Hapalochochlaena sp. are found in the IndoWest Pacific and Indian Oceans. They are very common in shallow waters around the coast of Australia particularly in the cooler areas along the southern coast. Hapalochochlaena lunulata specifically is found along the coasts of Northern Australia and farther north in the tropic western Pacific Ocean.

(Ellis 1991, Environment Australia 1999, Norman 1998, Roper and Hochberg 1988)

Biogeographic Regions: indian ocean (Native ); pacific ocean (Native )

A soft body that rapidly changes color and texture characterizes the family Octopodidae. An octopus has no skeleton and therefore is astonishingly compressible; Octopodidae can ooze through an opening no bigger than one of its eyeballs. Its incredible flexibility comes from its musculature, which consists of fibers that run in three directions, permitting it to change shape. Like all Mollusca, Octopodidae possesses a mantle. However, the mantle is fused with the cephalized head on the dorsal side. The "skin" of Octopodidae is equipped with chromatophores, which are pigment cells that an animal can expand or contract by muscular action. These cells vary in color, and as the animals expands some or contracts others, its color changes. The nervous system consisting of a well-developed brain, controls the color changes an Octopodidae makes in response to its moods and surroundings. The central nervous system of the octopus is the largest and most complex in the invertebrate world, rivaling that of many vertebrates, including mammals. Also analogous with the vertebrates, members of Octopodidae possess two large, complex eyes that are camera-like in structure, and their vision is acute. Although Octopodidae has a closed circulatory system like higher animals as well, the blood is a poor carrier of oxygen. As a result, Octopodidae tires easily. To stay alive, it relies on a system involving three hearts and permanently high blood pressure. A major distinguishing feature of Octopodidae is its eight muscular arms, which radiate out from the body around the beak-like jaws. In males, the third right arm is modified into a hectocotylus for mating. Each arm bears two rows of whitish suckers that can move independently. Each sucker may have 10,000 neurons to handle both taste and touch, and an octopus has thousands of suckers. Octopodidae has an ability to regenerate an injured or lost arm. It usually takes about 6 weeks for an arm to regenerate. It has been found that, along with arms, Octopodidae can even regenerate part of an eye that is damaged.

The blue-ringed octopi actually include four closely related species Hapalochochlaena marculsa, Hapalochochlaena lunulata, Hapalochochlaena fasciata, and Hapalochochlaena nierstraszi . Its larger rings distinguish Hapalochochlaena lunulata, the Greater blue-ringed octopus, from the other species. Hapalochochlaena lunulata is about 20 cm at maximum spread, but under normal circumstances, it appears much smaller than this. H. lunulata is dark brown to dark yellow in color, but with brilliant blue rings thought to be warning coloration that "glow" when it is angry. The reason the rings are blue is thought to be that the visual range of the octopus is most sensitive in the blue part of the spectrum. At the small beak at the junction of its eight arms rather than manufacturing ink, H. lunulata makes poison like the tetrodotoxin found in poisonous puffer fishes. Bacteria in their salivary glands produce it. The venom, contained in its saliva and designed to subdue or kill its prey is particularly lethal to human beings.

(Campbell 2000, Ellis 1991, Encarta 1998, Environment Australia 1999, Norman 1998, Roper and Hochberg 1988, Stewart 1997)

Range mass: 10 to 100 g.

-H. lunulata- is found in shallow coral and rock pools, particularly after storms, digging around for crabs. It tends to hide in crevices amongst rocks, inside seashells, and discarded bottles and cans because of its soft-bodied vulnerability. It is easy to identify the home of -H. lunulata - or any Octopodidae: The area immediately in front of the opening is littered with the shells and hollowed-out legs of various crustaceans. It occupies a particular nest for a long time and ventures forth only to hunt for food or look for a mate. However, it cannot resist a new nest when one is offered. They, as well as other Octopodidae, are bottom dwellers and are not found in open water. Although Octopodidae may venture onto dry land in pursuit of a crab, if it remains there Octopodidae is doomed: Within half an hour, it will die from suffocation.

(Campbell 2000, Ellis 1991, Encarta 1998, Environment Australia 1999, Stewart 1997)

Aquatic Biomes: reef ; coastal

H. lunulata is carnivorous, feeding primarily on fish, crabs, mollusks and other small marine animals. It hunts every thing that it is able to overpower. It ambushes prey from the background. H. lunulata often lures its victim by wiggling the tip of an arm like a worm; or it glides near and pounces on a crab, trapping the prey in its arms and dragging it towards its powerful beak-like jaws. Once it has bitten its prey, the octopus injects it with poisonous saliva to kill it. Either H. lunulata cracks prey open with its jaws or it disarticulates them, and with the tips of its arms, removes any vestige of the edible parts. H. lunulata does not employ its beak other than to take from the suckers the portions that it has removed.

(Hutchinson 1998, Ellis 1991, Encarta 1998, Environment Australia 1999)

A male interested in mating approaches a female just close enough to stretch out a modified arm, the hectocotylus, and caress the female. This arm has a deep groove between the two rows of suckers and ends in a spoon-like tip. After a period of caressing the female with the tip of the hectocotylus, the male inserts its arm under the mantle of the female, and the spermatophores then travel down the groove on the hectocotylus to the female's oviduct. Soon after mating, the female begins to lay 60-100 eggs, which she carries in a cluster underneath her tentacles. She then guards them for the next 50 days. The eggs hatch into planktonic paralarvae and spend their first weeks as ocean plankton, drifting at the surface. After gaining weight, they drop to the bottom. Because she stops eating while brooding her eggs, the mother dies almost as soon as they hatch. The young are ready to reproduce around four months after hatching.

(Ellis 1991, Encarta 1998, Environment Australia 1999, Stewart 1997, Roper and Hochberg 1988)

Poison from Hapalochochlaena sp. has proven to be fatal to humans especially to young children. There is no antivenom for this poison. Of the several human fatalities attributed to this animal, all have involved the animal being picked up. The bite itself may not even be felt. Five minutes or so later however, the victim may complain of dizziness and increasing difficulty in breathing. The powerful venom acts on the victim's voluntary muscles, paralyzing the muscles required for body movement and breathing. Artificial respiration is necessary to maintain life. The poison gradually wears off after 24 hrs, apparently leaving no side effects. (Campbell 2000, Environment Australia 1999, Norman 2000)

Although other Octopodidae are used for biomedical research, behavioral research, and as gourmet food source, Hapalochochlaena sp. are too small and too dangerous for much. of these uses. Medical and psychological research are interested in the tetrodotoxin neurotoxin found in its venom for its aphrodisiac effect and its ability to block voltage-sodium channels so action potential in neurons is inhibited or reduced. They also have value as an unusual luxury item. As strange as it may seem, a H. lunulata individual was sold for $4000 at an auction in Sidney, Australia recently.

(Brenner and Elgar 1999, Ellis 1991, Melki 2000)