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Human contact with venomous marine creatures is common, with serious harm resulting from biological toxins or mechanical injury inflicted by the stinging apparatus. Envenomation occurs from both vertebrate and invertebrate animals. Venomous invertebrates include the phylum Cnidaria (jellyfish, anemones), Mollusca (snails, octopods), and Echinodermata (sea stars, sea urchins). Sea snakes and spiny fish are the common venomous vertebrates.

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 with few randomized 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) originated in the Ediacaran period more than 750 million years ago and includes more than 9,000 species, of which approximately 100 are known to injure humans. Commonly referred to as jellyfish, they are the oldest lineage of venomous animals; however, their phylogenetic designations separate “true jellyfish” and other organisms into distinct classes (Table 116–1; Fig. 116–1A, B).

TABLE 116–1Characteristics of Common Cnidaria
FIGURE 116–1.

(A) North Atlantic Portuguese man-of-war Physalia physalis with multiple tentacles dangling in the water. The tentacles filled with venomous nematocysts ...

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