''Hydranthea'' is a genus of

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 th ...

ns belonging to the family

Lovenellidae __NOTOC__ Lovenellidae is a family of hydrozoans. Their hydroids live together in upright stolonal or sympodial colonies, and their gonophores are pedunculate free-roaming medusae.Schuchert (2005) The relationships of this fairly small but d ...

. Like other Hydrozoans they are colonial. They have hydrorhiza connected to tubular

stolons In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

attaching them to other objects, like algae, kelp, rocks and crabs.

Description

Hydranthea have small smooth hydrophores placed irregularly along their hydrorhiza, of variable length - though they tend to be shorter. They have elongated polyps along their stems. Their bodies are pale gold in color, with a thin white band below the

hypostome In zoology, the hypostome can refer to structures in distinct animal groups: *Hypostome (trilobite), the ventral mouthpart plate in trilobites *Hypostome (tick) The hypostome (also called the maxilla, radula, or labium) is a calcified harpoo ...

, an appendage on their mouth. Their tentacles, of which they have 30 per

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral ...

, are long and colorless and connected to each other at their bases by an intertentacular web. They have around two to three

Nematocysts A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...

between each set of tentacles on this web. Hydranthea have oval gonophores, a reproductive structure, on their hydrorhiza. They are dieoecious, with usually only one sex, male or female, present within a single colony.

Behavior

Hydranthea are active and capable of stretching their tentacles, tending to bend to touch the substrate they are rooted in when disturbed.

Species and Classification

Species: *'' Hydranthea aloysii'' *'' Hydranthea diaphana'' *'' Hydranthea margarica'' A fourth species is in dispute, previously classified by some databases as '' Hydranthea phialiformis''. Latest databases accept the species as Hydractinia phialiformis (Antsulevich, 1983), a separate genus from Hydranthea. There was also a lack of consensus on the specific family Hydranthea belongs to. Several accounts noted it as belonging to the

Haleciidae Haleciidae is a family of hydrozoans. Their hydroid colonies emerge from a creeping hydrorhiza and usually form upright branching colonies, although some species' colonies are stolonal. Their gonophores are typically sporosacs, growing singly ...

, however recent research has moved Hydranthea to

Distribution

The species of this genus are found in oceans surrounding Europe, Japan and Australia. There have been sightings of Hydranthea margarica found in Scottish waters near Sanda Island, Argyll. This species has also been found in the Indian Ocean, south of Australia and the Seychelles, though the latter is hypothesized to potentially be a different species due to the lack of nematocysts on the samples found there. Species found in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, notably Hydranthea aloysii, have been cited with high confidence (≤95%) to be extinct, or at least extremely rare, due to their lack of sightings in recent scientific literature about the region.

References

Lovenellidae Hydrozoan genera {{Leptothecata-stub