There are over 750 species of cephalopods found throughout the oceans worldwide. Cephalopods are members of the phylum mollusca and include cuttlefish, squid, octopuses, and the nautilus. Several species of cephalopods are known or thought to be venomous, but only the blue-ringed octopus, genus Hapalochlaena, poses a significant threat to humans.
There are four known species of blue-ringed octopus. All are small; none exceed a few inches in size. The blue-ringed octopus is found in tide pools and shallow reefs across a wide area of the Indo-Pacific ranging from Japan to Australia. The blue-ringed octopus is generally not aggressive and is relatively nondescript when left in peace. When threatened, however, the animal will flash or pulsate with striking iridescent blue rings. Bites occur when the animal is disturbed or inadvertently handled. It may be found hiding in old bottles or shells in tidal pools and in this way poses a hazard to collectors. Like other cephalopods, the blue-ringed octopus has a beak that can be powerful enough to penetrate a wet suit. Some bites may be relatively painless.
Blue-Ringed Octopus. The beautiful but highly venomous blue-ringed octopus. (Photo contributor: Russell C. Gilbert, MD.)
Blue-Ringed Octopus. The blue-ringed octopus demonstrates its iridescent blue colorations, seen when the animal is threatened. (Photo contributor: Kevin J. Knoop, MD, MS.)
Blue-ringed octopus venom has several identified components. The most powerful component of the venom, tetrodotoxin, is a potent sodium channel blocker that is identical to the toxin found in pufferfish. Once the victim is bitten, symptoms may develop within 10 minutes and include perioral paresthesias, facial weakness, nausea, and vomiting. In some patients, especially children, hypotension may develop. As symptoms progress, flaccid paralysis and respiratory arrest may result.
Management and Disposition
Treatment for a blue-ringed octopus bite is entirely supportive, as no antivenin currently exists. The patient almost always has a normal sensorium unless profoundly hypoxic or hypercarbic. Primary management of severe envenomation includes management of hypotension and prolonged ventilatory support until the toxin can be degraded and excreted.
No antivenin exists for a blue-ringed octopus envenomation.
The victim’s mental status is usually normal. The victim may be fully conscious despite being paralyzed and apneic.