Blue-ringed octopuses belong to the genus Hapalochlaena. There are several species; they are typically found in tidal pools in the Pacific Ocean from Japan to Australia.
These species all have characteristic blue and black rings or maculae, which brighten and pulsate when the octopus is alarmed. The brown patch inside the maculae also darkens.
They hunt small crustaceans like hermit crabs and shrimp, using their venom to paralyze prey. You can watch one hunting on the reef in this video.
Blue-ringed octopuses are one of the most venomous marine animals in the world. Even though they rarely grow beyond 20 centimeters in size, their venom is powerful enough to kill a person.
The venom contains a number of poisons, including a neurotoxin called tetrodotoxin, which is also found in pufferfish and cone snails, and is 10,000 times more toxic than cyanide.
Tetrodotoxin, produced by bacteria living in the octopus’ salivary glands, can cause complete body paralysis, including respiratory arrest, and hence victims may die of a heart attack.
There is no antivenine for blue-ringed octopus bites, and treatment involves applying pressure to the wound and artificial respiration when the respiratory muscles become paralyzed, often within minutes of being bitten.
In the hospital, the victim is placed on a medical ventilator until the venom has been metabolized and its effects have faded away after a number of hours.
Matthew Oldfield is a freelance photographer based in Bali, Indonesia, specializing in editorial and documentary images from both above and below the waves. He works primarily with charities, NGO’s, and other organizations working to conserve the environment, endangered species, and disappearing cultures.
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