What Are the Predominant Body Forms of Jellyfish?

Jellyfish are creatures with a simple body design; they are not equipped with brains, blood or hearts. Only about 5 percent of the body of a jellyfish is made up of solid organic matter; the remaining 95 percent is constructed from water.

  1. Species

    • There are a large number of species of jellyfish, ranging in size and geographic dispersal. Most jellyfish are found in the majority of major oceans around the world living near the coasts in shallow waters, with a small number of species found in waters with depths reaching 12,000 feet. The jellyfish is a member of the marine species Phylum Cnidaria, made up of both mobile and stationary sea creatures. Stationary members of the species include coral and sea whips that attach themselves to hard surfaces. The jellyfish is a mobile member of the Phylum Cnidaria family that is affected by the movement of water through wind and currents.

    Body

    • The body of the jellyfish is made up of three major components: the outer layer or epidermis, the inner layer known as the gastro dermis and the middle layer between the epidermis and gastro dermis called the mesoglea, meaning middle jelly. The epidermis is the external covering of the jellyfish, while the gastro dermis is the lining for the gut of the animal. The body of the jellyfish is designed around a central axis, meaning the animal is capable of moving and reacting to stimuli from each side. Instead of being equipped with a brain, the jellyfish is equipped with a central nervous system allowing it to smell, recognize light and respond to stimuli.

    Intestine

    • A single digestive cavity of a jellyfish acts as gullet, stomach and intestine within the animal. The jellyfish is equipped with a single opening leading to and from the digestive cavity, which acts as both mouth and anus for the introduction of food and removal of waste from the body of the animal. The jellyfish's mouth and anus opening is surrounded by between four and eight oral arms that are used to transfer food held in the tentacles of the jellyfish into its mouth.

    Tentacles

    • Each species of jellyfish is equipped with tentacles ranging in size up to 100 feet in length, which are used to capture and inject poison into the bodies of sea creatures captured for food. Jellyfish hold venom in a body part called a nematocyst; there can be thousands of nematocysts on a single tentacle of a jellyfish. The nematocyst holds poisonous venom and a trigger in a coiled barb. When the tentacle of a jellyfish feels an object, it presses against the object and uncoils the barb to release the venom.