Octopus Envenomation

Octopus Envenomation

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Octopuses, which are organisms of the class Cephalopoda in the phylum Mollusca, are generally harmless and unlikely to be aggressive unless provoked.

Their bites are rarely life threatening, except for the bite of the greater blue-ringed octopus, Hapalochlaena lunulata and the southern blue-ringed octopus (also known as the Australian spotted octopus) Hapalochlaena maculosa, which are found in coastal waters and tide pools around Australia and other Western Pacific tidal pools. [1, 2] A third species, the blue-lined octopus Hapalochlaena fasciata, has also been described. These octopuses grow up to 20 cm in length with tentacles extended. They are normally light-colored with dark brown bands and blue rings or patches. When disturbed, their bodies darken, and the blue circles turn iridescent blue. Their venom can be released into the water to paralyze their prey, but its effects on humans primarily occur by injection of the venom upon biting. [3, 4, 5, 6, 7, 8, 9]

The blue-ringed octopus is shown below.

See Deadly Sea Envenomations, a Critical Images slideshow, to help make an accurate diagnosis.

There are many fractions in the venom secreted from the salivary glands of the blue-ringed octopus, one of which is identical to tetrodotoxin. This substance has also been found in multiple other tissues in H lunulata and H fasciata through fluorescent light microscopy. [10] Tetrodotoxin blocks voltage-gated fast sodium channel conduction, blocking peripheral nerve conduction, which can lead to paralysis and death from respiratory failure. [11] Nerve conduction studies in tetrodotoxin-poisoned (puffer fish) [12] persons have demonstrated reduced motor and sensory conduction velocities consistent with inhibition of sodium currents at the node of Ranvier. [13, 14]  Reported central nervous system effects of tetrodotoxin in humans have included nausea and emesis, miosis, diabetes insipidus, and depressed cortical activity.

Other fractions of the venom include 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine. [15]

Envenomations usually occur when an individual picks up a blue-ringed octopus or accidentally steps on one.

United States

The blue-ringed octopus does not naturally dwell in the coastal waters of the United States.


Rare cases of octopus envenomation occur in the Indo-Pacific region.

Individuals bitten by a blue-ringed octopus would have to be old enough and mobile enough to be able to walk or swim in the tide pools and coastal waters of Australia.

The prognosis for octopus envenomation is generally excellent, unless significant hypoxia has occurred. Patients should be warned that anaphylactic reactions may result in ongoing symptoms (eg, joint pains, effusions) for up to several weeks.

Mortality is rare. Full recovery is expected when appropriate measures are undertaken.

Individuals in Australian coastal waters must be educated to take care where they step in tide pools and not to pick up an octopus. [16]

For patient education resources, visit the First Aid and Injuries Center. Also, see the patient education article Stingray Injury.

Walker DG. Survival after severe envenomation by the blue-ringed octopus (Hapalochlaena maculosa). Med J Aust. 1983 Dec 10-24. 2(12):663-5. [Medline].

Flachsenberger WA. Respiratory failure and lethal hypotension due to blue-ringed octopus and tetrodotoxin envenomation observed and counteracted in animal models. J Toxicol Clin Toxicol. 1986-87. 24(6):485-502. [Medline].

Kizer KW. Marine envenomations. J Toxicol Clin Toxicol. 1983-84. 21(4-5):527-55. [Medline].

Auerbach PS. Marine envenomations. N Engl J Med. 1991 Aug 15. 325(7):486-93. [Medline].

McGoldrick J, Marx JA. Marine envenomations. Part 2: Invertebrates. J Emerg Med. 1992 Jan-Feb. 10(1):71-7. [Medline].

Nimorakiotakis B, Winkel KD. Marine envenomations. Part 2–Other marine envenomations. Aust Fam Physician. 2003 Dec. 32(12):975-9. [Medline].

Fernandez I, Valladolid G, Varon J, Sternbach G. Encounters with venomous sea-life. J Emerg Med. 2011 Jan. 40(1):103-12. [Medline].

Balhara KS, Stolbach A. Marine envenomations. Emerg Med Clin North Am. 2014 Feb. 32(1):223-43. [Medline].

Hornbeak KB, Auerbach PS. Marine Envenomation. Emerg Med Clin North Am. 2017 May. 35 (2):321-337. [Medline].

Williams BL, Stark MR, Caldwell RL. Microdistribution of tetrodotoxin in two species of blue-ringed octopuses (Hapalochlaena lunulata and Hapalochlaena fasciata) detected by fluorescent immunolabeling. Toxicon. 2012 Dec 1. 60(7):1307-13. [Medline].

Lorentz MN, Stokes AN, Rößler DC, Lötters S. Tetrodotoxin. Curr Biol. 2016 Oct 10. 26 (19):R870-R872. [Medline].

Kosker AR, Özogul F, Durmus M, Ucar Y, Ayas D, Regenstein JM, et al. Tetrodotoxin levels in pufferfish (Lagocephalus sceleratus) caught in the Northeastern Mediterranean Sea. Food Chem. 2016 Nov 1. 210:332-7. [Medline].

Oda K, Araki K, Totoki T, et al. Nerve conduction study of human tetrodotoxication. Neurology. 1989 May. 39(5):743-5. [Medline].

Pratheepa V, Vasconcelos V. Binding and Pharmacokinetics of the Sodium Channel Blocking Toxins (Saxitoxin and the Tetrodotoxins). Mini Rev Med Chem. 2016 Jul 28. [Medline].

Watters MR, Stommel EW. Marine Neurotoxins: Envenomations and Contact Toxins. Curr Treat Options Neurol. 2004 Mar. 6(2):115-123. [Medline].

Cavazzoni E, Lister B, Sargent P, Schibler A. Blue-ringed octopus (Hapalochlaena sp.) envenomation of a 4-year-old boy: a case report. Clin Toxicol (Phila). 2008 Sep. 46 (8):760-1. [Medline].

Chang FCT, Spriggs DL, Benton BJ, et al. 4-Aminopyridine reverses saxitoxin (STX)- and tetrodotoxin (TTX)- induced cardiorespiratory depression in chronically instrumented guinea pigs. Fundam Appl Toxicol. 1997 Jul. 38(1):75-88. [Medline].

Jon Mark Hirshon, MD, MPH, PhD Professor, Department of Emergency Medicine, University of Maryland School of Medicine

Jon Mark Hirshon, MD, MPH, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Public Health Association, Society for Academic Emergency Medicine

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Pfizer.

John T VanDeVoort, PharmD Regional Director of Pharmacy, Sacred Heart and St Joseph’s Hospitals

John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists

Disclosure: Nothing to disclose.

James Steven Walker, DO, MS Clinical Professor of Surgery, Department of Surgery, University of Oklahoma College of Medicine

James Steven Walker, DO, MS is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Osteopathic Emergency Physicians, American Osteopathic Association

Disclosure: Nothing to disclose.

Joe Alcock, MD, MS Associate Professor, Department of Emergency Medicine, University of New Mexico Health Sciences Center

Joe Alcock, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Dana A Stearns, MD Assistant Director of Undergraduate Education, Department of Emergency Medicine, Massachusetts General Hospital; Associate Director, Undergraduate Clerkship in Surgery, Massachusetts General Hospital/Harvard Medical School; Assistant Professor of Surgery, Harvard Medical School

Dana A Stearns, MD is a member of the following medical societies: American College of Emergency Physicians

Disclosure: Nothing to disclose.

Octopus Envenomation

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