Blue-ringed Octopus: Profile and Information

Blue-ringed Octopus

The blue-ringed octopuses are four highly venomous species of octopuses comprising the genus Hapalochlaena, that live in coral reefs and tide pools in the Indian and Pacific Oceans, from Japan all the way to Australia.

This species of octopuses can be identified by their characteristic blue and black rings and yellowish skin.

The blue and black circles on their skin dramatically change colors when they feel threatened.

The blue-ringed octopuses feed on small crustaceans, including hermit crabs, shrimps, crabs, and other little animals.

Scientific classification

  • Kingdom: Animalia
  • Phylum: Mollusca
  • Class: Cephalopoda
  • Order: Octopoda
  • Family: Octopodidae
  • Genus: Hapalochlaena

Type species

Hapalochlaena lunulata


  • H. fasciata
  • H. lunulata
  • H. maculosa
  • H. nierstraszi

These octopuses are recognized as one of the most venomous marine animals in the world.

Despite the small size of these octopuses—12 to 20 cm (5 to 8 in)—and their relatively docile nature, the blue-ringed octopuses are dangerous to humans when handled and provoked because of their venom that contains the powerful neurotoxin tetrodotoxin.

This species of octopus have been discovered to have a lifespan of about two years.

However, their lifespan may vary depending on factors like temperature, nutrition, and the intensity of light in their habitat.


The genus of these octopuses was first described in 1929 by British zoologist Guy Coburn Robson.

There are four already confirmed species of Hapalochlaena, and about six possible species are being studied:

  • Greater blue-ringed octopus (Hapalochlaena lunulata)
  • Southern blue-ringed octopus or the lesser blue-ringed octopus (Hapalochlaena maculosa)
  • Blue-lined octopus (Hapalochlaena fasciata)
  • Hapalochlaena nierstraszi (this one was described first in 1938 using a single specimen caught from the Bay of Bengal and in 2013 from a second specimen).


The blue-ringed octopuses spend most of their time taking cover in crevices while displaying their camouflage patterns using their dermal chromatophore cells.

Like every other species of octopus, the blue-ringed octopus can easily change shape, allowing them to squeeze into tiny holes and places you never thought it could fit into.

Their camouflage and shape-shifting abilities, together with their habit of piling up rocks outside the entrance to their homes, help to protect them from predators.

If they feel provoked, these octopuses quickly change color, turning a bright yellow with each of their 50-60 rings shining in a brilliant iridescent blue color within a third of a second as a warning display.

In greater blue-ringed octopuses (Hapalochlaena lunulata), the rings on their bodies have multi-layer light reflectors known as iridophores.

These layers are arranged to shine a blue-green light in a broad viewing direction.

Underneath and around every ring is layers of darkly pigmented chromatophores which can expand within a second to boost the contrast of the rings.

Above the rings, there are no chromatophores, which is an unusual case for cephalopods as they usually use chromatophores to shield or modify iridescence spectrally.

They achieve the fast flashes of their blue rings by using muscles that are in neural control.

Under normal circumstances, muscle contractions above the iridophores hide each of their rings.

When these muscles relax and the muscles outside their ring contract, the iridescence becomes exposed, revealing a blue color.

Like most other Octopoda, the blue-ringed octopus can swim by pumping out water from a funnel, just like jet propulsion.


The blue-ringed octopus feed typically on shrimps and small crabs.

They are also opportunistic feeders as they also tend to take advantage of small-sized injured fish if they can catch them.

The blue-ringed octopus kills its prey by pouncing on it, seizing it with its tentacles (arms), and pulling it as fast as it can toward its mouth.

It has a horny beak which it uses to pierce through the hard shrimp or crab exoskeleton, releasing its harsh venom.

The octopus venom paralyzes the muscles needed for movement, which eventually kills the prey.


The mating process for the blue-ringed octopus starts when a male octopus approaches a female and starts to caress her with its modified arm called the hectocotylus.

A male blue-ringed octopus mates with a female by grabbing onto her, which may sometimes completely obscures her vision throughout the process, then he transfers sperm packets into the female by repeatedly inserting his hectocotylus into her mantle cavity.

The pair continues to mate until the female has had her fill, and in at least one of the species, the female blue-ringed octopus, has to detach the over-enthusiastic male by force.

The males are known to attempt copulation with other members of their particular species, no matter the size or sex.

However, sexual interactions between males do not last long and end once the mounting octopus withdraws the hectocotylus without struggle or packet insertion.

Blue-ringed octopus females lay only one clutch of about 50 eggs in their lifetimes towards the end of autumn.

Eggs are laid and then incubated underneath the female’s arms for about six months; during this process, she does not eat.

After the eggs hatch, the female dies, and the new offspring will reach maturity and be able to mate by the next year.


The blue-ringed octopus, regardless of its small size, packs enough venom to end the lives of twenty-six adult humans in a matter of minutes.

The bites of these octopuses are tiny and usually painless, with several victims not knowing they have been envenomated until they begin to experience respiratory depression and paralysis.

As of 2019, there has been no blue-ringed octopus antivenom available.


The octopus makes venom that contains histamine, tetrodotoxin, tryptamine, taurine, octopamine, dopamine, and acetylcholine.

The toxin can lead to respiratory arrest, nausea, heart failure, severe and, at times, complete blindness, and paralysis, and can sometimes lead to death within a few minutes if not treated.

Death usually results from suffocation as a result of paralysis of the diaphragm.

The primary neurotoxin component that the blue-ringed octopus has is a compound formally known as mycotoxin but later discovered to be identical to tetrodotoxin, which is a neurotoxin found in pufferfish, and in some species of poison dart frogs.

It has been found that tetrodotoxin is about 1,200 times more toxic than cyanide.

Tetrodotoxin kills by blocking sodium channels and causes motor paralysis and respiratory arrest within a few minutes of exposure.

Tetrodotoxin is made by bacteria present in the salivary glands of the blue-ringed octopus.

There has to be direct contact with the species to be envenomated. When faced with danger, a blue-ringed octopus’s first instinct is to run away.

If the threat continues, the octopus will assume a defensive stance and reveal its blue rings.

If a person can corner and touch the octopus, the person would be at risk of being bitten and envenomated by the animal.

Tetrodotoxin is present in nearly every gland and organ of the blue-ringed octopus body.

You can even find it in sensitive areas of its body, such as Needham’s sac, nephridia, branchial heart, and gills.

Tetrodotoxin is harmful to other creatures, but it does not affect the creature’s normal functions.

This may occur through a peculiar blood transport. The mother octopus will inject the neurotoxin into eggs to make them generate their own venom before they hatch.


Tetrodotoxin is known to cause severe and usually total body paralysis. A victim of tetrodotoxin envenomation will be fully aware of their surroundings but too weak to move.

Because victims of the envenomation become paralyzed, there is no way they can signal for help or even indicate that they are in distress.

The patient remains alert and conscious, like pancuronium bromide or curare.

This weakening effect is only temporary and will gradually fade over a couple of hours as the tetrodotoxin gets metabolized and excreted by the body.

The symptoms of envenomation vary in severity, with kids being most at risk due to their tiny body size.


First aid treatment for envenomation is intense pressure on the wound, and artificial respiration immediately after the paralysis disables the victim’s respiratory muscles, which often happens within minutes of being bitten.

The venom basically kills through paralysis, so victims are mostly saved if artificial respiration is given and maintained before there is a development of marked cyanosis and hypotension.

Efforts must be continued even when the victim doesn’t appear to be responding. Steady respiratory support until the arrival of medical assistance will improve the victim’s possibility of survival.

It is vital that rescue breathing is maintained without pause until the paralysis reduces and the victim can breathe on their own.

Artificial respiration is a stressful physical prospect for one individual.

Still, with the aid of a bag valve mask respirator, you can reduce fatigue to sustainable levels until you get help.

Hospital treatment for the envenomation involves placing the victim on a medical ventilator until the body eliminates the toxin.

Victims who are able to survive the first twenty-four hours of envenomation usually recover fully.

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