Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in fresh water and marine environments, including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites. Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living, jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. Cnidarians are also some of the only animals that can reproduce both sexually and asexually.
A cnidocyte is an explosive cell containing one large 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. Cnidocytes are single-use cells that need to be continuously replaced.
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.
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 Indonesia, Cambodia, Malaysia and Singapore, 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.
Chironex is a genus of box jellyfish in the family Chirodropidae. Their stings are highly venomous, and have caused human fatalities. Based on present knowledge, the genus is restricted to the central Indo-Pacific, ranging from southern Japan to northern Australia.
Medusozoa is a clade in the phylum Cnidaria, and is often considered a subphylum. It includes the classes Hydrozoa, Scyphozoa, Staurozoa and Cubozoa, and possibly the parasitic Polypodiozoa. Medusozoans are distinguished by having a medusa stage in their often complex life cycle, a medusa typically being an umbrella-shaped body with stinging tentacles around the edge. With the exception of some Hydrozoa, all are called jellyfish in their free-swimming medusa phase.
The Irukandji jellyfish are any of several similar, extremely venomous species of rare jellyfish. With a very small adult size of about a cubic centimetre, they are both the smallest and one of the most venomous jellyfish in the world. They inhabit the northern marine waters of Australia, and cost the Australian government $AUD 3 billion annually through medical costs associated with stings and tourism losses. This type of jellyfish reproduces sexually with eggs and sperm. They fire their stingers into their victim, causing a condition known in humans as Irukandji syndrome, which can be fatal and difficult to immediately recognise due to the delayed effects of the venom. 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.
Chirodropidae is a family of venomous box jellyfish within the class Cubozoa. Like other members of the order Chirodropida, they have branched pedalia, in contrast to the unbranched pedalia of box jellyfish in the order Carybdeida. Each branch houses its own individual tentacle. Nematocyst composition and type can vary among individuals within this family based on body size and life stage. Like other box jellyfish, chirodropids can be found in coastal and shallow marine areas, but they have also been found to occur at benthic depths.
Alatina alata(Reynaud, 1830), often called a sea wasp, is a species of box jellyfish found in the Pacific, Indian and Atlantic Oceans and in the Caribbean and Arabian Sea.
Malo is one of a genus of box jellies in the family Carybdeida in the Phylum Cnidaria. It has four known species, three of which were described by the Australian marine biologist Lisa-Ann Gershwin. The genus was discovered in 2005. Many of the species are known for their paralytic and deadly affect. Many species in the Malo genus are very small and hard to capture and study. Many species of Malo have been captured on the Western and Eastern cost of Australia. Malo appear to be solidarity jellies.
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.
Carybdea marsupialis is a venomous species of box jellyfish, in the small family Carybdeidae within the class Cubozoa.
Chironex yamaguchii, commonly known as ハブクラゲ and as "hub jellyfish" due to erroneous machine translations, is a species of box jellyfish found in coastal waters around Japan, on Okinawa and the Ryukyu Islands, and in the Philippines. Discovered in 2009, it is highly venomous and has been the cause of several deaths in Japanese waters.
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.
Aiptasia mutabilis, also known as the Trumpet anemone, Rock anemone, and Glass anemone, is a species of anemone typically found attached to substrates in cold waters of the Atlantic Ocean. Its unique trumpet shape gives it its common name and it can grow to be 12 cm, having a column between 3 and 6 cm in size. Like many cnidarians, they rely on nematocysts for protection and to capture prey. They are not difficult to care for, and can be kept in a home aquarium, although due to their speed of reproduction, can quickly become overpopulated.
Chironex indrasaksajiae, locally known as Mangkaprun Klong, Mangkaprun Sarhai or Sarong, is a species of box jellyfish in a coastal water of the northern and eastern Gulf of Thailand. It has been accused of causing fatalities in the area as it is a member of the genus Chironex.
Chiropsella bronzie is a species of box jellyfish. It is considered much less of a threat to humans than some of its relatives. The species was described in 2006, and is one of four species in the genus Chiropsella. Chiropsella bronzie can be found in shallow waters off the coast of Queensland, Australia.
Tamoya haplonema is a species of box jellyfish in the genus Tamoya. It is the type species of the genus and was described in 1859. The medusa possesses four tentacles, one each on an inter-radial pedal.
