With the main focus on great white sharks in Cape Cod waters, another dangerous animal can be easily overlooked. Though not very common here, the Portuguese Man-of-War (Physalia physalia) occasionally arrives on the Cape via the Gulf Stream. This mainly tropical species of jellyfish was first seen by English sailors traveling around Portugal. It can be found throughout the world. Like most jellyfish, the man-of-war has tentacles with stinging cells called nematocysts that paralyze its prey, such as small fish. The difference here is that these tentacles can stretch as long as fifty feet in length. A marathon swimmer might be able to avoid the floating sail of the animal at the surface of the water, but could easily come into contact with the trailing tentacles.
And that could prove to be fatal. The stinging cells are very strong and toxic. It is one of the most poisonous animals in the ocean. Large welts will appear on the skin of the victim if contact is made. Even if washed up on a beach, the animal retains its toxicity for a long time. I know someone who went into a coma after touching the tentacles of a beached man-of-war. Fortunately, he survived the ordeal.
The animal is easily seen and identified by its bluish-pink float (pneumatophore) which functions like sail and is steered by the wind. Of course the animal also travels in currents, such as the Gulf Stream, and ends up in colder waters such as Cape Cod. The float is filled with gases and can be around one foot long.
What is really fascinating about the man-of-war is that it is an example of a colonial animal, consisting of many individuals with a division of labor, yet functioning as a single animal. These individuals, or polyps, have specialized functions such as feeding, reproduction, or defense. When they feed however, the entire colony benefits. Not all animals are adversely affected by the man-of-war. Sea turtles nibble on its tentacles without any negative effects. There is also a small fish called Nomeus which is unaffected by the stinging cells. In fact Nomeus may even assist the man-of-war by attracting other fish into the trap.
Sightings of the Portuguese Man-of-War on Cape Cod are rare. Still they have been seen in recent years on several beaches, and this situation will probably occur again as surface sea temperatures continue to rise. No one really knows all the implications of climate change, but it does seem possible that more species that are normally found in tropical waters may find their way to the shoreline of Cape Cod.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.