Irukandji Jellyfish | Carukai barnesi & Malo kingi
This extremely minuscule but highly poisonous jellyfish inhabits the marine waters of Australia. They are typically no bigger than 1 cm3, although their four tentacles can range up to 1m in length.
The irukandji jellyfish has stingers not only on its tentacles but also on its bell, that is to say, its head. While biologists are not sure why this is, it is speculated that it is so they can act somewhat more like fish when preying upon other marine life.
Irukandji syndrome is the product of the small amount of venom that the jellyfish will inject into its prey. The symptoms include severe pains in areas: typically muscle crams in the arms, legs, as well as severe pain in the back, kidneys, a burning sensation of the skin and face, headaches, nausea, restlessness, swearing, vomiting, increase of heart rate and blood pressure. Hospitalisation is usually needed for treatment, and while it is not normally fatal, there has been two deaths so far.
(Image via vuv14.anu.edu.au)