page_title: Blue-ringed octopus
section_title: Behavior
hierarchical_section_title: Blue-ringed octopus / Behavior
caption_attribution_description: English: Original caption: "Figure 1. Variable ring patterns on mantles of the blue-ringed octopus Hapalochlaena lunulata. Note the small fleck of blue in the ring indicated in panel A, which is missing from the corresponding ring in panel B. The individual in panel C bears disproportionally small rings near the head, as well as merged rings left side. All photographs by Roy Caldwell."
context_page_description: 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 yellowish skin and characteristic blue and black rings that change color dramatically when the animal is threatened. They eat small crustaceans, including crabs, hermit crabs, shrimp, and other small animals.
  They are recognized as one of the world's most venomous marine animals. Despite their small size—12 to 20 cm —and relatively docile nature, they are dangerous to humans if provoked when handled because their venom contains the powerful neurotoxin tetrodotoxin.
  The species tend to have a lifespan of approximately two years. This can vary depending on factors such as nutrition, temperature and the intensity of light in its habitat.
context_section_description: Blue-ringed octopuses spend most of their time hiding in crevices while displaying effective camouflage patterns with their dermal chromatophore cells.  Like all octopuses, they can change shape easily, which helps them to squeeze into crevices much smaller than themselves. This, along with piling up rocks outside the entrance to its lair, helps safeguard the octopus from predators.
  If they are provoked, they quickly change color, becoming bright yellow with each of the 50–60 rings flashing bright iridescent blue within a third of a second as an aposematic warning display.  In the greater blue-ringed octopus (Hapalochlaena lunulata), the rings contain multi-layer light reflectors called iridophores.  These are arranged to reflect blue–green light in a wide viewing direction. Beneath and around each ring there are dark pigmented chromatophores which can be expanded within 1 second to enhance the contrast of the rings. There are no chromatophores above the ring, which is unusual for cephalopods as they typically use chromatophores to cover or spectrally modify iridescence. The fast flashes of the blue rings are achieved by using muscles which are under neural control. Under normal circumstances, each ring is hidden by contraction of muscles above the iridophores.  When these relax and muscles outside the ring contract, the iridescence is exposed thereby revealing the blue color.
  In common with other Octopoda, the blue-ringed octopus swims by expelling water from a funnel in a form of jet propulsion.
caption: Variable ring patterns on mantles of Hapalochlaena lunulata
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