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73-428: Candidia is a genus of small cyprinid freshwater fish endemic to Taiwan . There are currently two recognized species in this genus. This Cyprinidae -related article is a stub . You can help Misplaced Pages by expanding it . Cyprinid and see text Cyprinidae is a family of freshwater fish commonly called the carp or minnow family , including the carps , the true minnows , and their relatives

146-409: 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

219-626: 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

292-410: 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

365-479: A chewing plate formed by a bony process of the skull . The pharyngeal teeth are unique to each species and are used by scientists to identify species. Strong pharyngeal teeth allow fish such as the common carp and ide to eat hard baits such as snails and bivalves . Hearing is a well-developed sense in the cyprinids since they have the Weberian organ , three specialized vertebral processes that transfer motion of

438-529: 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 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

511-548: A management tool to control various factors in the aquatic environment, such as aquatic vegetation and diseases transmitted by snails. Unlike most fish species, cyprinids generally increase in abundance in eutrophic lakes. Here, they contribute towards positive feedback as they are efficient at eating the zooplankton that would otherwise graze on the algae, reducing its abundance. Cyprinids are highly important food fish; they are fished and farmed across Eurasia . In land-locked countries in particular, cyprinids are often

584-481: 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

657-403: 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

730-695: 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

803-500: A radical move, though reasonable, is probably premature. The tench ( Tinca tinca ), a significant food species farmed in western Eurasia in large numbers, is unusual. It is most often grouped with the Leuciscinae, but even when these were rather loosely circumscribed, it always stood apart. A cladistic analysis of DNA sequence data of the S7 ribosomal protein intron   1 supports

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876-954: A rare genetic mutation, E. peregrina is not sterile. On the other hand, polyploidization can also be 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

949-408: Is Paedocypris progenetica , reaching 10.3 mm (0.41 in) at the longest. All fish in this family are egg-layers and most do not guard their eggs; however, a few species build nests and/or guard the eggs. The bitterlings of subfamily Acheilognathinae are notable for depositing their eggs in bivalve molluscs , where the young develop until able to fend for themselves. Cyprinids contain

1022-559: Is a major pest species in Australia impacting freshwater environments, amenity, and the agricultural economy, devastating biodiversity by decimating native fish populations where they first became established as a major pest in the wild in the 1960s. In the major river system of eastern Australia, the Murray-Darling Basin , they constitute 80–90 per cent of fish biomass. In 2016 the federal government announced A$ 15.2 million to fund

1095-469: Is discovered, for example: Psilorhynchus Probarbinae Parapsilorhynchini Labeonini Garrini Torinae Smiliogastrinae Cyprinini Rohteichthyini Acrossocheilini Spinibarbini Schizothoracini Schizopygopsini Barbini Allopolyploid 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

1168-446: 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

1241-698: 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

1314-885: 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

1387-514: 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

1460-473: 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

1533-433: 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

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1606-623: 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

1679-440: 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

1752-435: 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

1825-412: 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

1898-579: Is the giant barb ( Catlocarpio siamensis ), which may grow up to 3 m (9.8 ft) in length and 300 kg (660 lb) in weight. Other very large species that can surpass 2 m (6.6 ft) are the golden mahseer ( Tor putitora ) and mangar ( Luciobarbus esocinus ). The largest North American species is the Colorado pikeminnow ( Ptychocheilus lucius ), which can reach up to 1.8 m (5.9 ft) in length. Conversely, many species are smaller than 5 cm (2 in). The smallest known fish

1971-624: 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

2044-584: Is the plant Erythranthe peregrina . Sequencing confirmed that this species originated from E. × robertsii , 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

2117-551: 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

2190-546: The Cultrinae and Leuciscinae, regardless of their exact delimitation, are rather close relatives and stand apart from Cyprininae  – but the overall systematics and taxonomy of the Cyprinidae remain a subject of considerable debate. A large number of genera are incertae sedis , too equivocal in their traits and/or too little-studied to permit assignment to a particular subfamily with any certainty. Part of

2263-519: The Labeoninae or Squaliobarbinae also remain doubtful, although the latter do appear to correspond to a distinct lineage. The sometimes-seen grouping of the large-headed carps ( Hypophthalmichthyinae ) with Xenocypris , though, seems quite in error. More likely, the latter are part of the Cultrinae. The entirely paraphyletic "Barbinae" and the disputed Labeoninae might be better treated as part of

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2336-847: The aquarium and fishpond hobbies, most famously the goldfish , which was bred in China from the Prussian carp ( Carassius (auratus) gibelio ). First imported into Europe around 1728, it was originally much-fancied by the Chinese nobility as early as 1150   AD and, after it arrived there in 1502, also in Japan . In addition to the goldfish, the common carp was bred in Japan into the colorful ornamental variety known as koi — or more accurately nishikigoi ( 錦鯉 ) , as koi ( 鯉 ) simply means "common carp" in Japanese — from

2409-413: The barbs and barbels , among others. Cyprinidae is the largest and most diverse fish family, and the largest vertebrate animal family overall, with about 3,000 species ; only 1,270 of these remain extant, divided into about 200 valid genera . Cyprinids range from about 12 mm (0.5 in) in size to the 3 m (9.8 ft) giant barb ( Catlocarpio siamensis ). By genus and species count,

2482-546: 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

2555-550: The gas bladder to the inner ear. The vertebral processes of the Weberian organ also permit a cyprinid to detect changes in motion of the gas bladder due to atmospheric conditions or depth changes. The cyprinids are considered physostomes because the pneumatic duct is retained in adult stages and the fish are able to gulp air to fill the gas bladder, or they can dispose of excess gas to the gut. Cyprinids are native to North America , Africa , and Eurasia . The largest known cyprinid

2628-436: The moderlieschen , are opportunistic predators that will eat larvae of the common frog in artificial circumstances. Some cyprinids, such as the grass carp , are specialized herbivores; others, such as the common nase , eat algae and biofilms , while others, such as the black carp , specialize in snails, and some, such as the silver carp , are specialized filter feeders . For this reason, cyprinids are often introduced as

2701-664: 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

2774-420: 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

2847-510: The 18th century until today. Other popular aquarium cyprinids include danionins , rasborines and true barbs . Larger species are bred by the thousands in outdoor ponds, particularly in Southeast Asia , and trade in these aquarium fishes is of considerable commercial importance. The small rasborines and danionines are perhaps only rivalled by characids (tetras) and poecilid livebearers in their popularity for community aquaria . Some of

2920-691: The Cyprininae, forming a close-knit group whose internal relationships are still little known. The small African " barbs " do not belong in Barbus sensu stricto – indeed, they are as distant from the typical barbels and the typical carps ( Cyprinus ) as these are from Garra (which is placed in the Labeoninae by most who accept the latter as distinct) and thus might form another as yet unnamed subfamily. However, as noted above, how various minor lineages tie into this has not yet been resolved; therefore, such

2993-475: The National Carp Control Plan to investigate using Cyprinid herpesvirus 3 (carp virus) as a biological control agent while minimising impacts on industry and environment should a carp virus release go ahead. Despite initial, favourable assessment, in 2020 this plan was found to be unlikely to work due to the high fecundity of the fish. Numerous cyprinids have become popular and important within

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3066-561: The Rasborinae as the basal lineage with the Cyprininae as a sister clade to the Leuciscinae. The subfamilies Acheilognathinae , Gobioninae , and Leuciscinae are monophyletic. The 5th Edition of Fishes of the World sets out the following subfamilies: With such a large and diverse family the taxonomy and phylogenies are always being worked on so alternative classifications are being created as new information

3139-425: 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

3212-575: 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

3285-567: 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

3358-437: The common name of durum or macaroni wheat, and hexaploid (six sets of chromosomes) with 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

3431-407: 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,

3504-581: 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

3577-471: 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

3650-412: 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: 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 ,

3723-411: The family makes up more than two-thirds of the ostariophysian order Cypriniformes . The family name is derived from the Greek word kyprînos ( κυπρῖνος 'carp'). Cyprinids are stomachless, or agastric , fish with toothless jaws. Even so, food can be effectively chewed by the gill rakers of the specialized last gill bow. These pharyngeal teeth allow the fish to make chewing motions against

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3796-504: The first and only known example of androgenesis in a vertebrate, in the Squalius alburnoides allopolyploid complex. Most cyprinids feed mainly on invertebrates and vegetation , probably due to the lack of teeth and stomach; however, some species, like the asp , are predators that specialize in fish. Many species, such as the ide and the common rudd , prey on small fish when individuals become large enough. Even small species, such as

3869-604: 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

3942-436: 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

4015-425: 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

4088-509: 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

4161-648: 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

4234-568: The grass carp ( Ctenopharyngodon idella ) are the most important of these, for example in Florida . Carp in particular can stir up sediment , reducing the clarity of the water and making plant growth difficult. In America and Australia, such as the Asian carp in the Mississippi Basin , they have become invasive species that compete with native fishes or disrupt the environment. Cyprinus carpio

4307-429: 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

4380-910: The major species of fish eaten because they make the largest part of biomass in most water types except for fast-flowing rivers. In Eastern Europe, they are often prepared with traditional methods such as drying and salting. The prevalence of inexpensive frozen fish products made this less important now than it was in earlier times. Nonetheless, in certain places, they remain popular for food, as well as recreational fishing , for ornamental use, and have been deliberately stocked in ponds and lakes for centuries for this reason. Cyprinids are popular for angling especially for match fishing (due to their dominance in biomass and numbers) and fishing for common carp because of its size and strength. Several cyprinids have been introduced to waters outside their natural ranges to provide food, sport, or biological control for some pest species. The common carp ( Cyprinus carpio ) and

4453-518: 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

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4526-547: The most popular cyprinids among aquarists , other than goldfish and koi, include the cherry barb , Harlequin rasbora , pearl danios , rainbow sharks , tiger barbs , and the White Cloud Mountain minnow . One particular species of these small and undemanding danionines is the zebrafish ( Danio rerio ). It has become the standard model species for studying developmental genetics of vertebrates , in particular fish. Habitat destruction and other causes have reduced

4599-408: 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

4672-417: 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

4745-715: 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

4818-545: 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

4891-796: 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

4964-460: 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

5037-419: 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

5110-413: The solution seems that the delicate rasborines are the core group, consisting of minor lineages that have not shifted far from their evolutionary niche , or have coevolved for millions of years. These are among the most basal lineages of living cyprinids. Other "rasborines" are apparently distributed across the diverse lineages of the family. The validity and circumscription of proposed subfamilies like

5183-538: The view that it is distinct enough to constitute a monotypic subfamily. It also suggests it may be closer to the small East Asian Aphyocypris , Hemigrammocypris , and Yaoshanicus . They would have diverged roughly at the same time from cyprinids of east-central Asia, perhaps as a result of the Alpide orogeny that vastly changed the topography of that region in the late Paleogene , when their divergence presumably occurred. A DNA-based analysis of these fish places

5256-670: The wild stocks of several cyprinids to dangerously low levels; some are already entirely extinct . In particular, the cyprinids of the subfamily Leuciscinae from southwestern North America have been hit hard by pollution and unsustainable water use in the early to mid-20th century; most globally extinct cypriniform species are in fact leuciscinid cyprinids from the southwestern United States and northern Mexico. The massive diversity of cyprinids has so far made it difficult to resolve their phylogeny in sufficient detail to make assignment to subfamilies more than tentative in many cases. Some distinct lineages obviously exist – for example,

5329-412: 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

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