Sarah Zylinski
The little Japetella heathi octopus can switch from transparent to opaque in an instant, enabling it to hide from bioluminescent predators.
By
updated 11/10/2011 1:45:25 PM ET 2011-11-10T18:45:25

Two deep-ocean species of cephalopod, an octopus and a squid, can go from transparent to opaque in the blink of an eye, a new study finds.

This impressive camouflage swap is an adaptation that likely keeps the cephalopods safe from two different types of predators. The first are deep-sea creatures that hunt by looking upward for prey silhouetted against the light filtering down through thousands of feet of water. The second are fish that spotlight prey in "biological" headlights. These fish use bioluminescence, their own body-driven light source, to hunt for food.

To avoid being seen as a dark silhouette, it pays to be transparent, said study researcher Sarah Zylinski, a postdoctoral scientist at Duke University in North Carolina. But when a bioluminescent light hits a transparent surface, the effect would be like a flashlight shining on a windowpane at night, Zylinski said: very reflective, and extremely obvious.

Sarah Zylinski
LED lights similar to a predator's bioluminescent "spotlights" trigger red pigment.

"Being pigmented is the best strategy at that point," Zylinski told LiveScience. The octopus and squid species essentially have the best of both worlds, she said: "Being able to switch very rapidly between the two enables you to optimize your camouflage."

Masters of disguise
Many octopus, squid, cuttlefish and other cephalopods have the ability to rapidly change colors to disguise themselves from predators. Some octopus species even mimic the shapes of various fish and other sea life.

But those are all shallow-water creatures. Zylinski and her colleagues wanted to look deeper, at animals that live about 2,000 to 3,000 feet (600 to 1,000 meters) below the ocean surface. There is little light at this depth, though enough light filters down so that sharp-eyed fish can swim below prey, peering upward and looking for shadowy silhouettes.

On board research vessels in both the Sea of Cortez and over the Peru-Chile trench, Zylinski waited for deep trawling nets to pull catches out of the water. The nets are raised with painstaking slowness, Zylinski said, so that the pressure and light changes are not so abrupt for the animals caught inside.

Sarah Zylinski
Most of the time, the Japetella heathioctopus is transparent.

"It's a bit like Christmas, because you never know what you're going to get in the net," she said. "Sometimes it's like that really bad Christmas where you don't get what you want, and sometimes it's really exciting."

Presto-chango
When Zylinski scored a cephalopod catch, she quickly moved the animals from the dark nets into a dark, cool room so as not to expose them to daylight or boat lights. Then she tried various methods of stimulating color changes.

"The first set of experiments I did, we were using the kinds of stimuli that I would expect to get a response from shallow animals," Zylinski said, including looming objects or shadows passing overhead.

The deep-water creatures didn’t respond. So Zylinski tried a new method. She knew that bioluminescence is an important hunting tool in the deep sea, so it stood to reason that some animals might have developed ways to evade light. She shone bluish-white LED lights, very similar to bioluminescent light, on the cephalopods. In two species, the 3-inch (7.6-centimeter) Japetella heathi octopus and the 5-inch (12.7-cm) Onychoteuthis banksii squid, the response was instantaneous: A sudden switch from transparency to opaque red.

"This is pretty unique, just in the speed in which it was happening," Zylinski said. "It was so rapid."

The cephalopods are able to change color so quickly because their color-changing skin cells are under neural control. The squid sees the flash of light, and that visual stimulus triggers skin pigments called chromatophores to turn red. As soon as the light is gone, the pigments vanish, leaving the cephalopods transparent except for their guts and eyes.

  1. Science news from NBCNews.com
    1. NOAA
      Cosmic rays may spark Earth's lightning

      All lightning on Earth may have its roots in space, new research suggests.

    2. How our brains can track a 100 mph pitch
    3. Moth found to have ultrasonic hearing
    4. Quantum network could secure Internet

Camouflage strategies
Not all deep-sea cephalopods have the ability to switch their appearance from transparent to opaque, Zylinski said. Some come up with other ways to disguise themselves from predators. Some species are very reflective, so they reflect ambient light to hide their silhouettes. Others create their own bioluminescence to match the light filtering down from the ocean's surface, essentially beaming fake sunlight from their bellies.

Zylinski now plans to study how the chromatophores of the Japetella octopus change with age. Younger, smaller octopuses live higher in the water column, she said. They have fewer chromatophores and rely on transparency, which serves them well because there are fewer searchlight fish in lighter water. Mature adults live deeper, where bioluminescence is more prevalent, Zylinski said, and their greater number of chromatophores allows them to become more opaque.

"I'm hoping I'll get to go back out," she said. "There's so much out there for a visual ecologist, so many amazing things."

The research appears in the November issue of the journal Current Biology.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Explainer: Top 10 oddballs of the animal world

  • Image: Platypus
    Healesville Sanctuary

    From the outside, the platypus looks like a grade-school art project assembled by a kid too busy making spitballs to pay attention in class. The creature, which is classified as a mammal, has a duck's bill and webbed feet, lays eggs like a reptile, but has fur and rears its young on milk.

    Researchers say the platypus genome is equally cobbled together from bird, reptile and mammalian lineages. One more oddity: Males can deliver venom from tiny spurs on each hind limb. Click on the "Next" arrow above to learn about nine more oddballs in the animal world.

    More info: Mixed-up platypus genome unscrambled

    — By John Roach, msnbc.com contributor

  • Colossal squid has plate-sized eye

    AP

    In April 2008, scientists in New Zealand looked a thawing colossal squid in the eye and discovered that the eye is, well, colossal — about the size of a dinner plate. That makes it the largest animal eye on Earth. Fishermen caught the 1,000-pound creature last year in Antarctic waters and froze it intact for scientific study. Colossal squids can reach 46 feet in length and have tentacles equipped with suckers and hooks. Scientists believe the creatures can descend to 6,500 feet and are active, aggressive hunters.

    More info: Huge squid caught, could be biggest ever

  • Aye-aye gives grubs the finger

    Duke University Lemur Center

    The aye-aye is a bushy-tailed primate from Madagascar with big eyes and bat ears. But call it funny-looking and it just might extend its extra-long middle finger in your general direction. The member of the lemur family otherwise uses the extended digit to fish out grubs from the crevices of trees. Captive aye-ayes such as the one shown here from Duke University are teaching scientists about the evolution of color vision.

    Learn more about the brainiac of all lemurs

  • Star-nosed mole sniffs out food, fast

    Image: Star-nosed mole
    Kenneth C. Catania / Vanderbilt

    The fleshy appendages that ring the snout of the star-nosed mole, shown here, make it one strange-looking creature. But when it comes to eating, those 22 tentacles help the mole detect and devour food faster than the human eye can follow — in a fraction of a second. Researchers say the speedy feeding allows the mole to prey on small insect larvae that would otherwise be too energetically costly to eat. The creature lives and forages under the cover of marshes and wetlands along the east coast of North America.

  • Burrowing toad is genetically different

    Robert Puschendorf

    For an amphibian, the stocky and squat Mexican burrowing toad doesn't look all that strange, but it's actually unique. A global conservation program called EDGE of Existence ranks the toad as the most "evolutionarily distinct" amphibian in the world. A fruit bat, polar bear, killer whale, kangaroo and human are all more closely related to one another than the toad is to any other species, according to the program. The Mexican burrowing toad, as its name suggests, spends most of the year underground, coming out only after particularly heavy rains to breed in pools of water.

    Learn about other bizarre amphibians under threat

  • Yeti crab lurks on the ocean bottom

    A Fifis  /  AP

    Named after the legendary shaggy man-beast that tromps through the snows in some of the world's tallest mountains, the Yeti crab blindly scurries about hydrothermal vents along a ridge at the bottom of the Pacific Ocean. First observed in 2005, the crab, officially named Kiwa hirsute, sports a carpet of pale yellow hairs on its arms. Scientists suspect the crab uses those hairs either to farm bacteria or to feel its way around the seafloor for food and potential mates.

    More info: Scientists to list all species on Web

  • Narwhals, the 'unicorn' whales

    Glenn Williams / Harvard Medical School

    Unicorns are purely mythical creatures, but the myths may have been inspired by narwhals. Most males and some females among the 2,200- to 3,500-pound whales sport an 8-foot-long appendage that emerges from the left side of their upper jaw. Scientists recently discovered that the elongated tooth is packed with nerve endings, making it extraordinarily sensitive. The whales may use it to determine the salinity of water and search for food. Male narwhals are also known to rub their tusks together, presumably because it gives off a unique sensation.

    More info: Mystery of 'unicorn' whale solved

  • Sucker-footed bats stick to Madagascar

    Field Museum (left); Bat Conservation Int'l (right)

    In January 2007, scientists announced the discovery of a new species of bat that uses suckers on its thumbs and hind feet to stick to broad-leafed plants such as the traveler's palm. The new species, Myzopoda schliemanni (left image), was found on the dry, western side of the African island nation of Madagascar and is closely related to another sucker-footed bat called Myzopoda aurita (right image) that lives in the humid eastern forests. Conservationists were heartened by the discovery because it suggests the bats can adapt to pioneering broad-leafed plants in deforested areas. Only about 8 percent of the island's original forest cover remains.

    Watch NBC video: What's killing all the bats?

  • Long-eared jerboa hops onto the screen

    Image: Long-eared jerboa
    ZSL

    In December 2007, conservationists released the first known footage of an endangered rodent they've nicknamed the "Mickey Mouse of the Desert." Known more formally as the long-eared jerboa, the little critter has ears about one-third larger than its head, and legs that allow for hopping like a kangaroo. The International Union for Conservation of Nature lists the species as endangered. One threat: the domestic cat.

    More info: Mongolian 'Mickey Mouse' caught on tape

  • Ligers, wholphins and grolar bears, oh my!

    Image: Liger
    TODAY show

    Every now and again, trysts between two different species result in oddball offspring that capture the public's fascination. Ligers, which are a cross between a male lion and a female tiger, were immortalized in the 2004 cult movie "Napoleon Dynamite": The main character of the 2004 cult movie, played by Jon Heder, describes it as "pretty much my favorite animal." (A real one is shown above.) Other popular hybrids include wholphins, which are a cross between false killer whales and Atlantic bottlenose dolphins; and the "grolar bear," a cross between a grizzly bear and polar bear.

    Watch NBC video of a liger
    Whale-dolphin hybrid has baby wholphin
    Hairy hybrid: Half grizzly, half polar bear

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments