Squid are highly adept swimmers with several adaptations that allow them to move swiftly through the water. This shell provides the otherwise soft body of the squid with rigidity and helps maintain body shape. Like many marine organisms, squid have gills that they use to obtain essential oxygen from water.

Squid contribute to the ecosystem by providing food for other creatures. Humans are probably the squid’s greatest natural enemy, but sharks, seals, whales, dolphins, seabirds, deep-sea fish, and other squid also eat these tubular, multi-armed cephalopods.

Squid Habitat Squid are found in oceans all around the world. Not all species live in all parts of the world. Some squid prefer warmer, tropical waters while others thrive in the cold seas where krill and other food can be found, but as a species they can be found almost everywhere.

They play an important role in the open water food web. The two long tentacles are used to grab prey and the eight arms to hold and control it. The beak then cuts the food into suitable size chunks for swallowing. Squid are rapid swimmers, moving by jet propulsion, and largely locate their prey by sight.

Many of these creatures have special pigment cells called chromatophores in their skin. By controlling the size of the cells they can vary their color and even create changing patterns. In squid, color changes also occur when the animal is disturbed or feels threatened.

The giant Pacific octopus has three hearts, nine brains and blue blood, making reality stranger than fiction. A central brain controls the nervous system. In addition, there is a small brain in each of their eight arms — a cluster of nerve cells that biologists say controls movement. Two hearts pump blood to the gills.

Though octopuses and squid are both formidable fighters in the wild, they aren’t typically dangerous to people. That doesn’t mean they’re always harmless. Some species are particularly well equipped for defending themselves against larger creatures, and they’re strong enough to kill a human if they felt threatened.

The squid would be able to hang on to the shark with its serrated suction cups and break through the body of the shark. The shark would either take heavy damage on its body or lose a fin. In either situation, the shark will die, either from a loss of blood or from drowning.

Although octopuses usually go after prey smaller than themselves, they can use their strength to overpower substantial adversaries, including sharks. In fact, it was also in Seattle, at the Seattle Aquarium, that a giant Pacific octopus was filmed killing a shark a few years ago.

The two creatures engage in a fierce battle, at the end of which, the octopus strangles the shark after the shark dismembers some of its tentacles, causing it to bleed to death.

octopuses, see below for variants) are soft-bodied, eight-limbed molluscs of the order Octopoda (/ɒkˈtɒpədə/, ok-TO-pə-də). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Most species grow quickly, mature early, and are short-lived.

Octopuses have blue blood, three hearts and a doughnut-shaped brain. But these aren’t even the most unusual things about them! Known for their otherworldly look and remarkable intelligence, octopuses continue to reveal astonishing qualities, abilities and behaviour.

Possibly they do. Octopuses and their relatives the squids change their skin colours and patterns when they feel alarmed. Other scientists are examining the possibility that animals feel not just basic emotions such as joy, anger, fear and love, but also the more complex emotions of jealousy, guilt and shame.

Elsewhere octopuses have plugged their tanks’ outflow valves, causing them to overflow. This apparent problem-solving ability has led cephalopods (particularly octopuses, because they’ve been studied more than squid or cuttlefish) to be recognised as intelligent.

CHIMPANZEES. RECKONED to be the most-intelligent animals on the planet, chimps can manipulate the environment and their surroundings to help themselves and their community. They can work out how to use things as tools to get things done faster, and they have outsmarted people many a time.

In particular, the Coleoidea subclass (cuttlefish, squid, and octopuses) is thought to be the most intelligent invertebrates and an important example of advanced cognitive evolution in animals, though nautilus intelligence is also a subject of growing interest among zoologists.