Among the organisms of the oceans that are armed and dangerous, there is one elite group of jetsetters that grow fast and are blessed with brains, looks, and a talent for disguise. Though most don’t live long, they can react with lightning-quick speed and deploy amazing defensive countermeasures. They are the stars of film and literature, playing oversized and aggressive monsters with a killer appetite. Most of the oceans’ cephalopods, however, are not out for a fight; when trouble calls, the majority of squids, cuttlefishes, and octopuses prefer to hide or run away. They are also much stranger in fact than in fiction, with truly astonishing capabilities and many bizarre characteristics. Their diverse ranks have come a long way from their distant and rather simple cousin, the clam.
More than eight hundred species of cephalopods reside within the world’s oceans and include squids, octopuses, cuttlefishes, the nautilus, and a unique deep-sea crossover — the vampire squid. They are all mollusks, with a heredity distantly connected to shellfish such as clams, oysters, and snails. Oddly, what was once a foot evolved to become mostly a head along with a bevy of arms, and all but the nautilus lost their protective outer shells.
Cephalopods grow fast and most reach maturity within two years. To fuel their rapid growth, most squids, octopuses, and cuttlefishes are voracious and well-equipped hunters, feeding on live prey, such as crustaceans, fishes, shellfish, and other cephalopods. They have eight muscular, suckered arms, which they use to grab and immobilize their victims. Squids and cuttlefishes also have two longer, elastic tentacles that may be tipped with hooked clubs and can be deployed in an instant to lash out at potential victims, aka food. Suckers on a squid’s tentacles may be teethed for better gripping. Because cephalopods have relatively small mouths, these hunters must chop, drill, or soften up their catch before swallowing. To do this, they often use their hard, parrot-like beaks, which can tear apart flesh and crush bone. Within their mouths, they also have rasping tongues lined with small teeth, which some octopuses use to drill through their prey’s outer shell or exoskeleton. And cephalopods have acidic, venomous spit. Their salivary glands produce digestive enzymes and toxins, the latter of which vary in potency with species. The saliva of the small blue-ringed octopus contains one of the deadliest venoms on the planet. These potential “death spitters,” however, seem to be rather timid creatures and use their potent saliva mainly for feeding. A cephalopod’s spit is typically used to paralyze prey. When feasting on crabs, an octopus wields its spew with purpose. It drills a small hole into a crab’s carapace and then injects saliva to destroy its prey’s attachment muscles and begin the digestion process. And being picky, fastidious eaters, octopuses make the most of each meal. Piles of disarticulated shells or crustacean carapaces just outside an octopus’s lair are often picked clean of meat.
Most cephalopods use their excellent vision to hunt down their prey, but they are also able to feel out their victims or seek them through “smell” or chemical cues in the water. Some are also able to sense vibrations produced by an organism’s movements. Once prey is located, cephalopods are well outfitted for the chase. In the open ocean, a squid can outswim and outmaneuver many other animals. Its streamlined, torpedo-shaped body includes a jet-propulsion system that uses muscular contractions to force water into its mantle or bag-like body and out through a maneuverable pipe-like siphon, enabling the squid to become an agile, speedy jetfighter or stealthy hovercraft. Fins along its sides or rear are used for steering and stability, and sometimes for swimming. And when they go from hunter to huntee, some species of squid can even rocket out of the water and glide for up to 50 meters (164 feet) — though Hollywood has yet to produce Attack of the Killer Flying Squid. Though probably not as fast or as agile as squids, many cuttlefishes and octopuses also rely on in-body jet packs for swimming. In contrast, deep-water octopuses use fins for slow-motion sculling, and have webbing between their arms that acts like a parachute or sail. Octopuses that live on the bottom are extremely mobile creatures as well, which can crawl over just about any obstacle, can walk on their arms if need be, and are expert contortionists, able to squeeze through incredibly small openings while on the hunt or to avoid predators.
Hunting strategies vary among the cephalopods. An octopus may grab or pounce on its prey and then drag it back to its lair for stockpiling. As tactile feeders, they may poke and prod looking for food, or simply spread their arms or webbing out and eat whatever they find and capture. Other cephalopods, such as the squids, stealthily stalk their prey or choose a more direct approach and attack head-on, like a ballistic missile strike. With excellent skills at camouflage and mimicry, some of this group may also lure in unsuspecting prey. One deep-sea octopus has special suckers along the length of its arms that emit blue-green light. They may glow dimly or blink on and off, and are thought to attract potential quarry. Beneath its webbed arms, this octopus also produces mucus (seems like under the sea almost everyone does), which may ensnare small crustaceans that drift or swim into it, like a slimy net.
While on the hunt, cephalopods must always be wary of predators. Having lost the protection of an outer shell, their naked, soft bodies of- fer energy-rich, enticing meals. Just about every type of marine carnivore eats cephalopods, including whales, dolphins, seals, seabirds, and fishes such as the billfishes, tuna, groupers, and sharks. Even the cephalopods eat cephalopods.
To avoid the oceans’ hungry masses, cephalopods have developed an extraordinary array of defenses. Roger Hanlon of the Marine Biological Laboratory in Woods Hole, Massachusetts, has been studying cephalopods for decades. He discovered that when confronted, their first line of defense is camouflage, and that they are the fastest, best-equipped animals on the planet when it comes to hiding in plain sight. Occasionally, even he has been fooled by their amazing ability to disappear into their surroundings. Cephalopods are able to quickly and precisely take on the appearance of the bottom and become very uncephalopod-like. They can match the brightness, color, pattern, and texture of the seafloor in seconds, create optical illusions, and change the shape of their bodies to mimic in 3-D. Much of their success as disguise artists lies in their sophisticated “smart” skin.
Scattered throughout a cephalopod’s skin are thousands of small color organs called chromatophores, essentially little muscular, elastic sacs containing pigment. When muscular contractions stretch these pigment sacs into flat disks, a cephalopod’s skin is visibly colored or patterned. Individual or groups of chromatophores can be contracted at a time, creating an astonishing assortment of hues and designs. The cephalopods’ prowess as dress designers is not only impressive — it is also fast. In the blink of the eye, they may become striped, polka-dotted, or covered in psychedelic waves of color. An octopus may appear as if painted ruby red one minute and within seconds go ghostly pale or become a dull, mottled brown that replicates the underlying rock or sand bottom. The blue-ringed octopus can cause its namesake circular markings to flash brightly, and many cephalopods can create waves of color that wash over their bodies like a passing cloud. They can also produce patterns that disrupt the outlines of their bodies so that they become nearly unrecognizable. Surprisingly, their chromatophores contain only red, orange, yellow, black, or brown pigments, yet cephalopods exhibit a full rainbow of colors. The mystery of how they do this was solved when scientists discovered that they also have reflecting cells in their skin that act like mirrors or prisms. These iridophores and protein-based leucophores are used in combination with their chromatophores to create a wide variety of striking colors that include vibrant blues, purples, greens, and silver. How cephalopods respond so quickly and create so many patterns is, however, about more than just the color of their skin.
An intricate nervous system runs throughout a cephalopod’s epidermis, connecting its colored pigment organs and reflector cells to its relatively large brain and complex eyes. They are, in fact, the brainiest of all invertebrates, having the largest of the group along with especially well developed eyes. Hanlon’s research team has discovered that cephalopods use their exceptional vision as their primary means of detecting the brightness and patterns within their surroundings, which they then quickly replicate for camouflage. But, ironically, Hanlon’s team also found that most, if not all, cephalopods are color-blind. How then do they perfectly match the color of their surroundings? He suspects that the cephalopods’ skin has some sort of color-sensing capability, but what it is and how it works remain unknown.
As true masters of disguise, octopuses and cuttlefishes can also change the texture of their skin, creating bumps, ridges, or algae-like frills; this too appears to be a vision-based skill. Posing perfectly still or moving in an uncephalopod-like manner, they can imitate their surroundings in 3-D, becoming part of a rock, hiding among seaweed, or “impersonating” another organism. Octopuses have been seen to change their bodies to look and move like a flounder, a sea snake, or a drifting tumbleweed of algae. By hovering motionless and pointing their arms upward, a squid can be- come nearly unrecognizable within a stand of algae. Within the animal kingdom, the cephalopods’ rapid camouflage capabilities are simply the uncontested best. Even the iconic chameleons cannot match their speed or capabilities as quick-change artists.
Some cephalopods also have an illuminating means of camouflage. Using photophores or light organs on their undersides, squids can produce light that matches the radiance downwelling from above. This counter-illumination renders them invisible to predators looking up from below.
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