Jellyfish; Portuguese Man-of-War

Jellyfish and Portuguese Man-of-War

Hawaiian Names: Pololia and Pa‘imalau

Jellyfish are found in all of the world’s oceans, from the polar seas to the tropics. 

In a reaction that is the fastest explosive event known among living things, the nematocysts on the tentacles of the box jellyfish fire their venom within microseconds of contact. 

Even when the jellyfish is dead on the beach, the nematocyst fires on contact, so don’t touch!

[Illustration: Jellyfish]


Box jellyfish have a stingier sting than Portuguese man-of-war.  Man-of-war are blown in by trade winds, and the air bladder of the man-of-war keeps it afloat on the surface of the water.  In Hawaiian waters, most stings from man-of-war occur on the windward sides of the Hawaiian Islands.

The box jellyfish is self-propelling, unlike the Portuguese man-of-war, which is at the whim of the winds and currents.  Most box jellyfish stings occur along south-facing shores, including O‘ahu’s Waikīkī, Ala Moana and along the Wai‘anae Coast. 

On June 23, 2003, jellyfish stung hundreds of swimmers and beachgoers along O‘ahu’s southern shores, where an estimated 2,700 box jellyfish washed up on the beaches. 

Lifeguards treated at least 330 individuals for stings.  Two people suffered severe allergic reactions to the stings, and had to go to a hospital for additional treatment.  The following day, June 24, about 100 people were treated for stings and about 500 jellyfish washed ashore.

Following are brief descriptions of the box jellyfish and Portuguese man-of-war.


Winged Box Jellyfish

Hawaiian Name: Pololia

Family: Carybdeidae

Indigenous: Warm oceans worldwide.

The box jellyfish (Carybdea alata) has a nearly invisible cube-like body (bell) about 2 inches (5 cm) wide by 3 inches (7.5 cm) long on each side with four pink tentacles trailing up to 2 feet (61 cm) behind. 

Box jellyfish spend most of their time feeding on plankton from 10 to 60 feet (3 to 18 m)  below the surface, off leeward shores of the Hawaiian Islands.  This is also the ocean area commonly explored by divers, which is why they sometimes get stung by the jellyfish.

Box jellyfish usually arrive near shore on south facing beaches, particularly on O‘ahu, about seven to ten days after a full moon.  The jellyfish swim about 2 miles per hour (3.2 km./hr) along the shoreline mostly between midnight and 4 a.m.  Thousands may wash up on the beach in a single night.

Though relatively little is known about box jellyfish arrival patterns, researchers theorize that the arrival of the jellyfish may be timed just perfect for them to feed on another organism that spawns during the full moon.

One location jellyfish go to spawn is the sheltered waters at the eastern (Diamond Head) end of Ala Moana Beach on O‘ahu.  Other areas where box jellyfish sometimes are a problem include Waikīkī Beach, Hanauma Bay, Mākaha Surfing Beach and Pōka‘i Bay. 

Jellyfish may be attracted by the lights of populated areas.  If jellyfish become beached and die, they are often eaten by sand crabs.


Jellyfish Reproduction

Jellyfish reproduction differs in different species, but in some species the females release young in the form of planulae that attach to the ocean bottom and develop into the polyp stage. 

The polyp goes through a process called strobilation, and little jellyfish bud off the main polyp.  These tiny jellyfish then develop into the adult medusae, which are often bell-shaped with trailing tentacles.



The nematocyst of the box jellyfish has fishhook-like spines that grab on so venom may be injected.  The stings can cause skin rashes and a burning sensation that usually lessens within in less than an hour, but sometimes may persist longer. 

Severe cases may cause breathing difficulties and/or cramps, and may require emergency medical treatment.  Some cases have lasted up to 10 months.

Researchers are still investigating the biochemical components of the jellyfish venom in an attempt to design clinical treatments to inactivate the venom.  If a sting produces a severe reaction, always seek emergency medical treatment. 


Portuguese Man-of-War (Physalia physalis)

Hawaiian Name: Pa‘imalau

Family: Physaliidae

Indigenous: Warm oceans worldwide.

Unlike the box jellyfish, the Portuguese man-of-war is a colonial hydroid.  The Portuguese man-of-war has a helmet-shaped body sac about 1½ inches (3.8 cm) long, with long trailing blue tentacles, which are poisonous. 

A strange half-invisible creature, the man-of-war’s translucent, bluish-purple body sac makes it difficult to see in the water. 

Like the box jellyfish, the tentacles of the Portuguese man-of-war may also sting even when the animal is dead on the beach (so be careful).  However, the tentacles of the man-of-war likely won’t penetrate human skin, unlike the box jellyfish tentacles, which embed a hook into the skin as the nematocyst fires its venom.


“What if I'm Stung?!”

Be cautious if there are jellyfish or man-of-war in the area where you are swimming.  Talk to local lifeguards to find out about lunar and tidal patterns that bring jellyfish near to the beach. 

If a jellyfish stings you, you should get to shore and remain calm.  Remember, no one has died from jellyfish or man-of-war stings in the Hawaiian Islands.  Stings may hurt, but you will almost certainly be totally fine, so just stay calm (and try to endure the stinging pain).

Man-of-war stings usually just cause a redness and a stinging sensation that goes away in less than an hour.  Box jellyfish stings, however, may cause red welts and more severe pain lasting up to eight hours. 

While small stings may simply be annoying, the tentacles of jellyfish may (for some people more than others) produce excruciating pain and rashes that last for days, or in some cases weeks or even months.

If you get stung, the first thing to remember is to stay calm.  Remove the tentacles from your skin, perhaps by using a credit card or some similar thin, rigid object to scrape them off.  The nematocysts are on all sides of the tentacles, so do not use your hands and do not rub the area. 

Pouring vinegar on any remaining tentacles may provide temporary relief, but it is recommended that you do not apply meat tenderizer, urine, or other remedies that in the past have sometimes been advocated, but may be potentially harmful.

Multiple stings may cause some people to become light-headed and/or disoriented, as well as to have difficulty breathing.  Other symptoms of more extreme reactions include chills, fever, abdominal pain, and vomiting. 

If you get stung severely (this is relatively rare), or have a particularly bad reaction, you could go into anaphylactic shock, in which case you should immediately seek emergency medical care. 

Remember, if the reaction is extreme, medical attention should be sought immediately, especially if the victim has any trouble breathing or has heart palpitations or muscle cramps. 

If you see this happening to someone, you should first call 9-1-1.  Then cover the person with a blanket to conserve body heat, and keep their head tilted back and airways clear.  Again, such extreme reactions to jellyfish stings are quite rare around the Hawaiian Islands.


Other Jellyfish Species

The jellyfish in Hawaiian waters are relatively tame compared to some jellyfish species living in places other than the Hawaiian Islands.  Perhaps the most irksome of all invertebrates is the Australian box jellyfish, considered the most venomous animal on Earth. 

With a body the size of a basketball, the Australian box jellyfish has 60 tentacles, each up to 15 feet (4.6 m) long, and together these tentacles contain enough venom to kill 65 adults.  The Australian box jellyfish is the only animal whose poison can kill a person in less than four minutes!

[Photograph: Jellyfish]