146-618: Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician , through the Silurian , and into the Devonian . Discosorids are unique in the structure and formation of the siphuncle , the tube that runs through and connects the camerae (chambers) in cephalopods, which unlike those in other orders is zoned longitudinally along the segments rather than laterally. Siphuncle structure indicated that
292-464: A squid , octopus , cuttlefish , or nautilus . These exclusively marine animals are characterized by bilateral body symmetry , a prominent head, and a set of arms or tentacles ( muscular hydrostats ) modified from the primitive molluscan foot. Fishers sometimes call cephalopods " inkfish ", referring to their common ability to squirt ink . The study of cephalopods is a branch of malacology known as teuthology . Cephalopods became dominant during
438-427: A "shell vestige" or "gladius". The Incirrina have either a pair of rod-shaped stylets or no vestige of an internal shell, and some squid also lack a gladius. The shelled coleoids do not form a clade or even a paraphyletic group. The Spirula shell begins as an organic structure, and is then very rapidly mineralized. Shells that are "lost" may be lost by resorption of the calcium carbonate component. Females of
584-399: A cloud of dark ink to confuse predators . This sac is a muscular bag which originated as an extension of the hindgut. It lies beneath the gut and opens into the anus, into which its contents – almost pure melanin – can be squirted; its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion. The ejected cloud of melanin
730-410: A clutch of eggs. Females will spend all their time aerating and protecting their eggs until they are ready to hatch. During senescence, an octopus does not feed and quickly weakens. Lesions begin to form and the octopus literally degenerates. Unable to defend themselves, octopuses often fall prey to predators. This makes most octopuses effectively semelparous . The larger Pacific striped octopus (LPSO)
876-540: A delicacy by humans in many parts of the world, especially the Mediterranean and the Asian seas. The scientific Latin term octopus was derived from Ancient Greek ὀκτώπους ( oktōpous ), a compound form of ὀκτώ ( oktō , 'eight') and πούς ( pous , 'foot'), itself a variant form of ὀκτάπους , a word used for example by Alexander of Tralles ( c. 525 – c. 605 ) for
1022-596: A den without having to retrace their outward route. They are not migratory. Octopuses bring captured prey to the den, where they can eat it safely. Sometimes the octopus catches more prey than it can eat, and the den is often surrounded by a midden of dead and uneaten food items. Other creatures, such as fish, crabs , molluscs and echinoderms , often share the den with the octopus, either because they have arrived as scavengers , or because they have survived capture. On rare occasions, octopuses hunt cooperatively with other species , with fish as their partners. They regulate
1168-451: A diversity of backgrounds. Experiments done in Dwarf chameleons testing these hypotheses showed that chameleon taxa with greater capacity for color change had more visually conspicuous social signals but did not come from more visually diverse habitats, suggesting that color change ability likely evolved to facilitate social signaling, while camouflage is a useful byproduct. Because camouflage
1314-443: A fish, and are enclosed in a cartilaginous capsule fused to the cranium. The cornea is formed from a translucent epidermal layer; the slit-shaped pupil forms a hole in the iris just behind the cornea. The lens is suspended behind the pupil; photoreceptive retinal cells cover the back of the eye. The pupil can be adjusted in size; a retinal pigment screens incident light in bright conditions. Some species differ in form from
1460-529: A flat fan shape with a mucus film between the individual tentacles, while another, Sepioteuthis sepioidea , has been observed putting the tentacles in a circular arrangement. Cephalopods have advanced vision, can detect gravity with statocysts , and have a variety of chemical sense organs. Octopuses use their arms to explore their environment and can use them for depth perception. Most cephalopods rely on vision to detect predators and prey and to communicate with one another. Consequently, cephalopod vision
1606-652: A gunshot-like popping noise, thought to function to frighten away potential predators. Cephalopods employ a similar method of propulsion despite their increasing size (as they grow) changing the dynamics of the water in which they find themselves. Thus their paralarvae do not extensively use their fins (which are less efficient at low Reynolds numbers ) and primarily use their jets to propel themselves upwards, whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins. Early cephalopods are thought to have produced jets by drawing their body into their shells, as Nautilus does today. Nautilus
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#17327975941491752-400: A hole in the shell to inject a nerve toxin . It used to be thought that the hole was drilled by the radula, but it has now been shown that minute teeth at the tip of the salivary papilla are involved, and an enzyme in the toxic saliva is used to dissolve the calcium carbonate of the shell. It takes about three hours for O. vulgaris to create a 0.6 mm (0.024 in) hole. Once the shell
1898-453: A jet as a propulsion mechanism. Squids do not have the longitudinal muscles that octopus do. Instead, they have a tunic. This tunic is made of layers of collagen and it surrounds the top and the bottom of the mantle. Because they are made of collagen and not muscle, the tunics are rigid bodies that are much stronger than the muscle counterparts. This provides the squids some advantages for jet propulsion swimming. The stiffness means that there
2044-402: A jet of water from the mantle through the siphon into the sea. The physical principle behind this is that the force required to accelerate the water through the orifice produces a reaction that propels the octopus in the opposite direction. The direction of travel depends on the orientation of the siphon. When swimming, the head is at the front and the siphon is pointed backward but, when jetting,
2190-406: A length of 8 metres. They may terminate in a broadened, sucker-coated club. The shorter four pairs are termed arms , and are involved in holding and manipulating the captured organism. They too have suckers, on the side closest to the mouth; these help to hold onto the prey. Octopods only have four pairs of sucker-coated arms, as the name suggests, though developmental abnormalities can modify
2336-515: A mantle pressure so high as to stop the heart from beating, resulting in a progressive oxygen deficit. Cirrate octopuses cannot produce jet propulsion and rely on their fins for swimming. They have neutral buoyancy and drift through the water with the fins extended. They can also contract their arms and surrounding web to make sudden moves known as "take-offs". Another form of locomotion is "pumping", which involves symmetrical contractions of muscles in their webs producing peristaltic waves . This moves
2482-474: A muscle, which is why they can change their skin hue as rapidly as they do. Coloration is typically stronger in near-shore species than those living in the open ocean, whose functions tend to be restricted to disruptive camouflage . These chromatophores are found throughout the body of the octopus, however, they are controlled by the same part of the brain that controls elongation during jet propulsion to reduce drag. As such, jetting octopuses can turn pale because
2628-512: A novel mechanism for spectral discrimination in cephalopods was described. This relies on the exploitation of chromatic aberration (wavelength-dependence of focal length). Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation. The unusual off-axis slit and annular pupil shapes in cephalopods enhance this ability by acting as prisms which are scattering white light in all directions. In 2015, molecular evidence
2774-509: A rapidly expanding siphuncle with segments that extend into the adjacent chambers, and parietal deposits within the siphuncle that overlap to form endocones. The Discosorida include these families, more or less in phylogenetic sequence beginning with the oldest: These form three basin evolutionary lineages. The first, formed by the Reudemannoceratidae, Cyrtogomphoceratidae, and Phragmoceratidae, are fundamentally endogastric with
2920-471: A rare form of physiological color change which utilizes neural control of muscles to change the morphology of their chromatophores. This neural control of chromatophores has evolved convergently in both cephalopods and teleosts fishes. With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina , all known cephalopods have an ink sac, which can be used to expel
3066-429: A shell-less subclass of cephalopods (squid, cuttlefish, and octopuses), have complex pigment containing cells called chromatophores which are capable of producing rapidly changing color patterns. These cells store pigment within an elastic sac which produces the color seen from these cells. Coleoids can change the shape of this sac, called the cytoelastic sacculus, which then causes changes in the translucency and opacity of
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#17327975941493212-488: A shelter, an example of tool use . Octopuses use camouflage when hunting and to avoid predators. To do this, they use specialised skin cells that change the appearance of the skin by adjusting its colour, opacity, or reflectivity. Chromatophores contain yellow, orange, red, brown, or black pigments; most species have three of these colours, while some have two or four. Other colour-changing cells are reflective iridophores and white leucophores. This colour-changing ability
3358-432: A single photoreceptor protein may use chromatic aberration to turn monochromatic vision into colour vision, though this sacrifices image quality. This would explain pupils shaped like the letter "U", the letter "W", or a dumbbell , as well as the need for colourful mating displays. Attached to the brain are two organs called statocysts (sac-like structures containing a mineralised mass and sensitive hairs), that allow
3504-407: A single indisputable record of an octopus in the hadal zone ; a species of Grimpoteuthis (dumbo octopus) photographed at 6,957 m (22,825 ft). No species are known to live in fresh water. Most species are solitary when not mating, though a few are known to occur in high densities and with frequent interactions, such as signaling, mate defending and evicting individuals from dens. This
3650-620: A startling array of fashions. As well as providing camouflage with their background, some cephalopods bioluminesce, shining light downwards to disguise their shadows from any predators that may lurk below. The bioluminescence is produced by bacterial symbionts; the host cephalopod is able to detect the light produced by these organisms. Bioluminescence may also be used to entice prey, and some species use colorful displays to impress mates, startle predators, or even communicate with one another. Cephalopods can change their colors and patterns in milliseconds, whether for signalling (both within
3796-425: A surface, the orifice between the two structures is sealed. The infundibulum provides adhesion while the acetabulum remains free, and muscle contractions allow for attachment and detachment. Each of the eight arms senses and responds to light, allowing the octopus to control the limbs even if its head is obscured. The eyes of the octopus are large and at the top of the head. They are similar in structure to those of
3942-435: A systemic or main heart that circulates blood around the body and two branchial or gill hearts that pump it through each of the two gills. The systemic heart becomes inactive when the animal is swimming. Thus the octopus tires quickly and prefers to crawl. Octopus blood contains the copper -rich protein haemocyanin to transport oxygen. This makes the blood very viscous and it requires considerable pressure to pump it around
4088-436: A water jet. Before it leaves the funnel, the ink passes through glands which mix it with mucus, creating a thick, dark blob which allows the animal to escape from a predator. The main pigment in the ink is melanin , which gives it its black colour. Cirrate octopuses usually lack the ink sac. Octopuses are gonochoric and have a single, posteriorly-located gonad which is associated with the coelom . The testis in males and
4234-446: Is Octopus wolfi , which is around 2.5 cm (1 in) and weighs less than 1 g (0.035 oz). The octopus is bilaterally symmetrical along its dorso-ventral (back to belly) axis; the head and foot are at one end of an elongated body and function as the anterior (front) of the animal. The head includes the mouth and brain. The foot has evolved into a set of flexible, prehensile appendages , known as "arms", that surround
4380-427: Is bilaterally symmetric with two eyes and a beaked mouth at the centre point of the eight limbs. The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. They trail their eight appendages behind them as they swim. The siphon is used both for respiration and for locomotion , by expelling a jet of water. Octopuses have a complex nervous system and excellent sight, and are among
4526-430: Is octopuses , that octopi is misconceived, and octopodes pedantic ; the last is nonetheless used frequently enough to be acknowledged by the descriptivist Merriam-Webster 11th Collegiate Dictionary and Webster's New World College Dictionary . The Oxford English Dictionary lists octopuses , octopi , and octopodes , in that order, reflecting frequency of use, calling octopodes rare and noting that octopi
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4672-480: Is a third-declension noun. Historically, the first plural to commonly appear in English language sources, in the early 19th century, is the latinate form octopi , followed by the English form octopuses in the latter half of the same century. The Hellenic plural is roughly contemporary in usage, although it is also the rarest. Fowler's Modern English Usage states that the only acceptable plural in English
4818-403: Is a spiked, muscular tongue-like organ with multiple rows of tiny teeth. Food is broken down and is forced into the oesophagus by two lateral extensions of the esophageal side walls in addition to the radula. From there it is transferred to the gastrointestinal tract , which is mostly suspended from the roof of the mantle cavity by numerous membranes. The tract consists of a crop , where the food
4964-516: Is acute: training experiments have shown that the common octopus can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The morphological construction gives cephalopod eyes the same performance as shark eyes; however, their construction differs, as cephalopods lack a cornea and have an everted retina. Cephalopods' eyes are also sensitive to the plane of polarization of light. Unlike many other cephalopods, nautiluses do not have good vision; their eye structure
5110-430: Is added to the pericardia of the branchial hearts. The octopus has two nephridia (equivalent to vertebrate kidneys) which are associated with the branchial hearts; these and their associated ducts connect the pericardial cavities with the mantle cavity. Before reaching the branchial heart, each branch of the vena cava expands to form renal appendages which are in direct contact with the thin-walled nephridium. The urine
5256-463: Is also capable of creating a jet by undulations of its funnel; this slower flow of water is more suited to the extraction of oxygen from the water. When motionless, Nautilus can only extract 20% of oxygen from the water. The jet velocity in Nautilus is much slower than in coleoids , but less musculature and energy is involved in its production. Jet thrust in cephalopods is controlled primarily by
5402-451: Is also used to communicate with or warn other octopuses. The energy cost of the complete activation of the chromatophore system is very high equally being nearly as much as all the energy used by an octopus at rest. Octopuses can create distracting patterns with waves of dark colouration across the body, a display known as the "passing cloud". Muscles in the skin change the texture of the mantle to achieve greater camouflage. In some species,
5548-500: Is an exception, as it can reproduce repeatedly over a life of around two years. Octopus reproductive organs mature due to the hormonal influence of the optic gland but result in the inactivation of their digestive glands. Unable to feed, the octopus typically dies of starvation. Experimental removal of both optic glands after spawning was found to result in the cessation of broodiness , the resumption of feeding, increased growth, and greatly extended lifespans. It has been proposed that
5694-570: Is aragonite. As for other mollusc shells or coral skeletons, the smallest visible units are irregular rounded granules. Cephalopods, as the name implies, have muscular appendages extending from their heads and surrounding their mouths. These are used in feeding, mobility, and even reproduction. In coleoids they number eight or ten. Decapods such as cuttlefish and squid have five pairs. The longer two, termed tentacles , are actively involved in capturing prey; they can lengthen rapidly (in as little as 15 milliseconds ). In giant squid they may reach
5840-522: Is based on a misunderstanding. The New Oxford American Dictionary (3rd Edition, 2010) lists octopuses as the only acceptable pluralisation, and indicates that octopodes is still occasionally used, but that octopi is incorrect. The giant Pacific octopus (Enteroctopus dofleini) is often cited as the largest known octopus species. Adults usually weigh around 15 kg (33 lb), with an arm span of up to 4.3 m (14 ft). The largest specimen of this species to be scientifically documented
5986-411: Is first formed in the pericardial cavity, and is modified by excretion, chiefly of ammonia, and selective absorption from the renal appendages, as it is passed along the associated duct and through the nephridiopore into the mantle cavity. Octopuses (along with cuttlefish ) have the highest brain-to-body mass ratios of all invertebrates; this is greater than that of many vertebrates. Octopuses have
Discosorida - Misplaced Pages Continue
6132-427: Is highly developed, but lacks a solid lens . They have a simple " pinhole " eye through which water can pass. Instead of vision, the animal is thought to use olfaction as the primary sense for foraging , as well as locating or identifying potential mates. All octopuses and most cephalopods are considered to be color blind . Coleoid cephalopods (octopus, squid, cuttlefish) have a single photoreceptor type and lack
6278-450: Is likely the result of abundant food supplies combined with limited den sites. The LPSO has been described as particularly social, living in groups of up to 40 individuals. Octopuses hide in dens, which are typically crevices in rocky outcrops or other hard structures, though some species burrow into sand or mud. Octopuses are not territorial but generally remain in a home range; they may leave in search of food. They can navigate back to
6424-418: Is more efficient, but in environments with little oxygen and in low temperatures, hemocyanin has the upper hand. The hemocyanin molecule is much larger than the hemoglobin molecule, allowing it to bond with 96 O 2 or CO 2 molecules, instead of the hemoglobin's just four. But unlike hemoglobin, which are attached in millions on the surface of a single red blood cell, hemocyanin molecules float freely in
6570-403: Is needed, compensating for their small size. However, organisms which spend most of their time moving slowly along the bottom do not naturally pass much water through their cavity for locomotion; thus they have larger gills, along with complex systems to ensure that water is constantly washing through their gills, even when the organism is stationary. The water flow is controlled by contractions of
6716-439: Is no necessary muscle flexing to keep the mantle the same size. In addition, tunics take up only 1% of the squid mantle's wall thickness, whereas the longitudinal muscle fibers take up to 20% of the mantle wall thickness in octopuses. Also because of the rigidity of the tunic, the radial muscles in squid can contract more forcefully. The mantle is not the only place where squids have collagen. Collagen fibers are located throughout
6862-432: Is penetrated, the prey dies almost instantaneously, its muscles relax, and the soft tissues are easy for the octopus to remove. Crabs may also be treated in this way; tough-shelled species are more likely to be drilled, and soft-shelled crabs are torn apart. Some species have other modes of feeding. Grimpoteuthis has a reduced or non-existent radula and swallows prey whole. In the deep-sea genus Stauroteuthis , some of
7008-457: Is referred to as a pseudomorph ). This strategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey. For more information, see Inking behaviors . The ink sac of cephalopods has led to a common name of "inkfish", formerly the pen-and-ink fish. Cephalopods are the only molluscs with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts ) that move blood through
7154-437: Is stored; a stomach, where food is ground down; a caecum where the now sludgy food is sorted into fluids and particles and which plays an important role in absorption; the digestive gland , where liver cells break down and absorb the fluid and become "brown bodies"; and the intestine, where the accumulated waste is turned into faecal ropes by secretions and blown out of the funnel via the rectum. During osmoregulation , fluid
7300-413: Is supplemented with fin motion; in the squid, the fins flap each time that a jet is released, amplifying the thrust; they are then extended between jets (presumably to avoid sinking). Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome , created by a fold in the mantle. The size difference between
7446-553: Is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light. Some squids have been shown to detect sound using their statocysts , but, in general, cephalopods are deaf. Most cephalopods possess an assemblage of skin components that interact with light. These may include iridophores, leucophores , chromatophores and (in some species) photophores . Chromatophores are colored pigment cells that expand and contract in accordance to produce color and pattern which they can use in
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#17327975941497592-423: Is the most complex of the invertebrates and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates. Captive cephalopods have also been known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on captive crabs, and return to their own aquarium. The brain is protected in a cartilaginous cranium. The giant nerve fibers of
7738-426: Is unknown, but chromatophores are under the control of neural pathways, allowing the cephalopod to coordinate elaborate displays. Together, chromatophores and iridophores are able to produce a large range of colors and pattern displays. Cephalopods utilize chromatophores' color changing ability in order to camouflage themselves. Chromatophores allow Coleoids to blend into many different environments, from coral reefs to
7884-504: Is used by the veined octopus when carrying stacked coconut shells. The octopus carries the shells underneath it with two arms, and progresses with an ungainly gait supported by its remaining arms held rigid. Octopuses are highly intelligent . Maze and problem-solving experiments have shown evidence of a memory system that can store both short- and long-term memory . Young octopuses learn nothing from their parents, as adults provide no parental care beyond tending to their eggs until
8030-400: Is used for multiple adaptive purposes in cephalopods, color change could have evolved for one use and the other developed later, or it evolved to regulate trade offs within both. Color change is widespread in ectotherms including anoles, frogs, mollusks, many fish, insects, and spiders. The mechanism behind this color change can be either morphological or physiological. Morphological change is
8176-417: Is usually mixed, upon expulsion, with mucus , produced elsewhere in the mantle, and therefore forms a thick cloud, resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen . However, a more sophisticated behavior has been observed, in which the cephalopod releases a cloud, with a greater mucus content, that approximately resembles the cephalopod that released it (this decoy
8322-474: The Ammonoidea (ammonites) and Belemnoidea (belemnites). Extant cephalopods range in size from the 10 mm (0.3 in) Idiosepius thailandicus to the 700 kilograms (1,500 lb) heavy Colossal squid , the largest extant invertebrate . There are over 800 extant species of cephalopod, although new species continue to be described. An estimated 11,000 extinct taxa have been described, although
8468-675: The Ordovician period, represented by primitive nautiloids . The class now contains two, only distantly related, extant subclasses: Coleoidea , which includes octopuses , squid , and cuttlefish ; and Nautiloidea , represented by Nautilus and Allonautilus . In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. Two important extinct taxa are
8614-825: The blue-ringed octopuses are known to be deadly to humans. Octopuses appear in mythology as sea monsters like the Kraken of Norway and the Akkorokamui of the Ainu , and possibly the Gorgon of ancient Greece . A battle with an octopus appears in Victor Hugo 's book Toilers of the Sea , inspiring other works such as Ian Fleming 's Octopussy . Octopuses appear in Japanese erotic art, shunga . They are eaten and considered
8760-414: The ovary in females bulges into the gonocoel and the gametes are released here. The gonocoel is connected by the gonoduct to the mantle cavity , which it enters at the gonopore . An optic gland creates hormones that cause the octopus to mature and age and stimulate gamete production. The gland may be triggered by environmental conditions such as temperature, light and nutrition, which thus control
8906-445: The polarisation of light. Colour vision appears to vary from species to species, for example, being present in O. aegina but absent in O. vulgaris . Opsins in the skin respond to different wavelengths of light and help the animals choose a colouration that camouflages them; the chromatophores in the skin can respond to light independently of the eyes. An alternative hypothesis is that cephalopod eyes in species that only have
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#17327975941499052-583: The sparkling enope squid ( Watasenia scintillans ). It achieves color vision with three photoreceptors , which are based on the same opsin , but use distinct retinal molecules as chromophores: A1 (retinal), A3 (3-dehydroretinal), and A4 (4-hydroxyretinal). The A1-photoreceptor is most sensitive to green-blue (484 nm), the A2-photoreceptor to blue-green (500 nm), and the A4-photoreceptor to blue (470 nm) light. In 2015,
9198-456: The species composition of the hunting group — and the behavior of their partners — by punching them. Nearly all octopuses are predatory; bottom-dwelling octopuses eat mainly crustaceans , polychaete worms , and other molluscs such as whelks and clams ; open-ocean octopuses eat mainly prawns, fish and other cephalopods. Major items in the diet of the giant Pacific octopus include bivalve molluscs such as
9344-535: The Discosorida evolved directly from the Plectronoceratida rather than through the more developed Ellesmerocerida , as did the other orders. Finally and most diagnostic, discosorids developed a reinforcing, grommet -like structure in the septal opening of the siphuncle known as the bullette, formed by a thickening of the connecting ring as it draped around the folded back septal neck. The origin of
9490-703: The Discosorida is unknown, thought at one time to be directly from the Plectronocerida . Evolution within the order begins with the lower Middle Ordovician Reudemannoceratidae and from there diverges into three main lineages. Questionable discosorids have been reported as early as the Middle Tremadocian - near the start of the Ordovician, however the first bona fide examples date to the Middle Ordovician. The diversification of
9636-487: The Discosorida resembled the Oncocerida , which lived about the same time, but evolved from a completely different stock. The two convergent groups differ in their internal detail. Cephalopod A cephalopod / ˈ s ɛ f ə l ə p ɒ d / is any member of the molluscan class Cephalopoda / s ɛ f ə ˈ l ɒ p ə d ə / ( Greek plural κεφαλόποδες , kephalópodes ; "head-feet") such as
9782-587: The Discosorida, in terms of genera, peaked at the beginning in the Middle Ordovician (modern Darriwilian stage) followed by a decline in the Upper Ordovician (modern Sandbian and Katian stages) only to peak again in the Middle Silurian. Afterwards their diversity declined drastically and remained low until their end in the late Devonian. Some were endogastrically curved, with the lower, siphuncle side concave, others were exogastrically curved with
9928-556: The ability to determine color by comparing detected photon intensity across multiple spectral channels. When camouflaging themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background may come from cells such as iridophores and leucophores that reflect light from the environment. They also produce visual pigments throughout their body and may sense light levels directly from their body. Evidence of color vision has been found in
10074-452: The acidity of the organic shell matrix (see Mollusc shell ); shell-forming cephalopods have an acidic matrix, whereas the gladius of squid has a basic matrix. The basic arrangement of the cephalopod outer wall is: an outer (spherulitic) prismatic layer, a laminar (nacreous) layer and an inner prismatic layer. The thickness of every layer depends on the taxa. In modern cephalopods, the Ca carbonate
10220-486: The adults. In the argonaut (paper nautilus), the female secretes a fine, fluted, papery shell in which the eggs are deposited and in which she also resides while floating in mid-ocean. In this she broods the young, and it also serves as a buoyancy aid allowing her to adjust her depth. The male argonaut is minute by comparison and has no shell. Octopuses have short lifespans, and some species complete their lifecycles in only six months. The Giant Pacific octopus , one of
10366-434: The air for distances of up to 50 metres (160 ft). While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion; water continues to be expelled from the funnel while the organism is in the air. The animals spread their fins and tentacles to form wings and actively control lift force with body posture. One species, Todarodes pacificus , has been observed spreading tentacles in
10512-454: The appearance of their surroundings is notable given that cephalopods' vision is monochromatic. Cephalopods also use their fine control of body coloration and patterning to perform complex signaling displays for both conspecific and intraspecific communication. Coloration is used in concert with locomotion and texture to send signals to other organisms. Intraspecifically this can serve as a warning display to potential predators. For example, when
10658-402: The arms are covered with circular, adhesive suckers. The suckers allow the octopus to anchor itself or to manipulate objects. Each sucker is usually circular and bowl-like and has two distinct parts: an outer shallow cavity called an infundibulum and a central hollow cavity called an acetabulum , both of which are thick muscles covered in a protective chitinous cuticle. When a sucker attaches to
10804-433: The blood. Respiration involves drawing water into the mantle cavity through an aperture, passing it through the gills, and expelling it through the siphon. The ingress of water is achieved by contraction of radial muscles in the mantle wall, and flapper valves shut when strong circular muscles force the water out through the siphon. Extensive connective tissue lattices support the respiratory muscles and allow them to expand
10950-403: The bloodstream. Cephalopods exchange gases with the seawater by forcing water through their gills, which are attached to the roof of the organism. Water enters the mantle cavity on the outside of the gills, and the entrance of the mantle cavity closes. When the mantle contracts, water is forced through the gills, which lie between the mantle cavity and the funnel. The water's expulsion through
11096-517: The body cavity; others, like some fish, accumulate oils in the liver; and some octopuses have a gelatinous body with lighter chloride ions replacing sulfate in the body chemistry. Squids are the primary sufferers of negative buoyancy in cephalopods. The negative buoyancy means that some squids, especially those whose habitat depths are rather shallow, have to actively regulate their vertical positions. This means that they must expend energy, often through jetting or undulations, in order to maintain
11242-517: The body is made of soft tissue allowing it to lengthen, contract, and contort itself. The octopus can squeeze through tiny gaps; even the larger species can pass through an opening close to 2.5 cm (1 in) in diameter. Lacking skeletal support, the arms work as muscular hydrostats and contain longitudinal, transverse and circular muscles around a central axial nerve. They can extend and contract, twist to left or right, bend at any place in any direction or be held rigid. The interior surfaces of
11388-415: The body slowly. In 2005, Adopus aculeatus and veined octopus ( Amphioctopus marginatus ) were found to walk on two arms, while at the same time mimicking plant matter. This form of locomotion allows these octopuses to move quickly away from a potential predator without being recognised. Some species of octopus can crawl out of the water briefly, which they may do between tide pools. "Stilt walking"
11534-418: The body. The blood vessels consist of arteries, capillaries and veins and are lined with a cellular endothelium which is quite unlike that of most other invertebrates . The blood circulates through the aorta and capillary system, to the vena cavae, after which the blood is pumped through the gills by the branchial hearts and back to the main heart. Much of the venous system is contractile, which helps circulate
11680-439: The body; octopuses' blood pressures can exceed 75 mmHg (10 kPa). In cold conditions with low oxygen levels, haemocyanin transports oxygen more efficiently than haemoglobin . The haemocyanin is dissolved in the plasma instead of being carried within blood cells and gives the blood a bluish colour. The systemic heart has muscular contractile walls and consists of a single ventricle and two atria, one for each side of
11826-527: The brain is unable to achieve both controlling elongation and controlling the chromatophores. Most octopuses mimic select structures in their field of view rather than becoming a composite color of their full background. Evidence of original coloration has been detected in cephalopod fossils dating as far back as the Silurian ; these orthoconic individuals bore concentric stripes, which are thought to have served as camouflage. Devonian cephalopods bear more complex color patterns, of unknown function. Coleoids,
11972-401: The capillaries of the gills . A single systemic heart then pumps the oxygenated blood through the rest of the body. Like most molluscs, cephalopods use hemocyanin , a copper-containing protein, rather than hemoglobin , to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when bonded to oxygen. In oxygen-rich environments and in acidic water, hemoglobin
12118-436: The cavity by entering not only through the orifices, but also through the funnel. Squid can expel up to 94% of the fluid within their cavity in a single jet thrust. To accommodate the rapid changes in water intake and expulsion, the orifices are highly flexible and can change their size by a factor of twenty; the funnel radius, conversely, changes only by a factor of around 1.5. Some octopus species are also able to walk along
12264-561: The cell. By rapidly changing multiple chromatophores of different colors, cephalopods are able to change the color of their skin at astonishing speeds, an adaptation that is especially notable in an organism that sees in black and white. Chromatophores are known to only contain three pigments, red, yellow, and brown, which cannot create the full color spectrum. However, cephalopods also have cells called iridophores, thin, layered protein cells that reflect light in ways that can produce colors chromatophores cannot. The mechanism of iridophore control
12410-399: The cephalopod mantle have been widely used for many years as experimental material in neurophysiology ; their large diameter (due to lack of myelination ) makes them relatively easy to study compared with other animals. Many cephalopods are social creatures; when isolated from their own kind, some species have been observed shoaling with fish. Some cephalopods are able to fly through
12556-520: The cockle Clinocardium nuttallii , clams and scallops and crustaceans such as crabs and spider crabs . Prey that it is likely to reject include moon snails because they are too large and limpets , rock scallops , chitons and abalone , because they are too securely fixed to the rock. Small cirrate octopuses such as those of the genera Grimpoteuthis and Opisthoteuthis typically prey on polychaetes, copepods , amphipods and isopods . A benthic (bottom-dwelling) octopus typically moves among
12702-402: The cold, ocean depths. The spoon-armed octopus ( Bathypolypus arcticus ) is found at depths of 1,000 m (3,300 ft), and Vulcanoctopus hydrothermalis lives near hydrothermal vents at 2,000 m (6,600 ft). The cirrate species are often free-swimming and live in deep-water habitats. Although several species are known to live at bathyal and abyssal depths, there is only
12848-490: The common octopus. The standard pluralised form of octopus in English is octopuses ; the Ancient Greek plural ὀκτώποδες , octopodes ( / ɒ k ˈ t ɒ p ə d iː z / ), has also been used historically. The alternative plural octopi is usually considered incorrect because it wrongly assumes that octopus is a Latin second-declension -us noun or adjective when, in either Greek or Latin, it
12994-533: The complex motor skills of octopuses are not organised in their brains via internal somatotopic maps of their bodies. The nervous system of cephalopods is the most complex of all invertebrates. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology ; their large diameter (due to lack of myelination ) makes them relatively easy to study compared with other animals. Like other cephalopods, octopuses have camera-like eyes, and can distinguish
13140-491: The depth of the ocean, from the abyssal plains to the sea surface, and have also been found in the hadal zone . Their diversity is greatest near the equator (~40 species retrieved in nets at 11°N by a diversity study) and decreases towards the poles (~5 species captured at 60°N). Cephalopods are widely regarded as the most intelligent of the invertebrates and have well developed senses and large brains (larger than those of gastropods ). The nervous system of cephalopods
13286-405: The eggs to completely develop. The female aerates them and keeps them clean; if left untended, many will die. She does not feed during this time and dies soon after. Males become senescent and die a few weeks after mating. The eggs have large yolks; cleavage (division) is superficial and a germinal disc develops at the pole. During gastrulation , the margins of this grow down and surround
13432-469: The expansion of the mantle at the end of the jet. In some tests, the collagen has been shown to be able to begin raising mantle pressure up to 50ms before muscle activity is initiated. These anatomical differences between squid and octopuses can help explain why squid can be found swimming comparably to fish while octopuses usually rely on other forms of locomotion on the sea floor such as bipedal walking, crawling, and non-jetting swimming. Nautiluses are
13578-427: The female's mantle cavity, after which he becomes senescent and dies, while the female deposits fertilised eggs in a den and cares for them until they hatch, after which she also dies. Strategies to defend themselves against predators include the expulsion of ink , the use of camouflage and threat displays , the ability to jet quickly through the water and hide, and even deceit. All octopuses are venomous , but only
13724-442: The female. He picks up a spermatophore from his spermatophoric sac with the hectocotylus, inserts it into the female's mantle cavity, and deposits it in the correct location for the species, which in the giant Pacific octopus is the opening of the oviduct. Two spermatophores are transferred in this way; these are about one metre (yard) long, and the empty ends may protrude from the female's mantle. A complex hydraulic mechanism releases
13870-413: The form of jetting. The composition of these mantles differs between the two families, however. In octopuses, the mantle is made up of three muscle types: longitudinal, radial, and circular. The longitudinal muscles run parallel to the length of the octopus and they are used in order to keep the mantle the same length throughout the jetting process. Given that they are muscles, it can be noted that this means
14016-456: The funnel can be used to power jet propulsion. If respiration is used concurrently with jet propulsion, large losses in speed or oxygen generation can be expected. The gills, which are much more efficient than those of other mollusks, are attached to the ventral surface of the mantle cavity. There is a trade-off with gill size regarding lifestyle. To achieve fast speeds, gills need to be small – water will be passed through them quickly when energy
14162-422: The mantle can take on the spiky appearance of algae; in others, skin anatomy is limited to relatively uniform shades of one colour with limited skin texture. Octopuses that are diurnal and live in shallow water have evolved more complex skin than their nocturnal and deep-sea counterparts. A "moving rock" trick involves the octopus mimicking a rock and then inching across the open space with a speed matching that of
14308-472: The maximum diameter of the funnel orifice (or, perhaps, the average diameter of the funnel) and the diameter of the mantle cavity. Changes in the size of the orifice are used most at intermediate velocities. The absolute velocity achieved is limited by the cephalopod's requirement to inhale water for expulsion; this intake limits the maximum velocity to eight body-lengths per second, a speed which most cephalopods can attain after two funnel-blows. Water refills
14454-410: The most intelligent and behaviourally diverse of all invertebrates . Octopuses inhabit various regions of the ocean , including coral reefs , pelagic waters, and the seabed ; some live in the intertidal zone and others at abyssal depths . Most species grow quickly, mature early, and are short-lived. In most species, the male uses a specially adapted arm to deliver a bundle of sperm directly into
14600-437: The mouth and are attached to each other near their base by a webbed structure. The arms can be described based on side and sequence position (such as L1, R1, L2, R2) and divided into four pairs. The two rear appendages are generally used to walk on the sea floor, while the other six are used to forage for food. The bulbous and hollow mantle is fused to the back of the head and is known as the visceral hump; it contains most of
14746-545: The muscle cells that control the suckers in most species have been replaced with photophores which are believed to fool prey by directing them to the mouth, making them one of the few bioluminescent octopuses. Octopuses mainly move about by relatively slow crawling with some swimming in a head-first position. Jet propulsion or backward swimming, is their fastest means of locomotion, followed by swimming and crawling. When in no hurry, they usually crawl on either solid or soft surfaces. Several arms are extended forward, some of
14892-442: The naturally short lifespan may be functional to prevent rapid overpopulation. Octopuses live in every ocean, and different species have adapted to different marine habitats . As juveniles, common octopuses inhabit shallow tide pools . The Hawaiian day octopus ( Octopus cyanea ) lives on coral reefs; argonauts drift in pelagic waters . Abdopus aculeatus mostly lives in near-shore seagrass beds. Some species are adapted to
15038-404: The non threatening herbivorous parrotfish to approach unaware prey. The octopus Thaumoctopus mimicus is known to mimic a number of different venomous organisms it cohabitates with to deter predators. While background matching, a cephalopod changes its appearance to resemble its surroundings, hiding from its predators or concealing itself from prey. The ability to both mimic other organisms and match
15184-452: The number of arms expressed. Octopus (traditional) See § Evolution for families An octopus ( pl. : octopuses or octopodes ) is a soft-bodied, eight-limbed mollusc of the order Octopoda ( / ɒ k ˈ t ɒ p ə d ə / , ok- TOP -ə-də ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids , cuttlefish , and nautiloids . Like other cephalopods, an octopus
15330-413: The octopus Callistoctopus macropus is threatened, it will turn a bright red brown color speckled with white dots as a high contrast display to startle predators. Conspecifically, color change is used for both mating displays and social communication. Cuttlefish have intricate mating displays from males to females. There is also male to male signaling that occurs during competition over mates, all of which are
15476-443: The octopus genus Argonauta secrete a specialized paper-thin egg case in which they reside, and this is popularly regarded as a "shell", although it is not attached to the body of the animal and has a separate evolutionary origin. The largest group of shelled cephalopods, the ammonites , are extinct, but their shells are very common as fossils . The deposition of carbonate, leading to a mineralized shell, appears to be related to
15622-444: The octopus must actively flex the longitudinal muscles during jetting in order to keep the mantle at a constant length. The radial muscles run perpendicular to the longitudinal muscles and are used to thicken and thin the wall of the mantle. Finally, the circular muscles are used as the main activators in jetting. They are muscle bands that surround the mantle and expand/contract the cavity. All three muscle types work in unison to produce
15768-593: The octopus to sense the orientation of its body. They provide information on the position of the body relative to gravity and can detect angular acceleration. An autonomic response keeps the octopus's eyes oriented so that the pupil is always horizontal. Octopuses may also use the statocyst to hear sound. The common octopus can hear sounds between 400 Hz and 1000 Hz, and hears best at 600 Hz. Octopuses have an excellent somatosensory system . Their suction cups are equipped with chemoreceptors so they can taste what they touch. Octopus arms move easily because
15914-497: The only extant cephalopods with a true external shell. However, all molluscan shells are formed from the ectoderm (outer layer of the embryo); in cuttlefish ( Sepia spp.), for example, an invagination of the ectoderm forms during the embryonic period, resulting in a shell ( cuttlebone ) that is internal in the adult. The same is true of the chitinous gladius of squid and octopuses. Cirrate octopods have arch-shaped cartilaginous fin supports , which are sometimes referred to as
16060-440: The other muscle fibers in the mantle. These collagen fibers act as elastics and are sometimes named "collagen springs". As the name implies, these fibers act as springs. When the radial and circular muscles in the mantle contract, they reach a point where the contraction is no longer efficient to the forward motion of the creature. In such cases, the excess contraction is stored in the collagen which then efficiently begins or aids in
16206-442: The posterior and anterior ends of this organ control the speed of the jet the organism can produce. The velocity of the organism can be accurately predicted for a given mass and morphology of animal. Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions. Some cephalopods accompany this expulsion of water with
16352-407: The product of chromatophore coloration displays. There are two hypotheses about the evolution of color change in cephalopods. One hypothesis is that the ability to change color may have evolved for social, sexual, and signaling functions. Another explanation is that it first evolved because of selective pressures encouraging predator avoidance and stealth hunting. For color change to have evolved as
16498-431: The radial and circular mantle cavity muscles. The gills of cephalopods are supported by a skeleton of robust fibrous proteins; the lack of mucopolysaccharides distinguishes this matrix from cartilage. The gills are also thought to be involved in excretion, with NH 4 being swapped with K from the seawater. While most cephalopods can move by jet propulsion, this is a very energy-consuming way to travel compared to
16644-402: The respiratory chamber. The lamella structure of the gills allows for a high oxygen uptake, up to 65% in water at 20 °C (68 °F). Water flow over the gills correlates with locomotion, and an octopus can propel its body when it expels water out of its siphon. The thin skin of the octopus absorbs additional oxygen. When resting, around 41% of an octopus's oxygen absorption is through
16790-441: The result of a change in the density of pigment containing cells and tends to change over longer periods of time. Physiological change, the kind observed in cephalopod lineages, is typically the result of the movement of pigment within the chromatophore, changing where different pigments are localized within the cell. This physiological change typically occurs on much shorter timescales compared to morphological change. Cephalopods have
16936-439: The result of natural selection different parameters would have to be met. For one, you would need some phenotypic diversity in body patterning among the population. The species would also need to cohabitate with predators which rely on vision for prey identification. These predators should have a high range of visual sensitivity, detecting not just motion or contrast but also colors. The habitats they occupy would also need to display
17082-424: The result of social selection the environment of cephalopods' ancestors would have to fit a number of criteria. One, there would need to be some kind of mating ritual that involved signaling. Two, they would have to experience demonstrably high levels of sexual selection. And three, the ancestor would need to communicate using sexual signals that are visible to a conspecific receiver. For color change to have evolved as
17228-429: The rocks and feels through the crevices. The creature may make a jet-propelled pounce on prey and pull it toward the mouth with its arms, the suckers restraining it. Small prey may be completely trapped by the webbed structure. Octopuses usually inject crustaceans like crabs with a paralysing saliva then dismember them with their beaks. Octopuses feed on shelled molluscs either by forcing the valves apart, or by drilling
17374-430: The same jumping genes that are active in the human brain, implying an evolutionary convergence at molecular level. The nervous system is complex, only part of which is localised in its brain, which is contained in a cartilaginous capsule. Two-thirds of an octopus's neurons are in the nerve cords of its arms. This allows their arms to perform complex reflex actions without input from the brain. Unlike vertebrates,
17520-549: The same class. Octopuses are generally not seen as active swimmers; they are often found scavenging the sea floor instead of swimming long distances through the water. Squids, on the other hand, can be found to travel vast distances, with some moving as much as 2000 km in 2.5 months at an average pace of 0.9 body lengths per second. There is a major reason for the difference in movement type and efficiency: anatomy. Both octopuses and squids have mantles (referenced above) which function towards respiration and locomotion in
17666-399: The same depth. As such, the cost of transport of many squids are quite high. That being said, squid and other cephalopod that dwell in deep waters tend to be more neutrally buoyant which removes the need to regulate depth and increases their locomotory efficiency. The Macrotritopus defilippi , or the sand-dwelling octopus, was seen mimicking both the coloration and the swimming movements of
17812-538: The same side convex. In some, the aperture was a simple opening. In others, it became contracted into a pattern of slits. In earlier, Ordovician forms, the bullette became quite large and readily noticeable. In later forms, the bullette became reduced, in some to the point of being vestigial. The Discosoridae, one of the last families to evolve, found in Silurian and questionably in Devonian rocks, are characterized by
17958-452: The sand-dwelling flounder Bothus lunatus to avoid predators. The octopuses were able to flatten their bodies and put their arms back to appear the same as the flounders as well as move with the same speed and movements. Females of two species, Ocythoe tuberculata and Haliphron atlanticus , have evolved a true swim bladder . Two of the categories of cephalopods, octopus and squid, are vastly different in their movements despite being of
18104-446: The sandy sea floor. The color change of chromatophores works in concert with papillae, epithelial tissue which grows and deforms through hydrostatic motion to change skin texture. Chromatophores are able to perform two types of camouflage, mimicry and color matching. Mimicry is when an organism changes its appearance to appear like a different organism. The squid Sepioteuthis sepioide has been documented changing its appearance to appear as
18250-489: The seabed. Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle. While most cephalopods float (i.e. are neutrally buoyant or nearly so; in fact most cephalopods are about 2–3% denser than seawater ), they achieve this in different ways. Some, such as Nautilus , allow gas to diffuse into the gap between the mantle and the shell; others allow purer water to ooze from their kidneys, forcing out denser salt water from
18396-406: The sensors recognise octopus skin and prevent self-attachment. Octopuses appear to have poor proprioceptive sense and must observe the arms visually to keep track of their position. The ink sac of an octopus is located under the digestive gland. A gland attached to the sac produces the ink , and the sac stores it. The sac is close enough to the funnel for the octopus to shoot out the ink with
18542-619: The siphuncle near the inside or longitudinally concave curvature. The second, formed by the Westonoceratidae, Lowoceratidae, and Discosoridae, are fundamentally exogastric with the siphuncle near the outside or longitudinally convex curvature, although the Discosoridae are somewhat different. The third, consisting of the Mandaloceratidae and Mesoceratidae are basically straight (orthoconic). Families differ primarily in
18688-400: The skin. This decreases to 33% when it swims, as more water flows over the gills; skin oxygen uptake also increases. When it is resting after a meal, absorption through the skin can drop to 3% of its total oxygen uptake. The digestive system of the octopus begins with the buccal mass which consists of the mouth with its chitinous beak, the pharynx, radula and salivary glands. The radula
18834-608: The soft-bodied nature of cephalopods means they are not easily fossilised. Cephalopods are found in all the oceans of Earth. None of them can tolerate fresh water , but the brief squid, Lolliguncula brevis , found in Chesapeake Bay , is a notable partial exception in that it tolerates brackish water . Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints, and in their >400 million year existence have never ventured into fully freshwater habitats. Cephalopods occupy most of
18980-440: The species and for warning ) or active camouflage , as their chromatophores are expanded or contracted. Although color changes appear to rely primarily on vision input, there is evidence that skin cells, specifically chromatophores , can detect light and adjust to light conditions independently of the eyes. The octopus changes skin color and texture during quiet and active sleep cycles. Cephalopods can use chromatophores like
19126-479: The species and water temperature. They feed on copepods , arthropod larvae and other zooplankton , eventually settling on the ocean floor and developing directly into adults with no distinct metamorphoses that are present in other groups of mollusc larvae. Octopus species that produce larger eggs – including the southern blue-ringed , Caribbean reef , California two-spot , Eledone moschata and deep sea octopuses – instead hatch as benthic animals similar to
19272-423: The sperm from the spermatophore, and it is stored internally by the female. About forty days after mating, the female giant Pacific octopus attaches strings of small fertilised eggs (10,000 to 70,000 in total) to rocks in a crevice or under an overhang. Here she guards and cares for them for about five months (160 days) until they hatch. In colder waters, such as those off Alaska , it may take up to ten months for
19418-536: The structural details of the siphuncle and in the nature of the aperture. Discosorids were probably benthic forms that crawled over the bottom in search of food or safety, or hovered close to the bottom. The general orientation during life was most likely head down, with the aperture of the shell facing the general direction of the sea floor and shell carried above. Nothing is known of what the animal itself may have looked like; how many tentacles they had and relative length or how well they may have seen. In general form
19564-420: The suckers adhere to the substrate and the animal hauls itself forward with its powerful arm muscles, while other arms may push rather than pull. As progress is made, other arms move ahead to repeat these actions and the original suckers detach. During crawling, the heart rate nearly doubles, and the animal requires ten or fifteen minutes to recover from relatively minor exercise. Most octopuses swim by expelling
19710-459: The tail propulsion used by fish. The efficiency of a propeller -driven waterjet (i.e. Froude efficiency ) is greater than a rocket . The relative efficiency of jet propulsion decreases further as animal size increases; paralarvae are far more efficient than juvenile and adult individuals. Since the Paleozoic era , as competition with fish produced an environment where efficient motion
19856-417: The timing of reproduction and lifespan. When octopuses reproduce, the male uses a specialised arm called a hectocotylus to transfer spermatophores (packets of sperm) from the terminal organ of the reproductive tract (the cephalopod "penis") into the female's mantle cavity. The hectocotylus in benthic octopuses is usually the third right arm, which has a spoon-shaped depression and modified suckers near
20002-493: The tip. In most species, fertilisation occurs in the mantle cavity. The reproduction of octopuses has been studied in only a few species. One such species is the giant Pacific octopus , in which courtship is accompanied, especially in the male, by changes in skin texture and colour. The male may cling to the top or side of the female or position himself beside her. There is some speculation that he may first use his hectocotylus to remove any spermatophore or sperm already present in
20148-404: The two largest species of octopus, usually lives for three to five years. Octopus lifespan is limited by reproduction. For most octopuses, the last stage of their life is called senescence. It is the breakdown of cellular function without repair or replacement. For males, this typically begins after mating. Senescence may last from weeks to a few months, at most. For females, it begins when they lay
20294-499: The typical octopus body shape. Basal species, the Cirrina , have stout gelatinous bodies with webbing that reaches near the tip of their arms, and two large fins above the eyes, supported by an internal shell . Fleshy papillae or cirri are found along the bottom of the arms, and the eyes are more developed. Octopuses have a closed circulatory system , in which the blood remains inside blood vessels. Octopuses have three hearts;
20440-405: The visceral hump leads, the siphon points at the head and the arms trail behind, with the animal presenting a fusiform appearance. In an alternative method of swimming, some species flatten themselves dorso-ventrally, and swim with the arms held out sideways; this may provide lift and be faster than normal swimming. Jetting is used to escape from danger, but is physiologically inefficient, requiring
20586-427: The vital organs. The mantle cavity has muscular walls and contains the gills; it is connected to the exterior by a funnel or siphon . The mouth of an octopus, located underneath the arms, has a sharp hard beak . The skin consists of a thin outer epidermis with mucous cells and sensory cells and a connective tissue dermis consisting largely of collagen fibres and various cells allowing colour change. Most of
20732-517: The yolk, forming a yolk sac, which eventually forms part of the gut. The dorsal side of the disc grows upward and forms the embryo, with a shell gland on its dorsal surface, gills, mantle and eyes. The arms and funnel develop as part of the foot on the ventral side of the disc. The arms later migrate upward, coming to form a ring around the funnel and mouth. The yolk is gradually absorbed as the embryo develops. Most young octopuses hatch as paralarvae and are planktonic for weeks to months, depending on
20878-707: The young octopuses hatch. In laboratory experiments, octopuses can readily be trained to distinguish between different shapes and patterns. They have been reported to practise observational learning , although the validity of these findings is contested. Octopuses have also been observed in what has been described as play : repeatedly releasing bottles or toys into a circular current in their aquariums and then catching them. Octopuses often break out of their aquariums and sometimes into others in search of food. Growing evidence suggests that octopuses are sentient and capable of experiencing pain . The veined octopus collects discarded coconut shells, then uses them to build
21024-416: Was an animal with a live mass of 71 kg (157 lb). Much larger sizes have been claimed for the giant Pacific octopus: one specimen was recorded as 272 kg (600 lb) with an arm span of 9 m (30 ft). A carcass of the seven-arm octopus , Haliphron atlanticus , weighed 61 kg (134 lb) and was estimated to have had a live mass of 75 kg (165 lb). The smallest species
21170-463: Was crucial to survival, jet propulsion has taken a back role, with fins and tentacles used to maintain a steady velocity. Whilst jet propulsion is never the sole mode of locomotion, the stop-start motion provided by the jets continues to be useful for providing bursts of high speed – not least when capturing prey or avoiding predators . Indeed, it makes cephalopods the fastest marine invertebrates, and they can out-accelerate most fish. The jet
21316-401: Was published indicating that cephalopod chromatophores are photosensitive; reverse transcription polymerase chain reactions (RT-PCR) revealed transcripts encoding rhodopsin and retinochrome within the retinas and skin of the longfin inshore squid ( Doryteuthis pealeii ), and the common cuttlefish ( Sepia officinalis ) and broadclub cuttlefish ( Sepia latimanus ). The authors claim this
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