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Home › Sea Life › Marine Animals › Invertebrate › Mollusk › Squid

Information and Facts about Squids

[Squid Phylum: Mollusca] [Class: Cephalopoda] [Order: Teuthida] [Subclass: Coleoidea]

The squid is one of the classic soft-bodied marine cephalopods with bilateral symmetry. They have eight (8) paired arms and two (2) elongated tentacles protected by an outer body wall - called a mantle.

This section contains a collection of fun and interesting facts about different squid species, such as where they live, what they eat, and how these ten-limbed mollusks reproduce.

Habitats and Geographical Range of Squids

Check out our list of marine molluscs and you'll only find a few that can survive in every ocean.

However, there are species of squid in all oceans worldwide, especially shallow marine habitats and inshore tidal pools in:

• South East Asia
• Europe
• United Kingdom

Like many shell-less cephalopods, squid are pelagic creatures. Hence, this diverse group of cephalopods move around in large schools with the natural movement of the water column close to the surface of major seas and oceans.

The squid classification contains more than three hundred (300) members. Some live a solitary lifestyle. But most of them tend to swim together in large groups - known as a "shoal" or "squad".

Interesting Fact: It's true to say that most marine biologists consider the giant squid (Architeuthis dux) as being largest of all squid species

Characteristics of Squids

The phylum of squid is mollusk, meaning they are typical examples of oceanic invertebrates that have a soft body (called a mantle), and they are "decapodiformes" - a cephalopod that displays (bilateralism) like the cuttlefish and octopus.

A soft, elongated mantle sits behind its head. It is a muscular space that contains and protects its internal organs and gills.

Squid also have a backbone-like structure made of chitin (called a pen). This forms an internal shell and helps to support the main part of the body (mantle). It also helps to produce the squid's torpedo-like shape.

Some of the mature adult females can grow to eighteen (18) metres long (60 feet) and weigh up to 275 kilograms (606 pounds).

Whereas the body length of pygmy squids (genus Idiosepius) is less than two (2) centimetres long and weighs less than one (1) gram.

In case you were wondering:

Squids move backwards through the water using a process of "jet propulsion". After filling their mantle with water, they eject it through a narrow funnel for fast movements and directional adjustments.

They use chromatophores (pigment-filled cells) to change their skin colour. Doing so helps them avoid capture and communicate with others, especially when hunting for food.

Like some species of octopus, squid can also squirt clouds of dark ink as a smokescreen distraction and if they feel threatened. There is also evidence that the Octopoteuthis deletron squid will break off its own arms to escape, or evade, its predators.

Pro Tip: Another section contains more information about the anatomy of a squid and how they use the different body parts for feeding, swimming, and mating.

What Do Squid Eat?

Squid are voracious open water predators and the majority of the species can deliver a venomous bite. They use their two elongated, retractable tentacles and suckers to grab prey and their eight sucker-lined arms to hold it.

The mouth contains a sharp, parrot-like beak made of chitin and their narrow oesophagus actually passes through the centre of the brain into the body.

As a consequence of that, they use a radula tongue-like structure and teeth to break their food into small portions before they can swallow it. The daily source of food for these carnivores may include a combination of:

• Copepods (including amphipods and isopods)
• Crabs (especially spider crabs)
• Crustaceans
• Echinoderms (e.g. sea urchins)
• Other cephalopod squid species (i.e. cannibalism)
• Polychaete worms
• Prawns
• Slow-moving fish
• Small sharks
• Small bivalve molluscs (clams, scallops, whelks)

After swooping down on a defenceless animal - and enveloping it with their arms - they pull the captured prey into their mouth for dissection and swallowing.

Different Species of Squids

5 Fun Facts about Squids

• Like other cephalopod molluscs, squid have a large brain (similar to a dog). They can count, use signals to communicate with each other, solve problems, and differentiate patterns. They have three hearts, two of them push blood through the gills and the third pumps blood around the body.
• The large image-forming eyes of the giant squid (Architeuthis dux) are about the same size as a volleyball. In fact, they have the largest eye of all creatures in the animal kingdom.
• Squid are considered as being sentient (capable of sensing or feeling) in the United Kingdom. Hence, the fact that they can feel distress, pleasure, boredom, excitement, and pain means their welfare is considered in government policymaking.
• Having a swimming fin on each side of the mantle, and a streamline shape, means squids can swim faster than most fish families. They use "jet propulsion" to move through the water via a tubular funnel (also called a siphon) and often break the surface (e.g. like a flying squid).
• Many squid species are negatively buoyant. As a result, they need to swim continuously to stay in the water column. Even so, some live in the deep ocean during the day and migrate vertically thousands of feet to the surface during the darkness to feed on sea shrimp and lanternfish (small mesopelagic fish).

How Do Squids Reproduce?

Compared with many other aquatic invertebrates, the average lifespan of a squid is short. In fact, most of them will die within two (2) years. Furthermore, male squid die soon after the mating ritual is complete. The females also die shortly after expelling masses of eggs.

After copulation takes place, the male will use a "guarding" technique to try and prevent other males from mating with his female.

Because most marine mollusks live close to fringing coral reefs and rock pile burrows, females can lay their eggs in areas with greater protection.

Nonetheless, the squid reproduction process and their mating rituals actually contribute to the premature death of both parents.

Here's the thing...

The male uses a special arm to deliver spermatophores into the mantle cavity of the female. Following that, he will die shortly after.

It gets worse. The female stops eating for several weeks after laying the eggs. Her endocrine system has a genetic program (aka cellular suicide) that kills her when the squid eggs (up to 400,000) have hatched into fry.

After the eggs have hatched, squid larvae drift in clouds of plankton, feeding on zooplankton as they start growing.

Threats and Predators

Most squid species are not considered as being endangered. Even so, there are several global threats to their long term survival, especially overfishing, climate change, and being consumed by humans.

Typical squid predators also include large sharks and bony fish, whales (e.g. sperm whales), seals, and sea birds (especially the grey-headed albatross)

Important: The IUCN Red List of Threatened Species is a comprehensive source of information about the global conservation status of animals, fungi, and plants. Currently, the IUCN lists the diamondback squid (Thysanoteuthis rhombus) and the colossal squid (Mesonychoteuthis hamiltoni) as being of "Least Concern" (LC).

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