Its common name comes from the relatively large size of its blue rings (7 to 8 millimetres [0.28 to 0.31 in] in diameter), which are larger than those of other members of the genus and help to distinguish this type of octopus.

There are variable ring patterns on the mantle of Hapalochlaena lunulata with varied coloration in correlation to their ambient environment, from yellow ocher to light brown or even white-ish (when inactive).

A black line, with thickness varying to increase contrast and visibility, borders the electric blue circles.

It was also found that after examining the blue rings (specifically the iridophores) were seen to shift to the UV end of the spectrum which is a defining characteristic of multi-layer reflectors.

It was also found that the iridophores are nicely tucked into the modified skin folds, kind of like pouches, which could be contracted by the muscles that connect the center of each ring to the rim.

After all of the testing was complete, it was determined that the muscle contracting mechanisms was key to how the blue-ringed octopus portrayed its iridescent signaling success.

[2] The greater blue-ringed octopus is a benthic animal that has a solitary way of life and is widespread throughout the tropical and subtropical waters of the Indo-West Pacific, from Sri Lanka to the Philippines and from Australia to Papua New Guinea, the Solomon Islands and Vanuatu.

The greater blue-ringed octopus is capable of inflicting a deadly bite to its predators that can potentially be fatal to humans.

For humans, the minimal lethal dose of tetrodotoxin is estimated to be about 10,000 MU, which is about 2 milligrams (0.031 gr) in crystal form.

The bite is painless to humans but effects appear any time between 15 and 30 minutes and up to four hours, though the rate of onset of symptoms varies by individual, and children are more sensitive to the toxins.

The victim may also suffer excessive sweating, severe headaches coupled with dizziness, speech problems, hypersalivation, moderate emesis, movement disorders, a feeling of weakness, cyanosis to extremities and lips and petechial hemorrhages on the body.

TTX selectively binds and blocks the ion-conducting pore of the voltage-gated sodium channel which are responsible for the ability of an organism to move.

It was found that the resistance was caused by a combination of amino acid substitutions in the TTX binding sites for the primary voltage-gated sodium ion channel.