The mantle (head section) of the octopus can reach about 25cm long, and arms about 1m long. Some may reach 3 m in total length. The eight tentacles or arms each has two rows of suckers and the lateral arms are the longest. The ventral siphon is important for swimming by jet propulsion although crawling over the ground by means of the arms is the usual means of locomotion. There is no shell which makes the common octopus extremely flexible. The skin can change colour and surface texture quickly for efficient camouflage.
Scientific Name: Octopus vulgaris
Common Names: Common octopus, seekat (Afrikaans)
Size: Up to a total length of 3 metres
The common octopus is found worldwide in tropical and sub-tropical waters.
The common octopus is generally found in the “near shore zone”. It inhabits a variety of substrates including rocky, sandy and reef. Although they have been found in deep water, most are found shallower than 100 meters, between 25 and 50 meters.
This octopus hunts at dusk. Crabs, crayfish, and bivalve molluscs are preferred; although the octopus will eat almost anything it can catch, including fish and small sharks. The prey is paralyzed by a nerve poison, which the octopus secretes, and the octopus is able to grasp its prey using its powerful arms equipped with two rows of suckers. If the victim is a shelled mollusc, the octopus uses its beak to punch a hole in the shell before sucking out the fleshy contents.
Octopi are loners which meet up for reproduction. The male transfers several spermatophores (packets of sperms) with a modified arm to the mantle cavity of the female. The female produces 120 000 to 400 000 eggs which it fastens in strings to the walls of a cavity in shallow water. During the next 25 to 65 days (depending on water temperature) the female cares for the eggs and does not feed – the male and female die after the planktonic para-larvae have emerged. During this time, most larvae become food for something else. The common octopus has a rather short lifespan of 12 to 18 months.
They are commonly collected in bottom trawls or octopus pots. These pots were traditionally made of clay but in modern times they are typically made of plastic or PVC. Octopus pots are not baited like crab and lobster traps, rather, they provide a deceptively safe home. The common octopus is commercially important and accounts for a large percentage of octopus fisheries. Between 20 000 and 100 000 tons are landed annually.
IUCN – NOT EVALUATED