Squid’s Hidden World: Adaptations, Reproduction & Species
Disclosure: Some links may be affiliate links. If you buy an item via links on our site, we may earn a commission. Learn more.
The ocean is brimming with life and packed with amazing creatures. Squid are among some of the most fascinating, and there are more than 300 species, each with its own unique adaptations and characteristics. Let’s dive into the depths and explore more about these incredible creatures.
Squid Overview
Squid belong to the same family as creatures such as cuttlefish and octopus; cephalopods. These are incredibly intelligent marine animals capable of precise hunting, building smart nests, and even using tools. Squid fall into a family within the cephalopod group called Teuthida and are characterized by their long bodies, ten arms, and unique head shape.
While squid have ten arms, only two of these are used for catching prey, and these are longer than the other eight, which also have suction cups.
Humans have been lucky enough to discover many ancient fossils of animals that are closely related to squid, which means we’ve been able to profoundly study these fascinating creatures. One such example of these fossils was a relative of the vampire squid, thought to be around 328 million years old.
With so many squid species, there are clear differences between each one in terms of appearance and size. For example, some squid can grow to more than 40 feet (12 meters), while others could fit in the palm of your hand. These creatures have a unique way of moving through the water using jet propulsion, which sees them expelling water through a siphon which in turn creates thrust for super quick movement. This comes in handy when capturing prey and trying to escape danger.
One of the biggest threats for squid are predator species such as sea birds, whales, and sharks. But because they are both predators and prey, they play an important role in keeping prey populations balanced and acting as a food source themselves. However, they do have some unique defense mechanisms, such as bioluminescence which they also use as a lure for prey and for communication.
These intelligent animals not only use bioluminescence for communicating with one another; they also use body language and visual cues. These signals are designed for things like mating, displaying their mood, and defending territory.
As well as varying sizes and appearances, squid live in different habitats and can be found in oceans all over the world. Some prefer the shallow waters of the coast, while others can be found at depths of up to 20,000 feet (6,096 meters), such as the bigfin squid.
But what’s perhaps most incredible about squid is how smart they are. These prehistoric animals are able to adapt to their environment and can even learn from their experiences. What’s more, they’ve been shown to have great problem-solving abilities. In fact, with more than 500 million neurons, scientists agree that they have more complex brains than rats!
Anatomy
Let’s now explore the intricacies of squid anatomy and uncover the distinct adaptations that allow it to thrive in the ocean environment.
Head
One of the most definable characteristics of a squid is its head. These animals have a very distinct shaped head that houses the eyes, brain, and beak. These organs are for sensory and feeding purposes, and squid have eyes that are larger than any other animal in the world. In some species, they can measure over 10 inches (25 cm)!
Because of their size and the ability to detect polarized light, squid have excellent vision, which allows them to see in low light and easily detect prey and predators in the water.
The brain is also much larger in comparison to other invertebrates, contributing to the squid’s intelligence. The brain is a ring of nerves that sits around the squid’s esophagus and is surrounded by ganglia which are attached to the sensory organs and pass information between them and the brain. Their nervous system is far more complex than similar creatures and even features chemoreceptors that help the squid to detect chemical changes in the water.
Squids’ heads also contain a mouthpart called a buccal mass which is, for all intents and purposes, a beak. This sharp chitinous structure aids the squid when eating and allows it to rip apart its prey. In addition to this, squid also have a radula which contains teeth and allows the animal to grasp its food.
Some species of squid are capable of bioluminescence which occurs because of photoreceptors on the head. There are other species that use chromatophores to change the color on their heads which allows them to camouflage and communicate with other squid. In some cases, these chromatophores also allow the squid to alter the pattern on the skin.
But perhaps the most fascinating part of the head is the siphon on the underneath. This is a special funnel through which the squid squirts water from the mantle, creating thrust for fast movement in a process known as jet propulsion. It is this same opening that enables a squid to release ink from an ink gland near the anus which it uses to scare away predators.
Mantle
The mantle is what makes up the majority of the squid’s body mass and is where we find many of the squid’s vital organs. This main body part is typically an elongated shape and is one of the most easily identifiable physical characteristics of these animals.
When performing jet propulsion, it is the mantle that creates the pressure to expel water from the siphon. There are powerful muscles within the mantle that, when contracted, draw in water from the environment. Contracting these muscles again, the squid can expel the water.
Additionally, the movement of water within the mantle contributes to the squid’s buoyancy, allowing it to move up and down in the water.
One of the reasons that squid are such good swimmers is the flexibility of the mantle. While it may look like a solid mass, it’s actually filled with flexible muscle fibers that can be controlled to change the shape of the squid. As the squid moves, mucus-producing tissue inside the mantle prevents friction.
The mantle is also essential in allowing the squid to ‘breathe’. Although they do not have lungs like us, squid still exchange oxygen and carbon dioxide using their gills which are located on the mantle. Water is taken into the mantle and, as it moves over the gills, these gasses are exchanged. In order to ensure consistency with the water flow, the mantle continually and gently contracts. Once oxygen has entered the bloodstream, blood vessels within the mantle transport this to the rest of the body.
As is the case with the head, the skin of the mantle also contains chromatophores, which allow the squid to change its color. This part of the body is also able to create bioluminescence in some species.
Tentacles
Squid have two tentacles which are two of the ten arms but are longer than the other eight and allow the squid to capture prey. These flexible appendages protrude from the squid’s head near the mouth, allowing the animal to easily pass food to its mouth with the help of the eight shorter arms.
Along the length of the tentacles are suction cups which are surrounded by strong muscles, enabling the squid to grip various objects and surfaces. The force of this grip is incredible and, in some species, can exceed 100 psi. This comes in handy when hunting and for self-defense by latching onto an attacker.
There are some species whose suction cups are equipped with serrations or hooks, which further improve their grip. This feature and even the arrangement of the suction cups varies between species, and each is specially adapted to its own environment and needs.
In some species, such as the opalescent squid, the tentacles are also used during mating, with the male grabbing the female with his tentacles which then turn red!
Arms
As well as their two long tentacles, squid have eight shorter arms which are set around the mouth in a circular pattern. These arms are used in feeding and allow the squid to move food from the tentacles to the mouth.
Just like the tentacles, squids’ arms are incredibly flexible, improving the agility and precision, but they are not equipped with suckers. However, they do have a lot of sensory receptors, making them easily able to pick up on chemical cues, vibrations, and touch.
As well as feeding, squid use their arms to groom themselves, removing debris from their bodies. Additionally, the arms may be used in mating rituals, and males even have a mating arm which they use to pass sperm to the female.
Reproduction & Life Cycle
Squid reproduce in a very interesting manner and engage in courtship displays and mating rituals in order to attract a mate. Moreover, squid go through several life stages before reaching maturity, and most species tend to live between one and three years, although some larger species may live up to five years.
Reproductive Strategies
Squid are sexually reproductive animals and this involves males and females coming together to combine gametes. However, unlike humans, whose gametes are combined inside the body, squid release their eggs and sperm into the water. Females can release up to 100,000 eggs and typically die soon after spawning.
The male releases sperm using a specialized mating arm known as a hectocotylus which transfers packets of sperm to the female who can then store them until they are needed. She does these using a special receptacle, which allows her to retain the sperm for a long period of time. The benefit of this is delayed fertilization meaning that females can fertilize their eggs at the optimal time. This also means she can fertilize the eggs internally, providing them with greater protection and a higher chance of reproductive success.
While mating occurs, males of some squid species will protect the females by guarding her from predators as she fertilizes the egg.
There are even instances where groups of squid will gather and release their gametes into the water at the same time. This ensures better genetic diversity and a greater chance of successful reproduction. The onset of mating is usually determined by several factors including seasonal changes, temperature, and light.
When the eggs are laid, they are covered by a capsule made from a gelatinous substance which improves their buoyancy and ensures they are protected. The color of this capsule also ensures camouflage and the exchange of oxygen and nutrients. While the female may attach her eggs to a surface, she doesn’t have much involvement with them after this. Although some species pay more attention to their eggs than others.
Early Life Stages
Inside the egg capsules is a yolk which sustains the developing embryos during this early stage of life. Within each capsule, there could be as many as 300 eggs, which take around six weeks to develop and be ready to hatch.
When squid babies hatch (they’re known as paralarvae), they don’t look all that dissimilar to their adult counterparts, aside from a few missing features, such as all of their tentacles. However, from the moment of birth, they benefit from fully developed eyes and excellent vision as well as the ability to change color. At this stage, however, they young are usually transparent and extremely delicate, and many do not survive.
They are born as a type of plankton and often drift along on the water current, close to the surface where they’re vulnerable to predatory attacks. In order to develop further, they feed on smaller plankton and this encourages the growth of tentacles and other features.
Growth & Maturity
While the growth rate of the paralarvae does vary between species, it is typically very fast owing to the need to develop and avoid predation. Moreover, environmental factors like habitat condition, food availability, and temperature can also influence growth rate. This speedy growth is a result of the paralarvae’s planktonic diet and, as they feed, they begin to grow new tentacles and features that ensure their survival as they reach their juvenile stage.
When they reach this stage, the young start looking much more like their adult counterparts, but growth is not yet finished. The tentacles begin to develop suction cups which better allow the individual to capture prey such as crustaceans and fish.
Additionally, juveniles continue the development of chromatophores, which allow them to alter their color to suit their environment; a key factor in avoiding predators. Not only this, but their ability to change color enables them to communicate with other squid.
Owing to their short lifespans, squid reach sexual maturity at quite a young age, although this varies between species. This also depends on their weight. For example, the giant squid is usually ready to reproduce by the age of three when it reaches around 1,000 lbs (454 kg).
Lifespan
It may surprise you to learn that squid do not have a lengthy lifespan. Scientists believe that some species, like the short-finned squid, only live for around 18 months. However, on average, most species live to between three and five years.
Species type is not the only thing that influences the lifespan of the squid. Other environmental factors like water temperature, predators, and the availability of food also play a part.
As a squid gets older, it undergoes the process of senescence and may begin eating less, reproducing less, and gradually deteriorating.
Defense Mechanisms
While squid are excellent predators, they are also preyed upon by larger animals like whales and sharks. Because of this, they have adapted several useful defense mechanisms.
Camouflage & Mimicry
In order to remain safe from predators, squid have adapted the ability to change color, which allows them to blend in with their surroundings. This adaptation also enhances communication between individuals, allowing them to defend their territory, signal the desire to mate, and much more.
Squid are able to do this because of cells called chromatophores, which are located on the skin. These cells contain pigment sacs and, as the muscles around them contract, the color of the cells changes. What’s truly incredible is that this happens in the blink of an eye, so squid are quickly able to conceal themselves. Moreover, they’ll often use this ability to distract predators.
The general color of a squid is darker on the top and lighter on the bottom. This is common in marine creatures and makes them more difficult to spot both above and below.
Not only that, but there are some species that can also change the texture of their skin by controlling muscular structures called papillae. This can result in a spiky, dented, or bumpy appearance to blend in with things like reefs and rocks.
As well as changing their color and texture, squid also use bioluminescence to defend themselves. This isn’t something that is seen in all species but is seen in many to varying degrees, especially deep sea species. Some use this in order to blend in with natural light, while others display bright lights that serve as a distraction and may also lure in prey.
Ink Defense
Squid have ink sacs that are located between their gills, and these sacs produce melanin that colors the ink. There is also a funnel that produces mucus, which makes up the main part of the ink, and this substance is used in self-defense.
When a squid feels threatened, it uses the same muscle contractions that it uses in jet propulsion to rapidly expel this ink and confuse its predator while the squid makes a quick escape. The ink acts as something of a smokescreen, concealing the squid while it makes its getaway.
Not only does the ink itself obscure the predator’s vision, but the melanin content makes the water darker, further decreasing visibility. However, squid are unlikely to use this defense tactic before they’ve employed all others, such as color changing and jet propulsion. They’re much more likely to try and evade predation altogether as opposed to having to confront an attacker.
Almost all cephalopods, apart from two species of deep sea octopus, are able to produce ink. But within squid species, this ink may have a slightly different composition. For example, some species’ ink contains other chemicals that have varying effects. It’s thought that some species’ ink contains chemicals that can deactivate the sensory abilities of their predators while others may act as an irritant.
Jet Propulsion
I’ve touched upon jet propulsion a couple of times already in this article, but I’d like to go into a little more detail. This is a defense mechanism that squids use in order to make a rapid getaway when faced with a threat and involves them shooting out water that generates thrust to enable this movement.
Water is taken into the mantle, and then the squid contracts its powerful muscles, sending the water out of the siphon at a very rapid rate. In turn, the generated force enables the squid to move at lightning speed.
While this may seem like a haphazard process, the squid actually has a great deal of control over what is happening. It can control the direction in which it moves by shifting its siphon which ensures it gets as far away from the threat as possible.
You might think that merely swimming away would be effective, but this requires the use of a lot of energy. Jet propulsion requires far less energy which is beneficial for the squid. However, they’re only able to cover short distances when they do this. That said, there are some smaller species that can shoot themselves 25 times their own body length in one burst. As with other adaptations, jet propulsion varies between species.
If a squid feels particularly threatened, it may combine jet propulsion with ink, in a dual attack against a predator. When this happens, the ink serves as a distraction, allowing the squid to make a quick getaway and improving its chances of survival.
Diet
All species of squid feed on a carnivorous diet, which may consist of fish, mollusks, crustaceans and sometimes, other squid. While this may be considered cannibalism, it’s normally a case of larger squid species preying on smaller ones. Of course, the diet of each species varies greatly according to their location, size, and other factors.
In any case, squid are amazing predators that are equipped with long suckered tentacles that allow them to grab their prey. They’re also known for their fast-movements and ambush tactics. Some species will remain close to the ocean floor and wait for food to pass by while others engage in vertical migrations. This usually happens in nocturnal species that move up the water column in search of food when there are fewer predators around.
After prey has been captured, the squid uses its eight arms to move it towards the mouthparts. This consists of a beak and radula that allow the squid to hold onto the food and break it apart.
Most squid species have a high metabolic rate which means they need to eat often. However, some deep sea species’ metabolic rates are much slower. For example, the colossal squid is thought to have such a slow rate of metabolism that it only needs around 1.05 ounces (30 grams) of food per day, despite adults weighing up to 1,100 lbs (499 kg)! This demonstrates the amazing adaptations of various species according to the environments.
Types of Squid Species
There are more than 300 species of squid in the world’s oceans, and they’re all unique in their own ways. Let’s meet some of the most intriguing species and find out a little more about them.
1. Giant Squid (Architeuthis dux)
The giant squid is perhaps one of the most well-known squid species, but it’s also extremely mysterious because it lives at depths of up to 2,000 feet (610 meters). In fact, it wasn’t until 2004 that photos were taken of these animals in the wild. In any case, the species has inspired many sea-monster stories and is often the subject of legend.
Giant squid are, as their name suggests, very large and may grow up to 43 feet (13 meters) in length. What’s more, with eyes that grow up to 10 inches (25 cm), they have the biggest peepers in the animal kingdom and amazing vision.
There is still much to learn about this species, and it is of great interest to scientists, but it’s not easy to study. However, it is believed that the giant squid possesses bioluminescent abilities as well as chromatophores that allow it to change color and blend in. We also know that the giant squid is a fantastic predator and is likely to play an important role in controlling prey populations in the deep ocean.
2. European Squid (Loligo vulgaris)
Out of all the squid species, the European squid is one of the most common and has a wide distribution around the Mediterranean Sea and the North Atlantic. Because of this, European squid are often harvested for dishes like calamari as well as being used as commercial fishing bait. Although the exact number of individuals in the wild is unknown.
European squid are not a large species and typically grow to around a foot in length. They live at depths of up to 1,600 feet (488 meters) but are also commonly found in coastal waters, where they’re easy to identify thanks to their reddish/pink coloration.
Only the males possess chromatophores, and they’re also larger than the females, growing more rapidly throughout their juvenile stages. However, this species is very short lived, not usually lasting longer than 12 months.
3. Colossal Squid (Mesonychoteuthis hamiltoni)
As you can probably tell from the name, the colossal squid is one of the largest creatures in the sea and can grow up to 40 feet (12 meters) in length. But while they’re massive, they’re not considered a threat to humans because they live so far below the surface; up to 3,280 feet (1,000 meters)!
They’re found in the Southern Ocean, particularly around Antarctica which again, means they very rarely come into contact with humans. This has also made it difficult to study these marine beasts, especially when you also consider their elusive nature. What we do know has largely come from deceased individuals that have been washed ashore.
Down in the ocean depths, it’s thought that the colossal squid feeds on fish as well as other squid. From what we know, they’re excellent hunters and have hooked tentacles that allow them to better capture prey. They’re also adept at spotting prey thanks to their large eyes and fantastic vision.
But, despite their size, colossal squid are not exempt from predation. It’s thought that the sperm whale is one of its main predators after scientists found undigested squid beaks in their specimens. Still, numbers are thought to be healthy, but we can’t be sure. The first colossal squid was discovered in 1925, and only 8 more have been found to date.
4. Humboldt Squid (Dosidicus gigas)
Most squid species are docile and avoid interactions with humans, but the humboldt squid is known for its more feisty and aggressive nature. These are large animals that grow to around 6.6 feet (2 meters) in length and, when it comes to hunting, this is where their aggression really shows. They voraciously attack their prey using their long tentacles and sharp beaks and are even known to eat one another!
While cannibalism among humboldt squids does happen, it’s usually reserved for when food sources are limited. In fact they’re actually team players and are known to group together in order to have more success when hunting. Individuals in these groups can number into the thousands.
What’s more, they may move up and down the water column in search of food in the Eastern Pacific waters they inhabit.
5. Firefly Squid (Watasenia scintillans)
Sometimes called the sparkling enope squid, the firefly squid has a stunning appearance thanks to its bioluminescent abilities. This comes in handy in the deep ocean where these squid and their larger than average eyes allow them excellent vision down there in the darkness.
Found in the western Pacific, firefly squid are tiny at just 3 inches (7.6 cm) in length. While they do inhabit the deep ocean, they actually rise to the surface for nocturnal hunting, and their translucent appearance makes them less obvious to predators.
Firefly squid are incredibly significant in certain parts of the world, including Japan where there are special festivals that celebrate them. Here, they’re known as hoturika and are even considered to be a local delicacy.
6. Southern Pygmy Squid (Idiosepius notoides)
As its name suggests, the southern pygmy squid is one of the smallest on the planet. Adults don’t grow to more than 0.4 inches (1 cm) in length and are often hidden among the seagrass around the waters of Australia and New Zealand. Being so small and owing to its transparent body and color changing abilities, the southern pygmy squid is easily able to blend in with its surroundings.
The southern pygmy squid may be small, but it has a very unique appearance with forward-facing eyes and a rounded body. It protects itself by using a special secretion to stick itself to the seagrass during the day and only comes out at night to hunt for tiny organisms and small shrimps and crabs. After mating, females protect their eggs by sticking them to their bodies using a similar method.
In addition to this, southern pygmy squids are able to produce ink as a distraction to predators like fish and even other squid.
7. Vampire Squid (Vampyroteuthis infernalis)
It’s not hard to see where the vampire squid got its name when you look at its webbed skin cloak and large red eyes. But despite their scary appearance, these squid are not at all dangerous. Moreover, they can live up to 3,000 feet (914 meters) below the surface so rarely come into contact with humans.
Interestingly, vampire squids are not considered a true squid but are still part of the cephalopod family. Not only do they have a very special appearance, but they’re also capable of bioluminescence, which they use to confuse prey. Additionally, they also use one of their arms to wrap around the body and act as a shield during an attack.
Vampire squid are found in oceans all over the world, including the Indian, Atlantic, and Pacific where they feed on marine particles that fall from the surface. Having a low rate of metabolism, these squid are perfectly adapted to deep sea life, but their location does mean that we still have a lot to learn about their behaviors.
8. Caribbean Reef Squid (Sepioteuthis sepioidea)
The Caribbean reef squid is undoubtedly one of the most adorable squid species with its pretty colors and small size that doesn’t usually exceed 8 inches (20 cm). They have large fins and a streamlined body with an ability to change color between red, white, brown, and blue.
These squid live in coral reefs where mating takes place and don’t tend to go deeper than around 30 feet (9 meters). However, there have been reports of adults diving up to 492 feet (150 meters) in open water, although this isn’t common.
When looking around the Caribbean reefs, you may notice these agile swimmers moving in groups. Within their social groups, these reef squids will use their color changing abilities to communicate and put on mating displays. And it’s not hard to get up close and personal with them since they’re often curious and friendly enough to approach humans in the water.
As well as being important for tourism because of their interactions with humans, Caribbean reef squid are also essential to their ecosystem, being both a predator and prey species.
9. Starry Bobtail Squid (Euprymna berryi)
Sometimes called the hummingbird bobtail squid, this small species only grows to around 2 inches (5 cm). But its small size doesn’t make it any less amazing. In fact, the starry bobtail squid is one of the most beautiful thanks to its incredible bioluminescent patterns.
This species is found in coastal regions of the Indo-Pacific, where it generates its light via a mutualistic relationship with a bacteria known as Vibrio fischeri. This relationship is of particular interest to scientists studying how organisms collaborate their abilities. Their illumination is intended to match the light from the moon, aiding them in camouflage, but they’re also able to create flashes of light which are used for communication.
In the day, the starry bobtail squid conceals itself under the sediment but comes out at night to hunt for crustaceans and small fish. They typically remain close to the ocean floor, where the females also lay their eggs.
10. Ram’s Horn Squid (Spirula spirula)
The ram’s horn squid, sometimes called the spirula, is the only creature within its genus and features a spiral-shaped shell that looks like a ram’s horn, which is where the squid takes its name. However, it’s important to remember that this isn’t a true squid and is classified as a cephalopod mollusk.
Found in many oceans around the world, the spirula is common but rarely encountered by humans as it lives thousands of feet below the surface in the bathypelagic zone. Down here, things are pretty dark, so it’s handy that the ram’s horn squid has bioluminescent abilities. For hunting and communication.
This is a small species that doesn’t usually exceed 6 inches (15 cm) in length, but despite being small, spirula can take care of itself thanks to its ink production, which is used to escape predators. In terms of feeding, this species uses its suckered tentacles to capture small fish and crustaceans and, owing to its unique shell and bioluminescence, it’s of great interest to scientists looking at life at the bottom of the ocean.
11. Long-Arm Squid (Loligo pealeii)
The long-arm squid is so named because of its extremely long arms, which can make up as much as 70% of their overall length. Adults can grow in excess of 26 feet (7.9 meters) and inhabit the depths of the ocean up to 8,000 feet (2,438 meters) below the surface. Although for the most part, they stay around 984 feet (300 meters). They’re typically found in the North American Atlantic.
Long-arm squids are brilliant swimmers with a streamlined body and arms that assist with movement. This enables them to hunt effectively for things like smaller squid and crustaceans. They have special suckers on their tentacles that allow them to latch onto prey and immobilize it.
Like many other species, the long-arm squid is able to quickly change its color thanks to chromatophores. It does this when threatened but also uses the ability during complex mating rituals.
12. Whiplash Squid (Mastigoteuthis)
Whiplash squid refers to several species of deep-sea squid that inhabit the bathypelagic and mesopelagic zones at depths of up to 13,123 feet (4,000 meters). Because of this, these species have been very difficult to study, although research into them is still ongoing.
Scientists have discovered that two of these squid species will hover vertically just above the ocean floor, which they’ve called the tuning fork position. Down here in the ocean depths, whiplash squid are excellent hunters and have long tentacles with a whip-like hooked tip that help them to capture prey like fish and crustaceans. Because they are both predators and prey, whiplash squid are considered to be important members of their deep sea ecosystems.
Compared to other squid, whiplash squid appear far more gelatinous and are comparably smaller than many other species, growing only to around 5.9 inches (15 cm), at most. They, like many other squid, have bioluminescent capabilities, which are thought to attract prey and deter predators.
13. Strawberry Squid (Histioteuthis heteropsis)
The strawberry squid takes its name from its vibrant red coloration as well as photophores that look like strawberry seeds. This certainly makes them one of the most unique-looking squid in our oceans, but they’re also super interesting.
Found at depths of more than 656 feet (200 meters), this is a deep sea species that possess bioluminescent abilities in order to attract prey, communicate, and deter predators. While some species may use this ability during mating, not much is known about the reproductive habits of the strawberry squid.
In terms of diet, the strawberry squid eats like many other squid species, feeding on things like small fish and crustaceans. They detect prey using visual cues before striking out and grabbing them with their long tentacles.
14. Market Squid (Doryteuthis opalescens)
The market squid is common around the coasts of North America and is of great commercial importance, used as a human food available at seafood markets. They’re not only popular in North American cuisine, but market squid are a prized food around the world.
This is a small species that only grows to around 7 inches (18 cm) in length and is typically found in coastal waters where it gathers in large groups, which can be seen near the surface at night when the squid are hunting.
Like many squid species, market squid use their long tentacles to capture prey and are opportunists eating everything from small fish to crustaceans and even other squid.
Market squid are sexually mature at around 4 months of age, and their fully developed organs allow them to breed once before they ultimately die at around the age of one year.
15. Googly-Eyed Glass Squid (Teuthowenia pellucida)
The googly-eyed glass squid is perhaps one of the most interesting in terms of appearance because of its transparent body, which is where it takes its name. The name was also inspired by the squid’s large eyes, which give it excellent vision.
Typically found at depths of around 3,000 feet (914 meters), these squid are found all over the southern hemisphere. As is common at these depths, googly-eyed glass squids are capable of emitting light via bioluminescence, which allows them to communicate and lure prey like small fish and crustaceans. Not only this, but it’s thought that this ability also serves to distract prey coupled with their transparency which makes them less obvious.
16. Neon Flying Squid (Ommastrephes bartramii)
Sometimes called the red flying squid, this species is one of the most interesting in terms of behavior and can be observed leaping out of the water. While scientists aren’t entirely sure about the mechanics behind this, they do know that it’s likely to do with muscle contraction in the mantle and jet propulsion. It happens very frequently, with squid often landing on boats.
The most likely reason that these squid behave this way is in order to escape potential threats which include things like swordfish and marlin.
Found in several areas, including the Indian, Atlantic, and Pacific Oceans, the neon flying squid is quite common. These squid are typically found in the upper part of the ocean, and not usually any deeper than around 656 feet (200 meters).
Like many squid species, the neon flying squid dies soon after breeding, so they’re only ever able to breed once during their short lives of around 12 months.
17. Bigfin Reef Squid (Sepioteuthis lessoniana)
Bigfin reef squid are easy to tell apart from other species thanks to their large, oval fins. These fins mean that this species is an adept swimmer in the Indo-Pacific waters where it lives.
The bigfin reef squid has, like other species, an elongated body, making it more streamlined for swimming. They also have long tentacles that feature up to 7 suckers each. A small species, bigfin reef squids don’t usually get much bigger than 12 inches (30 cm). However, their ability to change color and blend in helps to keep them safe from predators.
They also use this color changing ability for communication, with chromatophores on the head that allow for rapid color changes. These color changes are sometimes used in mating displays and also help when hunting during which, they use their tentacles to grab crustaceans and small fish.
18. Japanese Flying Squid (Todarodes pacificus)
Another species of flying squid is the Japanese flying squid which is a medium-sized species (around 24 inches (61 cm)) found in the North Pacific. These squid live both around the coasts and in open waters and are commonly harvested by fisheries for human and animal food as well as for fishing bait.
Like other flying squid species, Japanese flying squid propel themselves out of the water and can even glide along the surface. It’s thought that this behavior helps them to get away from predators but could also be used when hunting or looking for a mate. Some reports say that these squid can glide for up to 98 feet (30 meters) out of the water.
Japanese flying squid only live for around one year and quickly develop so that they can breed before they die. Females release around 4000 eggs, which is markedly less than some other species, but they develop extremely quickly, hatching in a matter of days.
19. Striped Pajama Squid (Sepioloidea lineolata)
The striped pajama squid has a very interesting striped appearance that looks just like a pair of striped PJs. However, looks can be deceiving as while it may be beautiful, it’s also one of the most poisonous types of squid.
Found in coastal areas, these tiny squid only grow to around 3 inches (8 cm) in length. They have toothed tentacles that they use for hunting and large eyes which allow them to spot incoming prey. It’s thought that their stripes aid in camouflage, but it also secretes a toxic slime to deter predators. While it is capable of jet propulsion, it is not a strong swimmer and tends to stay close to the sea bed.
When feeding, the striped pajama squid has poison in its saliva that contains a neurotoxin which immobilizes its prey.
Striped pajama squid have very complex mating rituals, and females have a unique behavior which involves attaching her fertilized eggs in clusters to her arms. While many squid species simply leave their eggs alone, female striped pajama squids care for them until they hatch.
20. Northern Shortfin Squid (Illex illecebrosus)
Found primarily in the Northwest Atlantic Ocean, the northern shortfin squid is a small species that grows to around 12 inches (30 cm) in length. Like the European squid, this species is commercially harvested for food. In fact, it’s estimated that this species makes up 65% of all the cephalopod catches in the world.
The northern shortfin squid lives in a variety of habitats, including coastal areas and deeper waters where they use their long suckered tentacles for hunting crustaceans and small fish; sometimes other squid.
However, owing to their small size, they’re also vulnerable to predation from many animals including seabirds, large fish, and marine mammals.
Northern shortfin squid, like many other species, only live for around a year and, during this time, only ever mate once. However, females can lay thousands of eggs; in some cases, up to 200,000!
Can Squid Adapt to Warming Seas?
When you think of how climate change affects animals, it’s usually a negative outcome. However, what’s interesting about squid is their ability to quickly adapt to changing conditions. In fact, it’s been reported that squid numbers are actually on the up because of warming ocean temperatures.
In most cases, the release of greenhouse gasses results in warmer temperatures that can wreak havoc on marine ecosystems, interfering with breeding, food availability, and other things. But where squid are concerned, they’re much more tolerant to thermal changes because they are ectothermic.
This basically means that their body temperature is related to the surrounding environment, and this is the case with other cephalopod species, like octopuses which are also very resistant to the effects of climate change. As temperatures change, squid are able to adjust their body temperature to their new environmental surroundings and are therefore less vulnerable to these changes.
However, that’s not to say that climate change hasn’t affected squid at all. The change in temperature has caused an apparent shift in their distribution. For example, more squid species are now being recorded in UK waters. Depending on the needs of the squid species, they may be inclined to migrate towards warmer or cooler waters. The problem with this is that squid may become invasive and compete with native marine life for food and resources.
Moreover, while adult squids may be able to adapt, their eggs are not and require a specific temperature for optimal development. If this isn’t given then it could result in smaller, less fit young. In the long run, this could make certain species more vulnerable.
While squid are able to adapt relatively quickly, there are factors that could interfere with this, such as overfishing and habitat loss, which could stress the squid and affect their ability to adapt as quickly.
What’s more, we have to consider that it isn’t just the ocean temperature that causes problems for marine life; ocean acidification is also a massive issue. Squid have certain calcified structures that help them navigate, retain their balance, and other things. But when the pH level of the water drops, this can have devastating effects on the squid’s senses and behavior. Additionally, reports have shown that squid born in low pH waters take longer to develop into adulthood, were generally smaller and had deformities of their calcified structures.
