WonderQuest with April Holladay, Article printer-friendly version
A: How long are an octopus' arms? It depends on the octopus. The smallest pygmy species — a mere seven tenths of an inch in body length — has about one-inch (2.5 cm) arms. Whereas, the biggest (2-foot body length) has over100 times longer arms. The common octopus has about five-foot (1.5-m) arms.
An octopus' siphon is a tube (see figure) that lets him jet through the sea, breathe out, and hide in an inky plume. "The siphon and the funnel are the same thing. I prefer to use the term funnel because water is not sucked in through the funnel, it is expelled," emails biologist Roy Caldwell, professor of integrative biology at the University of California at Berkeley.
The octopus sucks water into the mantle (body) cavity through a different tube and passes the water over the gills. His funnel/siphon tube expels the water, jet fashion. He can squeeze his body hard, thereby, expelling water fast and jetting fast, but usually, he squeezes the water out gently, and moves primarily by crawling the seafloor. If threatened, he shoots out a dark plume to mask a jet-away.
The plume is actually red, and made of melanin (the same dye that colors our hair and skin) but looks dark in the sea's dim lighting and when concentrated. Also, red light looks gray since water absorbs its long-wavelength light. Moreover, the ink contains an irritating compound (tyrosinase) that briefly destroys a predator's sense of smell, enhancing the wily octopus' vanishing act.
The boneless octopus, as symmetrical as a creature can be, needs much brain processing to control posture and orient itself spatially. "But that does not equate to intelligence," says Caldwell. Biologists debate an octopus' intelligence; the issue isn't decided. I'll explore this topic another time.
Why boneless? Well, it has at least one advantage: an octopus can slip through a hole as small as his eye.
This
octopus displays a brilliant orange. "Most octopuses will let you get close, maybe even touch them," says diving
submersible Alvin pilot and photographer Bruce Strickrott. In the Gulf of
Mexico, about 7500 feet (2300 m) deep. Photo courtesy of Woods Hole
Oceanographic Institution.An octopus changes colors by displaying pigments and sheens. An octopus starts with a couple of basic colors — brownish-red and yellowish-orange. His color organs are "a bag of colored material surrounded by muscles," says Caldwell. By stretching the muscles he can open the bag more and reveal more colors. Just as easily, he can cut off the colors by relaxing his muscular color bag, which then contracts to a "pinpoint of concentrated pigment" that we don't see. Moreover, he can adjust his skin color by changing small bodies (called iridocytes) below the pigment layer. Light bends and bounces off these cells to cast a blue-green sheen over his skin, like a peacock's feathers, subtly varying as light hits from different angles.
By the way, several octopus species drop their arms off their body when attacked. "The wiggling autotomized arms will even lock onto the predator with its suckers," says Caldwell. "This is usually sufficiently distracting to allow the octopus to escape." Re-growing lost arms is a snap for an octopus.
Why an octopus has three hearts, WonderQuest
What is octopus ink by Nancy King, Tonmo.com, the octopus news magazine online
International Wildlife encyclopedia, edited by Maurice Burton and Robert Burton
Octopus, Bandung International School, Bandung, West Java, Indonesia
Through the eye of an octopus by Eric Scigliano, Discover Magazine
A: The International Space Station averages 230 miles (370 km) above Earth, and flies at 17,500 mph (28,200 km/h).
Spotting the Space Station, WonderQuest
A: A: The USA government schedules its comprehensive tests (HANES studies)
about five years apart. I asked USA Public Affairs Specialist
Mary Jones of the
National Center for Disease Control when data from the next study will be
available. "It is in the collection stage; we don't have a release date as yet,
maybe some time next year," she said.
The Canadians collect their data "every two years," says statistician
Heather Orpana of Statistics Canada in Ottawa. "We will have another survey in the field
in 2007/2008, which will also be collecting measured height and weight data."
Women sizes: British, USA, Canadian and Mexican, WonderQuest
Body measurements, National Center for Health Statistics
(Answered Feb. 19, 2007)
Find this article at: http://www.wonderquest.com/octopus-women-size-schedule.htm