''Obelia'' is a genus of
hydrozoans, a
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differently ...
of mainly marine and some freshwater animal
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
that have both
polyp and
medusa
In Greek mythology, Medusa (; Ancient Greek: Μέδουσα "guardian, protectress"), also called Gorgo, was one of the three monstrous Gorgons, generally described as winged human females with living venomous snakes in place of hair. Those ...
stages in their life cycle. Hydrozoa belongs to the
phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature ...
Cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that ...
, which are aquatic (mainly marine) organisms that are relatively simple in structure with a diameter around 1mm.
There are currently 120 known species, with more to be discovered.
These species are grouped into three broad categories: ''O. bidentada'', ''O. dichotoma'', and ''O. geniculata''. ''O. longissima'' was later accepted as a legitimate species, but taxonomy regarding the entire genus is debated over.
''Obelia'' is also called sea fur.
''Obelia'' has a worldwide distribution except the high-Arctic and Antarctic seas. and a stage of ''Obelia'' species are common in coastal and offshore plankton around the world.
[Cornelius, P.F.S., 1995b. North-West European thecate hydroids and their Medusae. Part 2. Synopses of the British Fauna (New Series), No 50.] ''Obelia'' are usually found no deeper than from the water's surface, growing in intertidal rock pools and at the extreme low water of spring tides.
Life cycle
The polyp colony reproduces
asexually. During this stage of life, ''Obelia'' are confined to
substrate surfaces. In mature colonies there are individual
hydranths called