The smallest, Octopus Wolfi, is barely 2. Octopus, in general, are masters of camouflage. They have the ability to change both the color and texture of their skin.
Specialized cells called chromatophores expand and contract exposing different pigments within the skin. This can help octopus, and other cephalopods, blend in with nearly any background and communicate their feelings to friend and foe.
By contracting different muscles, octopus can also change the texture of their skin, hiding among rocks, boulders, seaweed, or corals with ease. Octopus have 3 hearts and 9 brains! There is one central brain, and then each arm has a rudimentary brain. At Birch Aquarium: Flamboyant Cuttlefish. Cuttlefish are both masters of disguise and communication. They are able to expertly flash colors and patters in psychedelically moving displays. Cuttlefish, on average, have the largest brain-size to body-size ratio and these big brains might have something to do with their complex communication.
Their flat bodies and cuttlebones the oval, calcium-rich bone is porous helps cuttlefish hover along the seafloor as they look for small prey.
Though cuttlefish may look cute and slow, they are expert predators. When food like small fish or shrimp is within range, the cuttlefish points and aims its arms at the prey and shoots out its tentacles with lighting-fast speed.
Squid have long, fusiform torpedo-like body shapes, allowing them to zip through the water with ease. Using jet propulsion as well as two small fins at the top of their long mantle, squid are able to move forward and backward in the ocean with great speed and maneuverability. There are more than types of squid that can be found in oceans world-wide. Squid are an important commercial fishery world-wide. Most squid are fished at night when huge lights are shined on the surface of the ocean to draw the squid up from the depths.
During the day, huge schools of squid stay in deeper water where the lack of sunlight allows them to hide from predators. At night, they migrate vertically to the surface in the safety of dark to hunt for prey.
In combination, these color and texture changing techniques allow a cephalopod to mimic almost any background. Experiments by Roger Hanlon show cuttlefish expertly mimicking mottled textures, stripes, spots, and a black and white checkerboard! Certain cephalopods have even mastered the ability to impersonate other animals, a self-defense tactic called mimicry. The mimic octopus is the pinnacle of shape-shifting wizardry.
It appears to imitate up to 15 different animals that we know of. Faced with a pesky damselfish it buries six of its arms in the sand leaving just two strategically placed and colored to look like the venomous banded sea snake a predator of the fish. It can also cruise along the sand like a flat, banded sole fish or swim up in the water column like the venomous, spiny lionfish. Light is created through a chemical reaction that produces light energy in the body of the animal, similar to how fireflies flash on a hot summer night.
A catalyst called luciferase sets off the light producing substance called luciferin. The result is an eerie glow, startling flash, or syncopated blinking.
Bioluminescence serves more than just a pretty display. The concentration of photophores on the bottom side of some squid suggests the light is used as a camouflage technique called counterillumination; the bright light protects the squid from lurking predators below by allowing it to blend in with light coming from the surface of the water. But for the cephalopods that want to stand out, light is used to lure prey or flash as a warning for predators.
The dazzling light displays of the firefly squid during mating season off the coast of Japan are quite the sight to see at night, though scientists are unclear whether the purpose of the light is to attract mates, deter predators, or something yet to be discovered. One of the most exciting light displays is performed by the vampire squid. Deep ocean dwellers, vampire squid rely on three types of light organs. Each of the eight arms is tipped with several simple light organs, tiny photophores dot the skin, and a third, more complex pair of light organs with photoreceptors sit near the fins.
When startled, luminescent clouds of mucus are emitted from the arm-tip light organs, leading scientists to think the glowing display is a defense mechanism. While some cephalopods, like the vampire squid, are able to produce light on their own, for others lighting up requires a bit of help.
The bobtail squid relies on a bacterium called Vibrio fischeri , and will selectively allow this bacterium to grow within its photophores. At birth, a young bobtail squid lacks the bioluminescent bacteria and must find the light producing microbes in the water column. Once one bacterium successfully enters the photophore it multiplies by the hundreds of thousands, a colonization that spurs the full development of the photophore.
Vibrio fischeri is a common bioluminescence partner with some other cephalopods that owe their glowing skills to the microbe. In a stressful situation, a cephalopod has one final defense tactic. Almost all cephalopods have an ink sac, a bladder that can suddenly release a plume of dense, black ink. When startled or attacked by a predator the ink jet works like a smokescreen, a distraction, or a cephalopod look-a-like that the predator attacks instead which allows the real cephalopod to make a quick escape.
The ink can also act as a warning cue to other cephalopods. In the presence of ink the California market squid will begin to swim, and the Caribbean reef squid will initiate camouflage coloring. The Japanese pygmy squid has figured out how to use ink to hunt for shrimp , rather than just hide from predators.
It squirts a few quick puffs in the direction of the shrimp and then darts through the ink to grab its meal. The ink is potentially used as a way to both hide from the prey and to distract the shrimp from noticing the incoming attack. For most cephalopods, sex is a once in a lifetime event—both the male and female die shortly after mating. A male sometimes initiates the interaction with a courtship display meant to attract and woo the female, though for most octopuses there is little foreplay.
If successful, the male will use his hectocotylus, a specialized arm, to deposit sperm packets called spermatophores on or in the female.
The story of how the name hectocotylus came to be is a tale of mistaken identity. Turns out, it was actually a male cephalopod arm, but the name stuck. In the paper nautilus, the hectocotylus detaches completely during sex and remains inside the female—this is what Cuvier mistook as a worm.
Fertilization varies from species to species and in some cases the female holds on to the hectocotylus in a specialized pouch and fertilizes the eggs as she lays them. In some squid and cuttlefish , mating occurs in mass gatherings and the males compete for access to the female as she spawns.
In the European squid, Loligo vulgaris , smaller males will skirt around the edges of the spawning ground and display patterns similar to a female, rather than challenge the dominant male. If a female octopus lives near the ocean floor, once her eggs are fertilized, she will scout out a shelter to lay her eggs and attach them to the ceiling or walls in long strings.
While most octopus mothers spend less than a few months watching over their brood, one deep-sea octopus, Graneledone boreopacifica , holds the record for the longest time spent watching over her eggs—over four and a half years! The long egg development time is most likely a response to the relatively cold environment of the deep sea. For some squids that live in the open ocean, the eggs are spawned in gelatinous masses that then drift within the water column.
The discovery of a mass squid graveyard off the coast of California indicates that once the female squid successfully reproduce, they die and sink to the bottom of the ocean to over 3, feet 1, m where they become food for deep-sea scavengers. Upon hatching, the tiny, baby cephalopods become planktonic, meaning they live in the water column.
Many hatchlings are already adept predators and will actively pursue prey. Little is known about the early life stages of specific species due to difficulties in identifying the very small young. A cephalopod is a strategic and cunning predator. Divers know that a telltale sign of an octopus den is a collection of empty crab shells littered on a rocky bottom.
Carnivorous predators, all cephalopods have evolved special tools to help eat their prey. They rely on a sharp beak that chops their prey into bite-size pieces. Inside the beak, a tongue-like radula is lined with tiny teeth which can push food down into the digestive tract or act like a drill to bore holes in shellfish.
In many cephalopods, not just the notoriously deadly blue ringed octopus , a salivary gland produces a paralyzing toxin that immobilizes and digests prey upon being bitten. The cephalopod esophagus runs through the brain, requiring food to be sufficiently pulverized so it can fit through the narrow space. The digestive tract also includes a stomach, which further mashes the food, and a caecum where some nutrients are absorbed.
Often, cephalopods are voracious consumers. A study of the California two-spot octopus found that an 80 percent decline in the octopus population spurred a percent explosion of their prey populations, gastropods snails and slugs and hermit crabs. They devour everything, even crabs, and lobsters, and oysters, and all shellfish.
Some oceanic cephalopods participate in daily movements, called diel vertical migrations. The cover of night allows them to hunt at the surface without the threat of predators seeing them. Once the sun comes up they make their way down to deeper, darker water. Although a formidable predator in its own right, the soft bodies of squid, octopus, and cuttlefish are delectable meals for other predators. Birds also eat cephalopods. Albatrosses will plunge up to 32 feet 10 meters deep to snatch a squid beneath the waves.
Scientists often find the tough beaks of squid and octopus in the stomachs of sperm whales and seals. Sperm whales that wash ashore can even have large sucker scars along their body, indicating the whales engage in epic battles with giant squid while eating them.
People have enjoyed eating cephalopods since ancient times. According to Paul Bartsch , Curator of Mollusks at the Smithsonian Museum of National History in the early s, the Greeks and Romans considered all kinds of octopus to be a delicacy.
In Rome, they would stuff the cavity within the body full of spices, cut off the arms, and bake it in a pie. During preparation, chefs refused to use iron knives claiming that the metal left an unsavory taste and would instead use special bamboo knives.
The Greeks, too, enjoyed octopus, and often sent one as a gift to parents the fifth day after a child was born, the naming day. One comedic Greek story tells the tale of Philoxenus of Cythera, a particularly greedy man. One night, Philoxenus desired an elaborate meal, which subsequently included a massive, three-foot octopus as its main dish. Upon consuming all eight arms by himself, the man fell ill and required the attention of a doctor.
In many places around the world, octopus, squid, and cuttlefish are common menu items at the dinner table. Over 4 million metric tons of cephalopods are fished from the ocean every year, the same weight as 27, adult whales. Squids make up a good chunk of the catch, accounting for about 75 percent of that total. In several areas like the Gulf of Thailand, evidence of squid fishing can even be seen from the international space station. Squid fishermen string hundreds of bright lights from their boats at night to attract plankton, a powerful lure for squid that follow their prey to the surface where they are then caught by the fisherman.
But octopuses and cuttlefishes are also culinary favorites. A United Nations Food and Agriculture Organization report found that roughly , metric tons of octopus were fished the previous year, and in recent years cuttlefishes have had similar totals.
Cephalopod ink itself is the featured ingredient in Italian risotto nero and Spanish arroz negro. In Asia where there is a prominent cephalopod fishery, the ink is also used in traditional medicine, having exhibited antimicrobial properties. There is also great interest in its use in anticancer drug development. Cephalopods reproduce rapidly and so overfishing is often less of a problem than it is with finfishes.
However, the giant cuttlefish Sepia apama experienced a significant decline in numbers during the s. These cuttlefish are quite famous for their annual breeding aggregations off the coast of Australia in the Spencer Gulf, a phenomenon that attracts scientists, filmmakers, tourists, and fishermen.
Cuttlefish meat is also a popular dish and although it is still unclear what is the exact cause of the population decline, exploitation of the easy to find cuttlefish is potentially a contributor. Local divers recall how in an area that once saw thousands of the cuttlefish, people are now thrilled to see a couple hundred.
One study found a 57 percent reduction in the Spencer Gulf population between and The Point Lowly spawning aggregation, also off the coast of Australia, went from , cuttlefish in to 18, in In , cuttlefish fishing was banned from the area and there is hope that the stricter regulations will help them rebound. The pearly white inner shell of the nautilus, called the nacre, is an admired and sought-after material. The increased harvest of nautilus for their shells has caused concern among scientists.
The United States imported roughly , shells between and , mostly to make jewelry. Nautilus population numbers are mostly unknown, and for now, scientists are relying on anecdotal information on fishing catches to estimate their decline. Fishermen in the remote islands of the Philippines use dugout canoes and pull the nautilus traps up by hand. In the early s on the Philippine island of Bohol , fishermen caught up to nautilus a day, but now they may only pull up a few. When fishing dries up in one area the shell buyers move and the fishermen usually follow.
Now scientists and governments are coordinating to try and save this ancient animal. An international proposal drafted by the U. A National Oceanic and Atmospheric Administration funded project is currently trying to find out how many of these animals are left in the waters of American Samoa and Fiji. Embedded in the mantle of every cephalopod is large neuron called the giant axon.
Up to a millimeter in diameter, it is visible to the naked eye, making it a prime candidate for scientific experimentation. Aided by this axon, in , scientists Alan Hodgkin and Andrew Huxley made a monumental discovery about the mechanism of neuron signaling.
The scientists were able to insert an electrode into the axon and record an action potential, the electrical impulse that is passed from one neuron to another like a baton in a relay race. The discovery was such a monumental leap in the field of neuroscience that the responsible scientists were awarded a Nobel prize for Physiology or Medicine.
A study found that evolution occurs in cephalopods differently than in any other organism that we know of. In general, evolution occurs through a series of incremental changes in the DNA code—a mutation occurs in DNA, which then is transcribed in the instructional RNA, which then tells the cell how to build an altered protein.
But cephalopods have found a way to hijack that system and instead edit the RNA. Combined with fossil data, scientists determine how old in geological time an organism is by looking at the number of mutations in a DNA sequence. Next, researchers plan to dive into why cephalopods evolved such a unique system of adaptation.
Human fascination with cephalopods began thousands of years ago. For hundreds of years seafarers have regarded octopus and squid with trepidation, fear, and awe—feelings that inspired many stories, like 20, Leagues Under the Sea , that depict squid as terrifying beasts.
Many other stories, movies, and artwork depict octopuses and squid as fearsome monsters. They also lay only one egg at a time and they produce a small number of eggs annually that take about 1 year to incubate that swim along the ocean reef. They do not swim in the open ocean and cannot move between habitats that are separated by deep ocean.
Given their slow growth, late maturity, low reproductive output, and low mobility, chambered nautiluses are particularly vulnerable to overfishing. These threats make it difficult for them to recover from overharvest or catastrophic events.
Research scientists have had little success breeding these animals in captivity; eggs will hatch but the young do not live long enough to reach maturity. Little is known about nautilus populations in the wild. The very first population estimate was made only in Watch a chambered nautilus and its unique way of moving in this video from the Monterey Bay Aquarium.
Chambered nautiluses are bottom scavengers and eat shrimp and crabs, but their diet in the wild is largely unstudied. They are nocturnal, making daily migrations up and down the continental shelf.
Their up to 90 tentacles do not sting their prey, but stick to it. Teleost fish, such as triggerfish and grouper, prey on nautilus in shallow waters, and other species such as sharks and snappers may also prey on nautilus. The nautilus shell appears front and center on the emblem of New Caledonia. Nautilus jewelry figured strongly in Australian aboriginal culture both for bartering and was incorporated into hunter-gatherer folklore.
Fish and Wildlife Service and the National Marine Fisheries Service have collaborated with range countries and species experts for several years, contributing funding to research that would help us better understand chambered nautilus biology and the effects of harvest and international trade.
See more about our efforts and results. Peter Ward, and fellow researcher Dr. The aims were to estimate population sizes, to understand the importance of chambered nautilus harvesting to local fisheries, and to evaluate the effects of fishing by comparing fished and unfished populations.
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