Danionin
Encyclopedia
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 water
s 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.
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 mandible
s; 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 controverisally, 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 Rasbora
s. 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.
Although boisterous and liable to chase each other and other fish, they are good community fish and will not generally attack each other or other fish, although they occasionally nip fins, more by accident than design and will, like most fish, eat eggs and any fish small enough to fit into their mouths.
They are best kept in a tank long enough for their active swimming, preferably with a current from a power filter (or at least airstone) as they often live in fast flowing streams in the wild. Generally this also results in them being sub tropical with temperatures of 20 to 22 degrees Celsius (low seventies degrees Fahrenheit) often being fine, however they are good jumpers and a tight fitting lid is recommended.
Minnow
Minnow is a general term used to refer to small freshwater and saltwater fish, especially those used as bait fish or for fishing bait. More specifically, it refers to small freshwater fish of the carp family.-True minnows:...
-type fish belonging to the family Cyprinidae. Members of this group are mostly in the genera Danio
Danio
The Danio genus comprises many of the species of danionins familiar to aquarists. The common name "danio" is used for members of the genera Danio and Devario.-Taxonomy:...
and Devario
Devario
The genus Devario comprises some danionins familiar to aquarists. Generally, they are larger fish than species of the genus Danio, they have short barbels , and generally have deeper bodies than Danio species, with species having vertical or horizontal stripes present...
. They are native to the fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
s of southeast Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. Many species are brightly coloured and are available as aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
fish worldwide. Danio
Danio
The Danio genus comprises many of the species of danionins familiar to aquarists. The common name "danio" is used for members of the genera Danio and Devario.-Taxonomy:...
tend to have horizontal stripes and long barbels, Devario
Devario
The genus Devario comprises some danionins familiar to aquarists. Generally, they are larger fish than species of the genus Danio, they have short barbels , and generally have deeper bodies than Danio species, with species having vertical or horizontal stripes present...
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. MyersGeorge S. Myers
Dr. George Sprague Myers spent most of his career at Stanford University, where he was one of the leading American ichthyologists of the twentieth century. He served as the editor of Stanford Ichthyological Bulletin as well as president of the American Society of Ichthyologists and Herpetologists...
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
Barilius
Barilius is a genus of fishes in family Cyprinidae. It contains about 29 species.- Species :* Barilius bakeri F. Day, 1865* Barilius barila * Barilius barna...
genus.
In a 1986 paper, Tyson Roberts noted that the danionin group was thought to include Parabarilius, Danio
Danio
The Danio genus comprises many of the species of danionins familiar to aquarists. The common name "danio" is used for members of the genera Danio and Devario.-Taxonomy:...
, Brachydanio and Danionella
Danionella
Danionella is a genus comprising the danionin species D. mirifica, D. translucida, and D. dracula, three of the smallest freshwater fishes.-Distribution:...
. 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
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
margin of the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
s; this feature is not noted in rasborins, esomins, bariliins, or chelins. However, all of these categories at that time were informal. Microrasbora
Microrasbora
Microrasbora is a genus of small fishes. The generic name means "small Rasbora", however these are more closely related to the danios than rasboras. They inhabit mainly Thailand and Myanmar, with one putative species in China.-Current Taxonomy:...
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
Paraphyly
A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants...
. 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
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
formed by Inlecypris and Chela
Chela (fish)
Chela is a genus of fish closely related to Devario. It currently consists of two species.- Species :* Chela cachius * Chela khujairokensis Arunkumar, 2000...
and, more controverisally, Esomus
Esomus
Esomus is a genus comprising the Flying Barbs. they are closely related to the Danio genus and are distinctive for their extremely long barbels.- Species :* Esomus ahli Hora & Mukerji, 1928* Esomus altus...
was found to be the sister group
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
of Danio. The relationships of Sundadanio
Sundadanio
Sundadanio is a genus of cyprinid fishes from the Malay Archipelago. There are currently eight described species in this genus.-Species:* Sundadanio atomus Conway, Kottelat & H. H. Tan, 2011* Sundadanio axelrodi...
, Danionella
Danionella
Danionella is a genus comprising the danionin species D. mirifica, D. translucida, and D. dracula, three of the smallest freshwater fishes.-Distribution:...
, Microrasbora
Microrasbora
Microrasbora is a genus of small fishes. The generic name means "small Rasbora", however these are more closely related to the danios than rasboras. They inhabit mainly Thailand and Myanmar, with one putative species in China.-Current Taxonomy:...
remained unresolved. The danionin notch was found to not supported to be a danionin synapomorphy
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
.
In 2007 in another paper by Tyson Roberts, Celestichthys margaritatus
Celestichthys margaritatus
The Celestial Pearl Danio, Danio margaritatus - often referred to in the aquarium trade as galaxy rasbora or "Microrasbora sp. 'Galaxy'" - is a small cyprinid from Myanmar. It has so far been found only in a very small area near Hopong east of Inle Lake, at an altitude of over 1,000 m...
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
Paedocypris
Paedocypris is a genus of cyprinid fish found in Southeast Asia where it occurs in Malaysia and Indonesia. Three species are known.Paedocypris progenetica has been claimed to be the smallest known species of fish and vertebrate in the world...
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
Tanichthys
Tanichthys is a genus of freshwater fish in the carp family of order Cypriniformes. Until recently, the type species, Tanichthys albonubes, was the only one known. In 2001, however, Freyhof and Herder described a new and very similar species, Tanichthys micagemmae, from the Ben Hai River in...
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 Rasbora
Rasbora
A rasbora is a member of a group of small minnow-type fish in the family Cyprinidae . Fish from genera such as Boraras, Microrasbora, Rasbora and Trigonostigma are commonly referred to as rasboras...
s. 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
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
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
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
and Myanmar
Myanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....
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.
In the aquarium
They are generally active swimmers occupying the top half of a tank and will eat just about any type of aquarium food. They will not, however, generally eat plants or algae.Although boisterous and liable to chase each other and other fish, they are good community fish and will not generally attack each other or other fish, although they occasionally nip fins, more by accident than design and will, like most fish, eat eggs and any fish small enough to fit into their mouths.
They are best kept in a tank long enough for their active swimming, preferably with a current from a power filter (or at least airstone) as they often live in fast flowing streams in the wild. Generally this also results in them being sub tropical with temperatures of 20 to 22 degrees Celsius (low seventies degrees Fahrenheit) often being fine, however they are good jumpers and a tight fitting lid is recommended.
Common names given to danionin species
Since 2004 many new danionins have been discovered which do not yet have scientific names and many other species, previously known only to the scientific fraternity have become available in Aquarist Shops. This has predictably led to total confusion as to the naming of some fish, with some species having up to five different common names in use and some common names bein used for up to four different species. As a result all danionin common names known to be in use are listed on a separate page:- Danionin Common Name DisambiguationDanionin Common Name DisambiguationSince 2004 many new Danionins have been discovered which do not yet have scientific names and many other species, previously known only to the scientific fraternity, have become available in Aquarist Shops...
Danionin species scientific names
Individual Danionin species are listed within the relevant pages for each Genera, however many Danionin species have been changed into different genera over the last decades in some cases repeatedly, similarly some species have been synomymised with other species and in some cases later unsynonymised, all of which has caused a lot of confusion. As a result a separate page has been created which lists all danionin species and also lists defunct species which have since been synonymised or renamed.- Danionin species disambiguationDanionin species disambiguationIn the last few decades, many Danionin species have been moved into different genera, in some cases repeatedly, similarly some species have been synonymised with other species and even in some cases later unsynonymised, all of which has caused a lot of confusion. With a large amount of recent...