Octopuses & Squids

Octopuses and squids move by "jet propulsion", sucking water into a muscular sac in the mantle cavity surrounding their bodies and quickly expelling it out a narrow siphon. Both octopuses and squids are related to snails and other molluscs. Unlike snails, octopuses no longer have any remnant of a shell. Squids possess a stiff structure known as a pen that acts as a flexible backbone. Both squids and octopuses have blue blood. Their blood is this colour because they use an oxygen-carrying molecule in their blood that contains copper. 

Octopuses live in dens on the sea floor, while squids live in the open oceans. Octopuses use their eight sucker-lined arms to capture their prey and move about on the ocean floor. Squids have eight arms lined with suckers and two specialized tentacles that they use to reach out and capture prey. Octopuses eat bottom-dwelling crustaceans: squids eat fishes and shrimps. Some deep water squids may be scavengers.  

Octopuses and squids have hard, parrot-like beaks. These are excellent for killing, and tearing pieces of flesh from their prey. Octopuses pierce the shells of their prey, injecting poison that causes paralysis. They then release salivary enzymes, loosening the meat from the inner shell. Squids use their two specialized tentacles to quickly reach out and capture fishes. They tear off bits of flesh and scrape the meat into their mouths with their beaks. 

Octopuses and squids can swim in any direction and can alter their course quickly. Squids use fins located on their heads to propel themselves when swimming at low speeds. These fins steer and stabilize the squids when moving slowly, and wrap around the body when they move quickly, by way of jet propulsion. Most octopuses do not have fins as adults. Some deepwater octopuses are exceptions.

Octopuses are solitary animals that live alone in dens. Some squids live in large schools, others are solitary. Some squids school when young and become solitary later in life.

The male octopus uses a specialized arm called a hectocotylus to transfer sperm to the mantle cavity of a receptive female. The female lays strings of fertilized eggs on the roof of her den. She guards, cleans and aerates the eggs with water expelled from her siphon until hatching. This can be anywhere from 30 days to a year, depending on the species. The female may build a wall of rocks to seal off the den and will remain in the den until just before she dies, after the eggs have hatched.  Squids often mate in large groups, and attach their egg capsules to the ocean floor or to seaweed. Most adult octopuses and squid die after reproducing. Their bodies are recycled in the food web, nourishing other animals, and ultimately providing food for their young when they hatch.

Most poisons produced by octopuses and squids are too weak to harm humans. The blue ringed octopus is an exception. This Australian native produces enough poison to paralyze and kill a human. Our local red octopus, Octopus rubescens, can inflict a nasty nip when provoked.

Yes, squid is commonly called "calamari" on menus. Black pasta is coloured using squid ink and Greek restaurants sometimes serve pickled octopus, called octopothi.

Fishers trawl for octopuses using weighted chains that drag along the ocean floor, scaring the octopuses into a net. Another method involves lowering traps and pots which octopuses will use as shelters. Spear fishing and drift fishing are also practiced. Fishers catch squids by jigging. They shine bright lights and drop lines into the water with special lures called jigs, which they jerk up and down, attracting squids to the light and movement. Recently, fishers have begun to use large seine nets that encircle the squids, forming pockets and trapping them. There are 15 major harvesting areas for squids worldwide, but only two have sustainable harvests today.

Common predators of octopuses and squids are moray eels, fishes, seals, whales, sea stars and several species of birds.

• Colouration: They can change colour and create countless intricate patterns on their bodies to blend with their surroundings.
• High-speed swimming: Some squids travel at high speeds using their fins as wings to leap out of the water, briefly flying away from their predators.
• Ink: Octopuses and squids can expel a dark cloud of ink from an ink sack. This confuses predators and gives the octopuses and squids time to escape
• Bioluminescence: Some squids produce light. In dark waters, this diverts attention by disguising their contours.
• Schooling: Some squids seek protection in numbers, making it difficult for a predator to focus the attack.
• Poison: Some octopuses and squids can release poisons to paralyze predators.

• Touch: Octopuses are extremely sensitive to touch, but cannot discriminate between heavy and light objects.
• Taste: Octopuses have taste receptors all over their bodies and are as much as 10 to 1,000 times more sensitive to taste than humans.
• Sight: Octopuses and squids have excellent vision, but may be colour-blind. Some have a 360 degree range of vision with eyes that are very similar in structure to human eyes.
• Smell: Octopuses and squids register smell in small pits located beneath the eyes.

In traditional narratives, a creature called a Kraken seized large boats and sank them. The animal they were describing may be the giant squid. Although this animal reaches 20 metres in length, it is unlikely that these stories are entirely true.