An Unwelcome Visitor: the Portugese man-of-war (Pa'i-malau) is coming to our shores.
Drifting with the Wind
by Keene Rees
Our strong tradewinds make the Portuguese man-of-war a frequent visitor to Waimanalo shores--both on our beaches and in the ocean offshore. This creature is a free-floating hydozoan that looks like a jellyfish. It has a transparent, gas-filled, bluish float. Attached to the underside of the float are numerous short tentacles and one very long tentacle which can reach several feet. The long tentacle carries stinging cells (nematocysts) which, when stimulated, discharge threads containing a highly irritating toxin. The man-of-war floats on the surface of the water, drifting with the wind and currents.
The man-of-war sting produces prickling, stinging, and burning sensations. Sometimes blisters occur. In cases where people have severe stings or allergic reactions, if signs of difficult or irregular breathing and/or cardiac irregularities are present, seek emergency aid immediately. This reaction is more likely to occur if stung on the head, neck, or chest.
Remove the tentacles from the skin immediately using tweezers, a stick or leaf, a towel, or sand. Do not use bare hands. Don't rub the area or apply fresh water--this will cause any untriggered stingers to fire. Apply full strength vinegar or rubbing alcohol. If pain persists, apply a paste of meat tenderizer and leave it on for 10 to 15 minutes. Old Hawaiian remedies include the direct application of green papaya or papaya leaves.
These creatures should be avoided if possible--they can be hard to see in the water. Don't touch them even when washed up on the beach. Their stinging tentacles remain toxic for hours--even days--after the organism is dead. Also, be careful when wading as waves can wrap the tentacles on ankle. People sometimes like to step on a man-of-war that has washed up on the beach causing its float to `pop.' While this may be fun, it is not a good idea because it leaves the stinging tentacles behind and makes it difficult for others to spot them. The Waikiki Aquarium suggests drawing a circle in the sand around a Portuguese man-of-war to warn people of its presence.
While humans may not be delighted with the arrival of the man-of-war, it does provide food for several other species including those little crabs known locally as "sand turtles." Thus they do have a place in the ocean's ecology. Summer would probably be nicer for us without these visitors, but being prepared for them will help.
Sources: Dangerous Marine Organisms of Hawaii by A.M. Clark and J.K. Sims
Injuries by Sea Creatures by Karl T. Pregitzer, M.D.