Floating in the Sea

During the pass month, there have been reports of Blue Bottles or Portuguese Man-of-war at the Andaman coast of Thailand. In fact, these animals are just one of many venomous animals related to jellyfish. Therefore, the knowledge about these animals will help us to understand their biology and know how to first aid the patients after got stung correctly.



Jellyfish is a free-swimming animal floating in the sea. The animal consists of two parts; the umbrella and the tentacles. The umbrella can contract and relax, helping the animal to move forward. The tentacles have venomous stings called nematocysts which can pierce through other animals’ skins and release venom. Normally, the venom of jellyfish is not fetal although it can cause severe pain. In Thai, jellyfish with strong venom can be called fire jellyfish. When got stung, the skin should be washed with vinegar or sea water. Freshwater, ammonia, alcohol or urine are prohibited because they can make the pain worse.

Box Jellyfish

Box Jellyfish

Although they are not closely related, box jellyfish look very similar to normal jellyfish. The district characteristic of box jellyfish is their cube or box shaped umbrellas. Box jellyfish have well developed nervous system; they have 4 eyes. Thus, the animal can move with certain directions. Box jellyfish are one of the most venomous marine creatures; they can even kill human. The first aid procedure after got stung is similar to those normal jellyfishes.


Portuguese Man-of-war

A Portuguese man-of-war or a blue bottle is not a single animal like a jellyfish or a box jellyfish; it is actually a colony of several animals. In addition, the umbrella of a Portuguese man-of-war is floating over the surface and cannot move, acting like a sail. Thus, this animal uses wind to help dispersing. The Portuguese man-of-war has nematocysts at its tentacles like other jellyfishes. Its venom is somehow comparable with box jellyfish’s, possibly fatal to human. The larger ones found in Atlantic Ocean seem to be more dangerous than the smaller ones found in Indian and Pacific Oceans. After got stung, unlike other jellyfishes, vinegar is not preferred as it can activate uncharged nematocysts and cause even more severe pain. Sea water should be used to wash away those tentacles and nematocysts from skin.

Blue Button
By-the-wind Sailors

Blue Button and By-the-wind Sailor

Blue buttons and by-the-wind sailors are close relatives of Portuguese man-of-wars. All of them cannot move their umbrellas and use wave and wind to help dispersing. However, blue buttons and by-the-wind sailors have small tentacles which are not harmful for human. In monsoon seasons, these animals are sometimes found stranded on the beach.

In recent years, these animals have been increasing in number due to several causes, such as climate change and depletion of hunters, in particular sea turtles. Plastic bags can confuse sea turtles to misunderstand as jellyfishes. If the turtles consume those bags, their digestive tracks could be clog up, making animals eventually die. Therefore, the simplest way to keep those sea turtles population is reducing the use of plastic bags. When we say “no bag please” at a convenience store, we might just safe a person in the other corner of the world from jellyfish sting.


 Story: Yingyod Lapwong

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Princess Maha Chakri Sirindhorn Natural History Museum
Prince of Songkla University
15 Karnjanavanich Rd., Hat Yai, Songkhla 90110
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