Cnidaria (silent c - pronounced // from New Latin cnida, fr. Gk κνιδη "nettle") is a phylum containing some 11000 species of relatively simple animals found exclusively in aquatic, mostly marine, environments. Cnidarians get their name from cnidocytes, which are specialized cells that carry stinging organelles. The corals, which are important reef-builders, belong here, as do the familiar sea anemones, jellyfish, sea pens, sea pansies and sea wasps. The names Coelenterata and Coelentera were formerly applied to the group, but as those names included the Ctenophores (comb jellies), they have been abandoned. Cnidarians are highly evident in the fossil records, having first appeared in the Precambrian era.

The basic body shape of a cnidarian consists of a sac with a gastrovascular cavity, with a single opening that functions as both mouth and anus. It has radial symmetry, meaning that whichever way it is cut along its central axis, the resulting halves would always be mirror images of each other. Their movement is coordinated by a decentralized nerve net and simple receptors. Several free-swimming Cubozoa and Scyphozoa possess rhopalia, complex sensory structures that can include image-forming eyes with lenses and retinas ^*, and a gravity-sensing statolith comparable in function to the otolith of the vertebrate inner ear. Tentacles surrounding the mouth contain nematocysts, specialized stinging cells, which they use to catch prey and defend themselves from predators. The ability to sting is what gives cnidarians their name.

There are four main classes of Cnidaria:

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@gehenna27 Cnidaria & Ctenophora. (:
andrewkew (Andrew Kew) Thu, 05 Nov 2009 11:53:57 -0000
@gehenna27 Cnidaria & Ctenophora. (:
There's nothing cute about these animals: Cnidaria, Nematoda, Athropoda, Platyhelminthes, Annelida & Chordata.
Sternenfee (Sunje) Tue, 03 Nov 2009 23:17:15 -0000
There's nothing cute about these animals: Cnidaria, Nematoda, Athropoda, Platyhelminthes, Annelida & Chordata.
Sounded like an untreatable disease RT @MrsBoo2u: Cnidaria. Scypohozoa anthozoa hydrozoa polyps medusa didnt know sponges were complicated
CrownMajesty (♕¢яσωиṃαנєѕтÿ ツ ) Tue, 03 Nov 2009 16:48:10 -0000
Sounded like an untreatable disease RT @MrsBoo2u: Cnidaria. Scypohozoa anthozoa hydrozoa polyps medusa didnt know sponges were complicated
Cnidaria. Scypohozoa anthozoa hydrozoa polyps medusa gastrovascularcavities didnt know sponges were complicated
MrsBoo2u (Boss Lady ) Tue, 03 Nov 2009 16:46:15 -0000
Cnidaria. Scypohozoa anthozoa hydrozoa polyps medusa gastrovascularcavities didnt know sponges were complicated
@LuisaOliveira RECEBI TUDO. mas meu celular morreu lá. foi FODA HAHAHA sou cnidária
ju182 (Júlia ) Mon, 02 Nov 2009 23:35:40 -0000
@LuisaOliveira RECEBI TUDO. mas meu celular morreu lá. foi FODA HAHAHA sou cnidária
@jehvicente Amigaaaaaaaaaaaaan Cnidária. tenho tanto pra te contar! hahaha
LuisaOliveira (Lu Oliveira) Thu, 29 Oct 2009 14:11:15 -0000
@jehvicente Amigaaaaaaaaaaaaan Cnidária. tenho tanto pra te contar! hahaha

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