Jellyfish
Jellyfish
Jellyfish (/ˈjɛlifɪʃ/), also known as jellies or sea jellies, are free-swimming marine animals belonging to the phylum Cnidaria. The term 'jellyfish' is derived from the Old English word 'geli' and the Middle English word 'fissh', both of which mean 'jelly' and 'fish' respectively.
Etymology
The term 'jellyfish' is a misnomer, as jellies are not classified as fish (ichthyoids). The term 'jelly' refers to the gelatinous body of the creature, while 'fish' was likely used due to its aquatic habitat.
Anatomy
Jellyfish have a simple, symmetrical body structure, consisting of a bell-shaped or umbrella-shaped body and trailing tentacles. The body of a jellyfish is composed of a soft, gelatinous substance that is easily deformed and damaged, hence their jelly-like appearance.
Life Cycle
The life cycle of a jellyfish consists of four stages: the fertilized egg, the polyp, the Ephyra, and the adult medusa stage. The adult medusa is the stage most commonly recognized as a 'jellyfish'.
Habitat and Distribution
Jellyfish are found in every ocean, from the surface to the deep sea. Some jellyfish live in freshwater. They are especially common in the warm coastal waters of the Pacific Ocean.
Diet
Jellyfish diet consists mainly of small fish, zooplankton, and sometimes other jellyfish. They catch their prey using their tentacles, which contain stinging cells called cnidocytes.
Related Terms
- Cnidaria: The phylum to which jellyfish belong.
- Polyp: The stage in the life cycle of a jellyfish following the fertilized egg.
- Ephyra: The stage in the life cycle of a jellyfish following the polyp stage.
- Cnidocyte: A type of cell found in jellyfish that is capable of ejecting a barbed thread, which can deliver a toxin to stun or kill prey.
External links
- Medical encyclopedia article on Jellyfish
- Wikipedia's article - Jellyfish
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