Danio

Danio
Danio rerio — zebra danio
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Cypriniformes
Family:	Cyprinidae
Subfamily:	Danioninae
Genus:	Danio Hamilton, 1822
Type species
Cyprinus (Danio) dangila Hamilton, 1822
Synonyms
Allodanio Hamilton, 1822 Brachydanio Weber & de Beaufort, 1916

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

The name "danio" comes from the Bengali name dhani, meaning "of the rice field". The native Bangla name for the fish is anju. The species Danio rerio was first described in the early 19th century by Francis Hamilton, a surgeon working for the British East India Company. About a century later (1916), the genus was split; the larger species into Danio and the smaller species, such as D. rerio, into the new Brachydanio.^[1] In 1991, though, the two genera were recombined; most larger species formerly within the Danio genus, such as the giant danio, have now been reclassified into the Devario genus. Also, Brachydanio is now a junior synonym of Danio.^[2]

Species

• Danio aesculapii S. O. Kullander & F. Fang, 2009
• Danio albolineatus (Blyth, 1860) (Pearl danio)
• Danio choprae Hora, 1928
• Danio dangila (F. Hamilton, 1822)
• Danio erythromicron (Annandale, 1918)
• Danio feegradei Hora, 1937
• Danio jaintianensis (Sen, 2007)
• Danio kerri H. M. Smith, 1931 (blue danio)
• Danio kyathit F. Fang, 1998
• Danio margaritatus (T. R. Roberts, 2007) (galaxy rasbora)
• Danio meghalayensis Sen & Dey, 1985
• Danio muongthanhensis V. H. Nguyen, 2001
• Danio nigrofasciatus (F. Day, 1870) (dwarf danio)
• Danio quagga S. O. Kullander, T. Y. Liao & F. Fang, 2009
• Danio quangbinhensis (T. T. Nguyen, V. T. Le & X. K. Nguyen, 1999)
• Danio rerio (F. Hamilton, 1822) (zebra danio)
• Danio roseus F. Fang & Kottelat, 2000
• Danio tinwini S. O. Kullander & F. Fang, 2009
• Danio trangi S. V. Ngô, 2003

The following are varieties recognized in the aquarium trade but are not considered valid species.

• D. abolineatus var. pulcher
• D. abolineatus var. tweediei
• D. rerio var. frankei

Some undescribed species or varieties, which may be represented by recently described species above, include:

• "Hikari"
• D. aff kyathit
• "KP01"
• "TW01"

Characteristics

They are native to the fresh water rivers and streams of Southeast Asia, but many species are brightly colored, and are available as aquarium fish worldwide. A number of the species, only recently discovered in remote inland areas of Myanmar, do not yet have scientific names.

They have two pairs of long barbels, and are generally characterised by horizontal stripes (with the exception of the glowlight danio, panther danio and black barred danio which have vertical bars). They range from 4-15 cm (1.75-6 in) in length. They generally do not live for more than two to three years, and are probably annual fish in the wild.

In the wild, these fish consume various small aquatic insects, crustaceans, and worms, as well as plankton in the case of fry.

In the aquarium

The care of members of the genus Danio are rather similar and easily generalized. They are easy to keep.

All of these fish are primarily surface feeders. They are omnivorous in the aquarium and will accept a wide variety of foods, though flake food is appropriate. Living in aquaria, live/frozen flaked foods are suitable, especially brine shrimp and sinking tablets. Danios are voracious eaters; timid feeders may starve in community tanks with danios. When conditioning danios for breeding, it is advisable to feed them plenty of fresh foods.

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; like most fish, they will 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 subtropical with cooler temperatures. They are good jumpers, so a tight-fitting lid is recommended.

As a schooling fish, they prefer to be in groups of six or more. Danios prefer water with a pH between 6.0 and 8.0 , hardness no more than 19.0 dGH,a carbon hardness of 8 to 12 KH, and a temperature range of 68–80°F (18–24°C), the lower end of the temperature range is ideal.

Breeding

Some species of Danio, such as the zebra danio, are among the easiest aquarium fish to breed. Other species, such as Danio kyathit, are far harder to spawn. All scatter their eggs over the substrate. The eggs are not adhesive, and hatch within two or three days. Eggs will be eaten enthusiastically unless protected by a layer of marbles or heavy substrate planting.

Hybrids between some Danio species have been bred; the young can be raised to maturity, but are sterile.

See also

• Danionins - full details of all fish related to the Danios, including those species known as danios which are no longer scientifically classified in the Danio genus
• Devarios - details of the species within the genus Devario

External links

• "Danios and Devarios". Danios and devarios website. http://www.danios.info. Retrieved October 1, 2005. 
• "Clarke, Matt (2005) - A fishkeeper's guide to danios and devarios.". Article on danionins at Practical Fishkeeping's website. Archived from the original on December 24, 2005. http://web.archive.org/web/20051224150256/http://www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=334. Retrieved October 1, 2005. 
• "LiveAquaria website". http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=941. 

References

• Froese, Rainer, and Daniel Pauly, eds. (2011). Species of Danio in FishBase. August 2011 version.

1. ^ Spence, Rowena and Gabriele Gerlach, Christian Lawrence and Carl Smith (2007). "The behaviour and ecology of the zebrafish, Danio rerio" (PDF). Biological Reviews for the Cambridge Philosophical Society 83 (1): 13–34. doi:10.1111/j.1469-185X.2007.00030.x. PMID 18093234. http://www.le.ac.uk/biology/staff/cs152/ZebraReview08.pdf. 
2. ^ Fang, Fang; Douglas, M. E. (2003). Douglas, M. E.. ed. "Phylogenetic Analysis of the Asian Cyprinid Genus Danio (Teleostei, Cyprinidae)". Copeia 2003 (4): 714–728. doi:10.1643/IA03-131.1.