Blue-lined octopus

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The blue-lined octopus (Hapalochlaena fasciata) is one of four species[1] of highly venomous blue-ringed octopuses. It can be found in Pacific Ocean waters that stretch all the way from Australia to Japan.[1] It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern Queensland and southern New South Wales. It is relatively small, with a mantle up to 45 millimetres (1.8 in) in length. In its relaxed state, it is a mottled yellow-brown with dark blue or black streaks covering the whole body apart from the underside of its arms, but its vibrant blue markings appear as a warning to predators when they feel threatened.[2] Along with its other closely related species, the blue-lined octopus is regarded as one of the most dangerous animals in the sea, and its venom can be fatal to humans.[1]


Blue lined octopuses tend to swim around shallow areas of coral reefs and tide pools.[3] They often hide in crevices of reefs, empty seashells, and other ocean resources they can find to conceal their identity.[3] They are diurnal creatures, hunting crabs and small fishes during the day.[3] They do not use their venom (known as tetrodotoxin) to kill their prey, but instead trap it inside their arms and pierce them with its parrot-like beak.[3]


Blue lined octopuses can be very lethal to humans. Their saliva contain a special neurotoxin called tetrodotoxin.[4] However, the species is more likely to flee and find shelter in an encounter due to their extremely shy in nature.[2] Nonetheless, there have been at least three reported human deaths from the blue lined octopus.[5] It poses most danger to those who pick up the octopus and physically touch it.[2]

If a human is to be attacked by the octopus, the injection may not be felt at first due to the small injection apparatus of the octopus.[2] After some time, symptoms of the injection include loss of feeling in the tongue/lips, muscle weakness/paralyzation, respiratory failure, unconsciousness, and eventually death.[2] The tetrodotoxin in blue lined octopuses is so lethal that it has been estimated that the venom from a single 25 gram octopus can kill about ten 75 kilogram humans.[4]


The blue lined octopuses start reproducing after a year of birth.[3] Males seek out female companions and then pounce on them. If they are successful, the female octopus will lay 50 to 100 eggs 30 days after the encounter.[3] During the 30 days, the female octopus hide her eggs under her arms and does not leave her hiding spot until the eggs hatch.[3] After laying her eggs, the female octopus dies.[3]


  1. ^ a b c Kim, Kwun, Bae, Park, Hey, Hyuck, Hanna, Jinsoon (March 2018). "First reliable record of he blue-lined octopus, Hapalochlaena fasciata (Hoyle, 1886) (Cephalopoda: Octopodidae), from Jeju Island, Korea". Journal of Asia-Pacific. 11: 21–24 – via Science Direct.CS1 maint: multiple names: authors list (link)
  2. ^ a b c d e "Blue-lined Octopus". The Australian Museum. Retrieved 21 January 2021.
  3. ^ a b c d e f g h Pacific, Aquarium of the. "Greater Blue-ringed Octopus". Retrieved 27 January 2021.
  4. ^ a b Townsend, Altvater, Thomas, Schuyler, Nette, Kathy, Jens, Michael, Qatar, Geoffrey (March 2012). "Death in the octopus' garden: fatal blue-lined octopus envenomations of adult green sea turtles". Marine Biology. 159 – via Gale Academic Offline.CS1 maint: multiple names: authors list (link)
  5. ^ Allan, Brownyn (2019). "Blue Ringed octopus". Australian Institute of Marine Science. Retrieved 27 January 2021.