Siphonophores: Strung Out

A recent article on the Scientific American website about a particular species of rare siphonophore called the Dandelion Siphonophore introduced me to these beautiful creatures.  Since then I have done some research on them and discovered some very interesting details which I am going to share with you in this article. There is a very informative website on siphonophores which I will link to at the end of the article.

There is a siphonophore among the roughly one hundred and seventy-five described species which everyone is likely familiar with but has most likely been confused with the similar jellyfish. That siphonophore is the familiar and deadly Portuguese Man O` War. What many may not be aware of is that siphonophores are not one creature but many.  Each siphonophore is composed of multiple, sometimes hundreds of individual creatures which are entirely dependent on one another for survival. Like jellyfish, siphonophores are composed of both a medusa and a polyp stage. However, unlike jellies, the siphonophore has both forms together. There are both medusa and polyp forms on each siphonophore. The polyps each produce tentacles. The tentacles are armed with stinging cells called nematocysts. These nematocysts fire when they make contact with anything, particularly the siphonophores favorite foods, particularly plankton such as krill and copepods.  The nematocysts contain a powerful neurotoxin, disabling the prey and enabling the siphonophore to capture it. Once the tentacles have captured their prey, the prey is passed the length of the siphonophore to provide nutrients to the entire creature.  Some siphonophores also produce their own light through a process called bioluminescence. They use this light to attract unsuspecting plankton to their awaiting tentacles.

Siphonophores have varying methods of locomotion. The familiar Portuguese Man O` War has an obvious above water sail, which allows the wind to push it through the water. Most siphonophores are swimmers, albeit weak ones. Others are simply drifters, floating through the waters of the deep ocean, collecting prey as they float. They are unable to resist strong currents or waves and thus are not frequently seen in coastal waters. The deepwater denizens rarely come to the surface during the day particularly those that rely on bioluminescence to attract their prey.

Siphonophores have a peculiar method of reproduction. Both the polyps and the medusa stages in the colony are descended from a single polyp. The polyp reproduced itself by a process called asexual reproduction.  This essentially amounts to the polyp either dividing itself in half or producing a tiny offshoot called a bud which will eventually break away and form a medusa.  The medusa form is the reproductive form.  After the first polyp forms, a small stem begins to form. The stem produces two areas called growth zones, which will be used to extend the stem as new polyps and medusa form.  When a siphonophore reproduces sexually, it basically broadcasts eggs or sperm into the water in the hope that they will find their opposite numbers.  Each fertilized egg will develop into a new colony. Each siphonophore has a pattern of polyps unique to the species.

Siphonophores are of interest to science for a number of reasons, the primary one being their colonial life aspect. Evolutionary scientists claim that siphonophores are evolutionary ancestors of jellyfish.  This claim, however, is specious at best. For one, siphonophores come in a vast array of shapes and body designs. This in itself would not be a problem, were it not that the different body designs are all tailored to different environments.  The Portuguese Man O` War is a prime example. It is clearly designed to use the wind for locomotion, essentially allowing the wind to push it into its food.  Further, in jellies, polyps and medusa are never found in the same stage of life. In jellies, the medusa stage is free swimming stage and the polyp is the reproductive stage.  This is the opposite of siphonophores, which reproduce using the medusa stage and use the polyp stage to reproduce.  Jellies are also rarely, if ever colonial, while siphonophores consist of dozens to hundreds of individuals in the same colony. While they share similar characteristics, such as nematocysts and tentacles, using this argument as proof of evolutionary ancestry is something akin to saying that because a car and an airplane both have wheels they are descended from the horse-drawn carriage millions of years ago.


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