"I was wheezing. I was in a lot of pain and I was starting to panic," she said. Yanagihara staggered ashore in search of a telephone to call for help, but fell unconscious. She awoke in an ambulance, suffering from anaphylactic shock — a severe allergic reaction that can be fatal.

Waikiki seems to attract box jellyfish more than anywhere else in the state, and lifeguards must post warning signs advising swimmers to stay out of the water while the "jellies" wash ashore during their spawning cycle, their stingers still fully armed, eight to 10 days after the full moon.

Researchers said the numbers of box jellyfish along O'ahu's southern shores appear to be growing each year, but no one knows for sure why.

Inspired research

After recovering from her wounds, Yanagihara, who works at the University of Hawai'i's Pacific Biomedical Research Center, was shocked to learn that no one had studied the biochemistry of box jellyfish. She was awarded a grant and launched into what has been more than eight years of research and a wealth of information about the jellies and their venom.

The animals use their toxin — contained in stinging cells called nematocysts — to paralyze fish and crustaceans that they later draw up to their bell-shaped bodies to eat.

"The venom is a very rich mixture of bioactive compounds," some of which may have medical applications, she said. One of these compounds appears to boost the immune system. Another puts small animals into a kind of suspended animation, temporarily slowing their heart rate, perhaps to keep the prey alive until the jellies get around to eating them.

The compounds also can cause red blood cells to burst and promote the release of histamine granules, which is what prompted Yanagihara's allergic reaction.

"I assumed because it is such a primitive animal, it might have a very simple venom, but no. It has this amazing, vast array of compounds."

It also has a fascinating means of delivering it. The jellyfish's four tentacles are armed with hundreds of thousands of essentially spring-loaded stinging cells. When a jellyfish runs into something, the cells fire, using a microscopic dart to inject toxins into its victim.

A 'magical' cycle

With the know-how of experience — and very cautiously — a lifeguard shows us a dead box jellyfish. Don't try it yourself. Advertiser library photo • Feb. 14, 1996

But "there's this magical monthly cycle," said University of Hawai'i researcher Mike Hadfield at the Kewalo Marine Laboratory. After spawning, the adult jellies die on the shore, and nobody really knows what happens to the new crop until they show up months later to spawn.

"They don't show up in plankton hauls, and they don't have the kind of directional swimming to come in from 50 miles out. To the best of my knowledge, nobody knows where they're coming from," Hadfield said.

They are found throughout the Hawaiian archipelago, from the Big Island to Midway, but scientists aren't sure why they show up in large numbers from Waikiki to Hanauma Bay, and hardly at all elsewhere in the state.

"We never see them. If we have, it's very rare," said Larry Davis, aquatics program administrator for Hawai'i County. "We get (Portuguese) man-of-war with onshore winds, but not the box jellyfish. I don't know why."

Maui County ocean safety operations chief Archie Kalepa said he has seen them in Lahaina Harbor, "but nowhere near like Waikiki. We hardly see them."

On Kaua'i, the beach at Po'ipu is closed on rare occasions because of the presence of box jellyfish, said David Kalani Vierra of the Kaua'i County Ocean Safety Bureau.

"It's very rare. We've had some reports in Po'ipu Beach, but that's the only place," Vierra said. "We have more of a problem with Portuguese man-of-war."

Box jellies have been occasional visitors at Po'ipu for decades. Retired zoologist Alison Kay remembers their showing up intermittently in the 1940s and '50s when she was a youngster on Kaua'i.

Yanagihara said she has been taking monthly samples for eight years and, while the month-to-month population of jellies changes dramatically, the overall population trend is clearly up.

Perhaps overfishing has removed the animals that feed on young jellyfish. Maybe changing water temperatures play a role.

Perhaps nutrients in the water from human activities on shore are increasing the amount of plankton they eat and thus promoting their growth. Waikiki Aquarium curator Jerry Crow said a degraded nearshore environment, with plenty of nutrients and sediment, could promote the jellyfish in their larval stage.

Or it may be a combination of those and other factors, said Yanagihara, who has attended international conferences looking into global jellyfish "blooms."

"This is a question that has been going on around the world, from Hawai'i to the Black Sea, to Chesapeake Bay and elsewhere," she said.