Hydroidolina
subclass of cnidarians
Hydroidolina is a subclass of Hydrozoa and makes up 90% of the class. Controversy surrounds who the sister groups of Hydroidolina are, but research has shown that three orders remain consistent as direct relatives: Siphonophorae, Anthoathecata, and Leptothecata.
Description and background
The phylum Cnidaria contains two clades: Anthozoa and Medusozoa. There are around 3800 species within the clade Medusozoa and it consists of Cubozoans, Scyphozoans, and Hydrozoans.
Hydroidolina are small predatory animals, ranging in 8-30 millimeters in size, exhibiting radial symmetry and are diploblastic (developed from two embryonic layers: ectoderm and endoderm).
The classification below is based on the World Register of Marine Species:
Subclass Hydroidolina
Order Anthoathecata
Order Leptothecata
Order Siphonophorae
Distribution
Hydroidolina are commonly found in a variety of marine environments across the world such as deepwater caves or brackish and fresh shallow waters, and can exist as solitary or colonial. Benthic polyps can be found on a variety of hard substrates, including both natural and artificial surfaces. Many of them live on other organisms such as fish, tunicates, algae, and crustaceans. Furthermore, they prefer not to settle on sand or similarly textured surfaces unless fauna or flora is present.
Because Hydroidomedusian polyps often settle on other organisms, they are also subject to partake in symbiotic relationships.
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This entry incorporates text from “Hydroidolina” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.