about them on “ Abbey Road”. People from all over the world enjoy eating them. [Sources: Natalie Angier, New York Times, August 11, 1998; Gilbert L. Voss Ph.D., National Geographic, December 1971]

Octopuses are mollusks that have completely lost their shell, although one species, the argonaut, creates a paper-thin replica of a nautilus shell from one of its arm. It uses the shell as a receptacle for its eggs. Octopuses generally mate once and waste away and die soon after that. Many species live a little over a year. It is rare for an octopus to live more than three years.

Jennifer A. Mather wrote in Natural History magazine, “Most mollusks are clams or snails that hide within hard shells and have little brainpower. But cuttlefish, octopuses, and squid (which along with nautiluses make up the cephalopod mollusks) are nothing like their shell-bound relatives. Evolution led them to lose their protective shells, but what they gained was far more interesting: dexterous, sucker-lined arms; ever-changing camouflage skin; complex eyes; and remarkably well-developed brains and nervous systems. The 289 known species of octopus range in size from the one-ounce Atlantic pygmy octopus, Octopus joubini, to the giant Pacific octopus, Enteroctopus dofleini.. They are all ocean-dwellers, and, though the group is distributed from the poles to the tropics, octopuses are reclusive beasts; individuals are hard to find, let alone study.” [Source: Jennifer A. Mather, Natural History, February 2007]

20110307-NOAA octopus_100.jpg The giant Pacific octopus can reach a length of around 15 feet long (13 foot long tentacles and a head the size of a football) and weigh around 100 pounds. Typically though y weigh about 40 pounds. Each of its eight arms are about five feet long and have 2000 suckers.The smallest are around an inch long when fully grown. Deep seas octopus found at depths of around 3,000 feet have suckers that no longer suck but instead glow in the dark. The glowing suckers are used to signal each other and attract prey.

Websites and Resources: National Oceanic and Atmospheric Administration noaa.gov/ocean ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Ocean World oceanworld.tamu.edu ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Montery Bay Aquarium montereybayaquarium.org

Websites and Resources on Fish and Marine Life: MarineBio marinebio.org/oceans/creatures ; Census of Marine Life coml.org/image-gallery ; Marine Life Images marinelifeimages.com/photostore/index ; Marine Species Gallery scuba-equipment-usa.com/marine

Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) coris.noaa.gov ; International Coral Reef Initiative icriforum.org ; Wikipedia article Wikipedia ; Coral Reef Alliance coral.org ; Global Coral reef Alliance globalcoral.org ; Coral Reef Pictures squidoo.com/coral-reef-pictures ; The Global Coral Reef Monitoring Network; the International Coral Reef Action Network.


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Octopuses, squid and cuttlefish are cephalopods, a class of mollusks whose name means "head-footed." There are two subclasses of Cephalopoda: 1) chambered nautiluses, with external shells and anatomy that has remained virtually unchanged for 450 million years; and 2) coleoidea, which includes octopuses, squids and cuttlefish. The latter are soft, fleshy mollusks with their shells inside their bodies instead of outside as is the case with most mollusks.

Cephalopods are common food sources in many counties, particularly in Asia. They reproduce quickly which means that even though two million metric tons of them are caught every year, they are not in danger of being overfished. In the past they were often caught with drift nets, which are now banned not because they caught too many squid but because they caught other animals like dolphins and sharks.

Cephalopods are regarded as more developed and sophisticated than mollusks like snails, clams and oysters. In fact they are considered the most advanced and developed invertebrates (animals without backbones). They have the largest brains and nervous systems of any invertebrate and their brains are much bigger in relationship to their bodies than those of fish. Most cephalopods grow quickly, mate once and die. Most live no more than 18 months.

Cephalopod Features

Cephalopods have a bird-like beak; well-developed eyes; and sucker-covered arms, or tentacles, used to catch prey, move about and transfer sperm from the male to female. The appendage at the top of their arms is not their head. It is actually a mantle that stores their organs.

Cephalopods propel themselves by forcing water through a tubular siphon that draws water behind the eyes and shoot it out under the head. They also have the ability to grown back their arms and tentacles and sometimes communicate by changing the shape of their arms. All cephalopods shoot out ink, which is actually a mix of ink and mucus. The ink isn't intended to hide the animal but serve as a decoy that predators attack while the cephalopod escapes.

Many cephalopods change color to blend in with their backgrounds or to express fear, aggression and sexual excitement. Color changes are caused by chromatophores, pigments sacs situated just under the skin that suddenly swell with signals from the brain. The sacs are yellow, red, black and brown. By expanding and contracting them cephalopods can produce a variety of shades and patterns.

The problem with using skin colors to send messages is that predators can also pick up on them and use them to their advantage such as attacking when the cephalopods are distracted by sexual matters. Studies by Lydia Mathgar and Roger Nento of Wood Holes Institute suggest that squids — and likely cuttlefish and octopuses too — get around this problem by using communication channels that they can see but predators can’t. Cephalopods have two distinct layers of skin: an inner layer of iridophone cells that is both iridescent and reflects light and an outer layer made up of pigment organs called chromatophores. They also have a complex visual system tuned to read the skin patterns that predators can’t pick up.

Shells, Mollusks, Octopus, Squids and Cuttlefish

Mollusks are creatures with shells. There are four kinds of mollusks in the phylum, Mollusca: 1) gastropods (single shell mollusks); 2) bivalves or Pelecypoda (mollusks with two shells); 3) cephalopods (mollusks such as octopuses and squids that have internal shells); and 4) amphineura (mollusks such as chitons that have a double nerve).

The world’s first shells emerged about 500 million years ago, taking advantage of the plentiful supply of calcium in seawater. Their shells were composed of calcium carbonate (lime), which has been the source of much of the world limestone, chalk and marble. According to a 2003 paper in Science, the use of large amounts of calcium carbonate for shell-building in early years of life on earth altered the chemistry of the atmosphere to make conditions more favorable for creatures living on land.

Animals with shells have been found living in the Mariana Trench, the deepest places in the ocean, 36,201 feet (11,033 meters) below the sea surface, and 15,000 feet above sea level in the Himalayas. Darwin’s discovery that there were fossil of sea shells at 14,000 feet in the Andes helped shape of theory of evolution and understanding of geologic time.

Some of the simplest eyes are found in shelled creatures like: 1) the limpet, which has a primitive eye made up of a layer of transparent cells that can sense light but not images; 2) Beyrich’s slit shell, which has a deeper eyecup that provides more information about the direction of the light source but still generates no image; 3) the chambered nautilus, which has small gap at the top of the eye that serves as a pinhole pupil for a rudimentary retina, which forms a dim image; 4) the murex, which has a fully enclosed eye cavity which acts as a primitive lens. focusing light on a retina for a clearer image: 5) the octopus, which possesses a complex eye with a protected cornea, colored iris and focusing lens. [Source: National Geographic ]

Octopus Characteristics

The appendage at the top of their arms is not their head. It is actually a mantle that stores their organs. The true head is small thing around the eyes. The “head” (body with the eyes on it) is soft and rubbery and pulses like bellows as its siphon system sucks water in through its gills so it can breath. An octopus eye is very similar to a human eye. They have pupils that dilate and contract and are often used to test new eye drugs. They also have the most complex brain of any mollusk.

Many species of octopus change color. Using pigment sacs they can change color to express different emotions, deter predators or attract prey. To scare off predators one species displays a zebra strip pattern of brown and white. Another species turns bright red whenever a crab approaches in what seems like an attempt to confuse the prey. Other species can change from blue-green to water and yet others can be different colors on different sides of their body.

Octopuses are largely solitary creatures. Most species hide in holes, crevasses and burrows during the day, often covering their hiding place with rocks, and hunt at night. They feed on shrimp, clams and crabs and other crustaceans and mollusks.

Reef octopuses on the hunt overturn rocks and search crevasses with their sensitive arms. describing an octopus on the prowl, John Forsysth of the University of Texas told the New York Times, "All eight arms are working at once, investigating every crack and crevice with suction cups and pulling things out from deep inside."

Octopus Dexterity and Octopus Tentacles

Octopus opening a container
with a screw cap
Most octopus have around 1,200 suckers on each of its eight arms. There are examples of octopus being born with six legs. Because they have no skeleton to support their body they have tough tendons which help to support and anchor the muscles. The tendons make the muscles much tougher than those found in bony fish which is why octopus meat has a rubbery texture to those who eat it.

Octopuses have a brain-like organ in each on of their tentacles. In his book “The Story of Sushi”, Trevor Corson wrote: “These ganglai receive a single command from the primary brain’such as “grab a crab” — and then execute an entire subroutine of action independent of the primary brain’s control. The tentacles require their own brains because their movements are so complex. Lacking a skeletal structure, each tentacle is of infinite degrees and directions of movement.”

An octopus is skillful enough to pass a pebble down its arm from one sucker to the next and nimble enough to grasp 25 crabs at one time and eat them one by one. Their dexterity is so admired by scientists that they have used them as models for robots.

Octopuses are relatively easy to keep in captivity, much easier than squid but it sometimes difficult to keep them confined to their tanks. "An octopus can pour its boneless body through unbelievable small apertures," biologist Gilbert L. Voss told National Geographic. “In our laboratory...octopuses flee their tanks...even when tops are fastened securely. [They] have escaped from covered tin cans, securely tied wooden boxes — even from steel strongboxes."

An octopus with foot-long tentacles and a tennis-ball-size body escaped from a Coke bottle by squeezing through the half inch opening by first running its tentacles through the aperture one by one and then squeezing its head through like compressed a rubber ball. The process takes about two minutes. Octopus have also been observed removing a rubber stopper from a bottle to get at a shrimp inside.

Feeding Octopus and Predators that Feed on Them

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drying octopus eaten in Asia
Like many spiders and predatory insects, octopuses use toxic saliva to paralyze prey and liquify tissue so they can eat it. An octopus eating a crab, first bites a hole in the crustacean's shell with its parrot-like beak, then liquefies the crabs flesh with a toxic enzyme in their saliva and finally sucks the meat out of the shell. They use a similar method to eat mollusks. They first balloon their bodies around the shell, injects a neurotoxins into the shell to kill the animal and then liquefies it so the octopus can eats it. Octopuses use 50 percent of the energy from the food the eat (compared to 10 percent with humans).

Octopuses employ a number of strategies to prey on mollusks.. The can pry open clams, break open thin-shelled mussels and drill into thick-shell clams with their radule. Young octopuses have been observed attaching nibbled-off tentacles of Portuguese man-of-wars to their suckers and using the powerful venom to stun and kill prey.

Sea creatures that feed on octopus include dolphins, sea birds, sailfish, tuna, sharks and particularly moray eels and conger eels. Octopuses use their ability to change color as camouflage and escape from their enemies under a cloak of ink and mucus. It best method of escape from it nemesis, the moray eel, is to dart into the nearest hole and hope it is to small for the eel to follow.

Some species of octopus can actually change their shape and imitate the appearance of flounders, shrimp, sea snakes, brittlestars and giant crabs. The also use camouflage and mimicking ability to hunt prey. One species from Indonesia, “ O. marginatus “ has been observed masquerading as a coconut with six of its tentacles while making an escape with its other two tentacles, which walking along the sea floor. A species from Australia, “ O. aculeatis”, uses a similar technique to look like “a clump of algae tiptoeing away.”

Mating Octopuses and Young Octopuses

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Baby octopus
The octopus mating ritual is often a violent affair with arm wrestling, the flashing of bright colors on their skin and beak thrusting. Mating is rarely observed. The female sometimes preys on her male suitor.

Octopuses mate facing each other. The male ejaculates on to one of its tentacles and then places the sperm on the female’s sex organ. Courting octopuses first approach each other with stylized touching motions. Their skin turns pebbly and changes in color from moldy brown to red to grey. The male uses an arm that is shorter than the others to pull sperm from his mantle and insert it into the female's mantle cavity with a spoon shaped organ called a hectocotylus at the end of one of his tentacles.

Male octopuses are the only known nonvertabrae to have an erection. The discovery was made by a scientist watching a male two-pot octopus mate with an unreceptive female. The scientist observed that as the male withdrew his arm it was larger than before. Closer studies revealed that the male had erectile tissues similar to this possessed by male mammals.

The sperm is potent until the female lays her eggs, which is sometimes months later. The female remains in her den and refuses all food during the 78 day incubation period. She stays with her eggs until they hatch and then dies. After mating, the male loses his ability to camouflage and loose his will to live and eventually dies from starvation.

Young octopuses grow in globule-like eggs that become more translucent with time as octopuses become more defined. When baby octopuses burst from their eggs they already can squirt clouds of ink, turn color and propel themselves around. One of the first things they do after hatching is head for cover.

Octopuses Behavior

Jennifer A. Mather wrote in Natural History magazine, “Twenty-five years ago, when I started my fieldwork on the behavior of juvenile common octopuses in the azure waters of Bermuda, I expected all my subjects to be much the same. I assumed their activities would be fairly limited; individuals would hunt, rest, and avoid predators, all in roughly the same way. In fact, I learned, their behavior is quite complex and variable. I watched as they carefully chose rocky crevices for their dens and blockaded the entrances with piles of rocks. I observed them navigate complicated routes across the sea bottom to and from their hunting grounds. But I was most intrigued to discover that individual octopuses are very different from one another. [Source: Jennifer A. Mather, Natural History, February 2007]

I could swear, for instance, that octopus number 45 never left its crevice--except that the discarded shells of clams, crabs, and snails kept appearing in front of the crevice. It must have been making secret hunting forays when my back was turned. By contrast, octopus number 26 was anything but shy. One afternoon I watched it as I floated in the shallow Bermuda water, hanging on to a rocky outcrop. The little octopus peered back at me from inside its den for some time, then suddenly jetted three or four feet directly toward me and landed on my dive glove. After about a minute of exploring, it must have decided the glove didn't taste good, and slowly jetted back home. I was hooked.

Around the same time, Roland C. Anderson, a marine biologist at the Seattle Aquarium who has since become my frequent collaborator, noticed that aquarium workers gave names to only three kinds of animals in their care: seals, sea otters, and giant Pacific octopuses. The workers named the octopuses for their distinctive behaviors. Leisure Suit Larry, for instance, was all arms. He touched and groped his keepers so often that had he been a person, he would have been cited for inappropriate behavior. Emily Dickinson, by contrast, hid permanently behind the artificial backdrop of her display tank, so retiring that eventually she had to be replaced by a more active octopus for aquarium visitors to watch. Then there was Lucretia McEvil, whose caretakers were afraid to approach her, and who ripped up the interior of her tank. All those "characters" set me to thinking about whether octopuses might just have something like human personality.

Twenty-five years ago it was hard to know what to expect of octopus behavior: the creatures had seldom been studied, and when they had, it was mostly in captivity. Furthermore, they are invertebrate mollusks, and so they are evolutionarily distant from vertebrates; it would have been hard to justify extrapolating the significance of their activities from the well-studied behaviors of mammals and birds.

Octopus Personality

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Jennifer A. Mather wrote in Natural History magazine, “The intelligence of octopuses has long been noted, and to some extent studied. But in recent years, research by myself and others into their personalities, play, and problem-solving skills has both added to and elaborated the list of their remarkable attributes. They turn out to be uncannily familiar creatures, not nearly as unlike you and me as one might expect--given their startlingly different physiques and the 1.2 billion years of evolution that separate us from these eight-armed marvels of the sea. [Source: Jennifer A. Mather, Natural History, February 2007]

Personality is hard to define, but one can begin to describe it as a unique pattern of individual behavior that remains consistent over time and in a variety of circumstances. I've adopted the model that developmental psychologists have applied to study the behavior of children. Psychologists begin with the idea of "temperament," or behavioral tendencies genetically programmed before birth. After birth the environment shapes an individual's temperament to give rise to an adult personality.

Many people assume that only human beings have personalities. Yet in the past fifteen years or so a number of investigators have reported evidence of personality in animals as diverse as guppies, hyenas, and rhesus monkeys. To pin down what can be a notoriously slippery concept, they have identified a number of personality traits, or "dimensions," such as activity, aggression, curiosity, and sociability. Many animals, including people, can be rated along each of those dimensions, and an individual's rating along one dimension can vary more or less independently of its ratings along the others.

Could a combination of differences in genes and life experience--personality--have made individual octopuses behave so differently from one another? Our experiences led Anderson and me to think so. We didn't expect to discover a sociability dimension because octopuses lead solitary lives, but we thought we might find differences along such dimensions as activity or aggression.

We gave "personality tests" to forty-four red octopuses (Octopus rubescens), natives of the West Coast of North America that weigh as much as a pound. We exposed each animal to three test conditions, seven times each, during a two-week period. We measured and recorded their responses when we opened the tank lid, when we touched them with a brush, and when we fed them a crab. The brush prompted the greatest variety of responses. Some octopuses grabbed it, stood their ground, and inflated their mantle to look bigger. Others jetted to the opposite end of the tank, leaving a cloud of obscuring dark ink in their wake. Individuals gave the same responses to the tests even after being exposed to them several times.

In all, the forty-four octopuses responded to the three tests with nineteen distinct behaviors. Statistical analysis enabled us to group the nineteen behaviors and place them along three personality dimensions: activity (how much the octopus moved around), reactivity (how strongly it reacted to the stimuli), and avoidance (how much it kept out of our way). An octopus could vary on all three dimensions independently. For example, among highly avoidant octopuses, which tended to remain in their dens during testing, some were extremely reactive, shrinking at the first sign of the brush. Others were not reactive at all, practically ignoring the brush. (By extension, Leisure Suit Larry, the touchy-feely giant Pacific octopus, would have rated high on activity and low on avoidance.)

So do octopuses have personality? Our answer is a qualified "yes." Because we didn't try to change their personalities by manipulating their experiences, we couldn't rule out the possibility that their behavioral variations might have been genetically preprogrammed. But given the octopus's legendary intelligence, behavioral flexibility, and learning ability, such preprogramming seems unlikely.

Octopus Personality Differences: Nature or Nurture

Jennifer A. Mather wrote in Natural History magazine, “How much of the behavioral differences among individual octopuses is inherited, and how much is learned? For his master's thesis, David L. Sinn, now a zoologist at the University of Tasmania in Hobart, raised laboratory-born California two-spot octopuses (Octopus bimaculoides) in small isolation chambers and gave juveniles the same three tests Anderson and I gave our red octopuses. The genetic effects were clear. Octopuses that shared at least a mother (female octopuses mate several times with any available male, so paternity was all but impossible to determine) reacted to the three tests more similarly than octopuses from different broods. Intriguingly, Sinn also discovered that as the animals matured, their responses to the tests changed in a predictable way. [Source: Jennifer A. Mather, Natural History, February 2007]

Sinn did not raise his subjects to maturity, so no one knows whether youthful experiences might have added a layer to the octopuses' temperaments to yield true adult personalities. It's too bad--it would be fascinating to know whether octopuses' differing experiences when young would result in differing adult personalities. Was Lucretia McEvil's destructiveness, for instance, the result of a "bad childhood"?

Another question about octopus personality is whether it has evolutionary benefits or drawbacks. The only scientific clue comes from Sinn's doctoral work, which showed that squid, too, vary along the personality dimensions of avoidance, activity, and reactivity. Shy female southern bobtail squid, Sinn found, mate with males that are shy, bold, or anything in between along the avoidance dimension. But bold females tend to reject shy males. Score one for the survival of the boldest. Sinn also found, however, that shy females are more successful than bold females at hatching their broods of eggs. No obvious pattern emerges, but personality clearly does affect survival and reproductive fitness.

Intelligent Octopuses

Octopus in a shell
Octopuses are widely recognized as the most intelligent of all invertebrates, which includes creatures like worms and insects. They display many cognitive, behavioral and affective traits once regarded as the sole domain of higher vertebrates. They can open a jar and take out a fish and reach inside a wine bottle to remove a cork. Roland Andersen of Seattle’s Aquarium told National Geographic they have also spit in the face of scientists, blocked their dens with rocks, shot water at plastic bottle targets (and at lab staff to amuse themselves), slipped out of their tanks to enter the tanks of fish to eat them, and dismantled pumps and blocked drains. There is also evidence they have distinct personalities, recognize individuals, and express emotions by changing color.

Relative to their size, octopuses have larger brains than most animals other than birds and mammals. They can learn how to a perform tasks by watching another octopus. They are the only invertebrate observed doing this which is seen as precursor to conceptual thought. [National Geographic, Geographica, December 1992].

When people pet octopuses, the octopuses sometimes pet back. Octopuses display play behavior, such as repeatedly placing bottles in tank currents and watching them float past, and displaying different temperaments such as aggression (attacking a crab as soon as they saw it), passivity (taking their time to move on the crab), and paranoia (shooting out ink when presented with a crab).

In December 2009, scientists at Melbourne’s Victoria Museum released a photograph of an octopus with its legs wrapped around a coconut shell, which it used to protect itself on the sea floor. The scientists said the octopus carries the shell with it and uses it as armor in what the scientists said was the first known example of an invertebrate using tools.

Octopus Intelligence

Evidence for the octopus's intelligence begins with its anatomy. Intelligent animals typically have large brains, and octopuses' brains are large for their body size compared to those of other animals--larger than fishes' brains and, proportionally, as large as those of some birds and perhaps some mammals. Moreover, three-fifths of an octopus's neurons aren't even in its brain. Instead, they are divided among its eight arms to coordinate the arms' remarkable flexibility. The big brain itself is mostly dedicated to learning, planning, and coordinating actions with stimuli. [Source: Jennifer A. Mather, Natural History, February 2007]

Broadly defined, intelligence is the measure of an animal's ability to acquire information from its environment and to change its behavior in response--in short, to learn. The octopus's behavioral repertoire has few fixed, preprogrammed responses, and it can respond to a given stimulus in a great variety of ways; those are both hallmarks of intelligence and learning. The sea slug, by contrast, has only a limited palette of reflexive responses, no matter what the stimulus. In one particularly vivid demonstration, published in 1970, the biologist William R.A. Muntz showed that octopuses could learn to tell complex visual figures apart by forming a new rule for each for each new set of figures. He concluded that octopuses aren't merely able to learn; they can also learn what to learn.

Anderson and I became interested in how octopuses apply their intelligence to predation. After capturing a clam, an octopus must break through the hard shell to get to the meat inside. To do so, it can deploy a veritable built-in Swiss Army knife of tools [see illustration on preceding page]. It can pull the shell's halves apart with its arms and suckers, chip at the shell's edge with its beak, or drill a tiny hole in the shell by alternately secreting acid to dissolve it and scraping at it with one of two tooth-covered organs in its mouth. (Which of the two organs it uses remains subject to debate.) If the octopus breaches the shell by chipping or drilling, it secretes a paralytic toxin into the clam's muscles so that it can more easily pull the shell halves apart--and then it's dinnertime.

We discovered that giant Pacific octopuses apply differing techniques to various clam species: they break fragile mussel shells, probably while pulling on them; they pull apart the stronger Manila clams; and they drill or chip at the strongest clams, the littlenecks. We placed individuals of each species on a device of our own design (which we darkly called the "clam rack"), and measured how much force it took to overcome the clam's muscles and pull the shell halves apart. Intriguingly, octopuses ate plenty of weak-muscled mussels when they had to open dinner by themselves, but they gobbled up littleneck clams--all but ignoring the mussels--when we offered all three species on the half shell. Maybe the mussels were less tasty but easier to get at than the littlenecks.

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Octopuses conduct the business of breaking into clams with the clams near their mouths, which are under their arms and so out of sight. There they dexterously manipulate the clams into position by touch. To pull clam shells apart, an octopus holds it with the umbo (the bump near the shell's hinge) toward its mouth. But if it chooses to chip at the shells' edge, it moves the clam's "sides," where the muscle insertions are, toward its mouth. And when it drills, it turns the broad side of the shell toward its mouth.

Giant pacific octopuses usually drill through the center of a clam's shell into its heart. But they must learn where to drill the holes. Anderson found that juveniles drill their first few holes randomly on the shell, but they soon master the art of drilling near the heart or the muscles that hold the shell halves together. Either place is a good target for injecting paralytic toxin.

We were curious about what octopuses would do with artificially strong Manila clams, whose shells they usually just pull apart. We gave each octopus Manila clams held together with strong wire. The octopuses simply switched tactics to drilling or chipping, thereby confirming the numerous studies such as Muntz's that had shown they are good problem-solvers. They can weigh effort against food reward, flexibly switch penetration tactics, and orient the clam to penetrate its shell most effectively--all good uses of intelligence, indeed.

After investigating a few octopus problem-solving skills, Anderson and I turned our attention to two less-studied categories of behavior that are also linked to intelligence: exploration and play. Philosophers and psychologists have debated for centuries about the nature of play, where it comes from, and what purpose it serves. When animals play with objects, their explorations move from "What does this object do?" to "What can I do with this object?"

Gordon M. Burghardt, a biologist at the University of Tennessee in Knoxville, recently offered a clear and useful definition of play in healthy animals. Play, he writes, is made up of voluntary, incomplete, repeated fragments of activity that have no obvious purpose, and which are often exaggerated and out of normal context. Some scholars still maintain that people are the only animals that truly play. But dog owners know that when their companion lowers its front end and raises its hind end, tail wagging, it has no purpose but to communicate that the next set of interactions should be just for fun. Crows slip down a playground slide over and over, or grasp a clothesline in their claws and spin round and round like a pinwheel, calling "Wheee" the whole time. Those behaviors clearly conform to Burghardt's definition, and other examples are documented in many animals, including dolphins, lab rats, and river otters.

Octopuses Play

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Jennifer A. Mather wrote in Natural History magazine, “Would an octopus play if given the chance? We decided to find out. Animals are more likely to play when they are satiated and secure, without any threat from predators. An aquarium tank is such an environment. There we presented eight well-fed giant Pacific octopuses with plastic pill bottles containing enough water that they floated at the surface of the tank. The octopuses followed a fairly predictable behavioral sequence. First, they grasped a pill bottle with one or more of their arms and explored it with their suckers. Then they pulled it to their mouths, and sometimes bit it with their parrotlike beaks. Gradually, both within each trial, and by the end of all ten trials, most of them lost interest in the bottle. [Source: Jennifer A. Mather, Natural History, February 2007]

But two of the octopuses independently did something very different in the later trials. Like most aquariums, their tanks had water-circulation systems; water entered the tank at one end and exited at the other. While sitting near the outflow, each animal released the bottle it had been holding and jetted water through its funnel, sending the bottle against the gentle current to the inflow end of its tank. (A funnel is a tubelike appendage that an octopus uses for breathing and for jetting through the water [see photograph on pages 30-31].) When the bottles returned on the current, the octopuses jetted them upstream again, repeating the process more than twenty times. Anderson, who had been skeptical that octopuses play, phoned me excitedly after watching the first playful octopus and said, "It's like she's bouncing a ball!"

In vertebrates, some kinds of play have benefits as well as simply being fun. They strengthen and define social relationships, as in the roughhousing of canines. Or they give young animals the chance to hone fragmentary actions into polished sequences, as when a kitten plays with a mouse to "practice" capturing prey in the future. Skeptics often dismiss play by nonhuman animals as functional, and thus in violation of Burghardt's definition that it have no obvious purpose.

But octopuses don't have social relationships--they're solitary creatures, except when they mate. And as for the argument that only the young play because only they need to practice their skills, Michael J. Kuba, a former graduate student of mine now at Hebrew University in Jerusalem, recently showed that adult common octopuses also engage in playlike behavior. They passed a plastic block from arm to arm or pulled it along when they swam just as often as the young did. Still, in our view, octopus play is neither as extensive as it is in mammals, nor as potentially adaptive. It may simply be a sign of an active mind at work.

Octopuses have personalities. They learn. They solve problems. They play. Does all that add up to a simple form of consciousness? The suggestion is even more contentious than the ideas that octopuses play or have personalities. Just defining consciousness is tricky; one general definition is that an animal with primary consciousness--a dog, for instance--is aware of the complexity of a given circumstance as well as its role there and its decision-making options. Higher-order consciousness has more stringent criteria: using language, being able to report on the content of one's thoughts, being able to think about thinking. Only people and perhaps chimpanzees exhibit that exalted form of consciousness.

But how could one tell whether octopuses have some form of primary consciousness? Some theorists say it is enough to show complex and flexible behavior, such as the octopus's clam-opening tactics. Others say an animal must be able to shift its attention from one set of stimuli to another, making decisions in rapidly changing conditions. Octopuses meet that criterion in their varied responses to a predator: they can flash unpredictable changes in pattern and color, jet off in an unexpected direction to escape, or squirt out ink to form a smoke screen.

Still other theorists argue that conscious animals build a complex, multidimensional set of internal impressions about the world on the basis of their sensory perceptions. For example, the human mind constructs a three-dimensional image of objects from the two-dimensional array of stimuli that arrive at the retina. Additional study of how octopuses analyze visual shapes might show whether they meet that criterion, too. Or perhaps a conscious animal must have a concept of self. What do octopuses see when they look in a mirror? Answering that question will be our next research project. It will be hard to say for sure whether octopuses possess consciousness in some simple form. But from what biologists already know about them, there's no denying they are some smart suckers.

Octopuses That Change Their Shape and Color

Octopus off Timor
Some species of octopus can change their color and shape so they ressemble a feather star, a flounder, a jawfish, a snake eel, a sea snake, a stingray, a baby cuttlefish, or even a crab. They can also imitate the swimming motion of flounder, bury themselves in the sand with only their eyes exposed like a jawfish and even float with arm looking like the tentacles of a jellyfish. It is believed the adopt the poses to deceive potential prey and ward off predators. [Source: Smithsonian magazine]

Some species of octopus use a hunting strategy called tent-hunting in which they spread their arms and webbing over a patch of a reef and change the color of their skin so that translucent patches appear, Prey view these patches as escape windows. When they try to escape the octopus catches and eats them.

Describing an octopus in Indonesia Les Kaufman wrote in National Geographic: “Just before jumping to a new spot it would darken (except for one bold white stripe), then crash to the ground with arms outstretched, the webbing between them blocking off routes for small creatures...The webbing then would turn nearly transparent white. To us — and perhaps to trapped prey — these white patchs looked like windows of light and escape. We speculate that this color-change act is a ruse to lure, small cowering animals up to the “windows” and thus towards the octopus’s mouth....When at rest, this octopus became camouflaged against the reef, with shifting pasterns of dark and light on its skin that matched the texture and color of the backdrop.”

Octopuses are color blind. Their retina lacks cells that receive and process color. Those that change their colors seem to respond to contrasts in shade and light.

Poisonous Octopuses

blue ring octopus
All octopuses produce venom, but only a few can cause death to humans. Three or four species of closely-related blue ringed octopus rank with some cone shells for the title of the world's most poisonous mollusks — and for that matter the most poisonous creature in the sea. Residing in the waters off of Australia, Indonesia, and parts of Southeast Asia, these species of octopus carry a toxin capable of killing a person in minutes, with some carrying enough toxin to kill 10 people. Fortunately the octopus are not aggressive, and bite only when taken out of the water and provoked.

The toxin, tetrodoxotin, a powerful nerve agent also found in the pufferfish consumed by the Japanese. It causes rapid onset of paralysis and breathing difficulty. Powerful toxins (lethal dose): 1) anthrax (0.0002); 2) geographic cone shell (0.004); 3) textrodoxotine in the blue ring octopus and puffer fish (0.008); 4) inland taipan snake (0.025); 5) eastern brown snake (0.036); 6) Dubois’s sea snake (0.044); 7) coastal taipan snake (0.105); 8) beaked sea snake (0.113); 9) western tiger snake (0.194); 10) mainland tiger snake (0.214); 11) common death adder (0.500). Lethal doses is defined as the amount in milligrams needed to kill 50 percent of the animals tested.

Blue ringed octopus species, which include the blue-lined octopus, are diminutive creatures that get their names from blue markings the animal displays when it is aroused or disturbed. Adults are generally 15 centimeters or less in length. They wards off predators with tetrodotoxotin and catch prey such as crabs with a second, less-potent toxin. The arousal display including a wide array of indigo rings and lines along their mantle and arms.

One man bitten on the toe by a blue-ringed octopus at Shoalhaven Beach in New South Wales, Australian was dead within five minutes. In June 2004, two people were killed and 85 other were hospitalized after eating poisonous octopuses in Vietnam. The trader said he sold more than 20 kilograms of blue ring octopus at a market in Nihn Thuan Province, 200 kilometers north of Saigon, said he sold the octopuses many times before but didn’t know the blue ring octopus was poisonous. Many of these admitted to the hospital suffered from diarrhea and vomiting. Seventy-two, including 28 children, remained hospitalized for a period of time.

Paul the World Cup Octopus

Paul picks Spain over Germany
Paul the octopus was an unlikely star of the 2010 World Cup. He successfully predicted the outcome of eight matches—the results of all seven of Germany’s games, and finished by picking the tournament winner Spain, who defeated the Netherlands 1-0 in the final — from his aquarium at the Sea Life centre in Oberhausen. Germany [Source: BBC, October 26, 2010]

The BBC reported: “Paul made his name by successfully choosing a mussel from one of two boxes bearing the flags of competing nations. He correctly guessed the outcomes of seven of Germany's World Cup matches, including their defeats, and had "enthused people across every continent". As the tournament progressed, the octopus's uncanny knack of selecting the correct box drew increasing interest from the world's media, culminating in his choice of Spain as the eventual winner.”

Paul became an instant hero in Spain, prompting a request to have him put on display at Madrid zoo. Amid the euphoria, he was even made an honorary citizen of a Spanish town before being made an ambassador for England's 2018 World Cup bid. A documentary was filmed, and books and toys were made.

Paul died in October 2010, a few months after the World Cup. Octopuses rarely live beyond two years so his death was not unexpected. He was two-and-a-half years old and had been hatched at another centre at Weymouth in England in 2008. "It's a sad day. Paul was rather special but we managed to film Paul before he left this mortal earth," said his agent, Chris Davies said after his death.

Image Source: National Oceanic and Atmospheric Administration (NOAA), Wikimedia Commons

Text Sources: Mostly National Geographic articles. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Natural History magazine, Discover magazine, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

Last updated March 2011

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