Animal Guide: Blue-Ringed Octopus

Blue-Ringed Octopus (Hapalochlaena maculosa)

  • Type: Cephalopod
  • Family: Octopodidae
  • Habitat: Shallow marine waters and tide pools
  • Location: Common off the coast of Australia and the western Pacific Ocean
  • Diet: Crabs, fish, and mollusks
  • Average lifespan in the wild: 2 years
  • Size: 5-7.8 in (12.7-20 cm)
  • Weight: .92 oz (26g)

With its fascinating coloring and delicate curling arms, the blue-ringed octopus may be a beautiful creature, but this small cephalopod is also deadly. The blue-ringed octopus appears grey or beige with light brown patches when it is at rest, but when agitated its 50 or 60 bright blue rings appear and pulsate with color, as a warning. Inside the salivary glands of the blue-ringed octopus live colonies of bacteria that produce tetrodotoxin, the potent neurotoxin found in pufferfish and other animals. A bite from a blue-ringed octopus can completely paralyze and kill an adult human in a matter of minutes. There is no known antidote. The octopus itself is not affected at all by the toxin-an evolutionary prerequisite for the symbiotic relationship that has developed between the blue-ringed octopus and the toxin-producing bacteria.

The blue-ringed octopus is commonly found in shallow, sandy areas surrounding the coastal reefs of Australia and the western Indio-Pacific. It is most active after dark, and spends most of its day hidden in its nest. Like all octopods, the blue-ringed octopus has no skeleton and is thus very flexible and maneuverable. It can squeeze into tiny crevices and make dens in bottles, aluminum cans, or mollusk shells. The blue-ringed octopus is also known to burrow into sand or gravel to conceal itself.

The blue-ringed octopus feeds primarily on crabs and mollusks, ambushing from behind and enveloping prey with its eight arms. Using its bird-like beak, the octopus bites a hole through its victim’s shell to inject toxic saliva. With its arms and beak, the creature tears soft pieces from the prey, sucking the rest of the meat from the shell once it becomes partially digested by the saliva.

Packets of sperm rest in the grooved tip of the male’s modified third arm, called a hectocotylus. When mating, the male slips this grooved tip under the mantle and into the oviduct of the female through a gill slit, and transfers multiple sperm packets, or spermatophores. The female lays her eggs in several unattached clumps, which she carries in her arms until they hatch. After the young emerge from their eggs, the mother dies.

Did you know: The blue-ringed octopus, like all octopuses, has three hearts and blue blood.

Related Episode: Encountering Sea Monsters

Photo © Gary Bell / Picture Quest

  • bob

    it rocks!!

  • tyler

    that was the greatest article ever!!!

  • Tommy boy

    bob does size really matter?, its still cooly deadly!

  • Lane

    hello people

  • dj

    ya are spid

  • tub tub

    that is a cool

  • Jayyne

    great information for marine studies assignment, thankksss. :)

  • babygurl

    its sad that the mommy dies after giving birth!

  • ChelseyAnn

    the fact that this tiny little creature is so deadly is quite shocking, in my opinion. I would not want to step on one of those things :)

  • sophie;)

    hey i am doing i report and i hope i get an a++++ and if i dont then it will not be a happy day well bye gyes I LOVE ANIMALS!!!!

  • madasynnn

    Wow.I’m impressed. These things are really cool, actually. And I’m not a nerd or anything(no offense)but i sort of like this stuff. And i think a predator is what eats it like the predator of the shark is the killer whale. Yeah that’s it.

  • marcus dukes Md3

    This is like super cool. The facts about this cephalopod is very interesting.It can kill u witin 10 seconds. Did u kno dat?CHECK IT OUT. BYE!!!!!!!!

  • Jane

    I’ve never know about the blue ring octopus untill now!

  • will

    it is so toatly wicked:I also never knew it could kill that many people with just its spit

  • vicster

    the predator of the blue-ring octopus is the moray eel

  • Alexa

    Really helped! This is an amazing species! Great to know more information :)

  • vicster

    yeah what ashley said

  • tenchi

    Wow guys, most of these comments helped me out alot, as did the article. I also have a project due on the Blue Ringed Octopus, and I have been putting it of for a while so it helps when I can find fast sites like this. ;DD

  • billy

    thnxs for information i needed it for an assighnment

  • Meenu

    this site was pretty useful for my marine project

  • phoebe

    this octopus is pitty cool i want see one live
    and this site is really good for my report

  • patti

    i love pbs..just when i thought i saw it all with the planet earth series pbs has equal intrest…great job

  • Amy

    This is the best website I have found for the Blue Ringed Octopus! It will really help with my assighnment. Thankyou!

  • teijhan

    all of you are ignoring dont you know your wasting time

  • frank


  • mikey

    they reproduce oddly

  • kelly

    thanx this helped me a lot! :)

  • rogerbatista

    be careful…

  • Rubi

    i am so suprised!

  • Poisonous studies

    I already knew alot about the blue ringed octopus. 3rd most poisonous in the world!!!!!!!
    if any body need any info on jelly fish talk to me!!!1

    By the way great article

    ALso the box jelly fish is the 1st most poisonous animal on the face of the earth.

  • beach lover :)

    me and a few mates took the boat out to sink beers in deck chairs on a sand bar and a baby one was swimming straight at my mate, so i caught it and now have it as a pet, it so so kool! Do young eat crabs ect also? Btw great artical!

  • conor

    the people who think this thing is cool havent seen somebody thats been biten


    Wow really cool, i used it for my project thx


    o f uck

  • xXxAngelxXx

    this is so awesome!!!! im definitely using this animal for my science project XD

  • Esther (STAR) ♡

    I am going to do a presentation on blue-ringed octopuses~!! It really helped!!! THANX!!!!
    Blue-ringed octopuses look real cute, but i guess they don’t act cute!!! LOLZ~!!!!

  • mico

    it’s really interesting to know about such species of mollusca

  • Amy

    Thankss so much! So much help on my marine science project!

  • carmen

    you cant keep a blue ring octopus has pet

  • someone

    this is dope

  • swimming pool chemicals

    I am all the time a bad are you going to get constructive response from me,still progressive and informative.thanx buddy.

  • devils child


  • haha


  • Chloe Sills

    Its Octopi, plural. Not Octopuses.

  • donovan oke

    this information is very helpful because i have a research paper on it and i want to be marine-biologist

  • Idonea

    I lived in Australia, and saw one of those things. Ran like hell. Your parents kind of drill things in your head: Brightly colored swiming animals are deadly. Clear ones are deadly. Everything wants to kill you! It’s still really pretty though.


    when was this article posted online? i’m doing a school project and and need the date of publication for MLA citations.

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  • Nicci Surtees

    As a tiny girl I used to sit at the edge of tidal pools, with my feet in the water, and look at the creatures trapped for a little while where I could see them. I used to gently turn over shells with a stick, and I came close to one of these creatures without realizing, because they are normally camoflauged with dark brown colouration. As I nudged it, it turned a beautiful, pulsing colour and I quickly went up the beach to my mother, because even as a small child I had been warned carefully about the lack of an antivenom. Very pretty, though, I still remember years and years afterwards.

  • unknown

    thx alot for the article, i needed alot for a project about the blue ringed octopus!
    the article is awesome!

  • C Steele-Mills

    !4/10/2011, Blue ringed octopus caught in Narrabeen lake, NSW 2102. Potential danger to children

  • king5 chichi

    awsome nigah

  • ljone207

    so not cool

  • ljone207

    well it is fasaniting and dangerous

  • ljone207

    so cool but dont really like them

  • ljone207

    so cool but i would like to see 1 in real life.

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  • Australia’s dangerous waters | Physics Tramp

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  • David Katz

    Amazing creatures. I wonder why the mothers die when the eggs hatch?

  • Shahrier

    im doing research on this, and so far this is the site with the most information. the only thing that can top this is if their was a video of an expert showing, telling, and interacting with and about the blue ringed octopus.

  • Corey

    @conor we think it’s cool because it’s a fascinating creature, yet we still understand it’s deadliness. i’m sorry if a family/friend of your’s got bitten by this animal but when we call it “cool” we aren’t supporting their ability to harm humans. they’re just trying to protect themselves.

  • Geezus

    Wow… My son and I caught one fishing off the dock in ma wan Hong Kong. Put it in a bottle to take to school for show and tell… Glad we found out about the poisonous bit!!!

  • John Yaple

    David Katz;

    The mother is typically eaten by her young to provide them with the nourishment they need in order to survive after birth. Not being able to immediately locate a food source and being unable to defend yourself, this is the way they continue their species. It is one of the most noblest acts found in nature, but is not unique to octopi.

  • Steffalopod

    David Katz,

    The mother is not eaten by her young, though kudos on a creative explanation. They typically die of starvation as they don’t eat or take care of themselves while caring for the eggs. If you look up “GIANT PACIFIC OCTOPUS GIVES BIRTH AT SIDNEY AQUARIUM” on youtube, you can learn more.

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