Squid

Squids are cephalopods similar to octopuses and cuttlefish evolving as early as the Jurassic period. Their elongated bodies, eight arms, and two long tentacles give them that unique appearance. No wonder, in the past, squids were often associated with tales related to sea monsters. They have a significant role in the food web of their ecosystem, acting as predators to fish and crustaceans and prey to larger species like sharks and seals.

Scientific Classification

Animalia
Mollusca
Cephalopoda
Decapodiformes

Scientific Classification

Animalia
Mollusca
Cephalopoda
Decapodiformes

These mollusks can change color for camouflage and signaling, while many species can eject ink clouds to distract predators. Squid are rapid swimmers and move via jet propulsion.

Types of Squid

List of the Common Types of Squid Species

There are over 300 species of squid worldwide. Here are some of them:

  • Giant Squid
  • Glass Squid
  • Colossal Squid
  • Deepsea Squid
  • Humboldt Squid
  • Robust Clubhook Squid
  • Grimaldi Scaled Squid
  • Ruppell’s Octopus Squid
  • Dana Octopus Squid
  • Sharpear Enope Squid
  • Southern Pygmy Squid
  • Umbrella Squid
  • Wonderful Firefly Squid
  • Diamondback Squid
  • Banded Piglet Squid
  • Roundear Enope Squid
  • Jewel Enope Squid
  • European Squid
  • Argentine Shortfin Squid
  • Glassy Flying Squid
  • Long Armed Squid
  • Sandal-Eyed Squid
  • Ram Horn’s Squid
  • Tropical Bottletail Squid
  • North Pacific Bobtail Squid
  • Toothed-fin Squid
  • Eye-flash Squid
  • Firefly Squid
  • Bush-club Squid
  • Joubin’s Squid
  • Market Squid
  • Japanese Flying Squid

Squid
Squid Animal

Physical Description and Appearance

Size: Length: 0.75 in -46 ft (1.6-140 cm)

The smallest known squid is the Southern pygmy squid at 0.75 in, while the colossal squid is the largest, reaching around 46 ft.

Weight: 0.02 oz – 1100 pounds (0.566 g – 500 kg)

Body and Coloration: They have a soft, elongated, tube-shaped body called mantle, ending in a flattened head.  Each side of the head has two large eyes giving them a 360°vision.

In the ventral part of their body lie eight arms and two long tentacles surrounding their mouth. The tentacles are of a greater length in comparison to their arms, also being retractile.

All of their ten arms (including the two tentacles) have disc-shaped suckers, with some of the suckers bearing hooks on them for a better grip.

The mantle contains most of their body mass, with a swimming fin along each side, though they are not the primary source of movement in most species. There are two feathery, white gills on both sides of the mantle.

Consistent coloration is not observed, ranging from sandy brown to vibrant red or ripple with bright metallic rainbows, due to the presence of chromophores, or color-changing cells.

Where are they found

Squids inhabit all oceans worldwide.

Squid Habitat
A Picture of Squid

Where do they live

The habitat of different squid species varies, some living in warmer, tropical, shallow sea waters while others in the cold depths of the oceans.  Some squids thrive in the seas of the polar regions.

How long do they live

Most squids live from 1-3 years, but some can live up to 5 years.

What do they eat

Carnivorous by nature, their diets mainly consist of fish and crustaceans like crabs. However, cannibalism has been observed in some species eating not only other squids but also members of their own species.

Some squids eat up to 30% of their total biomass, with certain species even eating more.

Squid Fish
Image of a Squid

Behavior

  • They are inquisitive creatures and are attracted to light sources.
  • Squids are often seen in groups called schools. However, they aren’t seen forming relationships among themselves.
  • While not as much as octopi or cuttlefish, squids are pretty intelligent. They have shown to be able to count and have demonstrated problem-solving skills. Squids also display pattern recognition capabilities and can communicate through several signals.
  • They locate their prey via sight and touch and then use their tentacles to grab and reel them in. Some squids use the hooks on their tentacles for a better grip.

Predators

The predators differ from one squid species to the other, but penguins, seals, and sharks are common for most of them. The giant squid is a staple part of the sperm whale’s diet.

Squid Eye
Squid Mouth

Adaptations

  • They use various forms of camouflage, such as active camouflage, to match their background color and reflect light through bioluminescence. Some species have color-changing chromophores, while other squids have light-reflecting iridophores. This acts as protection from their predators and allows them to approach their prey.
  • Squids have an internal ink sac. They eject a cloud of ink from this sac, which is a suspension of melanin particles, to escape from predators.
  • The strong beaks, located inside their mouths, are made of chitin. As a result, they are extremely stiff and hard. They help the squid crack open shells of certain prey like shellfish and crabs and then are used to cut food.
  • Their primary form of movement is jet propulsion. They fill the cavity inside their mantle with water and expel it at high speeds to propel themselves forward.
  • Inside their shells exists a gas-filled chamber that lets them stay buoyant while moving underwater.
  • In order to try to rest, they will either do so on the bottom of the sea in such a way to avoid getting mud in their propulsion system, or they will use their tentacles to grab onto a thick clump of plankton.
  • Their eyes are enormous, allowing them to view their surroundings in their entirety. This lets them both locate prey and alerts them of any impending danger.
  • The tentacles are longer than the other appendages and are prehensile, allowing them to extend their reach.

How do they reproduce

Courtship takes place in water, with the male squid selecting his mate of the opposite sex. They undergo elaborate courtship displays with males using a unique arm to transfer sperm packets to the females. Some species go through changes in their color, and body pattern during courtship, and mating, the Caribbean reef squid being one among them.

As the eggs pass through the female squid’s oviduct, they get coated in a gelatinous substance before reaching their mantle cavity where fertilization takes place. The mothers then lay hundreds of gelatinous eggs on the ocean, often in communal areas, hiding them under rocks or holes. After male and female mate, they both usually die.

Squid Eggs
Baby Squid

Life Cycle

After 4-8 weeks, baby squids hatch and are smaller versions of their parents. They feed on tiny creatures called plankton while they grow to adulthood. Very little is known about the life cycle of deep-water squid, though.

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Conservation

As per the IUCN, most species of squid do not have enough data to determine their conservation status, while those with enough data are considered “Least Concern” or “LC”.

Squid – FAQs

1. How many tentacles do squids have?

Squids have two long tentacles, one of their main physical features. They even have eight arms, or precisely two legs, and six arms.

2. Do squids have bones?

No, they do not possess either spinal cords or bones.

3. How fast are squids?

They are extremely fast, reaching speeds of 18 mph.

4. What is a group of squids called?

A group of squids is often referred to as a school, an audience, or a squad.

5. Are squids smart?

While not as smart as octopi, squids are believed to be as intelligent as a dog. Yes; they may not be at par with the octopus or cuttlefish in intelligence, and smartness. However. because of their increased social communications, and efficient problem solving skills, scientists have deemed them equivalent to dogs in smartness.

6. Do squids have venom?

Some squids possess venom, but most are not dangerous enough to kill humans.

7. Do squids have a closed circulatory system?

Unlike most invertebrates, squids have a more complex circulatory system, similar to humans, improving energy efficiency.

8. Can you keep squids as pets?

It is not recommended to keep squids as pets because they are short-lived, known to leap out of tanks, and eat any other occupants in the same tank as them.

Squid Images
Squid Pictures

Interesting Facts

  • Squids are a common foodstuff used in noodle, rice, and stir-fried dishes and are a good source of zinc and magnesium. In English calamari is the term used to refer to squid platters.
  • The giant squid is the inspiration of several myths like the Greek monster Gorgon and Scylla and the Norse myth the Kraken.
  • The 1870 science-fiction novel Twenty Thousand Leagues Under the Sea byJules Verne told a tale of a Kraken-like monster that a giant squid inspired.
  • Squidward Tentacles, a popular character on the animated show Spongebob Squarepants, is based on an octopus despite being named after a squid.