The blue-lined octopus (''Hapalochlaena fasciata'') is one of four

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of highly

venomous Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

blue-ringed octopus Blue-ringed octopuses, comprising the genus ''Hapalochlaena'', are four highly venomous species of octopus that are found in tide pools and coral reefs in the Pacific and Indian oceans, from Japan to Australia. They can be identified by their ye ...

es. It can be found in Pacific Ocean waters that stretch from

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

and southern

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

. 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 it feels threatened. 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 Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

can be fatal to humans.

Behavior

Blue-lined octopuses tend to swim around shallow areas of

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Co ...

s and

tide pool A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pool habitats are home to especially adaptable animals that ...

s. They often hide in crevices of reefs, empty seashells, and other ocean resources they can find to conceal their identity. They are diurnal creatures, hunting

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

s and small

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

during the day. They do not use their venom (known as

tetrodotoxin Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered ...

) to kill their prey, but instead trap it inside their arms and pierce them with its parrot-like beak.

Lethality

Blue-lined octopuses can be very lethal to humans. Their saliva contain a special

neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...

called

. However, the species is more likely to flee and find shelter in an encounter due to their extremely shy nature. Nonetheless, there have been at least three reported human deaths from the blue-lined octopus. It poses most danger to those who pick up the octopus and physically touch it. 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. After some time, symptoms of the injection include loss of feeling in the tongue/lips,

muscle weakness Muscle weakness is a lack of muscle strength. Its causes are many and can be divided into conditions that have either true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, includi ...

/ paralyzation,

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...

unconsciousness Unconsciousness is a state in which a living individual exhibits a complete, or near-complete, inability to maintain an consciousness, awareness of self and environment or to respond to any human or environmental Stimulus (physiology), stimulus. ...

, and eventually

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

. 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.

Reproduction

The blue-lined octopuses start reproducing at a year old. Males seek out female companions and then pounce on them. If they are successful, the female octopus will lay 50 to 100

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

30 days after the encounter. During the 30 days, the female octopus hides her eggs under her arms and does not leave her hiding spot until the eggs hatch. After laying her eggs, the female octopus dies.

References

{{Taxonbar, from=Q2120872 Octopuses