The giant squid (Architeuthis dux) is a type of squid that lives in the deep ocean and belongs to the family Architeuthidae. It can grow to a very large size, which is an example of a phenomenon called abyssal gigantism. Scientists estimate that female giant squids can reach about 5 meters (16 feet) in length, while males are slightly shorter, measured from the back of their body to the tips of their long arms. This makes the giant squid longer than the colossal squid, which is estimated to be about 4.2 meters (14 feet) long. However, the giant squid is much lighter because it has a less muscular body and longer arms. The body part called the mantle of the giant squid is about 2 meters (6 feet 7 inches) long, with females having longer mantles and males having shorter ones. The feeding tentacles of the giant squid, which are hidden when the squid is alive, can measure up to 10 meters (33 feet). Claims that giant squids can grow to 20 meters (66 feet) or more have not been proven by science.

Scientists have debated how many different species of giant squid exist. However, genetic studies suggest that only one species of giant squid is present.

In 2004, a group of scientists from Japan captured the first images of a living giant squid in its natural deep-ocean habitat.

Taxonomy

The closest relatives of the giant squid are believed to be four less well-known species of "neosquid" in the family Neoteuthidae. Each of these species is the only member of its own genus, just like the giant squid. Both the giant squid and the neosquid belong to the same superfamily, called Architeuthoidea.

Range and habitat

The giant squid lives in all of the world's oceans. It is often found near the edges of continents and islands, such as in the North Atlantic near Newfoundland, Norway, the northern British Isles, Spain, and the Azores and Madeira islands. It is also found in the South Atlantic near southern Africa, the North Pacific near Japan, and the southwestern Pacific near New Zealand and Australia. Giant squid are rarely seen in tropical and polar regions.

Scientists do not fully understand how deep giant squid live, but information from squid caught in fishing nets and the diving habits of sperm whales suggests they may live between 300 and 1,000 meters (about 980 to 3,280 feet) below the ocean's surface.

Morphology and anatomy

Giant squid, like all squid, have a body called a mantle, eight arms, and two longer tentacles. These tentacles are the longest of any cephalopod. The arms and tentacles make up most of the squid’s length, which helps it stay lighter than its main predator, the sperm whale. Scientists have measured giant squid and found that they weigh hundreds of kilograms, not thousands.

The inside of the arms and tentacles has many round suction cups, 2 to 5 cm (3⁄4 to 2 in) wide. Each cup is attached to a stalk, and the edge of the cup has sharp, finely toothed rings made of a material called chitin. These teeth and the suction from the cups help the squid hold onto its prey. Sperm whales often have circular scars on their heads from the squid’s suction cups.

Each tentacle is divided into three parts: the carpus (wrist), manus (hand), and dactylus (finger). The carpus has a group of suction cups in six or seven rows. The manus is wider toward the end of the tentacle and has larger suction cups in two middle rows. The dactylus is the tip of the tentacle. All the arms and tentacles are arranged in a circle around the squid’s single, beak-like mouth, like other cephalopods.

Giant squid have small fins at the back of their mantles that help them move. They swim by pulling water into their mantle and pushing it out through a tube called a siphon in gentle, repeated movements. They can also move quickly by filling their mantle with water and then squeezing it out forcefully. Giant squid use two large gills inside their mantle to breathe. Their circulatory system is closed, which is a feature shared by all cephalopods. Like other squid, they produce dark ink.

Giant squid have a complex nervous system and large brains, which interest scientists. Their eyes are the largest of any living creature except the colossal squid, measuring up to 27 cm (11 in) in diameter, with a 9 cm (3 1⁄2 in) pupil. These large eyes help them detect light, including bioluminescent light, which is rare in deep water. Giant squid likely cannot see color but can see small differences in brightness, which helps them in the dark ocean.

Giant squid and some other large squid species stay at the same depth in seawater using a salt solution called ammonium chloride, which is lighter than seawater. This is different from how most fish float, which uses a gas-filled organ called a swim bladder. The solution has a taste similar to salty candy and makes giant squid unappealing for people to eat.

Like all cephalopods, giant squid use special organs called statocysts to sense their position and movement in water. Scientists can estimate a giant squid’s age by counting growth rings in a part of the statocyst called the statolith, similar to how tree rings show a tree’s age. Much of what is known about giant squid’s age comes from these rings and from undigested beaks found in the stomachs of sperm whales.

Size

The giant squid is the second-largest mollusk and one of the largest living invertebrates. Only the colossal squid, Mesonychoteuthis hamiltoni, is larger. The colossal squid may have a mantle nearly twice as long as the giant squid. Some extinct cephalopods, like the Cretaceous coleoids Yezoteuthis and Haboroteuthis, and the Ordovician nautiloid Endoceras, may have grown even larger. The Cretaceous Tusoteuthis, with a mantle about 2 meters (6.5 feet) long, was once thought to reach sizes close to the giant squid (over 10 meters or 33 feet including arms). However, this claim is likely incorrect. The largest known specimen may belong to the genus Enchoteuthis, which had a total length of about 3 meters (9.8 feet).

The size of giant squids, especially their total length, is often exaggerated. Many reports claim they reach or exceed 20 meters (66 feet), but no scientific evidence supports these claims. According to expert Steve O'Shea, such lengths may result from stretching the squid’s tentacles like elastic bands.

Studies of 130 giant squid specimens and beaks found in sperm whales show that their mantles do not exceed 2.25 meters (7 feet 4.6 inches). Including the head and arms but not the tentacles, their length rarely exceeds 5 meters (16 feet). When measured after death, the maximum total length is estimated at 12 meters (39 feet) for females and 13 meters (43 feet) for females, and 10 meters (33 feet) for males, from the posterior fins to the tips of the long tentacles.

Giant squids show sexual dimorphism, meaning males and females differ in size. Female giant squids are estimated to weigh up to 275 kilograms (606 pounds), while males weigh up to 150 kilograms (330 pounds).

Reproductive cycle

Little is known about how giant squid reproduce. They are believed to reach the age when they can reproduce at about three years old. Males reach this stage at a smaller size than females. Female giant squid lay many eggs, sometimes more than 5 kg (11 lb). These eggs usually measure between 0.5 to 1.4 mm (0.020 to 0.055 in) in length and 0.3 to 0.7 mm (0.012 to 0.028 in) in width. Inside the body of a female, a single ovary is located near the back of the mantle cavity. Eggs move through paired, twisted oviducts and exit through the oviducal glands and then the nidamental glands. These glands create a gelatinous material that helps keep the eggs together after they are laid, as seen in other squid species.

In males, the single testis located near the back of the body produces sperm. This sperm travels through a series of glands that create spermatophores, which are stored in a long sac called Needham’s sac. The sperm is released through the penis, which is over 90 cm (35 in) long and extends from inside the mantle. The two lower arms of a male giant squid are specialized for reproduction, a feature called hectocotylization.

Scientists are still unsure how sperm is transferred to the eggs, as giant squid lack the hectocotylus used by many other cephalopods. One theory suggests that males inject small sacs of sperm, called spermatangia, into the female’s arms. This idea comes from a female specimen found in Tasmania, which had small, attached tendrils on each arm.

Young giant squid have been found in surface waters near New Zealand, and scientists plan to capture more to study them in an aquarium. In 2013, young giant squid were discovered off the coast of southern Japan and confirmed through genetic testing. In December 2015, a juvenile giant squid about 3.7 meters (12 feet) long was filmed alive in Toyama Bay, Japan. After being observed by many people, including a diver who swam close to it, the squid was guided out of the harbor into the bay.

Genetics

Scientists studied the mitochondrial DNA of giant squid from many places around the world. They found that the DNA of these squid has very little difference between individuals (only 181 genetic base pairs differ out of 20,331 total). This shows that there is likely only one species of giant squid globally. The tiny squid larvae might be carried by ocean currents over very long distances.

Ecology

Recent studies show that giant squid eat deep-sea fish, such as the orange roughy (Hoplostethus atlanticus), and other squid species. They use their two long tentacles to catch prey, holding it with sharp rings of suckers at the ends. Then, they pull the prey toward their strong beak and tear it apart with the radula, a tongue-like structure covered in small, tooth-like ridges, before swallowing it. Giant squid are thought to hunt alone, as only single individuals have been found in fishing nets. While many giant squid caught in New Zealand waters are linked to the local hoki (Macruronus novaezelandiae) fishery, hoki are not part of the squid’s diet. This suggests that giant squid and hoki may share similar prey.

Adult giant squid are hunted by sperm whales, pilot whales, southern sleeper sharks, and in some areas, killer whales. Young giant squid may be eaten by other large deep-sea predators. Because sperm whales are good at finding giant squid, scientists study them to learn more about the squid. Recently, it was discovered that giant squid may steal food from each other. In October 2016, a 9-meter (30-foot) giant squid was found on a beach in Galicia, Spain. A tourist named Javier Ondicol had photographed the squid alive shortly before it died. Examinations by the Coordinators for the Study and Protection of Marine Species (CEPESMA) showed that the squid was attacked and seriously injured by another giant squid. It lost parts of its fins, had damage to its body, one of its gills, and lost an eye. The squid’s body was intact, suggesting it slowly swam to shallow water and died from its injuries. This is the second recorded case of giant squid attacking each other in Spain, with the first happening in Villaviciosa. Evidence from squid stomachs in Tasmania, which contained beak parts from other giant squid, supports the idea that the species sometimes eats its own kind. These attacks may also be due to competition for food. Similar behavior has been seen in Humboldt squid, suggesting that cannibalism among large squid may be more common than previously believed.

Population

Scientists have not been able to find out the exact number of giant squid living worldwide. Estimates are made by looking at the number of giant squid beaks found in the stomachs of dead sperm whales, which are known to hunt giant squid. These estimates also consider the known population of sperm whales. From these observations, it is thought that sperm whales eat between 4.3 and 131 million giant squid each year. This suggests that there are millions of giant squid, but exact numbers are still hard to find.

Species

The classification of the giant squid, like many other cephalopod groups, has been a topic of discussion for a long time. Scientists who group species together or separate them may suggest as many as seventeen species or as few as one. The most extensive list includes these names:

It is not clear if these are separate species because no genetic or physical differences have been found to support this.

In the 1984 FAO Species Catalogue of the Cephalopods of the World, Roper and others wrote:

Many species have been given names within the single genus of the family Architeuthidae. However, these species are not well described or understood, which has caused confusion in how they are classified.

In Cephalopods: A World Guide (2000), Mark Norman wrote:

The exact number of giant squid species is unknown. Most scientists agree there are at least three species: one in the Atlantic Ocean (Architeuthis dux), one in the Southern Ocean (A. sanctipauli), and at least one in the northern Pacific Ocean (A. martensi).

In March 2013, researchers at the University of Copenhagen suggested that DNA evidence shows there is only one species:

… researchers at the University of Copenhagen, leading an international team, found that giant squids from all parts of the world are genetically very similar. This means they form a single global population and are, therefore, one species worldwide, despite earlier claims suggesting otherwise.

Timeline

Aristotle, who lived in the fourth century BC, wrote about a large squid, which he called teuthus, and he distinguished it from the smaller squid, the teuthis. He noted, "of the calamaries, the so-called teuthus is much bigger than the teuthis; for teuthi [plural of teuthus] have been found as much as five ells [5.7 m] long."

Pliny the Elder, who lived in the first century AD, also described a very large squid in his Natural History. He wrote that the squid had a head "as big as a cask," arms 9 meters (30 feet) long, and a carcass weighing 320 kilograms (700 pounds).

Stories about giant squids have been told by sailors since ancient times. These stories may have inspired the Norse legend of the kraken, a sea monster said to be as large as an island and capable of swallowing ships. Japetus Steenstrup, who studied a type of squid called Architeuthis, suggested that a giant squid was the creature described as a "sea monk" to the Danish king Christian III around 1550. The Lusca of the Caribbean and Scylla from Greek mythology may also be based on sightings of giant squids. Some stories about other sea monsters, like the sea serpent, are thought to be mistaken descriptions of giant squids. However, historian Otto Latva, who studied how humans and giant squids have interacted, pointed out that many old stories about sea monsters were not connected to giant squids until the late 1800s. Latva believed that natural historians and writers in the 19th century helped make giant squids seem like monsters. He also explained that sailors saw giant squids not as monsters, but as animals that could be used in different ways.

Steenstrup wrote several papers about giant squids in the 1850s. He first used the name Architeuthus (the spelling he chose) in a paper in 1857. In 1861, a part of a giant squid was found by the French ship Alecton, which helped scientists learn more about the species. Between 1870 and 1880, many giant squids washed up on the shores of Newfoundland. For example, a squid was found on 2 November 1878 in Thimble Tickle Bay, Newfoundland. Its body was reported to be 6.1 meters (20 feet) long, with one tentacle 10.7 meters (35 feet) long, and it was estimated to weigh 0.9 tonnes (1 short ton). Many of these squids were not saved for study; instead, they were used to make manure or animal feed. In 1873, a squid was reported to have attacked a small boat near Bell Island, Newfoundland. Similar events also happened in New Zealand during the late 1800s.

Although giant squids still wash up on shore today, these events are not as common as they were in the 1800s in Newfoundland and New Zealand. Scientists do not know why giant squids sometimes wash up on land, but it may be because the cold, deep water they live in changes temporarily. Many scientists believe these events happen in cycles and can be predicted. The time between these events is not known, but one scientist, Frederick Aldrich, suggested it might be about 90 years. He used this idea to correctly predict a small stranding that happened between 1961 and 1968.

In 2004, a giant squid, later named "Archie," was caught near the Falkland Islands by a fishing boat. It was 8.62 meters (28.3 feet) long and sent to the Natural History Museum in London for study. It was displayed at the Darwin Centre on 1 March 2006. Finding a large, complete giant squid is rare because most are found dead on beaches or inside the stomachs of dead sperm whales.

Scientists worked carefully to preserve the squid. It was sent to England on ice, then thawed over four days. The hardest part was thawing the thick body, which took longer than the tentacles. To stop the tentacles from rotting, scientists covered them in ice packs and bathed the body in water. They also injected the squid with a special chemical solution to prevent rotting. Today, the squid is displayed in a 9-meter (30-foot) glass tank at the Darwin Centre.

In December 2005, the Melbourne Aquarium in Australia paid A$100,000 for a 7-meter (23-foot) giant squid that had been preserved in a block of ice. It was caught by fishermen near New Zealand’s South Island that year.

By 2011, scientists had found about 700 giant squid specimens, and new ones are still discovered each year. Around 30 of these are displayed in museums and aquariums worldwide. The Museo del Calamar Gigante in Luarca, Spain, had the largest collection on public display, but many of its specimens were damaged in a storm in February 2014.

Scientists are still trying to find live giant squids, including young ones called larvae. These larvae look similar to those of other squid species but can be identified by the shape of the body attached to the head, the suckers on the tentacles, and the beaks.

By the start of the 21st century, the giant squid remained one of the few large sea animals that had never been seen alive in the wild or in captivity. Marine biologist Richard Ellis called it "the most elusive image in natural history." In 1993, a photo of a diver with a squid was published in a book, but the squid was later identified as a different species, Onykia robusta, not a giant squid. The first film of live giant squid larvae was taken in 2001 and shown on the Discovery Channel.

The first image of a live adult giant squid was taken on 15 January 2002 near Kyoto, Japan. The squid was about 2 meters (6 feet 7 inches) long and found near the water’s surface. It was tied to a dock and died overnight. Scientists later identified it as Architeuthis. It is now displayed at the National Science Museum of Japan.

The first photographs of a live giant squid in its natural habitat were taken on 30 September 2004 by Tsunemi Kubodera and Kyoichi Mori. They used a fishing boat and a camera with a flash to capture the squid near a sperm whale hunting ground 970 kilometers (600 miles) south of Tokyo

Aquarium keeping

The giant squid cannot be kept in aquariums because of its difficult-to-reach habitat, large size, and specific needs. In 2022, a live giant squid was discovered near the coast of Japan. Scientists tried to move it to the Echizen Matsushima Aquarium in the city of Sakai. The squid died during the transport and was later put on display at the aquarium.

Cultural depictions

Images of the giant squid have appeared in early stories about the kraken, as well as in books like Moby-Dick and Jules Verne's 1870 novel Twenty Thousand Leagues Under the Seas. These images also appear in other books, such as Ian Fleming's Dr. No, Peter Benchley's Beast (which became a movie called The Beast), and Michael Crichton's Sphere (which became a movie).

A common image shows a giant squid fighting a sperm whale. However, the squid is actually the whale's prey and not a match for the whale in battle.