Octopus cyanea is commonly known as Big blue octopuses. Octopus are marine molluscs classified as cephalopods, alongside squids and cuttlefish. Unlike other molluscs they do not have a shell.
It has a very large head with a parrot like beak, eight tentacles and its skin is brownish-red in colour with dark blue circles over it. It is able to blend into its surroundings and camouflage by changing its body colour. It has a mantle length of 16 cm and its tentacles length reaches 80 cm. Males have a longer third right tentacle.
This is a fast-growing species and O. cyanea reaches maturity between 13 and 15 months.
Adult females can weigh between 600 to 4800g, while adult males can weigh between 400 to 6600g.
Octopus cyanea is found in the Indio Pacific Region.
It is common in the coastal waters of Mauritius. They can be found in shallow coral lagoons and intertidal areas to reefs up to 100 meters in depth. They can also be found in seagrass beds and areas of muddy, sandy or rocky substrate.
They usually hide during the day and come out at night to hunt. Their diet consists of shellfish and crustaceans. Octopus cyanea create dens in crevices in their habitat and can spend up to 35 days in a den.
They breed only once in their life and females die 60 days after spawning and laying their eggs because they do not eat while they protect their eggs. The eggs will hatch after 20 to 30 days.
Octopus cyanea is recorded as ‘Least Concern’ according to the IUCN Red List. Monitoring of this species, however, is required. In Mauritius, there have been regular closures of the octopus fishery for the past two to three years, to allow populations to recover. The outcomes have been positive, resulting in greater catch sizes.
Octopuses possess venom that comes from bacteria that the host. A bite from a blue-ringed octopus can paralyse a human adult in a matter of minutes.
The largest octopus is the Giant Pacific Octopus, Enteroctopus dofleini that weighs about 15 kg with a tentacle length of 4.3m.