Octopus remains remarkable for many reasons

April 13, 2014 

A giant Pacific octopus.

POINT DEFIANCE ZOO & AQUARIUM

Hiding beneath the waves, the ocean’s smartest squishy animal rests inside a rocky den, waiting for its chance to go hunting along the sea floor. Meet the octopus.

All head and arms, the mysterious octopus seems like an alien from a science fiction movie. As an invertebrate animal, the octopus has no bones in its body, and moves almost like a liquid. But, this is no shapeless blob. Bulging, human-like eyes peer out from its small head at the front of a large, textured balloon. This muscular sac, called a mantle, holds the octopus’s internal organs, including its digestive system, three hearts, gills and reproductive parts, along with a water-squirting tube known as a funnel or siphon.

Don’t look for tentacles on an octopus. While their squid and cuttlefish cousins have arms as well as two longer tentacles (good for shooting forward to grab prey), octopuses have only arms. “Octo” means eight, and underneath the octopus’s head, we find eight long arms radiating out from its mouth, connected by stretchy webbing. Each arm is lined with two rows of sensory suckers, which move independently and can taste as well as feel and grip. This way, an octopus easily finds and fetches prey out of small cracks and crevices, pulling it up toward a sharp, parrot-style beak.

Octopuses come in many sizes, from the tiny Octopus Wolfi, measuring just over one-half inch, up to the giant Pacific octopus, which stretches its arms up to 20 feet across.

All of them start life as tiny plankton, drifting around in ocean currents. They grow fast, though, because their entire lifespan lasts about one to five years, depending on the species. Big growth means a big appetite, and these invertebrates are successful predators in oceans around the world, catching fish, crabs, mussels, clams and even other octopuses.

While many of their soft-bodied mollusk relatives, such as snails, clams and oysters, hide inside hard shells for safety, octopuses freely roam the ocean bottom, coral reefs and tide pools with no shell at all. Those same places are home to hungry seals, dolphins, eels, sharks and other large fish that would snap up an octopus. So, how does the flexible, squishy character avoid trouble?

If danger looms, a set of spy-quality adaptations does the trick:

First, they blend in like a chameleon. With sharp eyesight to guide them, octopuses are artists of camouflage. Their bodies are covered in chromatophores — quick-change color cells — special mirror cells that reflect the surroundings, and papillae — skin layers that can stick up or lie flat to create texture. Using these disguise tools, an octopus can seamlessly match its background in less than one second.

Second, look scary. Divers have shot video of the mimic octopus chasing off bothersome fish by changing its body shape to look like dangerous sea snakes and lionfish.

Third, make a magician’s getaway. Like a magician’s poof of smoke, an octopus can squirt a dark cloud of ink in a predator’s face to blind or confuse it while the octopus swims off at speeds up to 25 mph. Since its beak is its only hard part, the soft octopus can also disappear by cramming itself into places too small for predators to follow.

If those skills aren’t enough, an octopus can rely on its smarts. The octopus has proportionally the largest and most complex brain of any invertebrate. Researchers report that the curious animals will solve problems by trial and error. When given a bit of food sealed inside a puzzle box, octopuses will try different ways to break into the box. Once they succeed, the octopuses will quickly use the same approach for similar puzzles.

LEARN MORE

see giant Pacific octopuses: Visit Point Defiance Zoo & Aquarium and the Seattle Aquarium. Recreational divers and snorkelers can search for them at several local, protected popular dive sites, such as Les Davis Pier and Day Island in Tacoma. Check out “Wildlife Viewing” on the state Department of Fish and Wildlife website for a complete list and map: wdfw.wa.gov/viewing/ octopus.

Become an octopus Citizen Scientist: Recreational divers can join in the Seattle Aquarium’s annual giant Pacific octopus census, helping to count the creatures. See seattle aquarium.org/octopus-census for more information and past survey data.

Beach walks: Join Point Defiance Zoo & Aquarium naturalists on a summer beach walk to learn how to spot baby octopuses while checking out tidepools and to identify and record other tide pool animals. For dates and more information, visit pdza.org/explore-shore.

Videos: Watch a female giant Pacific octopus tending her eggs as they hatch at a West Seattle dive site, youtube. com/watch?v=-2tZMhoq0nI.

See examples of octopus camouflage and learn more about how it works: sciencefriday.com/video/08/05/2011/ where-s-the-octopus.html.

Watch the mimic octopus imitate various predators: youtube.com/ watch?v=H8oQBYw6xxc.

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