Animals & Nature
Octopus & Squid Quiz
Cephalopod intelligence, ink, chromatophores, and the giant Pacific octopus
Cephalopod intelligence, ink, chromatophores, and the giant Pacific octopus
An octopus has 9 brains and 3 hearts — and 2 of its hearts stop beating whenever the animal swims. Cephalopods are the most intelligent invertebrates on Earth, with complex nervous systems, remarkable camouflage, and problem-solving abilities that continue to astonish scientists. This quiz covers octopuses, squid, cuttlefish, and nautiluses — their anatomy, behaviour, extraordinary species, and ocean biology.
Each round presents 10 randomized questions from a pool of 50, with four multiple-choice options and instant feedback after every answer. Your final score comes with a performance tier and shareable results.
You'll explore how octopuses use tools, open jars, and navigate mazes; why their blood is blue; how chromatophores, iridophores, and leucophores create camouflage in colour-blind animals; the size of giant and colossal squid eyes; the legendary kraken; and species from the tiny blue-ringed octopus to the 13-metre giant squid.
Octopuses have 3 hearts: two branchial hearts that pump blood through the gills and one systemic heart that circulates oxygenated blood to the body. The two branchial hearts stop beating when the octopus swims, which is why octopuses prefer crawling — they tire quickly when swimming.
The colossal squid (Mesonychoteuthis hamiltoni) is the largest squid by mass, reaching an estimated 500 kg and 14 m. By total body length, the giant squid (Architeuthis dux) reaches up to 13 m. A colossal squid specimen caught in 2007 weighed 495 kg and is housed in New Zealand's Te Papa museum.
Octopus blood is blue because it uses haemocyanin — a copper-containing protein — to transport oxygen, rather than the iron-containing haemoglobin used by vertebrates. Haemocyanin turns blue when oxygenated, making the blood appear blue. It also performs better than haemoglobin in cold, low-oxygen deep-sea environments.
Last updated: April 2026