Cuttlefish look like broad squids but can very colorful and interesting-looking. They are cephalopods and mollusks like octopuses and squids. Among their more prominent features are a thick, chalky internal shell, called a cuttlebone, that fills with gas, which allows them gracefully rise and fall in the water column. They also have eight sucker-lined arms and two tentacles, usually concealed unless the cuttlefish is feeding. [Source: Natural History, April 2000]
Cuttlefish are found in temperate and tropical oceans everywhere except the Americas and prefer coastal environments such as reefs, mangroves and areas of sea grass. Like octopuses and squid, cuttlefish have very short lifespans, They generally only live long enough to reproduce, which is usually done 14 to 18 months after they are born. Adult cuttlefish begin to die off at the end of their breeding season. Cuttlefish are often eaten by larger fish, and are frequently fished for and eaten by humans. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
The earliest fossils of cuttlefish are from the end of the Cretaceous period (145 to 66 million years ago). Some creatures from Jurassic Period (201 to 145 million years ago). The cuttlebone or sepion of cuttlefish is calcareous and appears to have evolved in the Tertiary Period (66 million to 2.6 million years ago. The "cuttle" in cuttlefish comes from the Old English name for the species, cudele, which may be cognate with the Old Norse koddi (cushion) and the Middle Low German Kudel. The Greco-Romans valued cuttlefish for their unique brown pigment the creature releases from its siphon when it is alarmed. The word for it in both Greek and Latin, sepia, now refers to the reddish-brown color sepia in English and the order of cuttlefish.
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
cuttlefish and other creatures on an
ancient Greek fish plate Octopuses, squid and cuttlefish are cephalopods, a class of mollusks whose name means "head-footed." There are two subclasses of Cephalopoda: 1) chambered nautiluses, with external shells and anatomy that has remained virtually unchanged for 450 million years; and 2) coleoidea, which includes octopuses, squids and cuttlefish. The latter are soft, fleshy mollusks with their shells inside their bodies instead of outside as is the case with most mollusks.
Cephalopods are common food sources in many counties, particularly in Asia. They reproduce quickly which means that even though two million metric tons of them are caught every year, they are not in danger of being overfished. In the past they were often caught with drift nets, which are now banned not because they caught too many squid but because they caught other animals like dolphins and sharks. They are commonly hunted by sharks, seals, sea lions, dolphins and albatrosses.
Cephalopods are regarded as more developed and sophisticated than mollusks like snails, clams and oysters. In fact they are considered the most advanced and developed invertebrates (animals without backbones). They have the largest brains and nervous systems of any invertebrate and their brains are much bigger in relationship to their bodies than those of fish. Most cephalopods grow quickly, mate once and die. Most live no more than 18 months.
Cuttlefish are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature). Common cuttlefish have an average weight of three kilograms (6.6 pounds) and an average mantle length of 45 centimeters (17.7 inches). Those living in the subtropics have an average mantle length of 30 centimeters (11.8 inches) and weight of two kilograms (4.4 pounds) whiles those in temperate areas have an average mantle length of 49 centimeters (19.3 inches) and a weight of four kilograms (8.8 pounds). The largest recorded individual reached a mantle length of 60 centimeters. There is some sexual dimorphism (differences between males and females): Both sexes are roughly equal in size and look similar but sexes colored or patterned differently. [Source: Ae Lin Compton and Laura Wiley, Animal Diversity Web (ADW) /=]
Cuttlefish have powerful beak-like mouths strong enough to crush the shells of oysters and exoskeletons of crabs. They can detect motion the same way fish do. They propel themselves backward with surprising speed with a syphon, a funnel-like tube that shoots out water. Cuttlefish tentacles are lined with suckers, which vary in size. Their skin is covered with papillae, which can be altered in size and shape with changing body patterns. One of their most distinguishing features of cuttlefish is their cuttlebones, which is more of an internal shell than a bone. It is broad and flat and gives cuttlefish heads their characteristic shape. Cuttlebones are also porous, helping cuttlefish remain buoyant. [Source: Hannah Markowitz, Animal Diversity Web]
According to Animal Diversity Web: Common cuttlefish have large eyes and a mouth with beak like jaws located at the base of the mantle. The mantle houses reproductive and digestive organs, as well an internal shell called the cuttlebone. The cuttlebone shape is oblong with a rounded posterior end and an anterior end that tapers to a point. The body of the common cuttlefish is broad and dorso-ventrally flattened, having an oval shaped cross section. A pair of flat, wide fins runs the length of the mantle. The mouth is surrounded by eight arms and two longer tentacles, all equipped with suckers. Mature Common cuttlefish exhibit a zebra stripe pattern on the dorsal surface of their mantles during breeding season. Adult males are distinguished by white and black zebra bands on their fourth arm, as well as white arm spots. Common cuttlefish is able to change the color and even texture of its skin using structures called chromatophores, leucophores, and iridophores. These structures function to camouflage this species to its variable surroundings. Generally, however, Common cuttlefish has a mottled black or brown color. /=\
Cuttlefish Senses, Perception and Communication
Cuttlefish have a well-developed brain. The can change colors in response to its environment, to lure in prey and escape predators. Males put on displays to attract females. Some cuttlefish are able to go through mazes through use of visual cues.
Cuttlefish sense using vision, smell, touch and vibrations and communicate with vision and vibrations. Cuttlefish do not have ears; instead they have ciliated cells situated on their backs and sides laterally that allow them to detect vibrations around them. This is how they sense predators or prey.
Cuttlefish have very sensitive eyes which can change their shape, which helps the cuttlefish focus in on its prey, and have photoreceptors that allow them to detect light polarization. Their unusual W-shaped pupils can detect polarized light but not color and see forward and backward at the same time. They have 13 to 14 muscles, controlling their eyes compared to two for humans. Reshaping the eye allows it to focus on specific objects.
Cuttlefish communicate with other cuttlefish via color change patterns. They may even communicate in this way with other species but are likely color-blind. Active color changing has been observed during mating and hunting prey. The diverse components responsible for their color changing ability allows cuttlefish skin to make polarized reflective patterns between color patterns. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Cuttlefish are diurnal (active mainly during the daytime), motile (move around as opposed to being stationary), and social (associates with others of its species; forms social groups). They roam no more than a few square kilometers around from where they live. They do not actively defend a territory. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Cuttlefish are generally shy and solitary. They communicate by changing colors and changing the shape of their arms in a complex ways. A zebra pattern produced by males, accompanied by complex arm movements, warns other males to stay away. Generally, the only time cuttlefish gather in large numbers is when they are young and when they mate. They generally don’t form social structures.
Cuttlefish often reside in relatively shallow water at depths of 10 to 30 meters (33 to 98 feet). Their cuttlebone, which provides buoyancy, makes it difficult for them remain in deeper water. Then often hide in the crevices of coral reefs in order to evade predators and watch for prey.
Cuttlefish are often seen changing their body patterns when they are involved in different behaviors. For example, mating patterns differ from hunting patterns, which differ from camouflage patterns, and so on. Cuttlefish will also travel to shallower water if they are looking for a mate. Typically, males will go after females, and often compete with one another for mates.
Cuttlefish can change their color and patterns to blend in with their backgrounds, to frighten predators or prey, attract mates and to express fear, aggression and sexual excitement. "A single cuttlefish can become speckled, ocellata, stippled, lineated, whorled, black, white, brown, gray, pink, red, iridescent — all in different combinations and all in less than a second." In addition, cuttlefish have types of muscle groups and cells called papillae that allow them to change the texture of their skin to resemble seaweed or even a bumpy rock.
Cuttlefish are commonly hunted by sharks, seals, sea lions, dolphins and albatrosses. Their main defenses are hiding and camouflage. Not only are cuttlefish proficient at color manipulation, they also excel at changing the textural appearance of their integument (skin). Not only that they can change the shape body, by contracting circular muscles in their integument, and “sculpt” themselves so the resemble seaweed, debris, reef structures and other marine features, making the outline of their bodies less conspicuous and practically invisible. [Source: Hannah Markowitz, Animal Diversity Web]
Appearance changes in cuttlefish are facilitated by several components, including 34 chromatic components, six textural, eight postural, and six locomotor components. These components allow for changes in color, texture, posture, and movement. The color changes are caused by leucophores and chromatophores, pigments sacs situated just under the skins that suddenly swell with signals from the brain. The sacs are yellow, red, black and brown. By expanding and contracting them cuttlefish can reproduce a variety of shades and patterns. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Each species of cuttlefish has its own repertoire of color changes. Young cuttlefish can display almost the full array of patterns that adult cuttlefish can — a feature not seen in other cephalopods. Attracted by bright colors giant cuttlefish sometimes pull right up to divers in pink, yellow and green wetsuits.
Cuttlefish Food and Hunting Techniques
Cuttlefish feed on crabs, shrimp and fish and in turn are fed on by sharks and dolphins. Many cuttlefish hunt during the daytime for small fish and crustaceans when their acute vision is most useful. Some are known for preying specifically on certain kinds of shrimp but they can also be opportunistic feeders, eating whatever is available. Some species are especially adept at hunting crabs. When eating a crab, cuttlefish grab it prey with it arms and tears it apart with it beak or punches a hole in the shell and rasps the meat with its tongue. Many hunt for small prey along the bottom of the ocean by ejecting water from their bodies to move sand and flush prey from their hiding places.
Most cuttlefish mainly eat small fish and crustaceans, which they approach slowly and stealthily. When they are within striking distance, they thrust out their two tentacles (which are tucked away in a pouch located under their eyes) and seize the prey with a lighting fast grab. The tentacles then contract, bringing the prey to the cuttlefish’s beak, where the cuttlefish's arms enclose it and push into its mouth. . Cuttlefish also put their beaks to work cracking open the shells of prawns and crabs. Their teeth-lined radula, scrapes of tissue that is eaten.
Common cuttlefish typically spend the daytime hidden in sand and hunt at night. They prey on a wide variety of animals — primarily crustaceans and fish, and occasionally nemertean worms, polychaetes, gastropods, and even other cuttlefish. These cuttlefish are ambush predator that often hunt by blending in with the background and sneaking as up close to prey as they can. When the prey is close, the cuttlefish have two methods of attack. One is to shoot out the two longer tentacles, grab the prey using the suckers on the tentacular clubs at the tips of the tentacles and bring the prey into the cuttlefish’s beak to feed. The other is pounce on prey, with the cuttlefish using its arms to capture and maneuver the prey while it tears at the prey with its radula and beak. Both adult and immature cuttlefish hunt for food during the night. Some studies have shown that cuttlefish embryos have the ability to learn about prey items while still encased in their eggs using their fully-developed eyes to observe prey species. Hatchlings that observed crabs while inside their eggs preferred to eat crab over other prey items. [Source: Ae Lin Compton and Laura Wiley, Animal Diversity Web (ADW)]
Some cuttlefish species hunt prey using their changing and mesmerizing body patterns. They can also change colors to blend in with their surroundings which allows them to sneak up on prey and lay in wait and ambush them. When cuttlefish find something to eat, all tentacles are extended and their two feeding tentacles grab prey to pull it into their mouths. [Source: Hannah Markowitz, Animal Diversity Web]
Cuttlefish Mating and Reproduction
Cuttlefish are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in external reproduction in which sperm from the male fertilizes the female’s egg outside her body and employ sperm-storing (producing young from sperm that has been stored, allowing it be used for fertilization at some time after mating).[Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Cuttlefish engage in seasonal breeding. They do not live long after reproduction, although after copulation the female may move on to another male or move to place to release here eggs. The number of offspring ranges from 10 to 1,000. The gestation period is around a month or a month and a half, with independence occurring almost immediately after hatching. There is no parental involvement in the raising of offspring. Females usually do not return to the places where they leave their eggs. , and young cuttlefish eventually hatch and swim off on their own.
Many cuttlefish are polyandrous, with females mating with several males during one mating According to Animal Diversity Web: Broadclub cuttlefish males “tend to wait for females in coral reefs, where the females come to deposit their eggs. Males know females are ready to mate when they send certain signals. For instance, the skin of sexually active females turns a dark grey color, their arms flail, and their mantle texture becomes tougher.
Males also display pre-copulatory patterns and behaviors when they are attracting mates. Almost all of the transverse lines that are characteristic of the male cuttlefish disappear and their skin becomes a light grey color all over the body. Males proceed to reach their tentacles out toward a female and, if she does not respond, he propels himself in the water around her until she responds. More aggressive males will fight off weaker males that have paired up with a female. Male cuttlefish have been observed displaying an aggressive zebra stripe pattern when other males approach. ]
Broadclub cuttlefish have a dynamic mating procedure. When males are interested in mating with a female, they curl the tips of their tentacles and gently rub them across the foreheads or cheeks of the female in question. Males then blow water around the female in order to propel himself around her and draw her attention. Females signal receptivity by opening their tentacles. Successful males then open their tentacles as well and begin mating. While both sexes change color during mating, males are often a pale grey and female a dark grey color at the time. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=\
Mating begins when a male inserts spermatophores, or sperm packets, into a female. Male cuttlefish have one specialized “arm”, called a hectocotylus, that is used for this process. It is placed inside the buccal cavity of a female. Females store deposited sperm until they deposit their eggs post-coitally, after which they fertilize their eggs externally. Female cuttlefish attach their eggs to hard surfaces on the ocean floor or within coral reefs.
According to Animal Diversity Web: Fertilization of eggs occurs externally. Females first deposit their eggs and use stored sperm from a male to fertilize them. Broadclub cuttlefish have eggs of roughly 1.8 to two centimeters in diameter, and they take about 40 days from the time they are fertilized to hatch. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Because these eggs are transparent, young cuttlefish can be seen growing inside. Researchers have reported being able to see specific colors, patterns, and postures of baby cuttlefish inside their eggs. A study performed off the western coast of Guam showed that movement can be seen around day 15 of gestation, and the mantle and head can be seen at day 18. More detailed features such as eyes, heart, and cuttlebone are visible by day 20, and cuttlefish can change color and propel themselves within their egg sacs by day 30.
Juvenile broadclub cuttlefish eventually break out of the egg by propelling the pointed anterior ends of their cuttlebones at the egg sac wall with force. Newborn cuttlefish are about 14 millimeters in mantle length with arms of two millimeters. By the time they reach maturity they are about 160 millimeters long in mantle length. Growth is indeterminate, meaning they continue growing their whole life.
Cuttlefish and Humans
Cuttlefish are common food sources in many counties, particularly in Asia and the Mediterranean They reproduce quickly which means that even though two million metric tons of them are caught every year, they are not in danger of being overfished.
Cephalopods, particularly cuttlefish, are extensively fished throughout the Mediterranean, Southeast Asia, East Asia and elsewhere. Cuttlefish are a popular food item in these areas. The Romans ate them but they are rarely served as food in the United States except among Asians and Mediterranean people. Cuttlefish are prized as food in Korea. Around 1996, the market for cuttlefish exploded. The impact of cuttlefish fishing on their numbers is not known. [Source: Hannah Markowitz, Animal Diversity Web (ADW) /=]
Cuttlefish cuttlebones are sold at pet stores for birds such as parrots, and parakeets to chew on and get minerals. They also helps maintain bird beaks so they don’t become overgrown.
Cuttlefish ink has been utilized by humans throughout history as a source of ink. The genus name Sepia means “reddish brown,” a reference to the color of cuttlefish ink. In the old days cuttlefish ink was widely used in inks and dyes. Today it is mainly used in cooking to add color to sauces and certain dishes. Some researchers are looking into the medicinal possibilities of cephalopod ink. It has showed promise fighting the invasive fungus Aspergillus fumigatus responsible for some lung infections. /=\
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