This species is rare in the aquarium trade and normally expensive when available. It's one of the most easily-identifiable in the genus by the combination of usually 14 pectoral-fin rays, 10 segmented second dorsal-fin rays, relatively small adult size, unique colouration in males and the shape of the first dorsal-fin in males in which the fourth and fifth spines are…

The type locality is a stream with a mixed substrate of mud and stones which flows swiftly through an area of bamboo forest so is quite well-shaded. At time of collection the water was clear but slightly tannin-stained and sympatric species included Pethia thelys, Puntius sophore, Devario strigillifer, Rasbora daniconius, R. rasbora, Acanthocobitis botia, Notopterus notopterus, plus unidentified species of Oreichthys, Parambassis, Xenentodon, and Mastacembelus.

The genus is monotypic and distinguished from other cyprinid taxa by a combination of a moderately compressed, elongated body with two rows of teeth on the lower pharyngeal (throat) bone and lacking barbles, visible lateral line and a symphyseal knob on the lower jaw (Talwar & Jhingran, 1991).

Its small adult size evolved via a process known as miniaturisation characterised by sexually mature adults with a significantly reduced size of less than 20 mm SL. Among bony fishes cyprinids are one of the few groups in which this phenomenon occurs repeatedly…

This species is available in the trade on occasion and has been sold as Danionella sp. 'neon green' or 'flourescent green'. The specific name was inspired by its jaw morphology which according to current knowledge is unique among cypriniform fishes. Both upper and lower jaws contain a series of toothlike odontoid processes; these are only rudimentary in females but in males appear to form rows of teeth of which the front pair is large and fang-like. The upper fangs project th…

Apparently discovered close to the coastal town of Gwa in Rakhine State, western Myanmar. Rakhine is largely cut off from the rest of the country by the Rakhine Yoma/Arakan mountains which form a natural barrier along its eastern side.

Rakhine is located within a tropical monsoon region and has a pronounced rainy season between May and October, while at other times it can be quite dry. The streams thus swell in depth by a metre or mo…

Adult size is comparable to B. nigrofasciata, and in the description paper the authors hypothesise that the two are closely-related given they share other features such as similar barbel length (plus some additional merisitic counts), absent lateral line and spotted pelvic fins.

The two are easy to tell apart, however, since in B. tinwini the P+1 stripe is composed of a series of spots (vs. solid), it possesses an indistinct P+2 str…

This potentially-undescribed species first became available in 2002, and males and females were marketed as ‘Danio sp. hikari yellow’ and ‘D. sp. hikari blue’, respectively. Subsequent DNA testing in the United States revealed them to be the same species and genetically distinct from the very similar B. kerri. It can be told apart as the central body (P) stripe always extends into the caudal fin whereas in B. kerri it terminates at the caudal peduncle. Only a single population of B. kerri was sampled in the stu…

During winter months N. delicata retreats to streams or underflows where it remains dormant between October and April (Kano, 2000) before emerging to spawn. Other species living alongside it in nature include Rhinogobius flumineus, Cottus pollux and Phoxinus spp.

Niwaëlla is closely related to Cobitis and N. delicata, also the type species, was described as C. delicata (Niwa, 1937). The combination of characters used to tell it…

This species was formerly included in the genus Microrasbora although it’s long-been considered a danionin by certain authors, e.g., Kottelat and Witte (1999) and was placed within the genus Danio for a period.

In the aquarium trade it’s marketed under various names including ’emerald dwarf danio’, ‘thick band purple zebra danio’ and ‘cross-banded dwarf rasbora’.