How many legs does an octopus have ?
Aug 04, · An octopus has eight legs, but they are more commonly referred to as tentacles. The name "octopus" is directly derived from the prefix "oct-" which means eight and is found in other words such as "octagon." On each of the octopus' legs are suction . Octopus - a representative of the order of marine mollusks belonging to the class of cephalopods. For all individuals characteristic sacciform body. Further in the article we find out the features of these animals, how many octopus legs. Photos of mollusks will also be given below. Short description. The octopus has three hearts.
All cephalopods possess d limbs extending from their heads and surrounding their beaks. These appendages, which function as muscular hydrostatshave been what does bdl mean on a remington 700 termed arms, legs or tentacles.
In the scientific literature, a cephalopod arm is often treated as distinct from a tentaclethough the terms are sometimes manj interchangeably, often with the latter acting as an umbrella term for cephalopod limbs.
Generally, arms have suckers along most of their length, as opposed to tentacles, which have suckers only near their ends. The tentacles of Decapodiformes are thought to be derived from the fourth arm pair of the ancestral coleoidbut the term arms IV is used to refer to the subsequent, ventral arm pair in modern animals which is evolutionarily the fifth arm pair.
The males of most cephalopods develop a specialised arm for sperm delivery, the hectocotylus. Anatomically, cephalopod limbs function using a crosshatch of helical collagen fibres in opposition to internal muscular hydrostatic pressure. Cephalopod limbs bear numerous suckers along their ventral surface as in octopussquid and cuttlefish arms and in clusters at the ends of the tentacles if presentas in squid and cuttlefish. Both of these structures are thick muscles, and hxve covered with a chitinous cuticle to make a protective surface.
When a sucker attaches itself to an object, the infundibulum mainly provides adhesion while the central acetabulum is free. Sequential muscle contraction of the infundibulum and acetabulum causes attachment and detachment. Many octopus arm lrgs have been recorded,   including a 6-armed octopus nicknamed Henry the Hexapusoctops 7-armed octopus,  a armed Octopus briareus one with a forked arm tip,  octopuses with what is used for whitewashing or bilateral hectocotylization  and specimens with up to 96 arm branches.
Branched arms and other limb abnormalities have also been recorded in cuttlefish squid and bobtail squid. Cephalopod limbs and the suckers they bear are shaped in many distinctive ways, and vary considerably between species.
Some examples are shown below. For hectocotylized arms see hectocotylus variability. From Wikipedia, the free encyclopedia. Arm of Illex illecebrosus with two mzny of suckers along its length. Tentacle of Illex illecebrosus with a distal tentacular club right. The Telegraph. Retrieved 30 July To most of us it has always seemed obvious that an octopus has eight arms. Octopuses have two legs and six arms Claire Little, a marine ,any from the Weymouth Sea Life Centre in Dorset, said: 'We've found that octopuses effectively have six arms and two legs.
August Journal of Comparative Psychology. PMID London: Faber and Faber. ISBN As result, marine biologists tend to refer to them as animals with two legs and six arms. Mangold Cephalopoda Glossary. Tree of Life web project. Cephalopods: A World Guide. ConchBooks, Hackenheim. The numerous limbs of nautiluses are called tentacles. The ring of eight limbs around the mouth in cuttlefish, squids and octopuses are called arms. Cuttlefish and squid also have a pair of specialised limbs attached between the bases of the third and fourth arm pairs [ These are known as feeding tentacles and are used to shoot out and grab prey.
Histology of the long digital tentacles. In: W. Landman eds. Springer Netherlands. Archived from the original PDF on Retrieved Deep Intuition, LLC. Integr Comp Biol. Archived from the original on Journal of Molluscan Studies.
Leggs tips were fully functional. Journal of Zoology. The Nautilus 99— Proceedings of the Japan Academy. Pink TentacleJuly 18, Annotated Zoology of Japan.
Canadian Journal of Zoology. Cephalopod anatomy. Ammonoid shell Argonautid eggcase Nautiloid shell Orthocone. Dermal structures Fins wings Flotation devices "secondary fins" Funnel—mantle locking apparatus Tail. Branchial hearts Ctenidia gills Hepatopancreas digestive gland Ink sac and ink Needham's sac Nephridia "kidneys" Nidamental glands Osphradium Pericardial glands.
Aptychus Beak Odontophore Radula Spadix and antispadix. Nuchal crest occipital crest Nuchal folds occipital folds Occipital membrane Olfactory organ Nuchal organ. Eyes Statocysts. Chromatophores Photophores Nervous system Squid giant axon Squid giant synapse. Categories : Cephalopod zootomy. Hidden categories: All articles with dead external links Articles with dead external links from November Articles with permanently dead external links Articles with dead external links from November All articles lacking reliable references Articles lacking reliable references from November Namespaces Article What happened to flaming hot doritos. Views Read Edit View history.
Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version. Todarodes pacificus. Abraliopsis morisi. Ancistroteuthis lichtensteini. Architeuthis sp. Austrorossia mastigophora. Berryteuthis magister. Idioteuthis cordiformis. Mastigoteuthis glaukopis. Spirula spirula. Idioteuthis latipinna.
Magnapinna talismani. Mastigoteuthis agassizii. Mastigoteuthis atlantica. Mastigoteuthis dentata. Mastigoteuthis grimaldii. Mastigoteuthis magna. External anatomy Dermal structures Fins wings Flotation devices "secondary fins" Funnel—mantle locking apparatus Tail.
Aug 14, · BERLIN (Reuters) - Octopuses’ eight tentacles divide up into six “arms” and two “legs”, a study published by a chain of commercial aquariums said on Thursday. Octopuses are reckoned to be . Jan 07, · Octopuses (or octopi, if you prefer) are cephalopods, invertebrates that also include squid and cuttlefish. They have bulbous heads, large eyes, and eight very useful arms. Octo means eight. All octopus have eight legs, unless they lose one (to a moray eel?, ore in the process of mating). As octopus are frequently cannibalistic and females are larger than males, males have developed a strategy of leaving the sperm carrying leg with the female, while they get away. views.
Octopus pl. The order is grouped within the class Cephalopoda with squids , cuttlefish , and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beak , with its mouth at the center point of the eight limbs. 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 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 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 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 probably the Gorgon of ancient Greece. Octopuses appear in Japanese erotic art, shunga. They are eaten and considered a delicacy by humans in many parts of the world, especially the Mediterranean and the Asian seas.
Historically, the first plural to commonly appear in English language sources, in the early 19th century, is the latinate form; followed by the English form in the later 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 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" is based on a misunderstanding. 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.
The octopus is bilaterally symmetrical along its dorso-ventral 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 the mouth and are attached to each other near their base by a webbed structure.
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. The octopus can squeeze through tiny gaps; even the larger species can pass through an opening close to 2.
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 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 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.
The eyes of the octopus are large and are at the top of the head. They are similar in structure to those of a fish and are enclosed in a cartilaginous capsule fused to the cranium. The cornea is formed from a translucent epidermal layer and the slit-shaped pupil forms a hole in the iris and lies just behind.
The lens is suspended behind the pupil and photoreceptive retinal cells cover the back of the eye. The pupil can be adjusted in size and a retinal pigment screens incident light in bright conditions. Some species differ in form from 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; a systemic heart that circulates blood around the body and two branchial hearts that pump it through each of the two gills.
The systemic heart is inactive when the animal is swimming and thus it tires quickly and prefers to crawl. This makes the blood very viscous and it requires considerable pressure to pump it around the body; octopuses' blood pressures can exceed 75 mmHg 10 kPa. 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 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 auxiliary hearts and back to the main heart.
Much of the venous system is contractile, which helps circulate 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. The thin skin of the octopus absorbs additional oxygen. 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.
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 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 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 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. The octopus along with cuttlefish has the highest brain-to-body mass ratios of all invertebrates; it is also greater than that of many vertebrates.
Like other cephalopods, octopuses can distinguish the polarisation of light. Colour vision appears to vary from species to species, for example being present in O. Attached to the brain are two special organs called statocysts sac-like structures containing a mineralised mass and sensitive hairs , that allow 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. The common octopus can hear sounds between Hz and Hz, and hears best at Hz. Octopuses also have an excellent sense of touch. The octopus's suction cups are equipped with chemoreceptors so the octopus can taste what it touches. Octopus arms do not become tangled or stuck to each other because the sensors recognise octopus skin and prevent self-attachment.
The arms contain tension sensors so the octopus knows whether its arms are stretched out, but this is not sufficient for the brain to determine the position of the octopus's body or arms. As a result, the octopus does not possess stereognosis ; that is, it does not form a mental image of the overall shape of the object it is handling. It can detect local texture variations, but cannot integrate the information into a larger picture.
The neurological autonomy of the arms means the octopus has great difficulty learning about the detailed effects of its motions. It has a poor proprioceptive sense, and it knows what exact motions were made only by observing the arms visually.
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 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. Octopuses are gonochoric and have a single, posteriorly-located gonad which is associated with the coelom. The testis in males and 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. The gland may be triggered by environmental conditions such as temperature, light and nutrition, which thus control 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. 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 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.
About forty days after mating, the female giant Pacific octopus attaches strings of small fertilised eggs 10, to 70, in total to rocks in a crevice or under an overhang. Here she guards and cares for them for about five months days until they hatch. 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 the yolk, forming a yolk sac, which eventually forms part of the gut. The dorsal side of the disc grows upwards 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 upwards, 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 the species and water temperature.