Food energy is chemical energy that animals (including humans ) derive from their food to sustain their metabolism , including their muscular activity.
54-405: Coronamedusae is a subclass of jellyfish in the class Scyphozoa . It is the sister taxon of Discomedusae and contains about 50 named species, all included in the order Coronatae. Jellyfish in this subclass are either small medusae living in shallow marine environments, or large medusae living in the deep sea. The mouthparts of the members of this subclass are characterised by simple lips on
108-493: A " nerve net " is located in the epidermis . Although traditionally thought not to have a central nervous system , nerve net concentration and ganglion -like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction. In many species of jellyfish,
162-513: A backbone, though shellfish , cuttlefish and starfish are not vertebrates either. In scientific literature, "jelly" and "jellyfish" have been used interchangeably. Many sources refer to only scyphozoans as "true jellyfish". A group of jellyfish is called a "smack" or a "smuck". The term jellyfish broadly corresponds to medusae, that is, a life-cycle stage in the Medusozoa . The American evolutionary biologist Paulyn Cartwright gives
216-400: A complex life cycle , and the medusa is normally the sexual phase, which produces planula larvae. These then disperse widely and enter a sedentary polyp phase which may include asexual budding before reaching sexual maturity. Jellyfish are found all over the world, from surface waters to the deep sea. Scyphozoans (the "true jellyfish") are exclusively marine , but some hydrozoans with
270-415: A complex dish or meal can be approximated by adding the energy contents of its components. The first determinations of the energy content of food were made by burning a dried sample in a bomb calorimeter and measuring the temperature change in the water surrounding the apparatus, a method known as direct calorimetry . However, the direct calorimetric method generally overestimates the actual energy that
324-436: A few are anchored to the seabed by stalks rather than being motile. They are made of an umbrella-shaped main body made of mesoglea , known as the bell , and a collection of trailing tentacles on the underside. Via pulsating contractions, the bell can provide propulsion for locomotion through open water. The tentacles are armed with stinging cells and may be used to capture prey or to defend against predators. Jellyfish have
378-529: A free-swimming medusa is Burgessomedusa from the mid-Cambrian Burgess Shale of Canada, which is likely either a stem group of box jellyfish (Cubozoa) or Acraspeda (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent ctenophores instead. The main feature of a true jellyfish
432-439: A manufacturer of rowing equipment shows calories released from "burning" food as four times the actual mechanical work, plus 1,300 kJ (300 kcal) per hour, which amounts to about 20% efficiency at 250 watts of mechanical output. It can take up to 20 hours of little physical output (e.g., walking) to "burn off" 17,000 kJ (4,000 kcal) more than a body would otherwise consume. For reference, each kilogram of body fat
486-408: A medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after
540-413: A short manubrium as well as by robust marginal tentacles that arc away from the mouth. It is likely that these marginal tentacles are used to capture plankton , including crustaceans and small fish in the larger species. Coronatae is the only order in this subclass, with around thirty-five species having been described, most of them deepwater jellyfish. The thimble jellyfish ( Linuche unguiculata )
594-414: A similar appearance live in fresh water . Large, often colorful, jellyfish are common in coastal zones worldwide. The medusae of most species are fast-growing, and mature within a few months then die soon after breeding, but the polyp stage, attached to the seabed, may be much more long-lived. Jellyfish have been in existence for at least 500 million years, and possibly 700 million years or more, making them
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#1732801728160648-443: A similar table. Other components of the human diet are either noncaloric, or are usually consumed in such small amounts that they can be neglected. The food energy actually obtained by respiration is used by the human body for a wide range of purposes, including basal metabolism of various organs and tissues, maintaining the internal body temperature , and exerting muscular force to maintain posture and produce motion. About 20%
702-450: A solid surface by a basal disk, and resemble a polyp, the oral end of which has partially developed into a medusa with tentacle-bearing lobes and a central manubrium with four-sided mouth. Most jellyfish do not have specialized systems for osmoregulation , respiration and circulation , and do not have a central nervous system . Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around
756-463: Is a common name, its mapping to biological groups is inexact. Some authorities have called the comb jellies and certain salps jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa. The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with " ??? " on
810-455: Is a tiny species, and one of the few from shallow tropical seas; It is a zooxanthellate species. Coronatids have a characteristic constriction, the coronal groove, part way down the bell. Below this the bell is creased and lobed into four pedalia. Each pedalium bears a small non-retractible tentacle, and the margin of the bell bears either four or eight rhopalia (sensory organs) in the niches between flaps known as lappets. The coronal groove and
864-439: Is an intermediary to a better understanding of how visual systems evolved on Earth. Jellyfish exhibit immense variation in visual systems ranging from photoreceptive cell patches seen in simple photoreceptive systems to more derived complex eyes seen in box jellyfish. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: the evolution of jellyfish vision from simple to complex visual systems),
918-822: Is capable of multiple task-guided behaviors. Although they lack a true brain, cnidarian jellyfish have a "ring" nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement and culminates the emergence of photosensitive structures. Across Cnidaria , there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more "conventional" eyes similar to those of vertebrates . The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision. Increased habitat and task complexity has favored
972-473: Is equivalent to walking around 2.5 to 5 km ( 1 + 1 ⁄ 2 to 3 mi) per day in addition to the activities of sedentary living. These estimates are for a "reference woman" who is 1.63 m (5 ft 4 in) tall and weighs 57 kg (126 lb) and a "reference man" who is 1.78 m (5 ft 10 in) tall and weighs 70 kg (154 lb). Because caloric requirements vary by height, activity, age, pregnancy status, and other factors,
1026-454: Is roughly equivalent to 32,300 kilojoules of food energy (i.e., 3,500 kilocalories per pound or 7,700 kilocalories per kilogram). Many countries and health organizations have published recommendations for healthy levels of daily intake of food energy. For example, the United States government estimates 8,400 and 10,900 kJ (2,000 and 2,600 kcal) needed for women and men, respectively, between ages 26 and 45, whose total physical activity
1080-460: Is the result of about 40% efficiency of generating ATP from the respiration of food, losses in converting energy from ATP into mechanical work inside the muscle, and mechanical losses inside the body. The latter two losses are dependent on the type of exercise and the type of muscle fibers being used (fast-twitch or slow-twitch). For an overall efficiency of 20%, one watt of mechanical power is equivalent to 18 kJ/h (4.3 kcal/h). For example,
1134-409: Is the umbrella-shaped bell. This is a hollow structure consisting of a mass of transparent jelly-like matter known as mesoglea , which forms the hydrostatic skeleton of the animal. The mesoglea is 95% or more composed of water, and also contains collagen and other fibrous proteins, as well as wandering amebocytes that can engulf debris and bacteria. The mesogloea is bordered by the epidermis on
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#17328017281601188-447: Is used for brain metabolism. The conversion efficiency of energy from respiration into muscular (physical) power depends on the type of food and on the type of physical energy usage (e.g., which muscles are used, whether the muscle is used aerobically or anaerobically ). In general, the efficiency of muscles is rather low: only 18 to 26% of the energy available from respiration is converted into mechanical energy. This low efficiency
1242-558: The green fluorescent protein used by some species for bioluminescence . This protein has been adapted as a fluorescent reporter for inserted genes and has had a large impact on fluorescence microscopy . The stinging cells used by jellyfish to subdue their prey can injure humans. Thousands of swimmers worldwide are stung every year, with effects ranging from mild discomfort to serious injury or even death. When conditions are favourable, jellyfish can form vast swarms, which may damage fishing gear by filling fishing nets, and sometimes clog
1296-467: The metric (SI) unit of energy, the joule (J), and its multiple the kilojoule (kJ); or in the traditional unit of heat energy, the calorie (cal). In nutritional contexts, the latter is often (especially in US) the "large" variant of the unit, also written "Calorie" (with symbol Cal, both with capital "C") or "kilocalorie" (kcal), and equivalent to 4184 J or 4.184 kJ. Thus, for example, fats and ethanol have
1350-608: The EU regulations and UK regulations, are: (1) Some polyols, like erythritol , are not digested and should be excluded from the count. (2) This entry exists in the EU regulations of 2008, but not in the UK regulations, according to which fibre shall not be counted. More detailed tables for specific foods have been published by many organizations, such as the United Nations Food and Agriculture Organization also has published
1404-670: The USDA created the DRI Calculator for Healthcare Professionals in order to determine individual caloric needs. According to the Food and Agriculture Organization of the United Nations , the average minimum energy requirement per person per day is about 7,500 kJ (1,800 kcal). Although the U.S. has changed over time with a growth in population and processed foods or food in general, Americans today have available roughly
1458-541: The average daily energy intake of 8,800 kJ (2,100 kcal). The minimum food energy intake is also higher in cold environments. Increased mental activity has been linked with moderately increased brain energy consumption . Many governments require food manufacturers to label the energy content of their products, to help consumers control their energy intake. To facilitate evaluation by consumers, food energy values (and other nutritional properties) in package labels or tables are often quoted for convenient amounts of
1512-452: The bell pulsates, allowing box jellyfish to swim faster than true jellyfish. Hydrozoans are also similar, usually with just four tentacles at the edge of the bell, although many hydrozoans are colonial and may not have a free-living medusal stage. In some species, a non-detachable bud known as a gonophore is formed that contains a gonad but is missing many other medusal features such as tentacles and rhopalia. Stalked jellyfish are attached to
1566-450: The body can obtain from the food, because it also counts the energy contents of dietary fiber and other indigestible components, and does not allow for partial absorption and/or incomplete metabolism of certain substances. For this reason, today the energy content of food is instead obtained indirectly, by using chemical analysis to determine the amount of each digestible dietary component (such as protein, carbohydrates, and fats), and adding
1620-429: The body. For example, leucine plays an important role in the regulation of protein metabolism and suppresses an individual's appetite. Small amounts of essential fatty acids , constituents of some fats that cannot be synthesized by the human body, are used (and necessary) for other biochemical processes. The approximate food energy contents of various human diet components, to be used in package labeling according to
1674-484: The common moon jelly , Aurelia aurita , which migrates in response to changes in ambient light and solar position even though they lack proper eyes. Food energy Most animals derive most of their energy from aerobic respiration , namely combining the carbohydrates , fats , and proteins with oxygen from air or dissolved in water . Other smaller components of the diet, such as organic acids , polyols , and ethanol (drinking alcohol) may contribute to
Coronamedusae - Misplaced Pages Continue
1728-448: The cooling systems of power and desalination plants which draw their water from the sea. The name jellyfish, in use since 1796, has traditionally been applied to medusae and all similar animals including the comb jellies ( ctenophores , another phylum). The term jellies or sea jellies is more recent, having been introduced by public aquaria in an effort to avoid use of the word "fish" with its modern connotation of an animal with
1782-420: The creases provide flexibility in the otherwise rather stiff bell. The short manubrium is four-sided and has a large mouth at its tip. The mouth opens into a central stomach which is divided into four pockets by septa, on which are located the gastric filaments and the eight gonads. Most coronatids search for prey with outstretched tentacles; when food items are found, they are subdued and pushed rather stiffly into
1836-493: The dry weight of food. Ruminants can extract food energy from the respiration of cellulose because of bacteria in their rumens that decompose it into digestible carbohydrates. Other minor components of the human diet that contribute to its energy content are organic acids such as citric and tartaric , and polyols such as glycerol , xylitol , inositol , and sorbitol . Some nutrients have regulatory roles affected by cell signaling , in addition to providing energy for
1890-409: The energy input. Some diet components that provide little or no food energy, such as water , minerals , vitamins , cholesterol , and fiber , may still be necessary to health and survival for other reasons. Some organisms have instead anaerobic respiration , which extracts energy from food by reactions that do not require oxygen. The energy contents of a given mass of food is usually expressed in
1944-421: The exterior, perhaps supplying good oxygenation to the gonads. Near the free edges of the septa, gastric filaments extend into the gastric cavity; these are armed with nematocysts and enzyme-producing cells and play a role in subduing and digesting the prey. In some scyphozoans, the gastric cavity is joined to radial canals which branch extensively and may join a marginal ring canal. Cilia in these canals circulate
1998-694: The eye morphology and molecular structures of box jellyfish (including comparisons to vertebrate eyes), and various uses of vision including task-guided behaviors and niche specialization. Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900s, and a rich body of research has since covered evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex image-forming eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous receptors dedicated to single-function behaviors. More derived visual systems comprise perception that
2052-400: The fluid in a regular direction. The box jellyfish is largely similar in structure. It has a squarish, box-like bell. A short pedalium or stalk hangs from each of the four lower corners. One or more long, slender tentacles are attached to each pedalium. The rim of the bell is folded inwards to form a shelf known as a velarium which restricts the bell's aperture and creates a powerful jet when
2106-965: The following phylogenetic tree by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish. Anthozoa (corals) Polypodiozoa and Myxozoa (parasitic cnidarians) Staurozoa ( stalked jellyfish ) [REDACTED] Cubozoa ( box jellyfish ) [REDACTED] Discomedusae [REDACTED] Coronatae ( crown jellyfish ) [REDACTED] Aplanulata [REDACTED] Siphonophorae [REDACTED] Some Leptothecata e.g. crystal jelly [REDACTED] Filifera e.g. red paper lantern jellyfish [REDACTED] Limnomedusae , e.g. flower hat jelly [REDACTED] Narcomedusae , e.g. cosmic jellyfish [REDACTED] The subphylum Medusozoa includes all cnidarians with
2160-572: The following cladogram of the animal kingdom: Porifera Ctenophora (comb jellies) ??? [REDACTED] Cnidaria [REDACTED] (includes jellyfish and other jellies) Protostomia Ambulacraria Tunicata (includes salps ) ??? [REDACTED] Vertebrata Jellyfish are not a clade , as they include most of the Medusozoa, barring some of the Hydrozoa. The medusozoan groups included by authorities are indicated on
2214-497: The following general definition: Typically, medusozoan cnidarians have a pelagic , predatory jellyfish stage in their life cycle; staurozoans are the exceptions [as they are stalked]. The Merriam-Webster dictionary defines jellyfish as follows: A free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells. Given that jellyfish
Coronamedusae - Misplaced Pages Continue
2268-871: The greatest amount of food energy per unit mass, 37 and 29 kJ/g (9 and 7 kcal/g), respectively. Proteins and most carbohydrates have about 17 kJ/g (4 kcal/g), though there are differences between different kinds. For example, the values for glucose, sucrose, and starch are 15.57, 16.48 and 17.48 kilojoules per gram (3.72, 3.94 and 4.18 kcal/g) respectively. The differing energy density of foods (fat, alcohols, carbohydrates and proteins) lies mainly in their varying proportions of carbon, hydrogen, and oxygen atoms. Carbohydrates that are not easily absorbed, such as fibre, or lactose in lactose-intolerant individuals , contribute less food energy. Polyols (including sugar alcohols ) and organic acids contribute 10 kJ/g (2.4 kcal/g) and 13 kJ/g (3.1 kcal/g) respectively. The energy contents of
2322-510: The high-resolution visual systems common in derived cnidarians such as box jellyfish . Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. Extraocular photoreception (a form of non-directional photoreception), is the most basic form of light sensitivity and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans ) and other light-guided behaviors responsive to
2376-646: The intensity and spectrum of light. Extraocular photoreception can function additionally in positive phototaxis (in planula larvae of hydrozoans), as well as in avoiding harmful amounts of UV radiation via negative phototaxis . Directional photoreception (the ability to perceive direction of incoming light) allows for more complex phototactic responses to light, and likely evolved by means of membrane stacking. The resulting behavioral responses can range from guided spawning events timed by moonlight to shadow responses for potential predator avoidance. Light-guided behaviors are observed in numerous scyphozoans including
2430-470: The mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift. The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called
2484-548: The mouth by the tentacles. According to the World Register of Marine Species , Coronamedusae contains the following taxa: This Scyphozoa -related article is a stub . You can help Misplaced Pages by expanding it . Jellyfish Jellyfish , also known as sea jellies , are the medusa -phase of certain gelatinous members of the subphylum Medusozoa , which is a major part of the phylum Cnidaria . Jellyfish are mainly free-swimming marine animals , although
2538-447: The mouth, which also functions as the anus, at its tip. There are often four oral arms connected to the manubrium, streaming away into the water below. The mouth opens into the gastrovascular cavity , where digestion takes place and nutrients are absorbed. This is subdivided by four thick septa into a central stomach and four gastric pockets. The four pairs of gonads are attached to the septa, and close to them four septal funnels open to
2592-506: The oldest multi-organ animal group. Jellyfish are eaten by humans in certain cultures. They are considered a delicacy in some Asian countries, where species in the Rhizostomeae order are pressed and salted to remove excess water. Australian researchers have described them as a "perfect food": sustainable and protein-rich but relatively low in food energy . They are also used in cell and molecular biology research, especially
2646-402: The open lagoon, where they feed, and back again. Box jellyfish have more advanced vision than the other groups. Each individual has 24 eyes, two of which are capable of seeing colour, and four parallel information processing areas that act in competition, supposedly making them one of the few kinds of animal to have a 360-degree view of its environment. The study of jellyfish eye evolution
2700-415: The outside and the gastrodermis on the inside. The edge of the bell is often divided into rounded lobes known as lappets , which allow the bell to flex. In the gaps or niches between the lappets are dangling rudimentary sense organs known as rhopalia , and the margin of the bell often bears tentacles. On the underside of the bell is the manubrium, a stalk-like structure hanging down from the centre, with
2754-448: The polyps. Medusozoans have tetramerous symmetry, with parts in fours or multiples of four. The four major classes of medusozoan Cnidaria are: There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not. Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of
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#17328017281602808-853: The respective food energy contents, previously obtained by measurement of metabolic heat released by the body. In particular, the fibre content is excluded. This method is known as the Modified Atwater system, after Wilbur Atwater who pioneered these measurements in the late 19th century. The system was later improved by Annabel Merrill and Bernice Watt of the USDA , who derived a system whereby specific calorie conversion factors for different foods were proposed. The typical human diet consists chiefly of carbohydrates, fats, proteins, water, ethanol, and indigestible components such as bones , seeds , and fibre (mostly cellulose ). Carbohydrates, fats, and proteins typically comprise ninety percent of
2862-404: The rhopalia include ocelli , light-sensitive organs able to tell light from dark. These are generally pigment spot ocelli, which have some of their cells pigmented. The rhopalia are suspended on stalks with heavy crystals at one end, acting like gyroscopes to orient the eyes skyward. Certain jellyfish look upward at the mangrove canopy while making a daily migration from mangrove swamps into
2916-425: The same level of calories as the older generation. [1] Older people and those with sedentary lifestyles require less energy; children and physically active people require more. Recognizing these factors, Australia's National Health and Medical Research Council recommends different daily energy intakes for each age and gender group. Notwithstanding, nutrition labels on Australian food products typically recommend
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