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Human contact with venomous marine creatures is common and may result in serious harm from biological toxins or mechanical injury inflicted by the stinging apparatus. Significant morbidity results from envenomation by spiny fish, cone snails, octopi, sea snakes, and several species of jellyfish. Despite advances in basic science research regarding the biochemical nature of marine toxins and their mechanisms of action, our knowledge of the pathophysiology related to clinical syndromes in humans and the optimal therapies for human envenomation remain limited. Evidence for effective treatment is primarily derived from in vitro and in vivo animal research without the benefit of controlled human trials. However, current research in toxinology coupled with clinical observations allows the development of cogent treatment guidelines for victims of marine envenomation.



The phylum Cnidaria (formerly Coelenterata) includes more than 9000 species, of which approximately 100 are known to injure humans. They are commonly referred to as jellyfish; however, their phylogenetic designations separate “true jellyfish” and other organisms into distinct classes (Table 119–1; Fig. 119–1A). All species possess microscopic cnidae (the Greek knide means nettle), which are highly specialized organelles consisting of an encapsulated hollow barbed thread bathed in venom. Thousands of these stinging organelles, called nematocysts (or cnidoblasts), are distributed along tentacles. A trigger mechanism called a cnidocil regulates nematocyst discharge. Pressure from contact with a victim’s skin, or chemical triggers such as osmotic change, stimulates discharge of the thread and toxin from its casing. Penetration of flesh leads to intradermal venom delivery. Nematocysts of most Cnidaria are incapable of penetrating human skin, rendering them harmless. Cnidaria causing human envenomation, such as the box jellyfish, discharge threads capable of penetrating into the papillary dermis.136

TABLE 119–1.Characteristics of Common Cnidaria

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