Jellyfish

Information about Jellyfish:

Jellyfish – also called sea jellies or simply jellies – are free-swimming animals and members of the phylum Cnidaria, of which there are several hundreds of species. They are found in every ocean on earth in both freshwater and saltwater. They range in size from less than 1/4 inch to several yards long. Most jellyfish do not have a central nervous system or brains and instead use a system called a “nerve net” which is a loose series of nerves that detect various stimuli, including detecting prey and the touch of another animal which they can then react to. Also, they also do not have a respiratory system since their skin is thin enough that the body is oxygenated by diffusion.

Most jellyfish have no eyes, although they can detect light through sensitive organs called ocelli. Some species, such as the box jellyfish do have multiple eyes, including some that can detect color. They are mostly at the mercy of the ocean’s tides, but can move to a degree using their characteristic pulsing of their domes. Jellyfish reproduce both sexually and asexually, having a complex series of stages of life .

Jellyfish are predated upon by few animals, sea turtles and humans being some of the few that will eat them. They are known for their painful and sometimes fatal stings to humans, but as they have no brain this only can happen when they are accidentally encountered in the ocean.