Hydroida
Encyclopedia
Hydroida is an obsolete cnidaria
n order
which united such animals as hydras
, hydromedusae, and many marine attached hydroids
. However, the group is paraphyletic and not composed from close relatives. But for the largest part, this group makes up what today is usually considered the subclass
Leptolinae
(or Hydroidolina) which also includes the colonial jellies of the Siphonophora
which were not part of the Hydroida.
The "hydroid" cnidarians typically which grow up into large, elegantly branched forms. All the zooids of a colony are asexually
produced from one parent zooid.
Examples of "hydroids" are:
Cnidaria
Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
n order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
which united such animals as hydras
Hydra (genus)
Hydra is a genus of simple fresh-water animal possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by...
, hydromedusae, and many marine attached hydroids
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...
. However, the group is paraphyletic and not composed from close relatives. But for the largest part, this group makes up what today is usually considered the subclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Leptolinae
Leptolinae
Leptolinae are a cnidarian subclass of the Hydrozoa. They contain the bulk of the paraphyletic "Hydroida" which were one of the main groupings of the Hydrozoa in older classifications and were placed at order rank...
(or Hydroidolina) which also includes the colonial jellies of the Siphonophora
Siphonophora
Siphonophorae or Siphonophora, the siphonophores, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. They are colonial, but the colonies can superficially resemble jellyfish; although they appear to be a single organism, each specimen is actually a...
which were not part of the Hydroida.
The "hydroid" cnidarians typically which grow up into large, elegantly branched forms. All the zooids of a colony are asexually
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
produced from one parent zooid.
Examples of "hydroids" are:
- Craspedacusta sowerbyiCraspedacusta sowerbyiCraspedacusta sowerbyi is a freshwater jellyfish in the phylum Cnidaria. Since it is classified as a hydrozoan, it is one of many jellyfish that are also known as hydromedusae...
, the freshwater "jellyfish" - HydraHydra (genus)Hydra is a genus of simple fresh-water animal possessing radial symmetry. Hydras are predatory animals belonging to the phylum Cnidaria and the class Hydrozoa. They can be found in most unpolluted fresh-water ponds, lakes, and streams in the temperate and tropical regions and can be found by...
- Air fernAir fernNeptune plant or Air fern is a name given to a product that is composed of a species of marine animal called Sertularia argentea, also known as the "sea fir"....
s, novelty "plants" and aquarium ornaments. - ObeliaObeliaObelia is a genus in the class Hydrozoa, which consists of mainly marine and some freshwater animal species and have both the polyp and medusa stages in their life cycle...
- Aequorea victoriaAequorea victoriaAequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America. This species is thought to be synonymous with Aequorea aequorea of Osamu Shimomura, the discoverer of green fluorescent protein . ...
of the suborder LeptomedusaeLeptomedusaeLeptomedusae or Leptomedusa, commonly called thecate hydroids, are a cnidarian order in the subclass Leptolinae. They were formerly placed at suborder rank in the paraphyletic "Hydroida"...
, the crystal jelly- a bioluminescent jellyfish.