Jellyfish Venom :: Jellyfish Marine Life Essays

Jellyfish Venom Almost anyone who has ever spent time near or in an ocean has been warned about being stung by jellyfish. Jellyfish have been ascribed a reputation as dangerous, often lethal animals. The exact actions of jellyfish toxins are not well understood, and the true danger presented by jellyfish is often exaggerated. This paper will attempt to answer several questions about jellyfish and venom. It will discuss what toxins make up jellyfish venom and the method in which these toxins are delivered. The effects of jellyfish venom on the human body will be discussed, including the possible action of these toxins at a cellular level. Finally, first aid and treatments for jellyfish envenomations will be described. Background The 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 tissue types: endoderm and ectoderm, in addition to a single cell layer of jelly-like mesoglea between the endoderm and the ectoderm (Russell 21). Jellyfish exhibit radial symmetry and have tentacles with stinging cells known as cnidocytes. They range in size from a few millimeters up to a bell size of two meters across, with tentacles up to thirty-six meters long. Typically less than five percent of a jellyfish’s body is "solid organic material" (Halstead, Poisonous 96-97). Jellyfish have reproductive cycles that involve a sessile polyp and a free-living medusa state. The polyp is asexual, while the medusa is sexual (Williamson et al. 121). P. physalis actually consist of colonies of many small organisms. A single Man-of-War contains both polyp and medusal stage organisms, with several different types of polyps and medusae in a colony (Halstead, Poisonous 94-95) Jellyfish populations exhibit seasonality in their choice of habitats. Most jellyfish prefer temperate and warm water. P. physalis prefer open waters and move with the wind, tide, and currents. Scyphozoas are found in all seas of the world. These jellyfish prefer shallow water such as bays and estuaries but also inhabit open ocean (Halstead, Poisonous 94-97). They usually live in the warm or temperate waters favored by coral (Halstead, Poisonous 115). Jellyfish are most abundant in coastal areas during warm summer months, but are present along the shore at other times of year (Halstead, Poisonous 97). Likewise, in Australia, the largest numbers of jellyfish are found along shores during the summer months of November through April, with peak numbers occurring in December.