AskDefine | Define hydroid

Dictionary Definition

hydroid n : colonial coelenterates having the polyp phase dominant [syn: hydrozoan]

User Contributed Dictionary



  1. Any of many colonial coelenterates that exist mainly as a polyp; a hydrozoan


  1. Of or pertaining to such creatures

Extensive Definition

Hydroid may refer to:

Marine Biology

Hydroids are coral-like animals living in Antarctic seas (Ross sea, etc.).


In mosses, hydroids are water conducting tissues analogous to tracheids. However, they lack any pitting or surface texture.
Hydroids have been found in some Rhynie chert plants, including Aglaophyton, where they were initially mistaken for xylem vessels.

See also

  • Leptoid, a related sucrose-transporting vessel analogous the phloem of vascular plants


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