Author: Katrina Outland
Institution: Hawaii Pacific University
Date: February 2005
They come ten days after the full moon, swarming to shore, nearly invisible and wielding poison-loaded tentacles. A few days later, they disappear just as mysteriously as they had come, leaving behind their microscopic spawn. No, this isn't the plot of another science-fiction movie; it is a real, monthly occurrence on the beaches of Oahu, Hawaii. These creatures are aliens, but they aren't from space. They are an alien species of box jellyfish that has been invading Hawaii's waters for almost two decades. Lifeguards, tourists, and scientists all keep a wary vigilance for this particular box jelly, called Carybdea alata.
Named for their square shape, box jellyfish are the most highly evolved and the most dangerous of the jellyfish. Like corals and other members of the phylum Cnidaria, jellyfish tentacles are lined with microscopic cells called cnydocites that each house a powerful stinging thread called a nematocyst. When triggered, each nematocyst is released in a powerful spring-like action, piercing whatever might touch it. Box jellyfish not only have the most potent poison of all jellyfish in their nematocysts, but they have even developed complex eyes that can detect light. They don't just drift around,they can actively pursue prey.
Hawaii's C. alata is not the largest or the deadliest box jelly (a status reserved for the infamous sea wasp of Australia), but it is still a dangerous nuisance. Nearly every month brings a string of news reports about jellyfish stings, mostly on the southern and eastern shores of Oahu. For example, on a single day in July 2004, 318 people were stung at the tourist destination Waikiki, along with 45 stings at other beaches. No one is immune to a sting's pain; as lifeguard Landy Blair told reporters in 2001, "I have sent 30-year-old muscular surfers in tears and with breathing difficulties to the hospital."
Where are they from, where are they going?
Hawaii's box jellies are unique in their predictable arrivals: they come near shore to spawn 8 to 12 days after each full moon. John Culliney, Professor of Biology at Hawaii Pacific University, said that other members of the same phylum, including corals, also time their spawns based on the lunar cycle.
"They do this because it's easier to concentrate the eggs and sperm all together," Culliney said. What is unique about C. alata is that nowhere else in the world are box jellyfish quite so reliably on-time. No one is yet able to answer why.
The box jellyfish lifecycle. The sexually reproductive medusae bud off of the asexual polyps. Source: Ruppert and Barnes, Invertebrate Zoology: 6th Ed.
To add to the mystery, very little is known about the box jelly's lifecycle. A jellyfish, also called a medusa, is actually only one stage of the lifecycle; the medusae bud off of larval-stage polyps that are attached to the sea floor. According to Culliney, a box jellyfish polyp is longer-lived than other jellyfish polyps,perhaps even indefinite. The problem is that no one knows where the polyps live.
"There might be a chance to control the population if we knew what substrate [the polyps] live on," said Culliney, "but no one's been able to find them."
After spawning, the adult jellyfish disappear again, just as suddenly as they came. Where do they come from? Where do they go? How long do they live? So far, there are no answers.
Coming to Hawaii
Carybdea alata received its name from its place of origin,the Caribbean. So how did these mysterious invaders reach Hawaii? Researchers have several theories, though none have been proven. Some believe that the medusae were carried in ballast water in ships. Others, including Culliney, think it is more likely that the polyps were transported by attaching to the bottom of ships. Whatever the method of arrival, this box jellyfish has now spread worldwide.
First appearing on Oahu in the late 1800s, this box jelly has shown up regularly near beaches since the 1980s. "Always before then they'd disappear for a few years between sightings," said Culliney. "Now it looks like they're spreading around Oahu."
Originally only found on Oahu's south and east (leeward) shores, C. alata has been showing up more recently on the north and windward shores. With no means of controlling their numbers, many worry that the jellyfish may spread to the rest of Hawaii. Predictions are not promising. According to Culliney, "It's only a matter of time before they get to neighbor islands."
Oww! I've been stung!
So far, no one in Hawaii has died from a C. alata sting, but it can cause nasty welts, and even breathing difficulties and dizziness in people more sensitive to the venom. So, what should you do if you happen to encounter a box jelly? Some say to use vinegar, others say meat tenderizer, and still others say to urinate on stings. Traditional remedies' are so numerous that they can be more confusing than helpful. Few of these treatments have been scientifically tested until recently, and many of the results are contradictory. What really works and what doesn't?
There are a few things on which everyone can agree. For any species of jellyfish, white vinegar poured over the wound helps to deactivate the nematocysts, preventing further stings. After being doused in vinegar, any remaining tentacles should be picked off. Finally, never rub the wound with anything, as that can discharge any nematocysts that are still on the skin.
As for other remedies, studies are not conclusive. Traditional pain relief usually calls for a cold pack, but more recent research contradicts this idea. Dr. Craig Thomas and Susan Scott, authors of All Stings Considered, published a study in the Hawaii Medical Journal in 2001 that found application of a heat pack to a jellyfish sting could provide moderate pain relief. Another study, published in 2002 in the Medical Journal of Australia, also reported that heat could reduce the lethality of venom for other box jellyfish species.
Remedies for a jellyfish sting.
Traditional treatments, including applying meat tenderizer, freshwater, alcohol, steroid cream, and even human urine to jellyfish stings, are not supported by solid evidence; some of these remedies may even be harmful in certain instances. The general rule is: If it isn't proven, don't risk it.
The invasion continues
C. alatahas become one of the more recent additions to the long list of alien species introduced into Hawaii. Whatever effects it might have on the islands' unique ecosystem is only another unknown surrounding this creature. The only things about which we can be sure are that C. alatais unwelcome, and that it is not leaving any time soon.
Author's Note
14 March 2006: It has been recently brought to my attention that Carybdea alata has not been confirmed as an invasive species to Hawaii; there are ongoing studies to determine if this box jellyfish is introduced or native. I apologize for any confusion I might have caused in using the terms "invasive" or "alien." In addition, evidence has also been presented to me to disprove the hypothesis that C. alata might have been introduced via ballast water, as ships during the late 1800's used dry ballast instead of water. --Katrina Outland
References and Suggested Reading
Predicted box jellyfish arrivals: http://www.co.honolulu.hi.us/esd/oceansafety/boxjellymainpage.htm
Carrette T, et al. (2002). Temperature effects on box jellyfish venom: a possible treatment for envenomed patients? Medical Journal of Australia. http://www.mja.com.au/public/issues/177_11_021202/car10576_fm.html
Fenner PJ and JA Williamson. (1996). Worldwide deaths and severe envenomation from jellyfish stings. The Medical Journal of Australia. 165;658.
Thomas CS and SA Scott. (1997). All Stings Considered: First Aid and Medical Treatment of Hawaii's Marine Injuries. University of Hawaii Press.
Thomas CS, Scott SA, Galanis DJ, and RS Goto. (2001). Box jellyfish (Carybdea alata) in Waikiki: their influx cycle plus the analgesic effect of hot and cold packs on their stings to swimmers at the beach: a randomized, placebo-controlled, clinical trial. Hawaii Medical Journal. 60(4);100-7.
Thomas CS, Scott SA, Galanis DJ, and RS Goto. (2001). Box jellyfish (Carybdea alata) in Waikiki. The analgesic effect of sting-aid, Adolph's meat tenderizer and fresh water on their stings: a double-blinded, randomized, placebo-controlled clinical trial. Hawaii Medical Journal. 60(8);205-7, 210.