question: Why does octopus meat not have muscle fibers like pork or beef?
comment: Octopus have muscles too, but while mammals have mainly linear muscles, octopus have mainly circular muscles. This paper describes it well, although in very scientific terms: URL_0 Since the muscles are arranged circularly around the tentacle, there are no large fibrous strands to give the same texture as mammal meat. Edit ELI4: muscles in mammals are fibres. The fibres stretch and relax to change shape and move the body. Muscles in octopus are rings. Stretching and relaxing also changes shapes. Fibres and rings have different texture. One is grainy, the other is smooth. That’s why when you eat octopus it feels different.
passages: On top of its small size it also possesses a shorter life cycle (approximately 1 year), thinner arms, and a lower ratio between head size and arm length compared to other "Octopus" species. It is a promising model organism for studies of the molecular basis of plasticity and adaptation to harsh environmental conditions. To enable the study of these features the genome of "O. minor" has been sequenced, coming to 5.09 Gb in size and having 30,010 genes.
  
  Section::::Culinary use.
  
  In Korean cuisine, long arm octopuses are stir-fried into "nakji-bokkeum" (stir-fried octopus) or eaten raw as "san-nakji" (sliced raw octopus).
   Octopuses have also been depicted in cinema as hybrids, such as in "Octaman", which features a mutant humanoid octopus. In the Disney animated movie "The Little Mermaid", Ursula (the sea witch) is depicted as a human-octopus hybrid with the torso of a woman and the arms of an octopus in place of her legs. "Monster Shark" (1984) and "Sharktopus" (2010) feature fish-octopus hybrids.
   Some robotics research is exploring biomimicry of octopus features. Octopus arms can move and sense largely autonomously without intervention from the animal's central nervous system. In 2015 a team in Italy built soft-bodied robots able to crawl and swim, requiring only minimal computation. In 2017 a German company made an arm with a soft pneumatically controlled silicone gripper fitted with two rows of suckers. It is able to grasp objects such as a metal tube, a magazine, or a ball, and to fill a glass by pouring water from a bottle.
  
  Section::::External links.
   Section::::Description.:Distinctive features.
   Cephalopods have been depicted in animated feature films for family audiences. "Finding Nemo" (2003) includes a flapjack octopus among its cast of aquatic characters. The sequel "Finding Dory" features an East Pacific red octopus as a major supporting character. "Toy Story 3" (2010) features a toy rubber octopus named Stretch (voiced by Whoopi Goldberg) and "Shark Tale" (2004) features an octopus named Luca (voiced by Vincent Pastore). An octopus named Dave (voiced by John Malkovich) is the main antagonist in the 2014 "Penguins of Madagascar" movie. The Australian animated film "Dot and the Whale" (1986) features a giant octopus with magical powers.
   The large size of this species made it the focus of octopus wrestling championships, which reached the height of their popularity on the West Coast of the United States in the 1960s (see High, 1976:17; Norman, 2000:217; Roach, 2013).
  
  Morphological and genetic data points to "E. dofleini"—as currently circumscribed—encompassing a second, cryptic species, which has been called the frilled giant Pacific octopus, though it has yet to be formally described (Hollenbeck & Scheel, 2017; Hollenbeck "et al.", 2017).
  
  Section::::Maximum size.:Scientifically validated records.:Seven-arm octopus ("Haliphron atlanticus").
   Section::::Diet.
   Some octopuses exhibit the ability to alter speeds of sodium and potassium ion movement across cell membranes, allowing them to live in very cold water. Joshua Rosenthal, at the University of Puerto Rico's Institute of Neurobiology has found that they have altered protein synthesis, and can speed up potassium channels in cold water, to keep up with sodium ion exchange. He is now looking into whether individuals can alter their protein synthesis in response to changing temperatures, or if it is done over long-term adaptations. If changes are possible by the individual, octopuses may be able to adapt quickly to changing climate scenarios.
   Section::::Development.
   Pigs susceptible to porcine stress syndrome, or PSS, have an increased likelihood of developing PSE meat. These animals become easily stressed pre-slaughter, which leads to exaggerated glycolysis, an increase in body temperature, and higher production of lactic acid. In particular, the Halothane gene, "HAL", induces PSS in swine. It is a single point mutation in this gene that causes abnormal calcium channels within the muscle. "HAL+" pigs are five times more likely to develop PSE meat than "HAL-" hogs.
   Section::::Comics.
  
  Doctor Octopus and Lady Octopus are two supervillains from the Marvel Comics universe. The former was a scientist who augmented his human body by adding four mechanical arms (bringing his total number of limbs to eight). Another villain is Zitzbath Zark, otherwise known as the Octopus, from the hardboiled comic "Spirit". The DC Comics hero Aquaman had a pet octopus named Topo who assisted him in a variety of ways, often taking advantage of his multiple limbs.
  
  Section::::Film.
   To achieve both profitable and environmentally sustainable results, much research has been focused on paralarval rearing. In 2005, scientists from the principal research groups in the field concluded the key factor affecting paralarval mortality is nutrition, making nutritional research the highest priority. There is "no reason not to believe that the aquacultural rearing of octopus will be of great economic potential" as soon as the rearing technology and nutritional issues have been addressed. Research in these areas is promising.
  
  Section::::External links.
   The thin skin of the octopus absorbs additional oxygen. When resting, around 41% of an octopus's oxygen absorption is through 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.
  
  Section::::Anatomy and physiology.:Digestion and excretion.
   "Macroctopus maorum" is a large octopus and it is regularly described as a ‘robust’ species, it is a member of the "Octopus macropus" species complex. The morphological traits characteristic of this complex are a high number of gill lamellae, a robust conical copulatory organ and arms of varying length with long unequal dorsal arms generally four to six times longer than the mantle. Although being unequal, their arms are said to be long and evenly tapering and "Macroctopus maorum" are even known to regrow arms when one has been lost. Being the largest member of its complex arm span is said to exceed . They have four to six suckers on the first and second arm pairs which are usually about in size. Suckers are arranged in two rows down the arm length, there is thought to be no correlation between sexes and size of suckers however there was an increase in sucker size with body mass increase. Coloration of this species can vary "Macroctopus maorum" can be distinguished from other species by the colour, they will be either orange-brown or dark purple-grey. The octopus has numerous small iridescent white spots on the web, arms and dorsal arm crown but there are no spots present on the mantle. "Macroctopus maorum" has 12–14 gill lamella per demibranch, the mantle is described as broadly ovoid and exhibits a skin pattern of longitudinal ridges. Along the dorsum there are five rows of unbranched papillae and two more papillae appear individually above the eyes. Octopus papillae are camouflage specialised with the ability to change shape, such as by extending in and out from the body. Male "M. maorum" have a small ligula, the ligula is a specialised arm tip on the hectocotylized arm which grips to allow the transfer of spermatophores. Within the complex "O. macropus", "Macroctopus maorum" is thought to be the largest member. In a study estimating "M. maorum" size based on a sample of 90 beaks, the largest individual found had a body length of and body mass of 12 kg. "Macroctopus maorum" has an upper beak and lower beak, the upper beak can be used to differentiate "Macroctopus maorum" and "Enteroctpus zealandicus" as it has a lack of overlap in the ratio of upper hood length and upper chest length. "Macroctopus maorum" hatchlings are usually about 5.06 in size, they have 7–8 suckers per arm and each dorsal arm will have 6–11 chromatophores.
   Section::::Dishes by geography.:United States.
  
  Octopus is eaten regularly in Hawaii, since many popular dishes are Asian in origin. Locally known by their Hawaiian or Japanese names ("he'e" and "tako", respectively), octopus is also a popular fish bait.
  
  Section::::Nutritional value.
  
  According to the USDA Nutrient Database (2007), cooked octopus contains about 56 kilocalories (Calories) per 100 grams, and is a source of vitamin B, B, potassium, phosphorus, and selenium.
   "E. dofleini" preys upon shrimp, crabs, scallop, abalone, cockles, snails, clams, lobsters, fish, and other octopuses. Food is procured with its suckers and then bitten using its tough "beak" of chitin. It has also been observed to catch spiny dogfish ("Squalus acanthias") up to in length while in captivity. Additionally, consumed carcasses of this same shark species have been found in giant Pacific octopus middens in the wild, providing strong evidence of these octopuses preying on small sharks in their natural habitat. In May 2012, amateur photographer Ginger Morneau was widely reported to have photographed a wild giant Pacific octopus attacking and drowning a seagull, which would demonstrate the species is not above eating any available source of food within its size range, even birds.
   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.
   A gigantic octopus has been proposed as an identity for the large carcass, known as the St. Augustine Monster, that washed up in St Augustine, Florida, in 1896. However, samples of this specimen subjected to electron microscopy and biochemical analysis were found to be "masses of virtually pure collagen" and not to have the "biochemical characteristics of invertebrate collagen, nor the collagen fiber arrangement of octopus mantle". The results suggest the samples are "large pieces of vertebrate skin ... from a huge homeotherm".
  
  Section::::See also.
  
  BULLET::::- Akkorokamui
  
  BULLET::::- Colossal squid
  
  BULLET::::- Cryptozoology
  
  BULLET::::- "Enteroctopus", or giant octopuses
  
  BULLET::::- Giant squid
   Section::::Paralarva.
   Section::::Relationship to humans.:Fisheries and cuisine.
   Emus are farmed primarily for their meat, leather, feathers and oil, and 95% of the carcass can be used. Emu meat is a low-fat product (less than 1.5% fat), and is comparable to other lean meats. Most of the usable portions (the best cuts come from the thigh and the larger muscles of the drum or lower leg) are, like other poultry, dark meat; emu meat is considered for cooking purposes by the US Food and Drug Administration to be a red meat because its red colour and pH value approximate that of beef, but for inspection purposes it is considered to be poultry.
   Sole fish - This flat, poisonous fish is imitated by the mimic octopus by building up speed through jet propulsion as it draws all of its arms together into a leaf-shaped wedge as it undulates in the manner of a swimming flat fish.
  
  Section::::Observed behavior.
   Section::::Predators.
   "V. lentus" has been isolated from lesions found on the mantle and arms of the common octopus ("Octopus vulgaris"), where it forms rounded, hard lumps, and in more severe cases, loss of skin and exposure of the muscles beneath. Experimental introduction of the bacteria to healthy octopuses resulted in the formation of lesions, colonisation of the internal organs, and eventually death.
   Crustaceans, such as crabs and lobster are an important dietary constituent of both natural and captive populations of octopus. Fish are not as important. Fish-based diets have been shown to provide both lower growth rates and food conversion to growth ratios in captive octopus. This may be because of high lipid levels in fish flesh. Cephalopods, such as octopus and squids, show low lipid digestibility as a result of low lipid requirements. Consequently, a large component of the fish feed will not be taken up. Crustacean diets are favored possibly as a result of their high protein relative to lipid levels.
  
presuppositions: Octopus meat doesn't have muscle fibers.
corrections: Octopus meat has muscle fibers, but they are a different shape than pork or beef.
raw_presuppositions: Octopus meat doesn't have muscle fibers. Octopus meat doesn't have muscle fibers.
raw_corrections: Octopus meat has muscle fibers, but they are a different shape than pork or beef. Octopus meat has muscle fibers, but they are a different shape than pork or beef.