Jellyfish PoisonAlmost everyone who has spent time near or in an ocean has been warned of being stung by a jellyfish. Jellyfish have been given a reputation as dangerous and often deadly animals. The exact actions of jellyfish toxins are not well understood, and the true danger presented by jellyfish is often exaggerated. This article will attempt to answer several questions about jellyfish and venom. It will discuss what toxins make up jellyfish venom and the method by which these toxins are released. The effects of jellyfish venom on the human body will be discussed, including the possible action of these toxins at the cellular level. Finally, first aid and treatments for jellyfish poisonings will be described. Background Marine creatures commonly known as jellyfish are members of the phylum Cnidaria. Of the four classes of cnidarians, jellyfish come from both the Hydrozoa and Scyphozoa classes. Most jellyfish are schphozoids, while the Portuguese man-of-war (Physalia physalis) is a hydroid. As cnidarians, jellyfish possess two types of tissue: endoderm and ectoderm, as well as a single cell layer of gelatinous mesoglea between the endoderm and ectoderm (Russell 21). Jellyfish exhibit radial symmetry and have tentacles with stinging cells known as cnidocytes. Their size varies from a few millimeters up to a bell two meters in diameter, with tentacles up to thirty-six meters long. Typically less than 5% of a jellyfish's body is made up of "solid organic material" (Halstead, Poisonous 96-97). Jellyfish have reproductive cycles involving a sessile polyp and a free-living jellyfish state. The polyp is asexual, while the jellyfish is sexual (Williamson et al. 121). P. physalis is actually made up of colonies of many small organisms. A single man-of-war contains both polyp and jellyfish stage organisms, with several types of polyps and jellyfish in a colony (Halstead, Poisonous 94-95). Jellyfish populations show seasonality in habitat choice. Most jellyfish prefer temperate, warm water. P. physalis prefers open water and moves with the wind, tide and currents. Scyphozoans are found in all seas of the world. These jellyfish prefer shallow waters such as bays and estuaries, but also inhabit the open ocean (Halstead, Poisonous 94-97). They usually live in warm or temperate waters favored by corals (Halstead, Poisonous 115). Jellyfish are most abundant in coastal areas during the hot summer months, but are present along the coast at other times of the year (Halstead, Poisonous 97). Similarly, in Australia, the greatest numbers of jellyfish are found along the coasts during the summer months of November to April, with peak numbers occurring in December.