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Common octopuses are known for their intelligence. In fact, two fine specimens of this clever coleoid species are even practising opening bottles at Basel Zoo.

In the wild, common octopuses like to play with and open mussel and snail shells. In Basel Zoo’s vivarium, these inquisitive creatures are therefore being served their food in bottles with a variety of different closures, which the octopuses must then use their eight arms to open in order to access the tasty treats inside.

One of Basel Zoo’s common octopuses lives behind the scenes at the Vivarium and the other can be seen in display tank 43.

Blue-blooded and intelligent

Octopuses can move their eight arms independently, as each arm is controlled by its own nerve centre. This means that an octopus has nine brains, as well as having three hearts! The arterial heart circulates the blood around its body, whilst two additional branchial hearts increase the blood flow through the gills. Octopus blood is blue because its oxygen is transported by copper-containing haemocyanin, rather than the iron-containing haemoglobin found in human blood.

Offspring once a lifetime

Every year, around 300,000 tons of the 230 different species of octopus are caught for human consumption, the majority of which are common octopuses. However, this species is not classified as endangered on the Red List and can still be found in large numbers in the western Mediterranean. One reason for this is the common octopus’s high reproduction rate: a large female can produce up to 500,000 eggs, which she will guard until they hatch. The baby octopuses, which are just a few millimetres long, drift in the water like plankton after they have hatched. The female, who has not eaten anything whilst looking after her clutch of eggs, is then so exhausted that she dies. Male octopuses (which can be distinguished from females by their special tentacle designed for mating, which has fewer suction cups and a sperm channel) die immediately after the mating process.

Short lives

For octopuses, reproduction also means the death of the parents. In the wild, they will only be around three to four years old. In the aquarium, they generally die a year and a half to two years after their arrival – not because they live shorter lives in an aquarium, but because they are generally already a certain size when caught and are thus already adults. Octopuses in the Mediterranean are often found via items such as mussel and snail shells, which they collect in front of the caves where they live. Unfortunately, they are now increasingly playing with plastic waste such as PET bottles or boxes. The older an octopus is, the more toys it will have in front of its cave.

All octopuses are coleoids, but not all coleoids are octopuses

Like all coleoids, octopuses secrete ink when they sense danger and envelop their enemies in an ink cloud, allowing them time to reach the safety of the nearest cave. This secreted ink is characteristic of all the approximately 1000 species in the coleoid subclass. Eight-armed octopuses are just one family within this subclass. Other coleoids include squid, which have two additional tentacles (bringing their total number of arms to ten), and the ancient nautilus with up to 90 tentacles.