|Big blue octopus|
Gray, 1849 
Octopus cyanea, also known as the big blue octopus, day octopus and Cyane's octopus, is an octopus in the family Octopodidae. It occurs in both the Pacific and Indian Oceans, from Hawaii to the eastern coast of Africa. O. cyanea grows to 16 cm in mantle length with arms to at least 80 cm. This octopus was first described by the British zoologist John Edward Gray in 1849; the type specimen was collected off Australia and is at the Natural History Museum in London.
Living as it does on coral reefs, and hunting by day, O. cyanea is an expert in camouflage and can not only change colour frequently, but can also change the shape and texture of its skin, to help it remain invisible on the reef.
While most species of octopus are nocturnal, O. cyanea is diurnal, and most active at dawn and dusk. It has a den where it returns after foraging; a rock crevice, a hidden place under an overhang, a hiding place among coral heads or a hole excavated in rubble or sand. It is a predator and searches the reef for fish, crabs, shrimps and molluscs. Small items may be eaten where they are caught, while larger items are carried back to the den for consumption. Crabs may be killed by a bite and the injection of toxic saliva, then chewed up by the octopus' beak, while molluscs may have their shells drilled, the animal inside being predigested to ease extraction. Empty mollusc shells and crab carapaces may be discarded near the den in a midden.
O. cyanea has a lifespan of some twelve to fifteen months after settling from the planktonic larval state. During this time it grows from about 67 to 6,500 g (0.1 to 14.3 lb). In captivity it breeds at any time of year, probably depending on when the female reaches maturity. The male may mate with several different females, but after this, the suckers on the edge of his webbing expand in size. During the next two or three months they continue enlarging while the octopus goes into a decline and dies. The female meanwhile remains beside her eggs, which are deposited in a den, and dies soon after they hatch.
- Bouchet, Philippe (2010). "Octopus cyanea Gray, 1849". World Register of Marine Species. Retrieved 26 April 2017.
- Norman, M.D. 2000. Cephalopods: A World Guide. ConchBooks.
- Current Classification of Recent Cephalopoda
- "Day octopus". Monterey Bay Aquarium. Retrieved 26 April 2017.
- "Octopus cyanea: Big blue octopus". SeaLifeBase. Retrieved 26 April 2017.
- van Heukelem, William F. (1973). "Growth and life-span of Octopus cyanea (Mollusca: Cephalopoda)". Journal of Zoology. 169 (3): 299–315. doi:10.1111/j.1469-7998.1973.tb04559.x.