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Research & Exploration
Field Dispatch
JULY 2005

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Photograph by Paul A. Sutherland

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In Search of the Deadly Jelly

CRE: Box JellyfishTwo years ago a seven-year- old boy named Jareed Crook was swimming at Mission Beach in Queensland, Australia. Suddenly he screamed. His grandfather pulled him from the water, but the writhing boy soon collapsed. Within an hour he was dead of cardiac arrest—the most recent person known to have died from the venom of a box jellyfish.
Called marine stingers by Australians, these killers have captivated Jamie Seymour, an ecologist at James Cook University in Cairns. His interest goes beyond academics: It's a matter of life and death.
To help protect the public from box jellies, Seymour studies their movements, using sonic tags to track them. But how do you attach a tag to a ball of slime? Seymour resorts to nontoxic superglue. He uses tiny ultrasonic transmitters half an inch wide, which he glues to the jellies' bells—making him the first scientist to tag jellyfish.
The solution is imperfect: Only seven attempts have succeeded since Seymour began the work in 1999, and the tags stayed on for less than two days. Undaunted, he's working on a method to attach the tags inside the jellies' bells, where they'll be less likely to fall off.
Of the 28 or so species of box jellies, Seymour tags the largest, Chironex fleckeri. It
can reach the size of a basketball, trailing up to 60 tentacles—each as long as 15 feet (five meters)—with a total of some five billion stinging cells.
Box jellies don't deliberately hunt humans, but a random brush can lead to death within minutes. Survivors bear purple ropelike scars for life, as does Seymour himself. One night he encountered a large box jelly near a pier. "Before I knew it, my hands and feet were wrapped in tentacles. I came out and couldn't walk straight. Tears were streaming down my face." His Lycra suit helped save him—along with a quick dousing in vinegar. Because vinegar stops Chironex from firing venom, Australian lifeguards keep it on hand. (Sadly, it didn't save Jareed Crook.)
The best way to prevent contact is to understand where box jellies go, when, and why. Unlike most jellyfish, which are essentially blind drifters, Chironex fleckeri has 24 eyes and can swim in bursts of five feet a second, giving it sight and speed to hunt fish. Another oddity: Several box jellies Seymour tracked were lively during the day then lay still on the seafloor by night, behavior unknown in other jellyfish.
Seymour's colleague Teresa Carrette discovered that box jellies get more lethal with age. Juveniles, which hunt shrimp, have venom in only 5 percent of their stinging cells; adults have it in 50 percent of theirs, enabling them to hunt larger prey.
Fatalities from box jellies are in decline, thanks to public awareness. Many beaches now use "stinger nets" to keep them out of swimming areas. Seymour has helped by creating a computer model to predict the end of each box jellyfish season, which runs from about November to June. "City councils now use it to determine when it's safe to remove their stinger nets," he says. "That's the most gratifying part of our research." 
—John L. Eliot

Related Links

Tropical Australian Stinger Research Unit
This James Cook University site is replete with information about box jellyfish such as Chironex fleckeri. Learn about some of the research studies Jamie Seymour and colleagues are conducting on these cubozoans.
University of California, Berkeley's Museum of Paleontology
Visit this page on cubozoans and view a fossil record of one of its ancestors.


"Armed and Dangerous." New Scientist (November 8, 2003), 34-7.
Hutchins, Michael, Dennis A. Thoney, and Melissa C. McDade, eds. Grzimek's Animal Life Encyclopedia, 2nd ed. Gale, 2004.
Seymour, Jamie E. "One Touch of Venom: A Box Jellyfish Is a Killer Without a Peer." Natural History (September 2002), 72-5.
Seymour, Jamie E., Teresa J. Carrette, and Paul A. Sutherland. "Do Box Jellyfish Sleep at Night?" Medical Journal of Australia (December 2004), 707. Available online at www.mja.com.au/public/issues/181_11_061204/sey10757_fm.pdf .

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