JellyFish Facts

Jellyfish Taxonomy

Jellyfish Taxonomy picture

Jellyfish Taxonomy

The science of finding, describing, classifying and naming organisms is Taxonomy. The traditional classification of similar organisms into groups was established by the Swedish Naturalist, Carolus Linnaeus, in 1758, and later this developed into more complex classifications as discoveries were made of different organisms.

There are 200 known species of jellyfish, and the different species will fall under different taxonomic families. Jellyfish is not actually a fish, but comes under the Animal Kingdom. So any marine animal which comes within the class of Scyphozoa is a jellyfish. Many textbooks refer to Scyphozoans as the true jellyfish, but generally the word jellyfish is used to denote several types of Cnidarians which have the basic mushroom shape, and which might include also Staurozoans, Hydrozoans and Cubozoans. The Stalked jellyfish will come under Staurozoans and the Box jellyfish will come under the Cubozoans. Under a broader classification of jellyfish, some people include the members of Phylum Ctenophora, which are the Comb jellies.

The anatomical structure of the jellyfish is quite unique. It does not have a solid skeleton, but has a hydrostatic skeleton. This is a gelatinous mass filled with liquid, which helps the jellyfish to move around by contracting and pulsating its bell like body. The gelatinous mass or the "jelly" is called the Mesoglea, and is surrounded by two layers of Epithelial cells, forming the top and bottom surface of its body. For digestion it has a gastrodermal lining, in its gastrovasuclar cavity, where the nutrients are absorbed. The do not have a respiratory system, and their body is oxygenated by the process of diffusion, through their thin skin.

The jellyfish does not have a brain or a central nervous system. It has a loose network of nerves called the nerve net, which is located in the epidermis. These nerves help it to detect the touch of other animals, and react accordingly. Certain jellyfish are known to have light sensitive organs called the Ocelli. These cannot form images but are able to detect light shining on the water surface, and can gauge up and down directions.

Jellyfishes do have a gender, and are either male or female. Generally they reproduce by the male and female releasing the sperm and eggs respectively into the water where they fertilize and mature. The Moon Jellies the eggs become lodged in the oral arms, where it forms a temporary brood chamber to accommodate fertilization and early development.

Initially a larval form develops from the egg, called the Planula. This settles on a hard surface and develops into a Polyp. This Polyp then begins reproducing asexually by budding. Then they go on to the Medusae stage which is the most dominant, where they eventually mature into a full jellyfish.

The lifespan of a jellyfish differs according to its species. It may be from a few hours to several months. There is one species which has known to have a life span of 30 years as well. The Turritopsis Dohrnii species of the jellyfish is considered to be effectively immortal as it is able to transform, from the Medusa to the Polyp stage, thereby escaping death.

Learn more about Jellyfish, different Jellyfish Species, general Jellyfish Information, Jellyfish Pets and Jellyfish Safety

Written by and Sudarsana Sinha.

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