There are around 300 known species of squid. They can be found in all the world’s oceans and range in size from dime-size midgets to rare 12-meter-long collossal giant squids. At depths of between one mile and two miles there is large variety of squid, including translucent ones, polka-dotted ones blue eyed ones and aggressive large ones.
The majority of squid are under 60 centimeters (24 inches) long. The giant squid may reach 13 meters (43 feet) in length. The smallest known species are benthic pygmy squids Idiosepius, which grow to a mantle length of 10 to 18 mm (0.4 to 0.7 in), and have short bodies and stubby arms. [Source: Wikipedia]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems
Weird Squid Species
Some squids look truly weird. The strawberry squid (Histioteuthis heteropsis) lives in of the ocean's twilight zone. Stephanie Pappas wrote in Live Science: It has one large (and strikingly green) eye that looks upward to spot shadows cast by prey and one small eye that looks downward, seeking out signs of bioluminescence from prey swimming below. For weirdness, though, the strawberry squid doesn't hold a candle to the bigfin squid (Magnapinna), which has a body as long as a dollar bill and tentacles as long as a human. These distinctive squid are known for their tentacles that bend at a 90-degree angle, creating a weird "elbow." They've been sighted only about 20 times since their discovery more than a century ago.[Source: Stephanie Pappas, Live Science, April 20, 2022]
Taonius pavo (a species of glass squid) In 2016, Fox News reported: “A purple squid with eyes so googly it could easily be mistaken for a character in the movie "Finding Nemo" was recently spotted by scientists off the coast of Southern California. The so-called stubby squid (Rossia pacifica) is a species of bobtail squid native to the northern Pacific Ocean. The stubby squid's giant eyes, that "look painted on," delighted the scientists aboard the Exploration Vessel (E/V) Nautilus. "On that watch it happened to be a lot of geology folks or ecology folks, so a lot of the commentary was of course more like 'What is this thing, it's so cute!' and sometimes we have less of that when we see rocks," Samantha Wishnak, a science communication fellow aboard the E/V Nautilus, told Live Science.[Source: Fox News, August 18, 2016]
Longfin Inshore Squid
Longfin inshore squid (Scientific name: Loligo pealeii) are medium-sized squid that grow to about 50 centimeters (1.6 feet) long. They are very important to fishing industries throughout the world, including the United States, where they are pursued by both commercial and recreational fishers. In commercial fishing, they are sold to restaurants and stores. In recreational fishing they serve as bait for mahi-mahi, swordfish, and marlins [Source: Martha Rodriguez, Animal Diversity Web (ADW) /=]
Longfin inshore squid are also sought after as specimen in neurobiology research. Its neurons are a thousand times larger than human neurons but have similarities with them and provided scientists with opportunities to study things like as sodium and potassium ion pumps and helped scientists to gain insights into heart disease, cancer, Alzherimer's Disease, and kidney disease . /=\
Longfin inshore squid are native to the Atlantic Ocean and are typically found in coastal areas from Newfoundland to the Gulf of Venezuela, migrating to different places to spawn such as the Cape Cod area during the spring. These squid favor waters along the eastern continental shelf of North America, and in the Gulf of Mexico, coming into shallow waters near shore to lay eggs. The species are sometimes called the Woods Hole squid because they have been extensively studied at the Marine Biological Laboratory in Woods Hole, Massachusetts. /=\
Bigfin squid (Magnapinna sp.). are widely distributed throughout the world's deep ocean, and they can live deeper than any other known squid. While the squid seen in this video was at 2,385 meters (1.5 miles), the current depth record for a bigfin squid is 4,735 meters (3 miles). Large fins and long appendages (eight arms and two tentacles) with elbow-like bends give the bigfin squid its distinctive appearance. These squid can exceed 6 meters (19.7 feet) in length. However, that’s mostly arms and tentacles. The largest known bigfin squid was 6.4 meters (21 feet) long. It’s arms and tentacles were 6.1 meters (20 feet) long. That’s 20 times the length of its body! [Source: NOAA]
It’s only in the early 2000s that the bigfin squid family was officially described by scientists. How exactly bigfin squid use their arms and tentacles is unknown. But, these appendages have microscopic suckers on them, and scientists think it’s likely that squid use them to trap prey that bump into them as they hang down in the water below their body or drag along the seafloor.
Currently, scientists have officially described three species of bigfin squid, but there may be more. Sightings are pretty unusual; only a dozen or so sightings have been confirmed worldwide. So, when a NOAA ROV captured an adult bigfin squid on camera during Dive 10 of Windows to the Deep 2021 off the West Florida Escarpment in the Gulf of Mexico, it was big news. Before the videographer zoomed in on the “otherworldly” squid, it was thought to be a siphonophore or jellyfish. The first NOAA sighting of a bigfin squid took place in Keathley Canyon at a depth of 1,961 meters (6,434 feet) in the Northern Gulf of Mexico during Dive 13 of the Gulf of Mexico 2012 Expedition (leg 3).
In early 2021, Alan Jamieson, a deep-sea researcher from the University of Western Australia, led an expedition that found a new species of bigfin squid at the remarkable depth of 20,380 feet, or nearly four miles. Before this discovery the record for a specimen was 15,534 feet, or about three miles. “Bigfin squid are “really weird” Mike Vecchione, a zoologist at the Smithsonian Institution who studied Jamieson’s video, told Hakai Magazine. “They drift along with their arms spread out [with] these really long, skinny, spaghetti-like extensions dangling down underneath them,” the zoologist added. Vecchione says that bigfins use microscopic suckers on their tentacles to capture their prey. [Source: Matthew Hart, Nerdist, January 12, 2022]
Humboldt, or jumbo, squid are large creatures found in water waters from Chile to the Gulf of California off of Mexico that are known for their aggressive behavior. They can weigh as much as 70 kilograms and reach a length of four meters, with their tentacles extended. They illuminate themselves with flashes of red and white using bioluminescence. Because of their aggressive nature, they’re sometimes called “red devils.”
Jumbo squid have sharp beaks and toothy tentacles. They normally feed on small crustaceans fish but have been observed eating a wide variety of creatures, some of them quite large, including birds, rockfish and other squid. They consumer their prey voraciously and quickly, chomping food into bits and gobbling it down like a speed eater. Jumbos can reach speeds of 24 kph and sometimes hunt in group of 1,200 or more.
Jumbo squid can be quite promiscuous Katherine J. Wu wrote: Males shoot sperm-packed spermatophore capsules, all over. Humboldt squids are the sixth species of squid known to engage in same-sex sexual activity as documented in scientific literature for the first in 2019. These guys pretty much abide by a “live fast, die young” mentality when it comes to mating, and tend to go for quantity over quality. “That’s essentially why scientists think the cephalopods wind up mounting other males so frequently. They pretty much have nothing to lose by hooking up with both males and females because their bodies make sperm throughout their lifetime and they have 300 to 1,200 spermatophores locked and loaded at any given moment. [Source: Katherine J. Wu , Rachael Lallensack, Smithsonianmag.com, February 14, 2020]
Sonar Catches Jumbo Squid in the Act of Hunting
Sophia Li wrote in Discover magazine: Kelly Benoit-Bird uses sonar to watch the underwater movements of all kinds of creatures, from microscopic zooplankton to giant gray whales. Of all the marine life she studies, the most voracious is the six-foot-long Humboldt squid, also known as the jumbo squid. Scientists have long recognized the beast as a fearsome predator. But no one had seen large numbers of them in action until 2007, when Benoit-Bird — an Oregon State University oceanographer — found a way to use sonar to probe the 3,000-foot depths of the squid’s stomping grounds in the Sea of Cortez. Now, for the first time, researchers are able to study the sheer complexity and ruthless hunting techniques of this soft-bodied predator of the deep. [Source: Sophia Li, Discover magazine, September 26, 2012]
Benoit-Bird said: Five years ago, the prevailing knowledge was that you could not track squid with sonar. People said that squid are essentially bags of seawater, so why would you expect to see them? But we were curious. They are huge, and we wanted to see them gorge on their meals of fish and krill. Fortunately Oregon State’s Marine Mammal Institute donated time on a boat that was going to the Sea of Cortez for a different project.
“Our plan was to catch squid, tether them 15 to 20 feet beneath the boat, and send out pulses of sound waves to see if any signal bounced back. On the third day of the trip, around dusk, we finally proved that our technique worked. I saw an image of the squid on my computer screen and threw up my arms in excitement. Then, all of a sudden, I saw another object approaching on the monitor, twice as big as our squid. The two figures merged. I couldn’t separate them. Then one of them left, and I could see something only half the size of what was there before.
“I told my team over the radio what I had seen, and they said they had felt tugs on the ropes beneath the boat. They pulled the squid out of the water, and all that was left was the head. Our first successful test yielded an important lesson: Do experiments during the daytime. The squid start feeding at sunset, and clearly they have no problem eating each other.
Since then, we have used sonar to learn a lot more about jumbo squid. Most surprisingly, they work really well together, especially for cannibals. They move in coordinated patterns when they hunt at night — we jokingly call it the squid ballet. We have seen animals in groups of 40 or more that stay exactly the same distance away from each other and swim vertically to create a shape resembling a double helix. We think they are trying to get to fresh spots where the prey does not expect them. Then, once they have scared away everything, they shift over a couple of feet and resume their ballet from a new spot. You would never get to see that with your own two eyes, so it is an amazing thing to be able to see it using acoustics.
Aggressive Jumbo Squids Move Northwards
Jumbo squids have been observed lunging at fishing boats and are known to practice cannibalism. Mexican fishermen call them “ Daimblos rojos” (“red devils”) and often get squirted in the face by the creatures when they are hauled aboard fishing vessels.
Since 2002 large numbers of jumbo squid have been turning up north of their usual range, appearing off California and the northwest United States and seen as far north as Alaska. They were first seen off the United States in large numbers in 1997, an El Nino year, but disappeared when the weather and ocean patterns returned to normal. They showed up again in 2002, another El Nino year, but thus time stuck around. Their presence is disconcerting in that they are so aggressive and eat so much. Off California, Oregon and Washington they have been consuming large amounts of Pacific hake, an important commercial fish widely used in fish sticks and imitation crab meat.
When large numbers of jumbo squid showed up off of San Diego scuba divers there complained about attacked by the aggressive creatures One diver told AP, a large squid grabbed her from behind with its arm, ripped her buoyancy hose away and turned her round so she didn’t which way was up, “I just kicked like crazy,” she said, “the first thing you think is, “Oh my gosh, I don’t know if I’m going to survive this.” If that squid wanted to hurt me, it could have.” Another diver said, “As soon as we were underwater and turned on the video lights, there they were. They would ram into you, they kept hitting the back of my head.” He also said they scanned his wet suit seemingly to check out whether he was edible or not.
The jumbo squid seem to be thriving in part because their natural predators tunas and sharks have been overfished. They can often out-compete these creatures anyway because they can hunt better in low-oxygen environments, where small fish often hide out. William Gilly, a biologist at Hopkins Marine Station of Stanford University, Northwest fisheries will suffer. doesn’t buy reports of summer 2009 attacks on San Diego scuba divers. A squid might nudge with a toothed appendage to assess edibility, he says. “They’re smart and curious and really tactile.” Anyone in a wet suit would be deemed unfit for cephalopod consumption.
Flying, Fast and Furious Lives of Jumbo Squid
“For animals that live two years at most,” Gilly says, “they sure do live it up.” Eric Wagner wrote in Smithsonian magazine: In that time, the squid grow from larvae that could generously be called cute into far more menacing specimens that can be more than six feet long and weigh more than 80 pounds. They can swim more than 100 miles a week. [Source: Eric Wagner, Smithsonian magazine, December 2011]
Marc Silver wrote in National Geographic: The millions of Humboldt squid, aka jumbo flying squid, live “fast and furious” lives, says NOA Fisheries oceanographer Ken Baltz. “They hunt and eat and hunt and eat” for a year or two, then expire. Their diet is mainly fish, an occasional floating seabird — and sometimes each other. [Source: Marc Silver, National Geographic, August 18, 2010]
“Once in a great while they “fly” by ejecting themselves from the water. Given that a squid’s body plus tentacles can run six feet and top the scales at 80 pounds, that’s quite a feat. Flight might be a way to evade predators, although scientists don’t know exactly why squids soar. Nor do they understand why the squid can quickly change from red to pink to maroon: maybe to confuse prey, maybe to signal each other.” If salmon are also on the menu, adds Gilly, Northwest fisheries will suffer. [Source: Marc Silver, National Geographic, August 18, 2010]
Firefly squid (Scientific name: Watasenia scintillans) are small squids, with an average length of 7.62 centimeters (3 inches). They have special light producing organs called photophores that are found on many parts of their body, with large ones are usually found on the tips of their tentacles as well as around their eyes. These lights can be flashed in unison or alternated in patterns. This squid has arms with hooks and tentacles with hooks and one series of suckers. The mouth cavity has dark pigmentation. They live for about one year. [Source: Krupa Patel and Dorothy Pee, Animal Diversity Web (ADW) /=]
Finger-size bioluminescent firefly squid lives in the Western Pacific Ocean around Japan and are typically found at depths of 200 to 400 meters (656 to 1312 feet). They spend most of the day in deep water but swim up to the surface at night to capture prey. Firefly squid also rise up to the surface during their period of spawning, and gather in huge schools near the shoreline. One of the main known predators of firefly squid are Northern fur seals The squid’s photophores can be used against predators as a warning or as a form counter-illumination camouflage. /=\
Firefly squid feed on shrimp, crabs, fish, and planktonic crustaceans. The photophores on the tips of its tentacles are used in a flashing pattern to attract prey, especially fish. The photophores along the body and tentacles are also used to provide camouflage, frighten predators, and attract mates. Firefly squid sense communicate with vision and their photophores. They have highly developed eyes that contain three different types of light-sensitive cells and are believed to be capable of distinguishing different colors. /=\
Firefly Squid Mating, Reproduction and Development
Firefly squid are oviparous (young are hatched from eggs)and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. They engage in seasonal breeding and breed once a year, between April and June. On average females and males reach sexual maturity at age one year. [Source: Krupa Patel and Dorothy Pee, Animal Diversity Web (ADW) /=]
Bioluminescent photophores are believed to play a role in attracting mates and are used for communication between squids. During spawning season firefly squids gather in large numbers near the surface and relatively near the shore to release their eggs. Once the eggs have been released into the water and fertilized, the adult squid die. There is no parental involvement in the raising of offspring. Adult firefly squid die after eggs have been released into and fertilized. This completes their one-year life cycle. /=\
Fertilized eggs hatch in in six to 14 days depending on the water temperature, which varies from six to 16 degrees Celsius. Higher temperatures produce faster hatching. According to Animal Diversity Web: At 15 degrees Celsius, one hour after fertilization, polar bodies appear, followed in five hours with first cleaveage. By 10 hours, 100 or more cells have been formed, and around 16 hours the embryonic lobe has been developed. The embryonic lobe covers about half of the egg in a day and a half. In four days, primordial eyes are present and oral depression starts. A day later, primordial arms, mantle, and funnel appear and then chromatophores appear on the mantle and the eyes are developed. Final organ and chromatophore formation and hatching occurs in 8-8.5 days. /=\
Harvesting, Watching and Eating Firefly Squid in Japan
Firefly squid are a popular season food in Japan, where they are eaten raw,, known as Hotaruika in Japan, or cooked. For a brief period in Toyama Bay on the west coast of Japan between the months of April and June billions of these squid rise up from their home in the depths to the surface to mate. Fishermen in the town along the bay sponsor excursions to the places where the squid are found. Normally polite and well behaved Japanese tourist push and shove their way on to the boat to make sure they get a good spot. When the boat reaches the squid site the Japanese tourists dip nets into the water and pull up these living blue sparklers by the armful onto the decks of the boat, where every part of their body shrivels up except for their eyes which stick out grotesquely.
Firefly squid also draws large crowds to the shores of Toyama Bay during their spawning season. Large schools swim up to the shallow waters light up the dark water along the shore, giving tourists a nighttime show. This spectacle has led to the bay being named a Special Natural Monument and construction of a museum devoted to the species. /[Source: Krupa Patel and Dorothy Pee, Animal Diversity Web (ADW) /=]
Firefly squid is not protected under any conservation program. They have not been evaluated for the International Union for Conservation of Nature (IUCN) Red List and have have no special status according to the Convention on the International Trade in Endangered Species (CITES). Eating raw firefly squid infected with spirurina type X larvae, belonging to the phylum Nematoda, can cause abdominal pain, nausea and vomiting, diarrhea, creeping eruption, and ileus (bowel obstruction). /=\
Vampire squids (Scientific name: Vampyroteuthis infernalis) are small (30-centimeter, 12-inch-long) cephalopods found in deep temperate and tropical seas. Originally thought to be octopuses because they lack the two long tentacles that usually extend past a squid’s eight arms, vampire squid possesses characteristics of both squid and octopi, and occupy their own taxonomy order — Vampyromorphida. Many scientists say their name is a misnomer because it is not a squid but rather an octopus cousin. Source: NOAA]
Vampire squids have huge, bright blue eyes — proportionally the largest in the animal kingdom — dark color, and the velvety, cloak-like webbing that connect their arms are the source of the squids’ common name — the idea being the webbing looks like a vampire’s cloak. The squid’s scientific name, Vampyroteuthis infernalis, literally means “vampire squid of Hell”! While the cephalopod does not suck blood like a vampire squid, it is a “living relic” that evolved from an ancestor of the octopus, and its lineage goes back 165 million years in the fossil record.
Vampire squid are extremophile — inhabiting the dark ocean depths from 610-914 meters (2,000-3,000 feet). If threatened, they do not eject ink, as do most cephalopods. Nor can they change color to confuse intruders the way shallow-water cephalopods can. Living in the deep ocean as they do, where little light penetrates, color-changing is a pointless strategy. Instead, vampire squids squirt a copious cloud of sticky, bioluminescent mucus toward would-be predators (and the occasional research ROV).
The vampire squid occupy mesopelagic (intermediate) depths between about 200 and 1,000 meters (650 and 3,300 feet) and dark and cold bathypelagic (deep) depths between about 1000 and 3000 meters (3300 and 9800 feet) throughout the world's tropical and temperate oceans between 40̊N and 40̊S in waters between 2̊ to 6̊C (35.6 ̊ to 43̊F). Little light penetrates this area. The majority of vampire squids occupying depths of 1,500-2,500 meters (4920 to 8200 feet). Studies conducted at the Monterey Bay Aquarium indicate the squid do best at an average depth of 690 meters and oxygen levels of 0.22 milliliters per liter. /=\
Vampire squid and its habitat are not threatened. They have no special status on the International Union for Conservation of Nature (IUCN) Red List and the Convention on the International Trade in Endangered Species (CITES).
Vampire Squid Physical Characteristics
According to Animal Diversity Web: Vampire squids has eight long arms and two retractile filaments that can extend well past the total length of the animal and can be retracted into pockets within the web. These filaments function as sensors because of the cirri that cover the entire length of the arm with suckers only on the distal half. There are also two fins on the dorsal surface of the mantle. The vampire squid is so named because of its jet-black skin, webbing between the arms, and red eyes — supposedly characteristics of a vampire. The squid is considered small — reaching a maximum length of 28 centimeters with the approximate size of a football. There is Sexual Dimorphism (differences between males and females): in size: females are larger than males. [Source: Brad Johnson, Animal Diversity Web (ADW) /=]
The vampire squid has the consistency of a jellyfish, but its most intriguing physical characteristic is that it has proportionally the largest eyes of any animal in the world. A squid six inches long will have eyes that are an in inch across which are comparable to the eye size of a full grown dog. /=\
The vampire squid has black chromatophores with reddish-brown ones interspersed. In contrast to other cephalopods, these chromatophores are non-functional because they have lost the muscles that enable rapid color change. The vampire shares most other features with other octopods and decapods, but it has several adaptations that allow it to live in a deep-sea environment. The loss of most of the active chromatophores and the ink sac are just two examples. The vampire squid also has photophores which are large circular organs which are located posterior to each adult fin and are also distributed over the surface of the mantle, funnel, head, and aboral surface. These photoreceptors produce luminescent clouds of glowing particles that allow the vampire squid to glow. /=\
Vampire Squid Swimming, Luminesce and Behavior
According to Animal Diversity Web (ADW): The vampire squid was always thought to be a slow swimmer because of its weak-muscled gelatinous body, but it can swim surprisingly fast by using its fins to fly through the water. Their highly developed statocyst, the organ responsible for balance, also contributes to their agility. Through video analysis, the squid has been estimated to reach speeds around two body lengths/sec and to accelerate to these speeds in five seconds. Vampire squid can move rapidly over short distances, but it is not capable of long migrations or extended fight and flight responses. [Source: Brad Johnson, Animal Diversity Web (ADW) /=]
When threatened, the vampire squid makes an erratic escape by quickly moving the fins toward the funnel followed by a jet from the mantle as it zig-zags through the water. The squid's defensive posture occurs when the arms and web are spread over the head and mantle in a position known as the "pineapple posture". This position of the arms and web makes the squid more difficult to injure because of the protection provided to the head and mantle and also because this position exposes the heavy black pigmented regions on the animal which make it difficult to identify in the dark depths of the ocean. /=\
The vampire squid can luminesce for longer than two minutes as a result of the photophores which either glow simultaneously, flash one to three times per second, or pulsate. The arm tip organs can also luminesce by glowing or flashing which is usually followed by an escape response. The third and final form of luminescence are luminescent clouds which appear as a mucous matrix with glowing particles in it. The particles are thought to be released by the arm tip organs or an undiscovered visceral organ and can glow for up to 9.5 minutes. /=\
The vampire squid's principal escape response involves the glowing of the light organs on the tip of the arms and at the base of the fins. This glowing is followed by a flailing of the arms which makes it very difficult to determine exactly where the squid is in the water. The squid then ejects the luminescent mucous cloud. When the light show has ended, it is practically impossible to tell whether the squid has glided away or has blended into the abyssal waters. /=\
Vampire Squid Food, Reproduction and Development
According to Animal Diversity Web: The vampire squid has the lowest mass-specific metabolic rate of any cephalopod because of its decreased reliance on locomotion for escaping predators and capturing prey in the light-limited deep sea. The vampire squid uses its sensory filaments to find food in the deep sea and also has a highly developed statocyst indicating that it descends slowly and balances in the water almost effortlessly. Despite its name and reputation, Vampire squid is not an aggressive predator. While drifting, the squid deploys one filament at a time until one of them contacts an animal of prey. The squid then swims around in a circle hoping to catch the prey. [Source: Brad Johnson, Animal Diversity Web (ADW) /=]
Because small vampire squids occupy deeper water than larger squids, spawning probably occurs in very deep water. It is most likely that males transfer spermatophores to the female from their funnel. The female vampire squid is larger than the male and discharges the fertilized eggs directly into the water. Mature eggs are fairly large at 3-4 millimeters in diameter and are found free-floating in small masses in deep water. /=\
An interesting phenomenon in relation to the growth of the vampire squid occurs in the metamorphosis of the size, shape, and position of the squid's fins. When the squid's mantle is 15-25 millimeters in length, the squid begins to grow a second pair of fins more anteriorly than the first pair. When the new pair of fins reach maturity, the original pair is reabsorbed. The development of the new pair of fins changes the vampire squid's swimming style from jet propulsion to using the fins for propulsion. Another interesting development in the vampire squid has to do with the sensory filament which were first thought to be modified arms. Scientists now know that the composition and structure of the filaments is completely different from the arms. As a result, the sensory filaments are believed to be a "uniquely derived" trait. [Source: Brad Johnson, Animal Diversity Web (ADW) /=]
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated April 2023