Octopuses

Discover the incredible abilities of these eight-limbed wonders of the natural world

Octopuses are sort of like the superheroes of the animal kingdom, with so many amazing abilities and adaptations that they begin to look greedy. They can solve mazes, open screw-top jars and use tools. They can walk, they can swim and they can even propel themselves at high speed. They can change colour, imitate other animals, squirt ink, inject poison and jettison their own arms. When you can do all of that, who cares if you can predict the future or not?

Although they are molluscs, octopuses don’t have a shell or bones. The only hard part of their body is a small beak, made of keratin. This allows them to squeeze through extremely small gaps – an octopus a metre across can pass through a tube the size of a 50 pence coin. Octopuses mainly eat crabs and small fish that they pull out of crevices in rocks and coral reefs, but they can also tackle small sharks by enveloping the sharks’ gill openings and suffocating them.

Octopus blood uses a greenish-blue copper pigment called haemocyanin instead of the iron-based haemoglobin in our own blood. Haemocyanin can’t carry as much oxygen as haemoglobin, but is actually more efficient at low oxygen concentrations and in cold water. Despite this octopuses have poor circulation and quickly run out of energy. This may be one of the reasons for their intelligence – they don’t have the stamina for a prolonged chase and must rely on their cunning.

Male octopuses die almost immediately after mating. The females are even bigger martyrs. They guard their eggs for months, or sometimes years, and rather than leaving the nest to hunt they will eat some of their own arms. After that the female dies, and the eggs hatch into babies around the size of a walnut.

Chromatophores The colour-changing cells in the skin are funnel-shaped. By squeezing ink into the funnel from a bulb at the base, the octopus can control the size of the coloured dot. Colouration This blue-ringed octopus can change colour to match the sea bed or suddenly flash its bright, blue rings to startle predators. Suckers Twin rows run the length of the arms to allow the octopus to grip and to taste anything it touches. Eye This looks much like our own, with a lens and an iris, but it evolved in a different way. Octopuses don’t have a blind spot where the optic nerve passes through because the retina is positioned differently. Poison glands These evolved from salivary glands. As well as paralysing prey, they also soften up the flesh, making it easier to eat.