A Face-off Between Squid Vs. Octopus - What's the Difference?

Difference between squid and octopus
Squid and octopuses belong to the same class called 'molluscs'. Both are head-footed aquatic animals. However, while studying a squid vs. octopus comparison, it was found that both these animals varied in their physical characteristics, habitat, and behavior.
Did You Know!
Though squid and octopuses come under the class molluscs, they do not have shells on their bodies.
Squid and octopuses are cephalopods, members that fall under the molluscan class Cephalopoda. This class of animals is considered to be the most intelligent invertebrates around. Both these creatures live in salt water, and belong to the kingdom Animalia. They share the same phylum, class, subclass, order, and superorder. Their blood is blue due to the presence of copper in it, and they also have three hearts each. They can survive in both, tropic and temperate zones.
Appearance
Octopus Appearance
An octopus is a soft-bodied creature, as it does not possess a skeleton. It has two eyes, eight long arms with suckers, a round head, a bilaterally symmetric body and a mantle. It also has two lines of suckers in its tentacles that helps it taste its food. An octopus has a beak and a tongue, called a radula, which enables it to open and bore into the shells of prey. Once it breaks into the shell, it injects a paralyzing venom into the prey. It has a mouth at the center of the limbs.
These fascinating sea animals vary in length from 1 cm to more than 5 meters long. The Giant Pacific octopus has a lifespan of only four to five years, yet it can weigh up to 600 pounds. They have a short lifespan, which can vary from about 6 months to 5 years.
Squid Appearance
A squid has a soft body like that of an octopus, but a robust and pliable structure. It has a triangular-shaped head. It also has eight arms and a mantle. Additionally, it has two head fins, a pair of tentacles with hooks, or sucker rings, or both. The body is inside the mantle, which has two side fins. These creatures use these fins for swimming. On the inside of the body, they have a structure known as a pen.
Squid vary in size from 1 cm to around 40 feet. They live for around a year or so. Most do not grow more than 60 centimeters. However, the giant squid can grow up to 20 meters and weigh more than even 1,000 pounds.
Habitat
Octopus in Coral Reef
There are manifold regions where octopuses thrive, like coral reefs, pelagic waters, and the ocean floor. Most of the time, they live on the interior of caves or holes of the sea floor. They prefer living by themselves, and in brief, are solitary creatures.
They possess a number of defending mechanisms for saving themselves against various predators. They can use their camouflaging mechanism, diematic displays, body ink, ability to navigate fast through water and their ability to escape for this purpose.
Squid In Water
Squid like to live in the open sea. They thrive at various depths, and their habitat depends upon their species. Squid may also live by themselves like an octopus, but on most occasions, they live in groups in their early life. However, some live in solitary as they age.
For protecting themselves, squid change in color to mix in with the background or aura. Their skin is covered in chromatophores. On certain occasions, they release a black mucous ink from a sac to puzzle their predators.
Diet
An octopus eats crustaceans that dwell at the bottom of the sea, most of which include crabs, whelks, small fish, molluscs, clams and lobsters. Octopuses are also skilled hunters. They have the capability of bagging anything depending upon the waters they are staying in. Furthermore, their head and arms enable them to defend themselves well against enemies.
The supple arms of octopuses hold and pierce the shells of their prey, and release venom that makes the body unconscious, enabling them to consume the animal. They release salivary enzymes which takes out the meat from the inner shell, thereby enabling them to devour the meat.
Squid Eating Fish
Squid feed on shrimp, crabs and small fish. They are intelligent and furtive hunters that feed on other ocean creatures. With the help of their tentacles, they capture their prey. At the end of the tentacles, there are tentacle clubs enclosed within suckers that stick onto their prey. The squid then pulls the prey with its limbs and draws it into its mouth.
Intelligence
Octopuses and squid are highly intelligent invertebrates. They use complex reasoning to find and hunt their prey. Their large brains are capable of storing and processing complex information. Scientists have found that octopuses are capable of solving mazes and recalling solutions. They solve problems readily, learn quickly and can even remember what they have learned.
Octopuses have highly developed sensory organs. They possess taste receptors all over their bodies, which are 10 to 10,000 times more sensitive than that of humans. The suction cups are endowed with chemo receptors, so they can taste what they are touching. Their arms have tension sensors by which they know if their arms are spread out. Octopuses and squid have high quality vision. However, they may be color blind. They detect smell through the pits that are situated beneath their eyes.
Locomotion
Squid Eating Fish
Octopuses can crawl and swim. Their fastest mode of movement is jet propulsion, followed by swimming and walking. They crawl with the help of their arms on soft and tough surfaces.
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Squid Locomotion
For the squid, there is a siphon in their mantle that is used to bring out water and waste. They use this jet propulsion for locomotion. Squid pump out water from the mantle while surfing through the water; that is also how they inhale.
Reproduction
Octopus Mating
The male octopus uses an arm called 'hectocotylus' to carry spermatophores from the terminal organ of the reproductive tract into the female's mantle cavity. After laying eggs, females guard their eggs in their dens or make walls to close the caves to secure the eggs till they hatch. Males expire after a few months of mating, while females are capable of keeping the sperm alive inside her for weeks until the maturation of the eggs. Post fertilization, the female lays around 200,000 eggs.
Squid Mating
The male squid fertilize the female by using an arm that transfers the sperm to a specific layer in the female beak. Generally, they reproduce in schools. Their eggs are attached to the seaweeds or sometimes on the sea floor. After that, the squid die. Squid eggs are generally seen in clusters inside an egg case. The male dies a short time after mating, and the female dies once the eggs are laid.
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As Food
Takoyaki
Octopus is used as an ingredient in Japanese food like sushi, takoyaki and akashiyaki. In Greek restaurants, Octopothi, which is a pickled octopus is served. In Korea, certain species of octopus are eaten uncooked. Miruhulee, a Maldivian cuisine, is made with octopus tentacles and fried in curry leaves. Octopus is eaten with potatoes and olive oil in Portugal. In Spain, Greece and North and West Africa, octopus is a popular food item. It is popular in Mediterranean and Hawaiian cuisine too.
Stuffed Squid
The giant squid are meals to sperm whales, while the smaller kinds are food to albatrosses, fish and humans. As a menu item, a squid is known as 'calamari'. In black pasta, squid ink is used for decoration.
Health Benefits
The octopus is a low-calorie sea food and contains protein. It is also a good source of iron, potassium, phosphorous and selenium. It provides essential vitamins such as vitamin A, vitamin B, vitamin C, and some omega-3 fatty acids - a vital component to minimize the chance of heart disease, cancer, and depression. It was also found to enhance the immune system, as well as aid brain development in children.
The squid contains copper that covers most of the body needs. It helps cure arthritis and the damage caused by free radicals. They also contain phosphorous and vitamin B12.
After all this, there is yet a great deal about squid vs. octopuses that is unknown to us. Researchers are trying to discover more so that we are familiarized with new and interesting facts about these enamoring creatures.