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.
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larva that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.
The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish. It may include the extinct fossil group the Conulariida, whose affinities are uncertain and widely debated.
Aurelia aurita is a widely studied species of the genus Aurelia. All species in the genus are very similar, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus. The most common method used to identify the species consists of selecting a jellyfish from a harbour using a device, usually a drinking glass and then photographing the subject. This means that they can be released in to the harbour shortly afterwards and return to their natural habitat.
Hydrozoa are a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most living in salt 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 fresh water. Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria.
Obelia is a genus of hydrozoans, a class of mainly marine and some freshwater animal species that have both polyp and medusa stages in their life cycle. Hydrozoa belongs to the phylum Cnidaria, which are aquatic organisms that are relatively simple in structure.
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.
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, by-the-wind sailor, purple sail, little sail, or simply Velella.
Gonionemus is a genus of hydrozoans that uses adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce, or various types of algae instead of swimming. They are small and hard to see when hanging onto swaying seaweed. Nevertheless, they are capable of swimming when necessary. The bell is transparent, revealing the four orange to yellowish-tan gonads that lie along most of the length of the four radial canals. The pale yellow manubrium has four short, frilly lips. Up to 80 tentacles line the bell margin, with about an equal number of statocysts. Copepods are a favored prey.
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 sexually immature, colonial stage after having reached sexual maturity as a solitary individual. Others include the jellyfish Laodicea undulata and species of the genus Aurelia.
Trachymedusae belong to the phylum Cnidaria and the class Hydrozoa, among the 30 genera are 5 families containing around 50 species in all, the family Rhopalonematidae has the greatest diversity.
Anthoathecata, or the athecate hydroids, are an order of hydrozoans belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular group. It has also been called Gymnoblastea and, Anthomedusa,Athecata, Hydromedusa, and Stylasterina. There are about 1,200 species worldwide.
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 many-ribbed jellyfish. The species is often mixed up with some other members of the genus due to some similarities including the capability of bioluminescence.
The Medusae Fossae Formation is a large geological formation of probable volcanic origin on the planet Mars. It is named for the Medusa of Greek mythology. "Fossae" is Latin for "trenches". The formation is a collection of soft, easily eroded deposits that extends discontinuously for more than 5,000 km along the equator of Mars. Its roughly-shaped regions extend from just south of Olympus Mons to Apollinaris Patera, with a smaller additional region closer to Gale Crater.
Bougainvillia muscus is a marine invertebrate, a species of hydroid in the suborder Anthomedusae.
Aequoreidae is a family of hydrozoans. There are approximately 30 known species found in temperate and tropical marine coastal environments. Aequoreids include Aequorea victoria, the organism from which the green fluorescent protein gene was isolated.
Olindiidae is a family of hydrozoans in the order Limnomedusae. They have a polyp phase and a medusa phase. The polyps are generally small (1 mm) and solitary, but a few species are colonial. They have a varying number of tentacles and can reproduce by budding. In the largest species, the medusae can grow to 15 cm (6 in). Centripetal canals may be present or absent and the radial canals are unbranched. The gonads are beside the radial canals, except in Limnocnida, where they are on the manubrium. The fertilised eggs develop into planula larvae which become polyps. These multiply asexually or can bud off medusae. In some species, medusae are only produced when the water temperature exceeds a certain level. Most species are marine, but several can also be found in brackish water and a few, notably Craspedacusta and Limnocnida, are found in fresh water.
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.
Nemopsis bachei is a species of relatively small gelatinous zooplankton hydrozoa found in both marine and estuarine environments. This particular species was first found and described by Louis Agassiz in 1849 from samples that were taken from the coast of Massachusetts. It was also noted and described in 1857 by another name off the coast of South Carolina.
Cyanea versicolor is a species of jellyfish.
