''Danionella'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

danionin 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'', '' Devario'', and ''Rasbora''._They_are_primarily_native_to_the_ s_...''._They_are_primarily_nati ...

fish found in freshwater habitats in

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

and

West Bengal West Bengal (, Bengali: ''Poshchim Bongo'', , abbr. WB) is a state in the eastern portion of India. It is situated along the Bay of Bengal, along with a population of over 91 million inhabitants within an area of . West Bengal is the fou ...

, India. It includes some of the smallest fishes.

Distribution

Four out of Five Described species of ''Danionella'' are found in Myanmar. ''D. translucida'' is described from the

Ayeyarwady River The Irrawaddy River ( Ayeyarwady River; , , from Indic ''revatī'', meaning "abounding in riches") is a river that flows from north to south through Myanmar (Burma). It is the country's largest river and most important commercial waterway. Orig ...

basin, and ''D. mirifica'' was described from the Kaiming area in

upper Myanmar Upper Myanmar ( my, အထက်မြန်မာပြည်, also called Upper Burma) is a geographic region of Myanmar, traditionally encompassing Mandalay and its periphery (modern Mandalay, Sagaing, Magway Regions), or more broadly speak ...

. Danionella priapus can only be found in India.

Description

When first described, ''Danionella translucida'' was the smallest ostariophysan and the smallest adult

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...

to inhabit fresh water. Its adult size ranges from 10–12 millimetres (.43–.47 in) SL. ''D. mirifica'' gets slightly larger, at about 14 mm (.55 in) SL, but is still one of the smallest freshwater fishes. ''Danionella'' species lack

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

and

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...

, but possess a lateral line. ''D. mirifica'' has a single row of melanophores between the pelvic fins and the tips of the

cleithra The cleithrum (plural cleithra) is a membrane bone which first appears as part of the skeleton in primitive bony fish, where it runs vertically along the scapula. Its name is derived from Greek κλειθρον = "key (lock)", by analogy with "cla ...

, and there is a lack of melanophores on the underside of the abdomen. ''D. dracula'' reaches 17 mm in length. It is neotonous, lacking 44 bones that develop late in the related zebrafish ''

Danio rerio The zebrafish (''Danio rerio'') is a freshwater fish belonging to the minnow family (Cyprinidae) of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often ca ...

.'' They have teeth made of bone, rather than the true teeth of other fishes, and the males have a pair of boney fangs which the use for sparring for mates. Britz ''et al.'' believe the lineage lost true teeth about 50 Ma.Ralf Britz ''et al.,'' ''Royal Society's journal Proceedings B,'' March 2009

Species

* '' Danionella cerebrum''

Britz Britz () is a German locality (''Ortsteil'') within the Berlin borough (''Bezirk'') of Neukölln. History The village of ''Britzig'' was first mentioned in 1273. It was incorporated by the 1920 Greater Berlin Act. It is known for being the site ...

, Conway & Rüber, 2021 * '' Danionella dracula''

, Conway & Rüber, 2009 (Dracula fish) * '' Danionella mirifica''

, 2003 * '' Danionella priapus''

, 2009 * '' Danionella translucida'' T. R. Roberts, 1986

References

* {{Taxonbar, from=Q138091