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The danionins are a group of small minnow-type fish belonging to the family Cyprinidae. Members of this group are mostly in the genera ''Danio'' and ''Devario''. They are native to the fresh waters of southeast Asia. Many species are brightly coloured and are available as aquarium fish worldwide. ''Danio'' tend to have horizontal stripes and long barbels, ''Devario'' tend to have vertical bars and short rudimentary barbels, if barbels are present at all. All danionins are egg scatterers and breed in the rainy season in the wild. They are carnivores living on insects and small crustaceans. ==Taxonomy== The grouping of fish now deemed danionins has been the subject of constant research and speculation throughout the 20th century. Nearly all the fish classed within the ''Danio'' and ''Devario'' genera were originally placed in the ''Danio'' genus upon discovery. However, in the first part of the 20th century Dr George S. Myers split them into three genera, ''Danio'', ''Brachydanio'' and ''Daniops''. The sole species within Myers' ''Daniops'', ''Daniops myersi'' has long ago been found to be a synonym of ''Devario laoensis'', however his ''Brachydanio'' genus lasted for much longer, as it included most of the fish now classed as ''Danio'', whereas ''Danio'' included most of the fish now classed as ''Devario''. However ''Danio dangila'' and ''Danio feegradei'' both of which had most of the characteristics of the Brachydanios (with the exception that they were much larger than the Brachydanios) were placed within the ''Danios''. (Due to this and other mis-placing, both ''Danio'' and ''Brachydanio'' were found to be paraphyletic by Fang Fang in 2003.〔). In 1941 H.M. Smith attempted to unite all the ''Brachydanios'' and ''Danios'' into one genus on the basis of a fish from Thailand which was supposed to bridge the gap. He downgraded both ''Danio'' and ''Brachydanio'' into subgenera and erected a new subgenera of ''Allodanio'' with one member ''Allodanio ponticulus'', however Myers later pointed out that ''ponticulus'' was actually a member of the ''Barilius'' genus.〔 In a 1986 paper, Tyson Roberts noted that the danionin group was thought to include ''Parabarilius'', ''Danio'', ''Brachydanio'' and ''Danionella''. In this scheme, danionins were distinguished from other cyprinids by the uniquely shared character of the ''danionin notch'', a large and peculiarly shaped indentation in the medial margin of the mandibles; this feature is not noted in rasborins, esomins, bariliins, or chelins. However, all of these categories at that time were informal. ''Microrasbora'' was not considered to be a part of the danionins, nor even closely related to ''Danionella'', a part of the danionins as understood at that time. In the late 1980s and 1990s doubts grew about the validity of ''Brachydanio'', with species being referred to their original naming of ''Danio'', and in a 2003 paper Fang Fang determined that the genus ''Danio'', recognized up to that point, was paraphyletic. Fang restricted ''Danio'' to the species in the "''D. dangila'' species group", which at the time comprised nine species including ''D. dangila'', ''D. rerio'', ''D. nigrofasciatus'', and ''D. albolineatus''; the remaining ''Danio'' species were moved to ''Devario'', which at this time included ''D. malabaricus'', ''D. kakhienensis'', ''D. devario'', ''D. chrysotaeniatus'', ''D. maetaengensis'', ''D. interruptus'', and ''D. apogon''. The only Danios to have been consistently called ''Danio'' were ''D. dangila'' & ''D. feegradei''. As ''D. dangila'' was the first discovered ''Danio'' (or type) the name ''Danio'' had to remain with ''dangila'', which is why the vast majority of species were moved to ''Devario''. Also, in Fang's 2003 paper, the sister group to ''Devario'' was deemed to be a clade formed by ''Inlecypris'' and ''Chela'' and, more controversially, ''Esomus'' was found to be the sister group of ''Danio''. The relationships of ''Sundadanio'', ''Danionella'', ''Microrasbora'' remained unresolved. The danionin notch was found to not supported to be a danionin synapomorphy. In 2007 in another paper by Tyson Roberts, ''Celestichthys margaritatus'' was described as a new species of Danioninae. Apparently, it is most closely related to ''Microrasbora erythromicron''; the other ''Microrasbora'' species differ significantly from ''Celestichthys''. The genus is identified as a danionin due specializations of its lower jaw and its numerous anal fin rays. Though it lacks a danionin notch, ''Celestichthys'' exhibits the "danionin mandibular knob", a bony process on the side of the mandible behind the danionin notch or where the notch should be; it is perhaps diagnostic of danionins. This knob is better developed in males than females. The author notes that fish of Rasborinae almost invariably have anal fins with three spines and five rays. ''Celestichthys'' has 3 anal fin spines and 8½-10½ anal fin rays. Also, rasborins have the generalized cyprinid principal caudal fin ray count of 10/9, while all Asian cyprinids with fewer than 10/9 principal caudal fin rays are all diminutive species of Danioninae, including ''Celestichthys'', ''M. erythromicron'', ''Danionella'', and ''Paedocypris''. In 2007, an analysis of the phylogenetic relationships of the recently described genus ''Paedocypris'' was published, placing it as the sister taxon to ''Sundadanio''. The clade formed by these two genera was found to be sister to a clade including many danionin genera as well as some rasborin genera such as ''Rasbora'', ''Trigonostigma'', and ''Boraras'', making the danionin group paraphyletic without these rasborin genera based on these results. This paper considered the danionin genera to be within a larger Rasborinae. Also in 2007, another study by various authors analyzed the relationships of ''Danio''. These authors considered Rasborinae to have priority over Danioninae, suggesting that they have the same meaning. Also, ''Danio'' was found to be the sister group of a clade including ''Chela'', ''Microrasbora'', ''Devario'', and ''Inlecypris'', rather than in a clade exclusively with either ''Devario'' or ''Esomus'' as in previous studies. This paper supported the close relationship of ''"Microrasbora" erythromicron'' to ''Danio'' species; however, this study did not include ''Celestichthys'', which was noted by Tyson Roberts in his 2007 paper as being likely to include erythromicron but with further research needed.〔 ''Tanichthys'' is often regarded as a danionin by aquarists and grouped as such in some older aquatic publications, however there is no scientific basis for this, a fact stated on numerous occasions by Brittan and others.〔 It is more closely related to the Rasboras. The danionins can be classed as a subfamily Danioninae which is increasingly gaining credibility as a distinct subfamily from Rasboriniae within the Cyprinidae family. However, in Nelson, 2006, Danioninae was listed as a synonym of Rasborinae. On the other hand, neither inter- nor intrarelationships among the "rasborins" have as yet been thoroughly analyzed.〔 A number of the species have only been recently discovered, in remote inland areas of Laos and Myanmar and do not yet have scientific names. They are listed as ''Danio'' or ''Devario sp "xxxx"'' within the relevant genera and disambiguation pages, where details of the fish can be found by clicking on the hyperlink. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「danionin」の詳細全文を読む スポンサード リンク
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