The Melogold or Melogold grapefruit ( Citrus grandis Osbeck × C. Paradisi Macf.) is a citrus hybrid similar to the oroblanco ; both result from a cross between the pomelo and the grapefruit and is a fruit similar to a sweet grapefruit.
106-426: The intent was to obtain a grapefruit-like cross that is less bitter or acidic than grapefruit, instead achieving sweetness similar to the pomelo. It was to be smaller than the pomelo, and more flavourful, with characteristics linked to the grapefruit. The breeders intentionally used a tetraploid grapefruit and a diploid pomelo, with triploid progeny and seedless . Similar to oroblanco, Melogold can be eaten with
212-409: A Pneumocystis carinii infection, which indicates a weak immune system. Triploidy may be the result of either digyny (the extra haploid set is from the mother) or diandry (the extra haploid set is from the father). Diandry is mostly caused by reduplication of the paternal haploid set from a single sperm, but may also be the consequence of dispermic (two sperm) fertilization of the egg. Digyny
318-501: A common ancestor . The Eocene salmon's fossil from British Columbia provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred 10 to 20 million years ago during the Miocene . This independent evidence from DNA analysis and the fossil record indicate that salmon divergence occurred long before
424-464: A grapefruit spoon , or peeled as an orange . They turn from green to yellow during ripening. Melogold was once said to be preferred as a cash crop over oroblanco, since melogold has thinner skin, which is preferred by consumers. Exterior peel color is slower to develop than in Marsh grapefruit, but late in the season is comparable. Exterior peel texture is smooth to slightly pebbled. Average peel thickness
530-626: A hybrid genome with two sets of chromosomes derived from Triticum urartu and two sets of chromosomes derived from Aegilops speltoides . Each chromosome pair derived from the Triticum urartu parent is homoeologous to the opposite chromosome pair derived from the Aegilops speltoides parent, though each chromosome pair unto itself is homologous . Examples in animals are more common in non-vertebrates such as flatworms , leeches , and brine shrimp . Within vertebrates, examples of stable polyploidy include
636-410: A miscarriage ; those that do survive to term typically die shortly after birth. In some cases, survival past birth may be extended if there is mixoploidy with both a diploid and a triploid cell population present. There has been one report of a child surviving to the age of seven months with complete triploidy syndrome. He failed to exhibit normal mental or physical neonatal development, and died from
742-442: A few species of salmon remain in fresh water throughout their life cycle, the majority are anadromous and migrate to the ocean for maturation: in these species, smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation in the ocean. This body chemistry change is hormone-driven, causing physiological adjustments in the function of osmoregulatory organs such as
848-473: A fish returns after just one year's sea feeding, it is called a grilse in Canada, Britain, and Ireland. Grilse may be present at spawning, and go unnoticed by large males, releasing their own sperm on the eggs. Prior to spawning, depending on the species , salmon undergo changes. They may grow a hump, develop canine-like teeth, or develop a kype (a pronounced curvature of the jaws in male salmon). All change from
954-569: A high demand for wild forage fish . As a predator, salmon require large nutritional intakes of protein , and farmed salmon consume more fish than they generate as a final product. On a dry weight basis, 2–4 kg of wild-caught fish are needed to produce one kilogram of salmon. As the salmon farming industry expands, it requires more forage fish for feed, at a time when 75% of the world's monitored fisheries are already near to or have exceeded their maximum sustainable yield . The industrial-scale extraction of wild forage fish for salmon farming affects
1060-532: A lot of work on Henneguya salminicola was done by scientists at the Pacific Biological Station in Nanaimo in the mid-1980s, in particular, an overview report which states, "the fish that have the longest fresh water residence time as juveniles have the most noticeable infections. Hence in order of prevalence , coho are most infected followed by sockeye, chinook, chum and pink. As well, the report says, at
1166-846: A mechanism for a kind of 'reverse speciation', whereby gene flow is enabled following the polyploidy event, even between lineages that previously experienced no gene flow as diploids. This has been detailed at the genomic level in Arabidopsis arenosa and Arabidopsis lyrata . Each of these species experienced independent autopolyploidy events (within-species polyploidy, described below), which then enabled subsequent interspecies gene flow of adaptive alleles, in this case stabilising each young polyploid lineage. Such polyploidy-enabled adaptive introgression may allow polyploids at act as 'allelic sponges', whereby they accumulate cryptic genomic variation that may be recruited upon encountering later environmental challenges. Polyploid types are labeled according to
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#17328518208281272-481: A more common path to allopolyploidy because F 1 hybrids between taxa often have relatively high rates of unreduced gamete formation – divergence between the genomes of the two taxa result in abnormal pairing between homoeologous chromosomes or nondisjunction during meiosis. In this case, allopolyploidy can actually restore normal, bivalent meiotic pairing by providing each homoeologous chromosome with its own homologue. If divergence between homoeologous chromosomes
1378-403: A paleopolyploid. It is a middle aged polyploid. Often this refers to whole genome duplication followed by intermediate levels of diploidization. Ancient genome duplications probably occurred in the evolutionary history of all life. Duplication events that occurred long ago in the history of various evolutionary lineages can be difficult to detect because of subsequent diploidization (such that
1484-695: A polyploid starts to behave cytogenetically as a diploid over time) as mutations and gene translations gradually make one copy of each chromosome unlike the other copy. Over time, it is also common for duplicated copies of genes to accumulate mutations and become inactive pseudogenes. In many cases, these events can be inferred only through comparing sequenced genomes . Examples of unexpected but recently confirmed ancient genome duplications include baker's yeast ( Saccharomyces cerevisiae ), mustard weed/thale cress ( Arabidopsis thaliana ), rice ( Oryza sativa ), and two rounds of whole genome duplication (the 2R hypothesis ) in an early evolutionary ancestor of
1590-521: A seedy, white, tetraploid grapefruit. Two of the triploid offspring had particularly favorable characteristics. One was released in 1980 as 'Oroblanco'. The second was released as Melogold. Oroblanco was more similar to grapefruit, while Melogold was more similar to pomelo. Melogold was much larger than Marsh grapefruit and Oroblanco at all test locations. Weight at Riverside from 1967 through 1975 averaged 470 grams for Melogold, 360 grams for Oroblanco and 280 grams for Marsh. Tetraploid Polyploidy
1696-579: A sterile triploid hybrid between E. guttata and E. lutea, both of which have been introduced and naturalised in the United Kingdom. New populations of E. peregrina arose on the Scottish mainland and the Orkney Islands via genome duplication from local populations of E. × robertsii . Because of a rare genetic mutation, E. peregrina is not sterile. On the other hand, polyploidization can also be
1802-412: A technically demanding kind of sport fishing , not necessarily intuitive for beginning fishermen. A conflict exists between commercial fishermen and recreational fishermen for the right to salmon stock resources . Commercial fishing in estuaries and coastal areas is often restricted so enough salmon can return to their natal rivers where they can spawn and be available for sport fishing. On parts of
1908-436: Is a condition in which the cells of an organism have more than two paired sets of ( homologous ) chromosomes . Most species whose cells have nuclei ( eukaryotes ) are diploid , meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous chromosomes. However, some organisms are polyploid . Polyploidy
2014-836: Is a major contributor to the world production of farmed finfish, representing about US$ 10 billion annually. Other commonly cultured fish species include tilapia , catfish , sea bass , carp and bream . Salmon farming is significant in Chile , Norway , Scotland , Canada and the Faroe Islands ; it is the source for most salmon consumed in the United States and Europe. Atlantic salmon are also, in very small volumes, farmed in Russia and Tasmania , Australia. Salmon are carnivorous , and need to be fed meals produced from catching other wild forage fish and other marine organisms. Salmon farming leads to
2120-407: Is common among ferns and flowering plants (see Hibiscus rosa-sinensis ), including both wild and cultivated species . Wheat , for example, after millennia of hybridization and modification by humans, has strains that are diploid (two sets of chromosomes), tetraploid (four sets of chromosomes) with the common name of durum or macaroni wheat, and hexaploid (six sets of chromosomes) with
2226-680: Is derived from Middle English : samoun , samon and saumon , which in turn are from Anglo-Norman : saumon , from Old French : saumon , and from Latin : salmō (which in turn might have originated from salire , meaning "to leap". ). The unpronounced "l" absent from Middle English was later added as a Latinisation to make the word closer to its Latin root. The term salmon has mostly displaced its now dialectal synonym lax , in turn from Middle English : lax , from Old English : leax , from Proto-Germanic : * lahsaz from Proto-Indo-European : *lakso- . The seven commercially important species of salmon occur in two genera of
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#17328518208282332-446: Is dotted by past and recent whole-genome duplication events (see Albertin and Marullo 2012 for review). Several examples of polyploids are known: In addition, polyploidy is frequently associated with hybridization and reticulate evolution that appear to be highly prevalent in several fungal taxa. Indeed, homoploid speciation (hybrid speciation without a change in chromosome number) has been evidenced for some fungal species (such as
2438-491: Is especially common in plants. Most eukaryotes have diploid somatic cells , but produce haploid gametes (eggs and sperm) by meiosis . A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera , for example, are monoploid. Unlike animals, plants and multicellular algae have life cycles with two alternating multicellular generations . The gametophyte generation
2544-698: Is even across the two subgenomes, this can theoretically result in rapid restoration of bivalent pairing and disomic inheritance following allopolyploidization. However multivalent pairing is common in many recently formed allopolyploids, so it is likely that the majority of meiotic stabilization occurs gradually through selection. Because pairing between homoeologous chromosomes is rare in established allopolyploids, they may benefit from fixed heterozygosity of homoeologous alleles. In certain cases, such heterozygosity can have beneficial heterotic effects, either in terms of fitness in natural contexts or desirable traits in agricultural contexts. This could partially explain
2650-885: Is frequent in plants, some estimates suggesting that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy ( paleopolyploidy ) in their genomes. Huge explosions in angiosperm species diversity appear to have coincided with the timing of ancient genome duplications shared by many species. It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase. Polyploid plants can arise spontaneously in nature by several mechanisms, including meiotic or mitotic failures, and fusion of unreduced (2 n ) gametes. Both autopolyploids (e.g. potato ) and allopolyploids (such as canola, wheat and cotton) can be found among both wild and domesticated plant species. Most polyploids display novel variation or morphologies relative to their parental species, that may contribute to
2756-495: Is haploid, and produces gametes by mitosis ; the sporophyte generation is diploid and produces spores by meiosis . Polyploidy is the result of whole-genome duplication during the evolution of species. It may occur due to abnormal cell division , either during mitosis, or more commonly from the failure of chromosomes to separate during meiosis or from the fertilization of an egg by more than one sperm. In addition, it can be induced in plants and cell cultures by some chemicals:
2862-452: Is highly resistant to such exposures. The mechanism by which the genome is accurately restored involves RecA-mediated homologous recombination and a process referred to as extended synthesis-dependent strand annealing (SDSA) . Salmon all other members of Salmoninae Salmon ( / ˈ s æ m ən / ; pl. : salmon) is the common name for several commercially important species of euryhaline ray-finned fish from
2968-514: Is more rarely diagnosed than triploidy, but is observed in 1–2% of early miscarriages. However, some tetraploid cells are commonly found in chromosome analysis at prenatal diagnosis and these are generally considered 'harmless'. It is not clear whether these tetraploid cells simply tend to arise during in vitro cell culture or whether they are also present in placental cells in vivo . There are, at any rate, very few clinical reports of fetuses/infants diagnosed with tetraploidy mosaicism. Mixoploidy
3074-473: Is most commonly caused by either failure of one meiotic division during oogenesis leading to a diploid oocyte or failure to extrude one polar body from the oocyte . Diandry appears to predominate among early miscarriages , while digyny predominates among triploid zygotes that survive into the fetal period. However, among early miscarriages, digyny is also more common in those cases less than 8 + 1 ⁄ 2 weeks gestational age or those in which an embryo
3180-433: Is most commonly induced by treating seeds with the chemical colchicine . Some crops are found in a variety of ploidies: tulips and lilies are commonly found as both diploid and triploid; daylilies ( Hemerocallis cultivars) are available as either diploid or tetraploid; apples and kinnow mandarins can be diploid, triploid, or tetraploid. Besides plants and animals, the evolutionary history of various fungal species
3286-623: Is often associated with apomictic mating systems. In agricultural systems, autotriploidy can result in seedlessness, as in watermelons and bananas . Triploidy is also utilized in salmon and trout farming to induce sterility. Rarely, autopolyploids arise from spontaneous, somatic genome doubling, which has been observed in apple ( Malus domesticus ) bud sports . This is also the most common pathway of artificially induced polyploidy, where methods such as protoplast fusion or treatment with colchicine , oryzalin or mitotic inhibitors are used to disrupt normal mitotic division, which results in
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3392-440: Is part of cytology and, more specifically, cytogenetics . Although the replication and transcription of DNA is highly standardized in eukaryotes , the same cannot be said for their karyotypes, which are highly variable between species in chromosome number and in detailed organization despite being constructed out of the same macromolecules. In some cases, there is even significant variation within species. This variation provides
3498-435: Is present. There are also two distinct phenotypes in triploid placentas and fetuses that are dependent on the origin of the extra haploid set. In digyny, there is typically an asymmetric poorly grown fetus , with marked adrenal hypoplasia and a very small placenta . In diandry, a partial hydatidiform mole develops. These parent-of-origin effects reflect the effects of genomic imprinting . Complete tetraploidy
3604-412: Is quite commonly observed in human preimplantation embryos and includes haploid/diploid as well as diploid/tetraploid mixed cell populations. It is unknown whether these embryos fail to implant and are therefore rarely detected in ongoing pregnancies or if there is simply a selective process favoring the diploid cells. A polyploidy event occurred within the stem lineage of the teleost fish. Polyploidy
3710-441: Is quite high (perhaps as high as 40 to 50%). To lay her roe , the female salmon uses her tail (caudal fin), to create a low-pressure zone, lifting gravel to be swept downstream, excavating a shallow depression, called a redd. The redd may sometimes contain 5,000 eggs covering 2.8 m (30 sq ft). The eggs usually range from orange to red. One or more males approach the female in her redd, depositing sperm, or milt, over
3816-478: Is slightly greater than Marsh, but as a percentage of fruit diameter is equal to Marsh and thinner than Oroblanco; interior color and texture are the same as Oroblanco. As with Oroblanco the central core hollow is greater than Marsh at maturity. The flesh is tender and juicy, separating well from the segment membranes. Percent juice has been equal to Marsh and slightly higher than Oroblanco. In 1958, CRC 2240 (pomelo) Robert K. Soost and James W. Cameron crossed with
3922-946: Is strictly a fish parasite that cannot live in or affect warm blooded animals, including man". According to Klaus Schallie, Molluscan Shellfish Program Specialist with the Canadian Food Inspection Agency , " Henneguya salminicola is found in southern B.C. also and in all species of salmon. I have previously examined smoked chum salmon sides that were riddled with cysts and some sockeye runs in Barkley Sound (southern B.C., west coast of Vancouver Island ) are noted for their high incidence of infestation." Sea lice , particularly Lepeophtheirus salmonis and various Caligus species, including C. clemensi and C. rogercresseyi , can cause deadly infestations of both farm-grown and wild salmon. Sea lice are ectoparasites which feed on mucus, blood, and skin, and migrate and latch onto
4028-624: Is the Coast Redwood Sequoia sempervirens , which is a hexaploid (6 x ) with 66 chromosomes (2 n = 6 x = 66), although the origin is unclear. Aquatic plants, especially the Monocotyledons , include a large number of polyploids. The induction of polyploidy is a common technique to overcome the sterility of a hybrid species during plant breeding. For example, triticale is the hybrid of wheat ( Triticum turgidum ) and rye ( Secale cereale ). It combines sought-after characteristics of
4134-476: Is under development in Alaska . There, the young salmon are released into the ocean far from any wild salmon streams. When it is time for them to spawn, they return to where they were released, where fishermen can catch them. An alternative method to hatcheries is to use spawning channels. These are artificial streams , usually parallel to an existing stream, with concrete or rip-rap sides and gravel bottoms. Water from
4240-551: Is under- or over-represented are said to be aneuploid (from the Greek words meaning "not", "good", and "fold"). Aneuploidy refers to a numerical change in part of the chromosome set, whereas polyploidy refers to a numerical change in the whole set of chromosomes. Polyploidy occurs in some tissues of animals that are otherwise diploid, such as human muscle tissues. This is known as endopolyploidy . Species whose cells do not have nuclei, that is, prokaryotes , may be polyploid, as seen in
4346-610: The Cook Inlet Aquaculture Association , as a way to increase salmon populations in situations where they have declined due to overharvesting , construction of dams and habitat destruction or fragmentation . Negative consequences to this sort of population manipulation include genetic "dilution" of the wild stocks. Many jurisdictions are now beginning to discourage supplemental fish planting in favour of harvest controls, and habitat improvement and protection. A variant method of fish stocking , called ocean ranching,
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4452-484: The Japanese word for trout. On the other hand, the steelhead and sea trout , the anadromous forms of rainbow trout and brown trout respectively, are from the same genera as salmon and live identical migratory lives, but neither is termed "salmon" . The extinct Eosalmo driftwoodensis , the oldest known Salmoninae fish in the fossil record , helps scientists figure how the different species of salmon diverged from
4558-518: The Pacific Northwest and Alaska , salmon are keystone species . The migration of salmon represent a massive retrograde nutrient transfer, rich in nitrogen , sulfur , carbon and phosphorus , from the ocean to the inland freshwater ecosystems . Predation by piscivorous land animals (such as ospreys , bears and otters ) along the journey serve to transfer the nutrients from the water to land, and decomposition of salmon carcass benefits
4664-456: The Pacific coast of Canada , the louse-induced mortality of pink salmon in some regions is commonly over 80%. The risk of injury caused by underwater pile driving has been studied by Dr. Halvorsen and her co-workers. The study concluded that the fish are at risk of injury if the cumulative sound exposure level exceeds 210 dB relative to 1 μPa s. As can be seen from the production chart at
4770-504: The Quaternary glaciation began the cycle of glacial advance and retreat. There are several other species of fish which are colloquially called "salmon" but are not true salmon. Of those listed below, the Danube salmon or huchen is a large freshwater salmonid closely related (from the same subfamily) to the seven species of salmon above, but others are fishes of unrelated orders , given
4876-654: The Salmo and Oncorhynchus genera also contain a number of trout species informally referred to as salmon. Within Salmo , the Adriatic salmon ( Salmo obtusirostris ) and Black Sea salmon ( Salmo labrax ) have both been named as salmon in English , although they fall outside the generally recognized seven salmon species. The masu salmon ( Oncorhynchus masou ) is actually considered a trout ("cherry trout") in Japan , with masu actually being
4982-546: The basidiomycota Microbotryum violaceum ). As for plants and animals, fungal hybrids and polyploids display structural and functional modifications compared to their progenitors and diploid counterparts. In particular, the structural and functional outcomes of polyploid Saccharomyces genomes strikingly reflect the evolutionary fate of plant polyploid ones. Large chromosomal rearrangements leading to chimeric chromosomes have been described, as well as more punctual genetic modifications such as gene loss. The homoealleles of
5088-497: The forest ecosystem . In the case of Pacific salmon , most (if not all) of the salmon that survive to reach the headwater spawning grounds will die after laying eggs and their dead bodies sink to cover the gravel beds, with the nutrients released from the biodegradation of their corpses providing a significant boost to these otherwise biomass -poor shallow streams. Grizzly bears function as ecosystem engineers , capturing salmon and carrying them into adjacent dry land to eat
5194-588: The genera Salmo and Oncorhynchus of the family Salmonidae , native to tributaries of the North Atlantic ( Salmo ) and North Pacific ( Oncorhynchus ) basins. Other closely related fish in the same family include trout , char , grayling , whitefish , lenok and taimen , all coldwater fish of the subarctic and cooler temperate regions with some sporadic endorheic populations in Central Asia . Salmon are typically anadromous : they hatch in
5300-524: The myrtle zone . These dams can be overtopped at high tide and hold water at low tide. This provides refuges for juvenile salmon so they do not have to swim into large channels where they are subject to predation by larger fish. It has been discovered that rivers which have seen a decline or disappearance of anadromous lampreys , loss of the lampreys also affects the salmon in a negative way. Like salmon, anadromous lampreys stop feeding and die after spawning, and their decomposing bodies release nutrients into
5406-590: The otolith (annuli), analogous to the growth rings visible in a tree trunk. Freshwater growth shows as densely crowded rings, sea growth as widely spaced rings; spawning is marked by significant erosion as body mass is converted into eggs and milt. Freshwater streams and estuaries provide important habitat for many salmon species. They feed on terrestrial and aquatic insects , amphipods , and other crustaceans while young, and primarily on other fish when older. Eggs are laid in deeper water with larger gravel and need cool water and good water flow (to supply oxygen) to
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#17328518208285512-664: The salmonids and many cyprinids (i.e. carp ). Some fish have as many as 400 chromosomes. Polyploidy also occurs commonly in amphibians; for example the biomedically important genus Xenopus contains many different species with as many as 12 sets of chromosomes (dodecaploid). Polyploid lizards are also quite common. Most are sterile and reproduce by parthenogenesis ; others, like Liolaemus chiliensis , maintain sexual reproduction. Polyploid mole salamanders (mostly triploids) are all female and reproduce by kleptogenesis , "stealing" spermatophores from diploid males of related species to trigger egg development but not incorporating
5618-826: The subfamily Salmoninae . The genus Salmo contains the Atlantic salmon , found in both sides of the North Atlantic , as well as more than 40 other species commonly named as trout . The genus Oncorhynchus contains 12 recognised species which occur naturally only in the North Pacific, six of which are known as Pacific salmon while the remainder are considered trout. Outside their native habitats, Chinook salmon have been successfully introduced in New Zealand and Patagonia , while coho , sockeye and Atlantic salmon have been established in Patagonia, as well. Both
5724-420: The vertebrates (which includes the human lineage) and another near the origin of the teleost fishes . Angiosperms ( flowering plants ) have paleopolyploidy in their ancestry. All eukaryotes probably have experienced a polyploidy event at some point in their evolutionary history. A karyotype is the characteristic chromosome complement of a eukaryote species . The preparation and study of karyotypes
5830-468: The North American West Coast salmon sport fishing has completely replaced inshore commercial salmon fishing. In most cases, the commercial value of a salmon sold as seafood can be several times less than the value attributed to the same fish caught by a sport fisherman. This is "a powerful economic argument for allocating stock resources preferentially to sport fishing". Salmon aquaculture
5936-558: The Pacific Ocean, the second host releases a stage infective to salmon. The parasite is then carried in the salmon until the next spawning cycle. The myxosporean parasite that causes whirling disease in trout has a similar life cycle. However, as opposed to whirling disease, the Henneguya infestation does not appear to cause disease in the host salmon—even heavily infected fish tend to return to spawn successfully. According to Dr. Kieser,
6042-432: The adjacent stream is piped into the top of the channel, sometimes via a header pond, to settle out sediment. Spawning success is often much better in channels than in adjacent streams due to the control of floods, which in some years can wash out the natural redds. Because of the lack of floods, spawning channels must sometimes be cleaned out to remove accumulated sediment. The same floods that destroy natural redds also clean
6148-425: The agamic complexes of Crepis . Some plants are triploid. As meiosis is disturbed, these plants are sterile, with all plants having the same genetic constitution: Among them, the exclusively vegetatively propagated saffron crocus ( Crocus sativus ). Also, the extremely rare Tasmanian shrub Lomatia tasmanica is a triploid sterile species. There are few naturally occurring polyploid conifers . One example
6254-575: The allotetraploid yeast S. pastorianus show unequal contribution to the transcriptome . Phenotypic diversification is also observed following polyploidization and/or hybridization in fungi, producing the fuel for natural selection and subsequent adaptation and speciation. Other eukaryotic taxa have experienced one or more polyploidization events during their evolutionary history (see Albertin and Marullo, 2012 for review). The oomycetes , which are non-true fungi members, contain several examples of paleopolyploid and polyploid species, such as within
6360-567: The basis for a range of studies in what might be called evolutionary cytology. Homoeologous chromosomes are those brought together following inter-species hybridization and allopolyploidization , and whose relationship was completely homologous in an ancestral species. For example, durum wheat is the result of the inter-species hybridization of two diploid grass species Triticum urartu and Aegilops speltoides . Both diploid ancestors had two sets of 7 chromosomes, which were similar in terms of size and genes contained on them. Durum wheat contains
6466-432: The best known is colchicine , which can result in chromosome doubling, though its use may have other less obvious consequences as well. Oryzalin will also double the existing chromosome content. Among mammals , a high frequency of polyploid cells is found in organs such as the brain, liver, heart, and bone marrow. It also occurs in the somatic cells of other animals , such as goldfish , salmon , and salamanders . It
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#17328518208286572-608: The common name "salmon" simply due to similar shapes, behaviors and niches occupied: Salmon eggs are laid in freshwater streams typically at high latitudes. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts, which are distinguished by their bright, silvery colour with scales that are easily rubbed off. Only 10% of all salmon eggs are estimated to survive to this stage. The smolt body chemistry changes, allowing them to live in salt water. While
6678-457: The common name of bread wheat. Many agriculturally important plants of the genus Brassica are also tetraploids. Sugarcane can have ploidy levels higher than octaploid . Polyploidization can be a mechanism of sympatric speciation because polyploids are usually unable to interbreed with their diploid ancestors. An example is the plant Erythranthe peregrina . Sequencing confirmed that this species originated from E. × robertsii ,
6784-430: The developing embryos. Mortality of salmon in the early life stages is usually high due to natural predation and human-induced changes in habitat, such as siltation, high water temperatures, low oxygen concentration, loss of stream cover, and reductions in river flow. Estuaries and their associated wetlands provide vital nursery areas for the salmon prior to their departure to the open ocean. Wetlands not only help buffer
6890-407: The diploid species. A similar relationship exists between three diploid species of Tragopogon ( T. dubius , T. pratensis , and T. porrifolius ) and two allotetraploid species ( T. mirus and T. miscellus ). Complex patterns of allopolyploid evolution have also been observed in animals, as in the frog genus Xenopus . Organisms in which a particular chromosome, or chromosome segment,
6996-472: The elimination of beavers from large parts of the river system, salmon runs plummeted, even in the absence of many of the factors usually associated with the demise of salmon runs. Salmon recruitment can be affected by beavers' dams because dams can: Beaver dams are able to nurture salmon juveniles in estuarine tidal marshes where the salinity is less than 10 ppm. Beavers build small dams of generally less than 60 cm (2 ft) high in channels in
7102-581: The ends of a spectrum of divergence between parental subgenomes. Polyploids that fall between these two extremes, which are often referred to as segmental allopolyploids, may display intermediate levels of polysomic inheritance that vary by locus. About half of all polyploids are thought to be the result of autopolyploidy, although many factors make this proportion hard to estimate. Allopolyploids or amphipolyploids or heteropolyploids are polyploids with chromosomes derived from two or more diverged taxa. As in autopolyploidy, this primarily occurs through
7208-821: The estuary from silt and pollutants, but also provide important feeding and hiding areas. Salmon not killed by other means show greatly accelerated deterioration ( phenoptosis , or "programmed aging") at the end of their lives. Their bodies rapidly deteriorate right after they spawn as a result of the release of massive amounts of corticosteroids . Salmon are mid- level carnivores whose diet change according to their life stage. Salmon fry predominantly feed upon zooplanktons until they reach fingerling sizes, when they start to consume more aquatic invertebrates such as insect larvae , micro crustaceans and worms . As juveniles (parrs), they become more predatory and actively prey upon aquatic insects , small crustaceans, tadpoles and small bait fishes . They are also known to breach
7314-471: The evolved polyploids. The high degree of homology among duplicated chromosomes causes autopolyploids to display polysomic inheritance . This trait is often used as a diagnostic criterion to distinguish autopolyploids from allopolyploids, which commonly display disomic inheritance after they progress past the neopolyploid stage. While most polyploid species are unambiguously characterized as either autopolyploid or allopolyploid, these categories represent
7420-413: The exact stream where they themselves hatched to spawn , and tracking studies have shown this to be mostly true. A portion of a returning salmon run may stray and spawn in different freshwater systems; the percent of straying depends on the species of salmon. Homing behavior has been shown to depend on olfactory memory . Salmon are important food fish and are intensively farmed in many parts of
7526-443: The fish. There they deposit nutrient-rich urine and feces and partially eaten carcasses. Bears preparing for hibernation tend to preferentially consume the more nutrient- and energy -rich salmon roes and brain over the actual flesh , and are estimated to discard up to half the salmon they've harvested uneaten on the forest floor, in densities that can reach 4,000 kg (8,800 lb) per hectare, providing as much as 24% of
7632-604: The four expected if it were truly a tetraploid. This rodent is not a rat , but kin to guinea pigs and chinchillas . Its "new" diploid (2 n ) number is 102 and so its cells are roughly twice normal size. Its closest living relation is Octomys mimax , the Andean Viscacha-Rat of the same family, whose 2 n = 56. It was therefore surmised that an Octomys -like ancestor produced tetraploid (i.e., 2 n = 4 x = 112) offspring that were, by virtue of their doubled chromosomes, reproductively isolated from their parents. Polyploidy
7738-436: The frog, Xenopus (an extension of the work of Briggs and King in 1952) that were able to develop to the tadpole stage. The British scientist J. B. S. Haldane hailed the work for its potential medical applications and, in describing the results, became one of the first to use the word " clone " in reference to animals. Later work by Shinya Yamanaka showed how mature cells can be reprogrammed to become pluripotent, extending
7844-425: The fusion of unreduced (2 n ) gametes, which can take place before or after hybridization . In the former case, unreduced gametes from each diploid taxon – or reduced gametes from two autotetraploid taxa – combine to form allopolyploid offspring. In the latter case, one or more diploid F 1 hybrids produce unreduced gametes that fuse to form allopolyploid progeny. Hybridization followed by genome duplication may be
7950-509: The fusion of unreduced (2 n ) gametes, which results in either triploid ( n + 2 n = 3 n ) or tetraploid (2 n + 2 n = 4 n ) offspring. Triploid offspring are typically sterile (as in the phenomenon of triploid block ), but in some cases they may produce high proportions of unreduced gametes and thus aid the formation of tetraploids. This pathway to tetraploidy is referred to as the triploid bridge . Triploids may also persist through asexual reproduction . In fact, stable autotriploidy in plants
8056-648: The genus Phytophthora . Some species of brown algae ( Fucales , Laminariales and diatoms ) contain apparent polyploid genomes. In the Alveolata group, the remarkable species Paramecium tetraurelia underwent three successive rounds of whole-genome duplication and established itself as a major model for paleopolyploid studies. Each Deinococcus radiodurans bacterium contains 4-8 copies of its chromosome . Exposure of D. radiodurans to X-ray irradiation or desiccation can shatter its genomes into hundred of short random fragments. Nevertheless, D. radiodurans
8162-566: The gills, which leads to large increases in their ability to secrete salt. Hormones involved in increasing salinity tolerance include insulin-like growth factor I , cortisol , and thyroid hormones , which permits the fish to endure the transition from a freshwater environment to the ocean. The salmon spend about one to five years (depending on the species) in the open ocean, where they gradually become sexually mature. The adult salmon then return primarily to their natal streams to spawn. Atlantic salmon spend between one and four years at sea. When
8268-429: The large bacterium Epulopiscium fishelsoni . Hence ploidy is defined with respect to a cell. A monoploid has only one set of chromosomes and the term is usually only applied to cells or organisms that are normally diploid. The more general term for such organisms is haploid . A polyploid that is newly formed. That has become polyploid in more recent history; it is not as new as a neopolyploid and not as old as
8374-681: The left, the global capture reported by different countries to the FAO of commercial wild salmon has remained fairly steady since 1990 at about one million tonnes per year. This is in contrast to farmed salmon (below) which has increased in the same period from about 0.6 million tonnes to well over two million tonnes. Nearly all captured wild salmon are Pacific salmon . The capture of wild Atlantic salmon has always been relatively small, and has declined steadily since 1990. In 2011 only 2,500 tonnes were reported. In contrast, about half of all farmed salmon are Atlantic salmon. Recreational salmon fishing can be
8480-458: The longer the fish remain in fresh water, and they then deteriorate further after they spawn, when they are known as kelts. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning, a trait known as semelparity . Between 2 and 4% of Atlantic salmon kelts survive to spawn again, all females. However, even in those species of salmon that may survive to spawn more than once ( iteroparity ), postspawning mortality
8586-518: The males' DNA into the offspring. While some tissues of mammals, such as parenchymal liver cells, are polyploid, rare instances of polyploid mammals are known, but most often result in prenatal death. An octodontid rodent of Argentina 's harsh desert regions, known as the plains viscacha rat ( Tympanoctomys barrerae ) has been reported as an exception to this 'rule'. However, careful analysis using chromosome paints shows that there are only two copies of each chromosome in T. barrerae , not
8692-408: The number of chromosome sets in the nucleus . The letter x is used to represent the number of chromosomes in a single set: Autopolyploids are polyploids with multiple chromosome sets derived from a single taxon . Two examples of natural autopolyploids are the piggyback plant, Tolmiea menzisii and the white sturgeon, Acipenser transmontanum . Most instances of autopolyploidy result from
8798-446: The parasitic infection into a number of cysts that contain milky fluid. This fluid is an accumulation of a large number of parasites. Henneguya and other parasites in the myxosporean group have complex life cycles, where the salmon is one of two hosts. The fish releases the spores after spawning. In the Henneguya case, the spores enter a second host, most likely an invertebrate, in the spawning stream. When juvenile salmon migrate to
8904-417: The parents, but the initial hybrids are sterile. After polyploidization, the hybrid becomes fertile and can thus be further propagated to become triticale. In some situations, polyploid crops are preferred because they are sterile. For example, many seedless fruit varieties are seedless as a result of polyploidy. Such crops are propagated using asexual techniques, such as grafting . Polyploidy in crop plants
9010-715: The possibilities to non-stem cells. Gurdon and Yamanaka were jointly awarded the Nobel Prize in 2012 for this work. True polyploidy rarely occurs in humans, although polyploid cells occur in highly differentiated tissue, such as liver parenchyma , heart muscle, placenta and in bone marrow. Aneuploidy is more common. Polyploidy occurs in humans in the form of triploidy , with 69 chromosomes (sometimes called 69, XXX), and tetraploidy with 92 chromosomes (sometimes called 92, XXXX). Triploidy, usually due to polyspermy , occurs in about 2–3% of all human pregnancies and ~15% of miscarriages. The vast majority of triploid conceptions end as
9116-517: The preferred prey of seals and sea lions, which can eat 30 lampreys to every salmon, allowing more adult salmon to enter the rivers to spawn without being eaten by the marine mammals. According to Canadian biologist Dorothy Kieser, the myxozoan parasite Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Haida Gwaii Islands . The fish responds by walling off
9222-545: The prevalence of allopolyploidy among crop species. Both bread wheat and triticale are examples of an allopolyploids with six chromosome sets. Cotton , peanut , and quinoa are allotetraploids with multiple origins. In Brassicaceous crops, the Triangle of U describes the relationships between the three common diploid Brassicas ( B. oleracea , B. rapa , and B. nigra ) and three allotetraploids ( B. napus , B. juncea , and B. carinata ) derived from hybridization among
9328-408: The problems of rising costs for buying hatchery fish feed . Yet another attractive alternative is the increased use of seaweed . Seaweed provides essential minerals and vitamins for growing organisms. It offers the advantage of providing natural amounts of dietary fiber and having a lower glycemic load than grain-based fish meal . In the best-case scenario, widespread use of seaweed could yield
9434-796: The processes of speciation and eco-niche exploitation. The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels. Many of these rapid changes may contribute to reproductive isolation and speciation. However, seed generated from interploidy crosses , such as between polyploids and their parent species, usually have aberrant endosperm development which impairs their viability, thus contributing to polyploid speciation . Polyploids may also interbreed with diploids and produce polyploid seeds, as observed in
9540-460: The production of aneuploid gametes. Natural or artificial selection for fertility can quickly stabilize meiosis in autopolyploids by restoring bivalent pairing during meiosis. Rapid adaptive evolution of the meiotic machinery, resulting in reduced levels of multivalents (and therefore stable autopolyploid meiosis) has been documented in Arabidopsis arenosa and Arabidopsis lyrata , with specific adaptive alleles of these species shared between only
9646-419: The production of polyploid cells. This process can be useful in plant breeding, especially when attempting to introgress germplasm across ploidal levels. Autopolyploids possess at least three homologous chromosome sets, which can lead to high rates of multivalent pairing during meiosis (particularly in recently formed autopolyploids, also known as neopolyploids) and an associated decrease in fertility due to
9752-466: The regular streams. Spawning channels preserve the natural selection of natural streams, as there is no benefit, as in hatcheries, to use prophylactic chemicals to control diseases. Farm-raised salmon are fed the carotenoids astaxanthin and canthaxanthin to match their flesh colour to wild salmon to improve their marketability. Wild salmon get these carotenoids , primarily astaxanthin, from eating shellfish and krill . One proposed alternative to
9858-407: The roe. The female then covers the eggs by disturbing the gravel at the upstream edge of the depression before moving on to make another redd. The female may make as many as seven redds before her supply of eggs is exhausted. Each year, the fish experiences a period of rapid growth, often in summer, and one of slower growth, normally in winter. This results in ring formation around an earbone called
9964-503: The salmon population. This system is referred to as ranching . It was very common in countries such as Sweden, before the Norwegians developed salmon farming, but is seldom done by private companies. As anyone may catch the salmon when they return to spawn, a company is limited in benefiting financially from their investment. Because of this, the ranching method has mainly been used by various public authorities and non-profit groups, such as
10070-415: The shallow gravel beds of freshwater headstreams and spend their juvenile years in rivers , lakes and freshwater wetlands , migrate to the ocean as adults and live like sea fish , then return to their freshwater birthplace to reproduce . However, populations of several species are restricted to fresh waters (i.e. landlocked) throughout their lives. Folklore has it that the fish return to
10176-421: The silvery blue of a fresh-run fish from the sea to a darker colour. Salmon can make amazing journeys, sometimes moving hundreds of miles upstream against strong currents and rapids to reproduce. Chinook and sockeye salmon from central Idaho, for example, travel over 1,400 km (900 mi) and climb nearly 2,100 m (7,000 ft) from the Pacific Ocean as they return to spawn. Condition tends to deteriorate
10282-546: The skin of wild salmon during free-swimming, planktonic nauplii and copepodid larval stages, which can persist for several days. Large numbers of highly populated, open-net salmon farms can create exceptionally large concentrations of sea lice; when exposed in river estuaries containing large numbers of open-net farms, many young wild salmon are infected, and do not survive as a result. Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. On
10388-458: The stream. Also, along with species like rainbow trout and Sacramento sucker , lampreys clean the gravel in the rivers during spawning. Their larvae, called ammocoetes, are filter feeders which contribute to the health of the waters. They are also a food source for the young salmon, and being fattier and oilier, it is assumed predators prefer them over salmon offspring, taking off some of the predation pressure on smolts. Adult lampreys are also
10494-534: The survivability of other wild predatory fish which rely on them for food. Research is ongoing into sustainable and plant-based salmon feeds. Intensive salmon farming uses open-net cages, which have low production costs. It has the drawback of allowing disease and sea lice to spread to local wild salmon stocks. Another form of salmon production, which is safer but less controllable, is to raise salmon in hatcheries until they are old enough to become independent. They are released into rivers in an attempt to increase
10600-488: The time the studies were conducted, stocks from the middle and upper reaches of large river systems in British Columbia such as Fraser , Skeena , Nass and from mainland coastal streams in the southern half of B.C., "are more likely to have a low prevalence of infection." The report also states, "It should be stressed that Henneguya , economically deleterious though it is, is harmless from the view of public health . It
10706-467: The total nitrogen available to the riparian woodlands . The foliage of spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from the fished salmon. Beavers also function as ecosystem engineers; in the process of tree-cutting and damming , beavers alter the local ecosystems extensively. Beaver ponds can provide critical habitat for juvenile salmon . An example of this
10812-597: The use of wild-caught fish as feed for the salmon, is the use of soy -based products. This should be better for the local environment of the fish farm, but producing soy beans has a high environmental cost for the producing region. The fish omega-3 fatty acid content would be reduced compared to fish-fed salmon. Another possible alternative is a yeast-based coproduct of bioethanol production, proteinaceous fermentation biomass. Substituting such products for engineered feed can result in equal (sometimes enhanced) growth in fish. With its increasing availability, this would address
10918-417: The water to attack terrestrial insects such as grasshoppers and dragonflies , as well as consuming fish eggs (even those of other salmon). As adults, salmon behave like other mid-sized pelagic fish , eating a variety of sea creatures including smaller forage fish such as lanternfish , herrings , sand lances , mackerels and barracudina . They also eat krill , squid and polychaete worms . In
11024-568: The world, with Norway being the world's largest producer of farmed salmon, followed by Chile . They are also highly prized game fish for recreational fishing , by both freshwater and saltwater anglers . Many species of salmon have since been introduced and naturalized into non-native environments such as the Great Lakes of North America , Patagonia in South America and South Island of New Zealand . The Modern English term salmon
11130-412: Was induced in fish by Har Swarup (1956) using a cold-shock treatment of the eggs close to the time of fertilization, which produced triploid embryos that successfully matured. Cold or heat shock has also been shown to result in unreduced amphibian gametes, though this occurs more commonly in eggs than in sperm. John Gurdon (1958) transplanted intact nuclei from somatic cells to produce diploid eggs in
11236-621: Was seen in the years following 1818 in the Columbia River Basin. In 1818, the British government made an agreement with the U.S. government to allow U.S. citizens access to the Columbia catchment (see Treaty of 1818 ). At the time, the Hudson's Bay Company sent word to trappers to extirpate all furbearers from the area in an effort to make the area less attractive to U.S. fur traders. In response to
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