Smithsonian Marine Station at Fort Pierce

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Phylum Cnidaria: Jellyfishes, Corals, Hydroids & Anenomes

The following is a list of common descriptive terms used in the cnidarian species reports on this site. Definitions are taken from Ruppert & Barnes (1994). Please consult this reference using the citation below for other terms not defined in this glossary. Ruppert EE & RD Barnes. 1994. Invertebrate zoology, 6th edition. Saunders College Publishing. Orlando, FL. USA. 1056 pp. 

Acrorhagus pleural acrorhagi
- cnidocyte-covered elevation on specialized sweeper tentacles or on the column of anthozoans 

Cnida pleural cnidae;
- an eversible cnidarian organelle that occurs in the cnidocyte

Cnidocil
- a short, stiff, bristle-like cilium that is borne on the cnidocyte and acts as a trigger for the cnida or nematocysts 

Coelenteron
- the body cavity and gut of cnidarians and ctenophores; gastrovascular cavity 

Column
- the stalk portion of sea anemones 

Hydromedusa pleural hydromedusae
- hydrozoan medusa 

Hydrorhiza pleural hydrorhizae
- horizontal rootlike stolon of a hydroid colony that grows over the substratum 

Mesoglea
- connective tissue layer between the epidermis and gastrodermis of cnidarians and ctenophores 

Nematocyst
- stinging cnida of cnidarians 

Ocellus pleural ocelli
- a small cluster of photoreceptors; a simple eye

Oral Disk
- area around the mouth of an anthozoan polyp which bears eight to several hundred hollow tentacles 

Pedal Disk
- in some sea anemones, a flattened disc at the aboral end of the column for attachment 

Planula pleural planulae
- a cnidarian larva that is elongated and radially symmetrical but with anterior and posterior ends 

Septum pleural septa
- a double-walled tissue partition in the radial plane of a cnidarian

Spirocyst
- cnida with a long adhesive thread that functions in capture of prey and in attachment to a substratum 

Tentacle
- evagination of the body wall surrounding the mouth which aids in the capture and ingestion of food 

Zooxanthella pleural zooxanthellae
- a golden-brown alga, usually a dinoflagellate, that is symbiotic with various marine animals, especially cnidarians 

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