Questions people actually ask
Short answers, each with its source. Longer ones live on the topic pages.
How many hearts does an octopus have?
Octopuses have three hearts. Two branchial hearts push used blood through the gills, and a systemic heart pumps the fresh, oxygen-rich blood around the body. Smithsonian Ocean: Octopuses, squids and relatives
Why is octopus blood blue?
Their blood really is blue. It carries oxygen with a copper-based molecule called hemocyanin, while our blood uses iron. Smithsonian Ocean: Octopuses, squids and relatives
How many brains does an octopus have?
The rest of the neurons are in a doughnut-shaped brain wrapped around the octopus’s oesophagus (food pipe). Natural History Museum, London: Octopuses keep surprising us Counting the central brain and the eight arm ‘mini brains’, the Natural History Museum describes octopuses as having nine brains. Natural History Museum, London: Octopuses keep surprising us
Arms or tentacles?
Octopuses have eight arms. Squid and cuttlefish have eight arms plus two longer tentacles for snatching prey. Smithsonian Ocean: Octopuses, squids and relatives
How many octopus species are there?
There are roughly 300 species of octopus, and the number keeps changing as new species are discovered. Smithsonian Ocean: Octopuses, squids and relatives · checked 28 Oct 2026
What’s the biggest octopus?
The giant Pacific octopus is the largest octopus species. Monterey Bay Aquarium: Giant Pacific octopus Monterey Bay Aquarium: a full-grown giant Pacific octopus can weigh more than 50 pounds (23 kg). The heaviest on record weighed 200 pounds (91 kg) and measured nearly 20 feet (6 m) across. Monterey Bay Aquarium: Giant Pacific octopus · checked 28 Oct 2026
What’s the smallest octopus?
Britannica: the smallest octopus, Octopus arborescens, is about 5 cm (2 inches) long. Britannica: Octopus · checked 28 Oct 2026 Smithsonian Ocean: the smallest cephalopods, like the California lilliput octopus, could sit on the tip of your finger. Smithsonian Ocean: Octopuses, squids and relatives · checked 28 Oct 2026
How long do octopuses live?
Octopuses usually live no more than a year. The giant Pacific octopus is a long-lived exception, at about three to five years. Monterey Bay Aquarium: Giant Pacific octopus
Are octopuses venomous?
All octopuses are venomous, but only the blue-ringed octopuses are dangerous to people. Shedd Aquarium: Eight strange and wonderful facts about octopuses Its venom is tetrodotoxin, made by bacteria that live in its salivary glands. Australian Institute of Marine Science: Blue-ringed octopus
Are octopuses clever?
Octopuses can untie knots, open jars and get into toddler-proof cases, and they are expert escape artists. Smithsonian Ocean: Octopuses, squids and relatives Britannica says the common octopus is thought to be the most intelligent of all invertebrates. Britannica: Octopus
What do octopuses eat?
Giant Pacific octopuses eat mostly crabs, clams and other molluscs. Monterey Bay Aquarium: Giant Pacific octopus A telltale sign of an octopus den is a pile of empty crab shells on a rocky bottom. Smithsonian Ocean: Octopuses, squids and relatives
Octopuses or octopi?
Merriam-Webster lists three plurals: octopuses, octopi and octopodes. Octopuses is now the most common. Merriam-Webster: octopus