Centra with flat ends are acoelous, like those in mammals. These flat ends of the centra are especially good at supporting and distributing compressive forces. Amphicoelous vertebra have centra with both ends concave. This shape is common in fish, where most motion is limited. Amphicoelous centra often are integrated with a full notochord. Procoelous vertebrae are anteriorly concave and posteriorly convex. They are found in frogs and modern reptiles. Opisthocoelous vertebrae are the opposite, possessing anterior convexity and posterior concavity. They are found in salamanders, and in some non-avian dinosaurs. Heterocoelous vertebrae have saddle-shaped articular surfaces. This type of configuration is seen in turtles that retract their necks, and birds, because it permits extensive lateral and vertical flexion motion without stretching the nerve cord too extensively or wringing it about its long axis. In horses, the Arabian (breed) can have one less vertebrae and pair of ribs. This anomaly disappears in foals that are the product of an Arabian and another breed of horse. Regional vertebrae
Vertebrae are defined by the regions of the vertebral column that they occur in, as in humans. Cervical vertebrae are those in the neck area. With the exception of the two sloth genera (Choloepus and Bradypus) and the manatee genus, (Trichechus), all mammals have seven cervical vertebrae. In other vertebrates, the number of cervical vertebrae can range from a single vertebra in amphibians to as many as 25 in swans or 76 in the extinct plesiosaur Elasmosaurus.
Some preliminary laboratory experiments using the venom extracted from Malo maxima (the Broome Irukandji) on rat cardiovascular tissue in vitro has suggested that magnesium does in fact block many of the actions of this venom. Epidemiology
Reports of Irukandji syndrome have come from Australia, the United States (Hawaii and Florida), the French Antilles, Bonaire, the Caribbean, Timor Leste and Papua New Guinea. Cubozoan species other than Carukia barnesi are presumed to be responsible for envenomations outside Australia. History
In 1964 Jack Barnes confirmed the cause of the syndrome was a sting from a small box jellyfish: the Irukandji jellyfish, which can fire venom-filled stingers out of its body and into passing victims. To prove that the jellyfish was the cause of the syndrome, he captured one and deliberately stung himself, his 9-year-old son and a local lifeguard, then observed the resulting symptoms. Other cubozoans possibly can cause Irukandji syndrome; those positively identified include Carukia barnesi, Alatina mordens, Alatina alata, Malo maxima, Malo kingi, Carybdea xaymacana, Keesingia gigas, an as-yet unnamed "fire jelly", and another unnamed species. Culture and society
A 2005 Discovery Channel program, Killer Jellyfish, portrayed the severity of the pain from an Irukandji jellyfish sting when two Australian researchers (Jamie Seymour and Teresa Carrette) were stung. Another program aired on the Discovery Channel, Stings, Fangs and Spines, featured a 20-minute spot on Irukandji syndrome.