50 free Octopus trivia questions with answers — nature quiz, new questions added Aug 2026.
This octopus trivia quiz covers the ocean's strangest and smartest invertebrate. The easy questions handle the basics: how many arms and hearts it has, what colour its blood is, what it squirts at predators, how it changes colour and how long it lives. The harder end goes deeper: why two-thirds of its neurons live in its arms, the copper protein that makes its blood blue, the hectocotylus arm and the grim end that follows mating, the giant Pacific octopus and its 180,000 eggs, the tetrodotoxin of the blue-ringed octopus, coconut-carrying veined octopuses, the dumbo octopus photographed 6,957 metres down, the octopus plural argument, Hokusai's infamous print, and Paul, who picked World Cup winners. Every answer was checked against the encyclopaedia entry before publishing and the supporting sentence is stored with each question. Our ocean, sea creatures and animal quizzes are the natural next stop.
30 of 50 questions with answers and explanations. Play the quiz
Q 01To which class of molluscs do octopuses belong, along with squid, cuttlefish and nautiluses?
Cephalopoda
The order Octopoda holds around 300 species.
Q 02How many hearts does an octopus have?
Three
One main heart pumps blood round the body; two branchial hearts push it through the gills, and the main one stops when the animal swims.
Q 03Octopus blood is blue because it carries oxygen with which copper-rich protein?
Haemocyanin
It works better than haemoglobin in cold, low-oxygen water, but is so viscous that blood pressure can top 75 mmHg.
Q 04Roughly how many neurons does an octopus have, about the same as a dog?
Over 500 million
One part sits in a cartilaginous capsule around the brain; the rest is spread through the arms, which act with some independence.
Q 05What fraction of an octopus's neurons are located in its arms rather than its brain?
Two-thirds
A severed arm can still move and respond to stimuli.
Q 06Which is the only kind of octopus known to be deadly to humans?
Blue-ringed
All octopuses are venomous, but only these can kill a person; there is no antidote.
Q 07What toxin in the venom of the deadliest octopus causes paralysis by blocking nerve impulses to muscles?
Tetrodotoxin
Death comes by respiratory failure, but if breathing is kept going artificially, patients recover within 24 hours.
Q 08Which species is usually cited as the largest octopus?
Giant Pacific
Adults typically weigh 10 to 50 kg with an arm span up to 4.8 metres; the biggest scientifically documented weighed 71 kg.
Q 09What is the smallest octopus species, at around 2.5 cm and under a gram?
O. wolfi
At the other extreme, a seven-arm octopus carcass was estimated to have weighed 75 kg alive.
Q 10Even large octopuses can squeeze through a gap of roughly what size?
A little over 2.5 cm
The only hard part of the body is the beak; everything else is soft tissue.
Q 11What is the specially adapted arm a male octopus uses to transfer sperm packets called?
The hectocotylus
Usually it is the third right arm, with a spoon-shaped tip; Cuvier once mistook a detached one for a parasitic worm.
Q 12What happens to a male octopus after mating?
He becomes senescent and dies
Females die too, after brooding their eggs.
Q 13How many eggs can the largest octopus species lay in a single clutch?
180,000
The common octopus can lay 500,000; the female guards them for about five months without feeding.
Q 21What is an octopus's fastest way of moving?
Jet propulsion, swimming backwards
It is exhausting: the mantle pressure needed is so high it stops the main heart, so octopuses mostly crawl.
Q 22Octopus suckers are equipped with chemoreceptors, meaning the animal can do what?
Taste whatever it touches
The sensors also recognise octopus skin, which stops the arms sticking to each other.
Q 23Which sac-like organs let an octopus sense its orientation and possibly hear?
Statocysts
The common octopus can hear sounds between 400 and 1,000 Hz, best at around 600 Hz.
Q 14What is the maximum lifespan of an octopus?
Up to four years
Some species finish their entire lifecycle in under six months.
Q 15Which organs trigger senescence, the fatal decline after an octopus reproduces?
The optic glands
During senescence the animal stops eating, weakens, develops lesions and literally degenerates.
Q 16What is the main pigment in octopus ink?
Melanin
The ink is mixed with mucus on the way out and leaves the funnel as a thick, dark blob that acts as a decoy or smoke-screen.
Q 17What are the specialised skin cells that let an octopus change colour called?
Chromatophores
They hold yellow, orange, red, brown or black pigments; iridophores and leucophores add reflection and white.
Q 18What is the octopus display called in which waves of dark colour ripple across the body?
The passing cloud
The 'moving rock' trick is different: mimicking a rock and inching across open ground at the speed of the water.
Q 19Which octopus can impersonate more dangerous animals such as lionfish, sea snakes and eels?
Mimic
It combines a flexible body with colour change to pull off the disguise.
Q 20The veined octopus is famous for collecting and carrying what to build a shelter?
Discarded coconut shells
It 'stilt-walks' with the stacked shells tucked under it, a celebrated example of tool use.
Q 24Roughly what share of a resting octopus's oxygen is absorbed through its skin?
About 41%
That drops to about 33% while swimming and as low as 3% while digesting a meal.
Q 25How does an octopus get into a hard-shelled clam or crab?
It drills in with tiny teeth and dissolving saliva
An enzyme in the toxic saliva dissolves the calcium carbonate; it can take hours, then the prey dies almost instantly.
Q 26Octopuses sometimes hunt cooperatively with fish, and keep their partners in line by doing what?
Punching them
They regulate both the make-up of the hunting group and their partners' behaviour this way.
Q 27Which octopus has been described as particularly social, living in groups of up to 40?
Larger Pacific striped
Most octopuses are solitary and hide in dens surrounded by middens of uneaten food.
Q 28A dumbo octopus (Grimpoteuthis) holds the depth record for octopuses, photographed at what depth?
6,957 metres
It is the only indisputable record of an octopus in the hadal zone.
Q 29Cirrate octopuses such as the dumbo octopus differ from most octopuses in what way?
They have fins and swim with them rather than jetting
They also usually lack an ink sac and have an internal shell.
Q 30Which habitat has no known octopus species at all?
Fresh water
Some survive at -1.8 C off Antarctica, and Vulcanoctopus hydrothermalis lives at 2,000 m around vents.