These masters of disguise are some of the most curious creatures of the sea. We talked to Senior Aquarist Chris Payne from the Monterey Bay Aquarium to find out more.
1. There are over 120 distinct species of cuttlefish.
2. Cuttlefish can manually control their buoyancy.
A member of the cephalopod family, cuttlefish are among the most intelligent invertebrates. They spend their relatively short lives (a few years, max) in tropical and temperate oceans hunting for small prey and trying to avoid being eaten by larger carnivores. Smaller species tend to spend their whole lives on the floor of the ocean, searching for food and mates in a relatively limited range. But the larger species occasionally rise up into open water and swim in search of better territory.
To do so, these cuttlefish alter their internal buoyancy through the use of something called a cuttlebone, which isn't a bone but a porous internal shell. By adjusting levels of gas in the forward chamber and the level of water in the rear chamber of the cuttlebone—which isn't a particularly fast process—the cuttlefish can modulate its buoyancy and control where in the water column it will rest.
3. Baby cuttlefish and small adults use their arms to walk along the ocean floor.
Cuttlefish engaging in this odd behavior can "sometimes look like bulldogs with their arms pressed down and their backs arched," Payne says. He speculates that for smaller species, which don't swim long distances, "walking" like this allows them to move about without straying too far from the cover of sand.
4. They can change to be almost any color—even though they're colorblind.
Cuttlefish rely on their incredible camouflaging abilities to avoid predators, changing color almost instantaneously to match their surroundings—a pretty neat trick for an animal that's colorblind. Three different layers of cells expand and contract to saturate the visible skin with a different array of colors that can be rearranged on a small enough scale to mimic almost any background.
Scientists believe that even though cuttlefish are colorblind, they're able to see polarized light, which allows them to adjust to their surroundings. The video above from the New York Times Science Section explains a little more about how the color-changing process works.
5. They also mimic the shape and texture of objects around them to better hide.
Changing color is a nifty trick, but accurately replicating the shape and texture of the nearby coral or seaweed gives the cuttlefish an additional layer of camouflage. By extending and retracting individual papillae—tiny bumps across the cuttlefish's body—the animals can quickly and dramatically change the texture of their skin.
In addition to this, a 2011 study showed that cuttlefish can respond to visual clues to determine the optimal position for misleading mimicry. So if they're hiding near a particular plant, not only will they match it in color and texture, they'll also arrange their arms to best match the shape of the plant. Click here to see the mimicry in action.
6. Cuttlefish can see behind them.
An ability to accurately interpret visual stimuli around them for better camouflage is only part of the cuttlefish's impressive vision. They have distinct W-shaped pupils that allow them a wider horizontal range of vision, to the degree that they can see almost completely behind themselves.
Payne explains that just like people can shift the depth of their visual focus, cuttlefish can switch between forwards and backwards viewing. "If we’re trying to focus on something our lens might expand or contract, whereas they can just shift that front and back," he says.
7. Females can store multiple sperm packets, then select one for fertilizing.
A female cuttlefish likes to have options when it comes to selecting desirable genes for the next generation. During mating season, she'll play the field, taking on multiple sperm packets and storing the
m in her mouth cavity until she's comfortable enough to lay her eggs. Male cuttlefish know about this strategy, however, and they've developed a tactic of their own to counteract it: They'll initiate mating by shooting a jet stream of water into the female's mouth cavity to clear out sperm from previous males who have already laid claim.
After that, "they’ll transfer over their own sperm packets, and the female will either accept those and store those," Payne says, "or say no and get rid of them." Once the female has finished mating and finds a suitable spot to lay her eggs—somewhere protected from the currents by coral or rocks—she'll reach inside the cavity and retrieve the sperm packets, using whichever one she chooses to fertilize the eggs as she lays them.
8. Males will "cross dress" for access to a female.
Male cuttlefish use their color-changing ability to put on a dramatic show for females they're wooing. But this kind of ostentatious display runs the risk of attracting not just females but other males, as well. And in the competitive world of cuttlefish courtship—where males vastly outnumber females—alerting other males to the presence of a potential mate could jeopardize a cuttlefish's chance at reproducing.
To account for this, wily male cuttlefish employ some tricky gender-bending camouflage. With one half of their body they put on a colorful display for the female's benefit. With the other half, they disguise themselves as another female, mimicking the muted tones of the female they're courting so as not to attract the attention of nearby males.
In other instances, males will disguise themselves fully as female in order to sneak past larger males standing guard over a female after they've mated with her. To do so, the cross-dressing male not only changes his coloration, he will also hide his tell-tale fourth pair of arms (females only have three) and position himself to appear as if he's carrying eggs. A 2005 study showed that this deception works—almost half the time, the cross-dressing male gets the girl.
9. Cuttlefish use decoys as defense.
When they're threatened, cuttlefish, like most cephalopods, will release a cloud of ink to hide themselves from the would-be predator. But if simple smoke and mirrors won't cut it, the cuttlefish can mix its ink with mucus to create a smaller, denser cloud roughly in the same size and shape as its own body—or a decoy cuttlefish. These so-called pseudomorphs serve to distract and confuse the attacker while the cuttlefish scoots away.
10. Cuttlefish hunt using hypnosis.
Although they typically use their color-changing abilities to blend in to avoid getting eaten, when cuttlefish go on the offensive, they turn their bodies into pulsating light and color shows in an attempt to hypnotize potential prey.