| Revision as of 23:30, 5 September 2026 by OpenWiki (Updated from the starter corpus) | Revision as of 00:19, 6 September 2026 by OpenWiki (Updated from the starter corpus) | ||
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| − | The '''octopus''' (order ''Octopoda'') is a soft-bodied, eight-limbed mollusc. Around 300 species are recognised, in every ocean and at every depth from the intertidal zone to the abyssal plain. Together with squid, cuttlefish and nautiluses, octopuses make up the class | + | The '''octopus''' (order ''Octopoda'') is a soft-bodied, eight-limbed mollusc. Around 300 species are recognised, in every ocean and at every depth from the intertidal zone to the abyssal plain. Together with squid, cuttlefish and nautiluses, octopuses make up the class Cephalopoda, the most neurologically complex invertebrates known. |
| == Anatomy == | == Anatomy == | ||
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| Each arm carries two rows of suckers, which grip and also taste: the suckers are lined with chemoreceptors, so an octopus can detect what it is touching by touching it. Around two thirds of its roughly 500 million neurons lie in the arms rather than the brain, and a severed arm continues to react appropriately to stimuli for a time. The brain issues broad commands; the details of a movement are worked out locally. | Each arm carries two rows of suckers, which grip and also taste: the suckers are lined with chemoreceptors, so an octopus can detect what it is touching by touching it. Around two thirds of its roughly 500 million neurons lie in the arms rather than the brain, and a severed arm continues to react appropriately to stimuli for a time. The brain issues broad commands; the details of a movement are worked out locally. | ||
| − | Octopuses have three hearts. Two branchial hearts pump blood through the gills, and a systemic heart circulates it to the body. The systemic heart stops beating while the animal swims, which is one reason most species prefer to crawl.<ref>Wells, M. J. ''Octopus: Physiology and Behaviour of an Advanced Invertebrate''. Chapman and Hall, 1978.</ref> Their blood is blue, using copper-based haemocyanin rather than iron-based | + | Octopuses have three hearts. Two branchial hearts pump blood through the gills, and a systemic heart circulates it to the body. The systemic heart stops beating while the animal swims, which is one reason most species prefer to crawl.<ref>Wells, M. J. ''Octopus: Physiology and Behaviour of an Advanced Invertebrate''. Chapman and Hall, 1978.</ref> Their blood is blue, using copper-based haemocyanin rather than iron-based haemoglobin, which is more efficient in cold, low-oxygen water. |
| == Camouflage == | == Camouflage == | ||
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| Most octopuses live only one to two years, and reproduce once. The male passes a packet of sperm with a modified arm, the hectocotylus. The female lays tens of thousands of eggs, then stops feeding and spends weeks or months tending them, aerating them and driving off predators, dying at about the time they hatch. In 2014 researchers reported a deep-sea octopus brooding a single clutch for four and a half years, the longest brooding period recorded for any animal. | Most octopuses live only one to two years, and reproduce once. The male passes a packet of sperm with a modified arm, the hectocotylus. The female lays tens of thousands of eggs, then stops feeding and spends weeks or months tending them, aerating them and driving off predators, dying at about the time they hatch. In 2014 researchers reported a deep-sea octopus brooding a single clutch for four and a half years, the longest brooding period recorded for any animal. | ||
| − | This pattern | + | This pattern of short life, single reproduction and no parental contact with the next generation means that whatever an octopus learns dies with it. Octopus intelligence is, unusually, not cultural. |
| == Defence == | == Defence == | ||
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