Sep 4, 2020
The name Sifonofori may be unknown to most people. It is an order of marine organisms, which belong to the phylum of the Cnidarians. These contain much better known species such as corals, jellyfish and anemones. The Siphonophores, on the other hand, are a separate order, in fact, and are made up of very particular organisms, which some define as super-individuals. In fact, in the Siphonophores there are colonies of individuals that develop in a very different and specialized way, so as to constitute, all together, a super organism. In short, it looks like a single animal, but instead it is a colony of different animals, specialized in various functions. But we will understand it better just talking about the protagonist of this article: the Portuguese caravel (Physalia physalis).
Many confuse it with a jellyfish, but it is not. This colony animal is made up of individuals of four different types. Some, the dactylozoids, develop in length and form tentacles that reach up to 50 meters in length (normally they are about 10 meters). Others, called gastrozoids, change to form the food capture and digestion apparatus. Then there are the gonozoids, that is the reproductive organs (which are also single individuals) and finally the pneumatophore which forms a sac that can be filled with gas and which therefore allows the colony to float. This “organ” is transparent but also colored blue, pink or violet.
Generally the Portuguese caravel sails on the surface, with the pneumatophore emerging from the water and acting as a sail, pushed by the wind. Below, the very long tentacles, extremely poisonous and contractile, capture, in their movement, small fish, crustaceans and planktonic animals.
The floating bag full of gas must always remain moist, so it is often deflated, so that it can sink into the water, and then swell and rise again. In this way the caravel lives its whole life, of a year or so, a Portuguese caravel carried by winds and currents. Sometimes it ends up ashore, where it’s a big problem. In fact, even after death, its tentacles retain their poisonous properties for a long time. Touching the animal, perhaps out of curiosity, therefore becomes a danger. There are toxins in the tentacles that can cause severe pain in humans and even cardiac arrest. Cases of death due to contact with the Portuguese caravel are in fact rare, but known. Each year, around 10,000 people in Australia are affected by Physalia physalis, and the smaller Physalia utriculus. The pain usually subsides and disappears after about an hour, but if the toxins reach the lymph nodes the consequences are more severe.
The predators of the caravel, such as the common turtle (Caretta caretta), have the skin too thick to fear being stung. A particular type of octopus, the Tremoctopus violaceus, is known instead to be immune to poison; not only that, sometimes it tears the tentacles off the caravel and if it serves as a defense.
This species is found in tropical and sub-tropical seas all over the world, but it can happen to have finds of many individuals even on much colder coasts (England, Ireland …). It has also been sighted in the Mediterranean, off the coast of Spain, Corsica and in 2010 also in Malta.