Indo-Pacific Portuguese Man o’ War (Blue Bottle)

Physalia utriculus
Image by Live Beach Smart.

The blue bottle is named after its colour and shape.

Although commonly mistaken for a jellyfish, the man o’ war is not a jellyfish at all! It is not even a single organism. It is a colony of four minute zooids. These four zooids are highly specialized and perform different functions. They cannot live independently, as they only serve one single function, but together they can function as well as a unified organism.

One of the four zooids performs the function of an air bladder. It allows the blue bottle to float. It may be 9 to 30 centimeters in length and may extend as much as 15 centimeters above the surface of the water. In the event that the blue bottle is being attacked from the surface of the water, this air bladder is capable of deflating, allowing the blue bottle to sink under the water and escape the attack.

Below the bladder of the blue bottle are its tentacles. They are an average of one meter in length, but under certain conditions are known to grow as long as 50 meters. Each of these tentacles is lined with numerous nematocysts that contain a highly toxic venom. When the tentacles come in contact with a prey, the nematocysts are activated, and the toxin is infected into the flesh of the prey. It is sufficient to kill small prey like shrimp and young fish. The tentacles then help transport the food towards the digestive polyps, the gastrozooids – another type of polyp that digests the food with powerful enzymes.

It feeds on small fish and other small creatures. They typically envelope their prey with their tentacles, the poison is released and paralyzes its prey for consumption. These venom filled tentacles also protects the blue bottle from large predators. The toxins are strong enough to paralyze large fish, if not kill it, and enable a getaway. When looked at under a microscope their tentacles look like a string of barbed hooks which explains its ability to attach.

When the blue bottle comes in contact with the human body, they react in exact same way as they would when faced with danger, so they sting us. Blue bottle stings are known to be extremely painful. The sting can cause an extremely painful rash which doesn’t subside for at least an hour after the sting. Additionally, if a person has received multiple stings, they may be at risk of very severe pain and will require immediate medical attention. When stung, the best treatment is washing without touching the tentacles – when rubbed the tentacles release more poison!