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.
A cnidocyte is an explosive cell containing one giant secretory organelle called a cnidocyst that can deliver a sting to other organisms. The presence of this cell defines the phylum Cnidaria. Cnidae are used to capture prey and as a defense against predators. A cnidocyte fires a structure that contains a toxin within the cnidocyst; this is responsible for the stings delivered by a cnidarian.
The Portuguese man o' war, also known as the man-of-war, bluebottle, or blue bottle jellyfish, 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, which is found mainly in the Pacific Ocean.
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.
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 1870 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.
Irukandji syndrome is a condition that results from envenomation by certain box jellyfish. In rare instances the sting may result in cardiac arrest and death. The most common jellyfish involved is the Carukia barnesi, a species of Irukandji jellyfish. Those stung may experience severe or even excruciating pain.
Chironex fleckeri, commonly known as the Australian box jelly, and nicknamed the sea wasp, is a species of extremely venomous box jellyfish found in coastal waters from northern Australia and New Guinea to Malaysia, the Philippines and Vietnam. It has been described as "the most lethal jellyfish in the world", with at least 64 known deaths in Australia from 1884 to 2021.
The Irukanji jellyfish are any of several similar, extremely venomous species of box jellyfish. With a very small adult size of about a cubic centimetre (1 cm3), they are both the smallest and one of the most venomous jellyfish in the world. They inhabit the northern marine waters of Australia. They are able to fire their stingers into their victim, causing a condition known as Irukandji syndrome, which can be fatal. There are about 16 known species of Irukandji, of which Carukia barnesi, Malo kingi, Malo maxima, Malo filipina and Malo bella are the best-known.
Carybdea is a genus of venomous box jellyfish within the family Carybdeidae that currently consists of a total of 8 species. This genus of jellyfish are often found in warm waters around the world in waters such as the Mediterranean Sea, the Pacific Ocean, and off the coast of Africa. Their sting can cause a range of effects depending on the species. These invertebrates will go through both sexual and asexual reproduction as they transform from a polyp to medusa. Carybdea have a box-shaped bell with four tentacles and eye-like sensory structures. There are distinct physical markings that differentiate many species within the genus. While Carybdea use their venom to act as predators, they are also preyed on by turtles and various fish. They feed on plankton, invertebrates, fish, and some crustaceans.
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 some of the world's most potent venom, 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.
Carukia barnesi is an extremely venomous jellyfish found near Australia. Stings can result in Irukandji syndrome, and this species is commonly known as Irukandji jellyfish, although this name does not distinguish it from other Irukandji jellyfish such as Malo kingi.
Alatinidae is a family of box jellyfish within class Cubozoa, containing the following genera and species:
Wildlife attacks in Australia occur every year from several different native species, including snakes, spiders, freshwater and saltwater crocodiles, various sharks, cassowaries, kangaroos, stingrays and stonefish and a variety of smaller marine creatures such as bluebottles, blue-ringed octopus, cone shells and jellyfish.
Jellyfish stings in Australia can cause pain, paralysis and death for swimmers with exposed skin. Numerous venomous species of jellyfish occur in Australian waters, including the box jellyfish and Irukandji Jellyfish. Box jellyfish are believed to have caused at least 69 deaths since record keeping began in 1883. Although they are commonly mistaken for jellyfish, bluebottles are actually siphonophores.
Carukiidae is a family of box jellyfish within the Cubozoa class. Carukiidae can be easily classified by their lack of cirri clumps inside the cubozoan stomach, as well as the size and the placement of their nematocysts.
Malo maxima is a small, and extremely dangerous Irukandji Jellyfish that is known to cause Irukandji Syndrome. It is one of the four species of Malo, along with Malo bella, Malo filipina, and Malo kingi. The Malo maxima was first described in 2005 by Lisa-ann Gershwin, who also described the Malo bella and Malo kingi jellyfish along with over 200 other species of jellyfish. Malo maxima differs from other species of jellyfish in many ways but the most confusing one is that they swim more like fish than jellyfish, however the reason for this is still unknown.
Lisa-ann Gershwin, also known as Lisa Gershwin, is a biologist based in Launceston, Tasmania, who has described over 200 species of jellyfish, and written and co-authored several non-fiction books about Cnidaria including Stung! (2013) and Jellyfish – A Natural History (2016). She provides independent advice related to jellyfish worldwide to the media, online and via The Jellyfish App. She was a candidate in the 2021 Tasmanian state election running as an independent in the electorate of Clark.
Carukia shinju is a small and venomous jellyfish found off the waters of northwestern Australia. Specifically, located offshore of the coasts of Australian states including Queensland, The Northern Territory, Western Australia and South Australia.
Morbakka virulenta is a species of box jellyfish that is found in waters near the islands of Japan. The species was originally described in the genus Tamoya by Kamakichi Kishinouye in 1910. However, unlike other species of that genus, this jellyfish did not have the vertical gastric phacellae which protect the inside of the bell with nematocyst warts. As a result, it was reclassified to the genus Morbakka due to its distinctively shaped rhopaliar horns which resemble rabbit ears. Because of its painful stings, M. virulenta has been nicknamed Hikurage, which is “fire jellyfish” in Japanese.
Morbakka fenneri, also known as the Moreton Bay stinger or the fire jelly, is a small box jellyfish found in the waters of Australia and Thailand. It has a transparent bell shape with four mauve colored tentacles that are each 50cm long.
