The box jellyfish Chironex fleckeri is infamous. Its venom will kill a human within minutes. This much I’ve known for decades. What I didn’t know until yesterday is that C. fleckeri has 24 eyes and appears to sleep.

More than a decade ago, researchers in Australia superglued acoustic transmitters to several box jellyfish (without getting stung) and set them free. Using an underwater microphone, they were then able to track their movements. During the daytime, the jellyfish moved in straight lines, typically covering around 200 m an hour. At night, they basically stopped. “During these periods of “inactivity”, the jellyfish lie motionless on the sea floor, with no bell pulsation occurring and with tentacles completely relaxed and in contact with the sea floor,” wrote Jamie Seymour, a biologist at James Cook University in Cairns in The Medical Journal of Australia. A small disturbance – like a light or a vibration – “causes the animals to rise from the sea floor, swim around for a short period, and then fall back into an inactive state on the sand,” they reported.

The clear distinction between activity and rest raises the possibility that the box jellyfish is capable of sleep, a state most commonly associated with vertebrates. Why would a box jellyfish need to sleep? One possibility, suggested by Seymour and his colleagues, is that it uses its eyes to hunt. In the dark, when vision is limited, “it makes a lot of sense to become inactive, decrease your energy used in locomotion and divert it to growth.”

{ The Guardian | Continue reading }

photo { Melvin Sokolsky, Lip Streaks, 1967 }

Jellyfish stings are often not much more than a painful interlude in a seaside holiday—unless you happen to live in northern Australia. There, you might be stung by the most venomous creature on Earth: the box jellyfish, Chironex fleckeri.

Box jellyfish have bells (the disc-shaped “head”) around a foot across, behind which trail up to 550 feet of tentacles. It’s the tentacles that contain the stinging cells, and if just six yards of tentacle contact your skin, you have, on average, four minutes to live—though you might die in just two. Seventy-six fatalities have been recorded in Australia since 1884, and many more may have gone misdiagnosed or unreported. […]

Most jellyfish are little more than gelatinous bags containing digestive organs and gonads, drifting at the whim of the current. But box jellyfish are different. They are active hunters of medium-sized fish and crustaceans, and can move at up to twenty-one feet per minute. They are also the only jellyfish with eyes that are quite sophisticated, containing retinas, corneas, and lenses. And they have brains, which are capable of learning, memory, and guiding complex behaviors. […]

In Stung! On Jellyfish Blooms and the Future of the Ocean, biologist Lisa-ann Gershwin argues that after half a billion years of quiescence, they’re on the move:

If I offered evidence that jellyfish are displacing penguins in Antarctica—not someday, but now, today—what would you think? If I suggested that jellyfish could crash the world’s fisheries, outcompete the tuna and swordfish, and starve the whales to extinction, would you believe me?

[…]

On the night of December 10, 1999, 40 million Filipinos suffered a sudden power blackout. President Joseph Estrada was unpopular, and many assumed that a coup was underway. […] Fifty truckloads of the creatures had been sucked into the cooling system of a major coal-fired power plant, forcing an abrupt shutdown.

Japan’s nuclear power plants have been under attack by jellyfish since the 1960s, with up to 150 tons per day having to be removed from the cooling system of just one power plant.

{ The New York Review of Books | Continue reading }

image { Tim Hawkinson }

Bioengineers have made an artificial jellyfish using silicone and muscle cells from a rat’s heart. The synthetic creature, dubbed a medusoid, looks like a flower with eight petals. When placed in an electric field, it pulses and swims exactly like its living counterpart.

“Morphologically, we’ve built a jellyfish. Functionally, we’ve built a jellyfish. Genetically, this thing is a rat,” says Kit Parker, a biophysicist at Harvard University in Cambridge, Massachusetts, who led the work.

{ Nature | Continue reading | NERS/Discover }

artwork { Trevor Brown }

Jellyfish will not plague our oceans in the future as was previously thought, say researchers who have found no evidence for global increases in jellyfish blooms.

Despite media claims over the past few years that worldwide jellyfish numbers are increasing at an alarming rate, there has been no database of jellyfish numbers to back this up.

{ Cosmos | Continue reading }

artwork { Ellsworth Kelly, Study for Rebound, 1955 }

Four nuclear reactors in Japan, Israel and Scotland were forced to shutdown due to infiltration of enormous swarms of jellyfish, which clogged the plant’s cooling system.

Such massive invasions of the jellyfish species have raised speculations and scientists are trying to figure out the reason behind such unusual growing trends.

Recent studies have found out that jellyfish blooming occurs mostly during the summer and spring months. This may partly explain why the three recent power plant incidents happened in close succession. The conditions brought on by climate change may also be creating more jellyfish blooms than there used to be.

{ International Business Times | Thanks Rachel! }

Graham said there have been dozens of cases of jellyfish causing partial or complete shutdowns of coastal power plants in the past few decades, as well as shutdowns of desalination plants. Steve Haddock of the Monterrey Bay Aquarium Research Institute said a power plant in Australia was shut down by jellyfish as long ago as 1937. Such events aren’t surprising; all these plants draw water out of the ocean, and they are already fitted with filtration devices called flumes that remove jellyfish and other debris.

“Only when you have a huge influx of jellies do they overwhelm the flumes,” Graham told Life’s Little Mysteries. This happens when a jellyfish bloom — a huge swarm of adult specimens brought together by ocean currents — flows into a power plant’s filtration system.

{ LiveScience | Continue reading }

A local zoologist, Jamie Seymour, blamed King’s death on a nearly transparent jellyfish the size of a thumbnail. Covered from the top of its head to the tip of its four tentacles with millions of microscopic spring-loaded harpoons filled with venom, it’s one of at least ten related species of small jellyfish whose sting can plunge victims into what doctors call the Irukandji syndrome.

“The symptoms overwhelm you,” says Seymour, 40, who himself was stung by an irukandji on the lip, the only part of his body uncovered as he scuba-dived looking for specimens near an island off Cairns in late 2003. “On a pain scale of 1 to 10, it rated between 15 and 20,” he says, describing the vomiting, the cramps and the feeling of panic. “I was convinced I was going to die.” But he was lucky; not all species of irukandji administer fatal stings, and he recovered within a day. (…)

Most jellyfish are passive; they drift up and down in the water column, or are pulled to and fro by the tides and winds. They float through the oceans devouring tiny fish and microscopic creatures that bumble into their tentacles, and are no threat to humans.

But those known as box jellyfish, for the shape of their bell, or body, are a breed apart. Also called cubozoans, they’re voracious hunters, able to chase prey by moving forward—as well as up and down—at speeds of up to two knots. They range in size from the various irukandji species to their big brother, the brutish Chironex fleckeri, which has a bell the size of a man’s head and up to 180 yards of tentacles, each lined with billions of cells bursting with deadly venom. Also known as a sea wasp or marine stinger, Chironex, which is far deadlier than irukandji, boasts powerful stingers, or nematocysts, strong enough to pierce the carapace of a crab and quick enough to shoot out at the fastest speed known in the natural world—up to 40,000 times the force of gravity. And unlike other jellyfish, a box jellyfish can see where it’s going and alter its course accordingly; like an eerie creature sprung from science fiction or a horror movie, it has four separate brains and 24 eyes, providing it a 360-degree view of its watery world.

“A Chironex fleckeri can kill a human in one minute flat,” says Seymour, widely considered the world’s foremost box jellyfish researcher. (…)

“We hardly know anything about their lifestyle, how they breed, where they come from, how fast they grow, how long they live, or even how many species there are,” says Lisa-ann Gershwin, a 41-year-old California stockbroker-turned-jellyfish taxonomist. “But they’re like other cubozoans: they’re really neat, like aliens. They split from the other jellyfish, the scyphozoa, more than 300 million years ago, long before dinosaurs walked the earth, and have been making their own way along the evolutionary path ever since.” (…)

Death comes quickly to Chironex victims because—unlike venomous snakes, which inject a glob of venom that must pass through the lymphatic system before draining into the rest of the body—Chironex shoots its venom into the bloodstream, giving the venom a direct pathway to the heart.
In addition to their stinging cells, box jellyfish have another superlative weapon in their hunt for prey: one of the world’s most effective sets of eyes.

On a windy day at a beach 40 miles north of Cairns, I help a team led by Dan Nilsson, a zoology professor at Sweden’s Lund University and a renowned expert on animal eyes. (…) “They swim like fish, not like jellyfish,” he says with a smile. He plucks one from the bucket and shows me what keeps it from bumping into things: four tiny black dots, containing the jellyfish’s 24 eyes, on strands connected to each side of the cube of jelly. Under the microscope, Nilsson has detected in each dot something he calls a sensory club, which is an organ with a set of six eyes, including four that are—much like the eyes of other jellyfish—simply pits, limited to detecting light intensity in various directions. But the two other eyes in each sensory club have more in common with human eyes than the eyes of other jellyfish, with lenses, corneas and retinas. One eye, which points obliquely downward at all times, even has a mobile pupil that opens and closes. The other major eye points upward. “We’re not exactly sure what these eyes are doing,” Nilsson says, although he believes they may help the jellyfish “position itself in the right place where there is plenty of food.” They also help the animal situate the shoreline and the horizon—to avoid being dumped on the beach by a wave—and see obstacles that would tear its delicate tissue, such as a coral reef, a mangrove tree or a pier.

They also have the same stomach—or, rather, stomachs. Because a box jelly, as Jamie Seymour puts it, “charges around the ocean all day hunting mobile prey, prawns and fish,” its metabolic rate is ten times that of a drifting jellyfish. So, to swiftly access the energy it needs, the box jellyfish has developed a unique digestive system, with separate stomachs in each of its tentacles. All box jellies turn their food into a semi-digested broth in the bell, and then feed it down through the tentacles to be absorbed. Since a Chironex can have up to 60 tentacles, each as long as 3 yards, in effect it has up to 180 yards of stomach.

If box jellyfish eyes are a puzzle, its four primitive brains—positioned on each side of its body and attached to it by the same strand that anchors its eyes—are an enigma. Can the four separate brains communicate with each other? If so, do they merge the images they receive from the 24 eyes into one image? And how do they manage if different eyes detect radically different images? Nilsson shrugs. “They’ve evolved a rather advanced system unlike any other animal on earth,” he says. “But we have no idea what’s going on in their four brains, and I suspect it will be a long time before we find out.”

{ Smithsonian | Continue reading }

Despite its primitive structure, the North American comb jellyfish can sneak up on its prey like a high-tech stealth submarine, making it a successful predator. Researchers, including one from the University of Gothenburg, have now been able to show how the jellyfish makes itself hydrodynamically ‘invisible’.

{ PhysOrg | Continue reading }

For all their noble antiquity, jellyfish have long been ignored or misunderstood by mainstream science, dismissed as so much mindless protoplasm with a mouth. Now, in a series of new studies, researchers have found that there is far more complexity and nuance to a jellyfish than meets the eye — or eyes. In the May 10 issue of the journal Current Biology, Dr. Garm and his colleagues describe the astonishing visual system of the box jellyfish, in which an interactive matrix of 24 eyes of four distinct types — two of them very similar to our own eyes — allow the jellies to navigate like seasoned sailors through the mangrove swamps they inhabit.

{ NY Times | Continue reading | previously }

“It is a surprise that a jellyfish — an animal normally considered to be lacking both brain and advanced behavior — is able to perform visually guided navigation, which is not a trivial behavioral task,” said lead researcher Anders Garm of the University of Copenhagen. (…)

Box jellyfish have 24 eyes of four different types, and two of them — the upper and lower lens eyes — can form images and resemble the eyes of vertebrates like humans. The other eyes are more primitive. It was already known that box jellyfish’s vision allows them to perform simpler tasks, like responding to light and avoiding obstacles.

In the new study, scientists found that one species of the cube-shaped box jellyfish, Tripedalia cystophora, uses its upper lens eyes, which are mounted on four cuplike structures, to make sure it stays close to the prop roots of mangrove trees that define its habitat.

{ LiveScience | Continue reading | Neurophilosophy }

artwork { Ellen Gallagher, DeLuxe, 2004–05 [detail] | currently on view at the MoMA, NYC }

Jellyfish have traditionally been considered simple and primitive. When you gaze at one in an aquarium tank, it is not hard to see why.

Like its relatives the sea anemone and coral, the jellyfish looks like a no-frills animal. It has no head, no back or front, no left or right sides, no legs or fins. It has no heart. Its gut is a blind pouch rather than a tube, so its mouth must serve as its anus. Instead of a brain, it has a diffuse net of nerves.

A fish or a shrimp may move quickly in a determined swim; a jellyfish pulses lazily along.

But new research has made scientists realize that they have underestimated the jellyfish and its relatives - known collectively as cnidarians (pronounced nih-DEHR-ee-uns). Beneath their seemingly simple exterior lies a remarkably sophisticated collection of genes, including many that give rise to humans’ complex anatomy.

These discoveries have inspired new theories about how animals evolved 600 million years ago. The findings have also attracted scientists to cnidarians as a model to understand the human body.

“The big surprise is that cnidarians are much more complex genetically than anyone would have guessed,” said Dr. Kevin J. Peterson, a biologist at Dartmouth. “This data have made a lot of people step back and realize that a lot of what they had thought about cnidarians was all wrong.”

Renaissance scholars considered them plants. Eighteenth-century naturalists grudgingly granted them admittance into the animal kingdom, but only just. They classified cnidarians as “zoophytes,” somewhere between animal and plant.

It was not until the 19th century that naturalists began to understand how cnidarians developed from fertilized eggs, their body parts growing from two primordial layers of tissue, the endoderm and ectoderm.

Other animals, including humans and insects, have a third layer of embryonic tissue, the mesoderm, wedged between the ectoderm and the endoderm. It gives rise to muscles, the heart and other organs not found in cnidarians.

Cnidarians also have a simpler overall body plan. Fish, fruit flies and earthworms all have heads and tails, backs and fronts, and left and right sides. Scientists refer to animals, including humans, with this two-sided symmetry as bilaterians. In contrast, cnidarians seem to lack such symmetry completely. A jellyfish, for example, has the symmetry of a bicycle wheel, radiating from a central axis.

{ NY Times [2005] | Continue reading }

print { Constance Jacobson }

Usually when you see people who have been stung by box jellyfish with that number of the tentacle contacts on their body, it’s usually in a morgue. (…) The creature didn’t just sting the 10-year-old girl. It enveloped her: Its tentacles wrapped around her limbs and wouldn’t let go. She couldn’t see or breathe. The creature, which is capable of killing an adult in four minutes, wrapped its tentacles tighter and knocked her unconscious. (…) After several weeks in the hospital Shardlow is still feeling the effects - but the fact she is feeling anything at all - let alone doing as well as she is baffles Seymour. For now, besides scarring and memory loss, she is doing well.

{ CNN | Continue reading }

related { Nomura jellyfish }

An ‘immortal’ jellyfish is swarming through the world’s oceans, according to scientists.

Since it is capable of cycling from a mature adult stage to an immature polyp stage and back again, there may be no natural limit to its life span. Scientists say the hydrozoan jellyfish is the only known animal that can repeatedly turn back the hands of time and revert to its polyp state (its first stage of life).

{ Yahoo Green | Continue reading | Telegraph }

photo { Jackson Eaton }

A blood-orange blob the size of a small refrigerator emerged from the dark waters, its venomous tentacles trapped in a fishing net. Within minutes, hundreds more were being hauled up, a pulsating mass crowding out the catch of mackerel and sea bass.

The fishermen leaned into the nets, grunting and grumbling as they tossed the translucent jellyfish back into the bay, giants weighing up to 200 kilograms (450 pounds), marine invaders that are putting the men’s livelihoods at risk.

The venom of the Nomura, the world’s largest jellyfish, a creature up to 2 meters (6 feet) in diameter, can ruin a whole day’s catch by tainting or killing fish stung when ensnared with them in the maze of nets here in northwest Japan’s Wakasa Bay.

“Some fishermen have just stopped fishing,” said Taiichiro Hamano, 67. “When you pull in the nets and see jellyfish, you get depressed.”

This year’s jellyfish swarm is one of the worst he has seen, Hamano said. Once considered a rarity occurring every 40 years, they are now an almost annual occurrence along several thousand kilometers (miles) of Japanese coast, and far beyond Japan. (…)

In 2007, a salmon farm in Northern Ireland lost its more than 100,000 fish to an attack by the mauve stinger, a jellyfish normally known for stinging bathers in warm Mediterranean waters. Scientists cite its migration to colder Irish seas as evidence of global warming.

{ AP/San Francisco Chronicle | Continue reading }

illustration { Ernst Haeckel }