Jellyfish and sea jellies are the common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.
Box jellyfish are cnidarian invertebrates distinguished by their box-like body. Some species of box jellyfish produce potent venom delivered by contact with their tentacles. Stings from some species, including Chironex fleckeri, Carukia barnesi, Malo kingi, and a few others, are extremely painful and often fatal to humans.
Aurelia aurita is a species of the family Ulmaridae. 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 Atlantic sea nettle, also called the East Coast sea nettle in the United States, is a species of jellyfish that inhabits the Atlantic coast of the United States. Historically it was confused with several Chrysaora species, resulting in incorrect reports of C. quinquecirrha from other parts of the Atlantic and other oceans. Most recently, C. chesapeakei of estuaries on the Atlantic coast of the United States, as well as the Gulf of Mexico, was only fully recognized as separate from C. quinquecirrha in 2017. It is smaller than the Pacific sea nettle, and has more variable coloration, but is typically pale, pinkish or yellowish, often with radiating more deeply colored stripes on the exumbrella, especially near the margin.
The lion's mane jellyfish, also known as the giant jellyfish, arctic red jellyfish, or the hair jelly, is one of the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. It is common in the English Channel, Irish Sea, North Sea, and in western Scandinavian waters south to Kattegat and Øresund. It may also drift into the southwestern part of the Baltic Sea. Similar jellyfish – which may be the same species – are known to inhabit seas near Australia and New Zealand. The largest recorded specimen was measured off the coast of Massachusetts in 1865 and had a bell with a diameter of 210 centimetres and tentacles around 36.6 m (120 ft) long. Lion's mane jellyfish have been observed below 42°N latitude for some time in the larger bays of the East Coast of the United States.
A maculopapular rash is a type of rash characterized by a flat, red area on the skin that is covered with small confluent bumps. It may only appear red in lighter-skinned people. The term "maculopapular" is a compound: macules are small, flat discolored spots on the surface of the skin; and papules are small, raised bumps. It is also described as erythematous, or red.
Cassiopea is a genus of true jellyfish and the only members of the family Cassiopeidae. They are found in warmer coastal regions around the world, including shallow mangrove swamps, mudflats, canals, and turtle grass flats in Florida, and the Caribbean and Micronesia. The medusa usually lives upside-down on the bottom, which has earned them the common name. These jellyfish partake in a symbiotic relationship with photosynthetic dinoflagellates and therefore, must lie upside-down in areas with sufficient light penetration to fuel their energy source. Where found, there may be numerous individuals with varying shades of white, blue, green and brown.
Seabather's eruption is an itching dermatitis caused by a hypersensitivity reaction to the immature nematocysts of larval-stage thimble jellyfish, sea anemones and other larval cnidarians. The eruption is sometimes attributed to "sea lice" or "sea ants", but sea lice (Caligidae) are crustacean parasites of fish only.
Pelagia noctiluca is a jellyfish in the family Pelagiidae and the only currently recognized species in the genus Pelagia. It is typically known in English as the mauve stinger, but other common names are purple-striped jelly, purple stinger, purple people eater, purple jellyfish, luminous jellyfish and night-light jellyfish. In Greek, pelagia means "(she) of the sea", from pelagos "sea, open sea"; in Latin noctiluca is the combining form of nox, "night"", and lux, "light"; thus, Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark (bioluminescence). It is found worldwide in tropical and warm temperate seas, although it is suspected that records outside the North Atlantic region, which includes the Mediterranean and Gulf of Mexico, represent closely related but currently unrecognized species.
Discomedusae is a subclass of jellyfish in the class Scyphozoa. It is the sister taxon of Coronamedusae. Discomedusae contains about 155 named species and there are likely to be many more as yet undescribed. Jellyfish in this subclass are much more likely to have swarming events or form blooms than those in Coronamedusae. Discomedusae consists of two orders, Rhizostomeae and Semaeostomeae.
Chrysaora hysoscella, the compass jellyfish, is a common species of jellyfish that inhabits coastal waters in temperate regions of the northeastern Atlantic Ocean, including the North Sea and Mediterranean Sea. In the past it was also recorded in the southeastern Atlantic, including South Africa, but this was caused by confusion with close relatives; C. africana, C. fulgida and an undescribed species tentatively referred to as "C. agulhensis".
Malo kingi or the common kingslayer is a species of Irukandji jellyfish. It was first described to science in 2007, and is one of four species in the genus Malo. It has one of the world's most potent venoms, even though it is no bigger than a human thumbnail. As an Irukandji, it can cause Irukandji syndrome, characterized by severe pain, vomiting, and rapid rise in blood pressure.
Lychnorhiza lucerna is a species of jellyfish in the order Rhizostomeae. It is found off the Atlantic coasts of South America.
Chiropsalmus quadrumanus, commonly known as the four-handed box jellyfish, is a species of box jellyfish found in the western Atlantic Ocean, the Gulf of Mexico and the Pacific Ocean. The sting is venomous and dangerous to humans, especially children.
Copula is a monotypic genus of box jellyfish in the family Tripedaliidae of the phylum Cnidaria. The only species in the genus is Copula sivickisi, a very small gelatinous, bell-shaped jellyfish with four tentacles that is active only at night. It is unusual among box jellyfish in having a mating ritual and internal fertilization. Its scientific name honours the Lithuanian zoologist Pranciškus Baltrus Šivickis.
Catostylus tagi is a species of jellyfish from warmer parts of the East Atlantic Ocean and since the 2000s also found in the Mediterranean Sea. It is the only member of the family Catostylidae that is found in Europe. It has collagen in its bell which is currently being researched to see if it has biomedical uses as an intercellular matrix. The species is named after the Tagus river.
The thimble jellyfish is a species of cnidarian found in the warm West Atlantic Ocean, including the Caribbean. It is a tiny jellyfish with a straight-sided, flat-topped bell. This jellyfish is the most common cause of seabather's eruption, a reaction caused by the injection of juvenile jellyfish nematocysts into human skin.
Aglantha digitale is a species of hydrozoan in the family Rhopalonematidae. It is found in the Arctic and sub-Arctic where it is one of the most common jellyfish. It is unusual in having both a slow swimming action, through pulsating its bell, and a rapid escape response.
Poralia is a genus of jellyfish in the family Ulmaridae. It is a monotypic genus containing a single species, Poralia rufescens. This jellyfish is pelagic, and is found in deep water in most of the world's oceans.
Coronamedusae is a subclass of jellyfish in the class Scyphozoa. It is the sister taxon of Discomedusae and contains about 50 named species, all included in the order Coronatae. Jellyfish in this subclass are either small medusae living in shallow marine environments, or large medusae living in the deep sea.
