Animalia All you want to know about animals

Class

Hydrozoa

41 species

Hydrozoa (hydrozoans; from Ancient Greek ὕδωρ (húdōr) 'water', and ζῷον (zôion) 'animal') is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.

Some examples of hydrozoans are the freshwater jelly (Craspedacusta sowerbyi), freshwater polyps (Hydra), Obelia, Portuguese man o' war (Physalia physalis), chondrophores (Porpitidae), and pink-hearted hydroids (Tubularia).

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Portuguese man o' war

Physalia physalis

The Portuguese man o' war (Physalia physalis), also known as the man-of-war or bluebottle, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or bluebottle, which...

Hydra vulgaris

Hydra vulgaris, the fresh-water polyp, is a small freshwater hydroid with length from 10 mm to 30 mm and width about 1 mm.

Turritopsis dohrnii

Turritopsis dohrnii, also known as the immortal jellyfish, is a species of small, biologically immortal jellyfish found worldwide in temperate to tropic waters. It is one of the few known cases of animals capable of reverting completely to a...

Velella

Velella velella

Velella is a monospecific genus of hydrozoa in the Porpitidae family. Its only known species is Velella velella, a cosmopolitan free-floating hydrozoan that lives on the surface of the open ocean. It is commonly known by the names sea raft,...

Halitrephes

Halitrephes maasi

Halitrephes maasi, commonly known on the internet as the firework jellyfish, is a species of deep sea hydrozoan of the family Halicreatidae. The most recent account of the jelly has been found at a depth of 4,000–5,000 feet (1,200–1,500 m) near the...

Aequorea victoria

Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America.The species is best known as the source of aequorin (a photoprotein), and green...

Porpita porpita

Porpita porpita, or the blue button, is a marine organism consisting of a colony of hydroidsfound in the warmer, tropical and sub-tropical waters of the Pacific,Atlantic, and Indian oceans, as well as the Mediterranean Sea and eastern Arabian Sea.It...

Turritopsis nutricula

Turritopsis nutricula is a small hydrozoan that once reaching adulthood, can transfer its cells back to childhood. This adaptive trait likely evolved in order to extend the life of the individual. Several different species of the genus Turritopsis...

Craspedacusta sowerbii

Craspedacusta sowerbii or peach blossom jellyfish is a species of freshwater hydrozoan jellyfish, or hydromedusa cnidarian. Hydromedusan jellyfish differ from scyphozoan jellyfish because they have a muscular, shelf-like structure called a velum on...

Hydra viridissima

Hydra viridissima is a species of cnidarian which is commonly found in still or slow-moving freshwater in the Northern temperate zone. Hydra viridissima is commonly called green hydra due to its coloration, which is due to the symbiotic green algae...

Praya dubia

Praya dubia, the giant siphonophore, lives in the deep sea at 700 m (2,300 ft) to 1,000 m (3,300 ft) below sea level. It has been found off the coasts around the world, from Iceland in the North Atlantic to Chile in the South Pacific.Praya dubia is...

Hydra oligactis

Hydra oligactis, also known as the brown hydra, is a species of hydra found widely dispersed in the northern temperate zone. It is a common organism found in still waters from early Spring to late Autumn.It is commonly found attached to the stems of...

Bathyphysa conifera

Bathyphysa conifera, sometimes called the flying spaghetti monster, is a bathypelagic species of siphonophore in the family Rhizophysidae. It is found in the northern Atlantic Ocean and off the coast of Southwestern Africa and California.

Air fern

Sertularia argentea

The air fern (Sertularia argentea) is a species of marine animal in the family Sertulariidae. It is also known as the sea fir and Neptune plant.These so-called "ferns" are dead and dried colonies of hydrozoans, colonies of marine hydroids, class...

Marrus orthocanna

Marrus orthocanna species of pelagic siphonophore, a colonial animal composed of a complex arrangement of zooids, some of which are polyps and some medusae. Swimming independently in the mid-ocean, it lives in the Arctic and other cold, deep waters....

Millepora alcicornis

Millepora alcicornis, or sea ginger, is a species of colonial fire coral with a calcareous skeleton. It is found on shallow water coral reefs in the tropical west Atlantic Ocean. It shows a variety of different morphologies depending on its...

Flower hat jelly

Olindias formosus

The flower hat jelly (Olindias formosus) is a species of hydromedusa in the hydrozoan family Olindiidae. Although they look like a jellyfish, they actually belong in the class Hydrozoa, while true jellyfish belong in class Scyphozoa. Flower hat...

Apolemia uvaria

Apolemia uvaria, commonly known as string jellyfish, barbed wire jellyfish, and long stringy stingy thingy, is a siphonophore in the family Apolemiidae.As with all siphonophores, string jellyfish may appear to be a single organism, but each specimen...

Millepora dichotoma

Millepora dichotoma, the net fire coral, is a species of hydrozoan, consisting of a colony of polyps with a calcareous skeleton.

Gonionemus vertens

Gonionemus vertens, the clinging jellyfish, is a small species of hydrozoan in the family Olindiidae found in coastal regions throughout large parts of the Northern Hemisphere.

Pennaria disticha

Pennaria disticha, also known as the Christmas tree hydroid, is a species of athecate hydroid in the family Pennariidae. Colonies are common in the Mediterranean Sea growing on rocks close to the surface. This species has been used in research into...

Obelia longissima

Obelia longissima is a colonial species of hydrozoan in the order Leptomedusae. Its hydroid form grows as feathery stems resembling seaweed from a basal stolon. It is found in many temperate and cold seas world-wide but is absent from the tropics.

Clytia hemisphaerica

Clytia hemisphaerica is a small hydrozoan-group cnidarian, about 1 cm in diameter, that is found in the Mediterranean Sea and the North-East Atlantic Ocean. Clytia has the free-swimming jellyfish form typical of the Hydrozoa, as well as vegetatively...

Crossota millsae

Crossota millsae is a species of deep-sea hydrozoan. These small ocean-dwelling creatures are bioluminescent; the light emitted by these jellyfish serves as a defense or warning to other creatures. Males and females have both been described, and it...

Bougainvillia muscus

Bougainvillia muscus is a marine invertebrate, a species of hydroid in the suborder Anthomedusae.

Hippopodius hippopus

Hippopodius hippopus is a species of siphonophores in the family Hippopodiidae.

Bathykorus

Bathykorus bouilloni

Bathykorus bouilloni is a species of hydrozoan first described in 2010. It is a deep-sea species found in the Arctic Ocean, and appears to be common at depths below 1,000 m (3,300 ft). It is the only species in the monotypic genus Bathykorus. The...

Porpita prunella

Porpita prunella is a marine species of hydrozoan organisms within the family Porpitidae. It consists of colonies of zooids. Very little is known about this species, as there have been no confirmed sightings since its discovery in 1801 and naming by...

Crossota norvegica

Crossota norvegica is a species of hydrozoan in the family Rhopalonematidae. It is closely related to Crossota millsae and is found in the Arctic Ocean at depths below 1,000 m (3,300 ft). Crossota norvegica is also known as the deep red jellyfish....

Hydractinia echinata

Hydractinia echinata[1]

Hydractinia echinata is a colonial marine hydroid which is often found growing on dead, hermit-crabbed shells of marine gastropod species. This hydroid species is also commonly known as snail fur, a name which refers to the furry appearance that the...

Aequorea forskalea

Aequorea forskalea is a species of hydrozoan in the family Aequoreidae. Discovered in 1810 by Péron and Lesueur, A. forskalea was initially found in coastal to offshore waters of the Mediterranean Sea. This species is commonly referred to as the...

Millepora complanata

Millepora complanata, commonly known as blade fire coral, is a species of fire coral in the family Milleporidae. It is found in shallow waters in the Caribbean Sea where it is a common species. The International Union for Conservation of Nature has...

Cordylophora caspia

Cordylophora caspia (or freshwater hydroid) is a species of athecate hydroid in the family Cordylophoridae.

Turritopsis rubra

Turritopsis rubra, commonly referred to as the Crimson Jelly, is a hydrozoan within the family Oceaniidae. The species is native to New Zealand and southern Australia, typically appearing near shorelines in the summer months (December - March). The...

Clava multicornis

Clava is a monotypic genus of hydrozoans in the family Hydractiniidae. It contains only one accepted species, Clava multicornis. Other names synonymous with Clava multicornis include Clava cornea, Clava diffusa, Clava leptostyla, Clava nodosa, Clava...

Tubularia indivisa

Tubularia indivisa (oaten pipes hydroid) is a species of large hydroid discovered in 1758.

Liriope tetraphylla

Liriope is a genus of hydrozoan in the family Geryoniidae. It contains only one species, Liriope tetraphylla.

Ectopleura larynx

Ectopleura larynx, or ringed tubularia, is a hydroid in the family Tubulariidae.

Aglaophenia pluma

Aglaophenia pluma, the toothed feather hydroid or podded hydroid, is a colonial hydroid in the family Aglaopheniidae and is found worldwide. It lives from the shore to 120m under water.

Millepora boschmai

Millepora boschmai is a critically endangered species of fire coral. It was previously catalogued in two protected areas in Panama, the Coiba National Park and the Golfo de Chiriquí National Park.This species was typically found in upper, forereef...

Muggiaea atlantica

Muggiaea atlantica is a species of small hydrozoan, a siphonophore in the family Diphyidae. It is a cosmopolitan species occurring in inshore waters of many of the world's oceans, and it has colonised new areas such as the North Sea and the Adriatic...