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Octopus and Squid

• Octopi have no shell, eight arms, a pouch-shaped body, and two large, highly developed eyes. Their prey (crabs, lobsters, and other shellfish) is caught by the sucker-bearing arms and pulled into the web of tissue at the base of the arms, paralyzed and partially digested by a poisonous salivary secretion, and chewed by the horny, beak-like jaws and the radula, or tooth.
  
  
• An octopus can change colour rapidly due to pigment cells in the skin that the animal can expand and contract by muscular action. Waves of colour may sweep over an octopus, apparently reflecting its emotional state.
  
  
• The body of an octopus has no bones and is very flexible, making it difficult to contain. An octopus with an arm span of 30 cm can pass though a hole less than 1 cm in diameter.
  
  
• The largest of the 600 species of octopus is the Octopus dofleini, a bottom dwelling hunter found on the Pacific Coast of Canada. Mature males average about 23kg with an arm span of 2.5m, but one specimen, reported in 1957, was 9.6m in diameter and weighed an estimated 272kg.
  
  
• An octopus has three hearts.
  
  
• The octopus learns very quickly. Offered a closed glass jar containing a live lobster, it took one octopus only three tries to learn how to remove the stopper.
  
  
• One octopus can learn by watching another. At the Statzione Zoologica in Naples Italy, an untutored octopus was placed in a tank where it could watch another being trained to choose between red and white balls. Offered the same choices the untrained octopus chose correctly almost every time.
  
  
• The blue ringed octopus, found around Australia and parts of Southeast Asia, carries a neurotoxin so potent that its venom could cause the paralysis, and even death, of 10 adult humans.
  
  
• In December 1993, scientists in the submersible Alvin were astonished to find, at 2500m depth, two octopi apparently mating. This seemed bizarre because they were both males...and they were two different species.
  
  
• The 'vampire squid of the infernal depths' (Vampyroteuthis infernalis) is a strange animal halfway between octopus and squid. First collected in 1903, a typical 20cm-long specimen will have eyes 3cm across and is thought to drift slowly in the depths, almost like a jellyfish.
  
  
• The squid is one of the most highly developed invertebrates, and swims by expelling water in jets. It has 10 arms, two of which can seize prey, a well-developed nervous system and eyes very similar to those of humans.
  
  
• On Nov. 2, 1878 the largest reported specimen of giant squid ran aground in Thimble Tickle Bay, Newfoundland. It weighed 2.2 tonnes, its body was six meters long, and one of its tentacles was 10.6m long.
  
  
• Squid are the main food of sperm whales. Squid beaks are not easily digested and are often found in the stomachs of captured or stranded sperm whales. Finds of 5,000 to 7,000 squid beaks are not uncommon.
  
  
• In 1977 Malcolm Clarke, a British specialist in sperm whales, estimated that the world's 1.5 million sperm whales would consume about 100 million tonnes of squid per year. The total human squid fishery in 1994 was about 90 million tonnes.