Danio: from Dhani, a Bengalese vernacular term for small, minnow-like cyprinids.
aesculapii: genitive of Aesculapius (Latin form of Asklepios, Ἀσκληπιός), Ancient Greek god of medicine who carried a staff with one or two snakes wrapped around it, in reference to this species’ snakeskin colour pattern .
Endemic to the Rakhine Yoma/Arakan mountains in Rakhine state, western Myanmar; this range forms a natural barrier which cuts the state off from the remainder of the country.
It was originally collected from a handful of streams and rivers of the western, interior, slopes of which the type specimens originated from the Kananmae Chaung, a coastal rivulet draining into the Bay of Bengal (Kullander and Fang, 2009).
Myanmar can be considered a centre of diversity for the genus with eight officially-recognised species, seven of which are endemic to the country.
The type locality is a shallow (~30cm deep) section of the stream running close to the village of Leldee through what is described as “low forest” by the authors in an earlier (2004) paper but given as flowing out of the forest into agricultural land by 2009.
At time of collection this was around 3m wide and the substrate composed of a mixture of gravel, pebbles, rocks and leaf litter over which flowed clear, transparent water.
This was moving quite slowly resulting in the formation of a number of small pools within which the fish were found. Sympatric species included Rasbora daniconius, R. rasbora, Aplocheilus panchax, Lepidocephalichthys berdmorei, Batasio elongatus, Garra flavatra, Garra vittatula, Olyra burmanica, Pterocryptis cf. berdmorei and Sicyopterus fasciatus along with unspecified members of Danio (given as Danio sp. aff. dangila),Devario, Rasbora, Pangio, Channa, Mastacembelus, and Anguilla.
Most of the populations discovered inhabited similar environments although one was found in a stagnant pool with a substrate of sand and leaf litter where a small river flows for part of the year.
In fact all its habitats are seasonal in nature; 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 more and flow much more rapidly during the wet season.
Collection of fish, for both scientific and commercial purposes, is normally conducted during the dryer months in monsoon-affected areas due to difficulties encountered during times of high water levels and/or poor weather.
Maximum Standard Length
One of the smaller members of the genus reaching 25 – 30 mm in length.
Aquarium SizeTop ↑
A group will need an aquarium with base dimensions measuring upwards of 60 ∗ 30 cm.
This species looks particularly effective in a heavily-planted arrangement with a darkish substrate, and can appear a little washed out in sparsely-decorated set-ups.
We suggest keeping it in a well-planted aquarium or set-up designed to resemble a flowing river or stream with a substrate of variably-sized rocks and gravel and some large water-worn boulders.
The water should be well-oxygenated with a degree of flow although torrent-like conditions should be avoided as small danios tend to occupy calmer stretches and marginal zones in nature.
The tank can be further furnished with driftwood branches and hardy aquatic plants such as Microsorum, Bolbitis or Anubias spp. which can be grown attached to the décor.
The aquarium must have a very tightly-fitting cover as this species is an accomplished jumper and can fit through surprisingly small gaps.
Temperature: Water temperatures in its native streams have been recorded between 22 – 27 °C during warmer months of the year. Presumably consitions are cooler during the wet months of the monsoon but we don’t know to what extent.
pH: The pH in its natural waters has been measured at 6.9 – 7.1 and similar values are recommended in the aquarium.
Hardness: Use soft water of 18 – 90 ppm.
Almost certain to prey chiefly on insects and their larvae in nature. In the aquarium it’s a largely unfussy feeder and will accept most foods.
A good quality dried product can be used as the staple diet but this should be supplemented with regular meals of small live and frozen fare such as bloodworm, Daphnia, Artemia, etc. for the fish to show the best colouration and conditioning.
Behaviour and CompatibilityTop ↑
This species is generally peaceful making it an ideal resident of the well-furnished community aquarium.
As it places no special demands in terms of water chemistry it can be combined with many of the most popular fish in the hobby including other small cyprinids as well as tetras, livebearers, rainbowfishes, anabantoids, catfishes and loaches, though as always when selecting a compatible community of fish proper research is essential and its adult size must be taken into account.
A set-up based around fish from the western Rakhine Yoma will be more difficult to achieve as most are unavailable in the aquatic trade. There remain a few potential options though, some of which are listed in the ‘Habitat’ section above.
It’s a schooling species by nature and really should be kept in a group of at least 8-10 specimens.
Maintaining it in decent numbers will not only make the fish less nervous but result in a more effective, natural-looking display while males will also exhibit their best colours as they compete with one other for female attention.
Sexually mature females are usually rounder-bellied and a little larger than males.
The differences are especially clear when the fish are in spawning condition as the males intensify in colour and the females fill with eggs.
The dark bars in the front portion of the body also tend to be noticeably more thin and elongate in females.
Like many small cyprinids this species is an egg-scattering spawner that exhibits no parental care.
When the fish are in good condition they will spawn often and in a densely-planted, mature aquarium it’s possible that small numbers of fry may start to appear without intervention.
However if you want to increase the yield of fry a slightly more controlled approach is required.
The adult group can still be conditioned together but one or more smaller, say 10-15 litre, containers should also be set up and half-filled with water.
These should be very dimly lit and the base covered with some kind of mesh of a large enough grade so that the eggs can fall through it but small enough so that the adults cannot reach them.
The widely available plastic ‘grass’-type matting can also be used and works very well; alternatively filling much of the tank with Java moss or other fine-leaved plant can also yield good results.
The water itself should be very soft, of slightly acidic to neutral pH with a temperature towards the upper end of the range suggested above.
A small power filter can be added initially and this should be positioned so that the flow is directed down the full length of the tank; alternatively simply install a mature sponge-type filter.
When the adult fish are well-conditioned and the females appear full of eggs one or two pairs should then be introduced to each container.
Spawning can be initiated by adding small amounts of cool water every few hours in such a way that the tank is gradually topped up and feeding small amounts of live and frozen foods.
The pair should spawn the following morning. The easiest and quickest way to tell is simply to look at the female since if the fish have spawned she will be noticeably slimmer.
The adults will eat any eggs they find and are best removed after a couple of days at which point the power filter (if using) should be switched for a sponge-type unit in order to avoid fry being sucked into the mechanism.
Incubation is temperature-dependant to an extent but usually takes around 36 hours with the young free-swimming 3-4 days later.
Initial food should be Paramecium or a proprietary dry food of sufficiently small (5-50 micron diameter) grade, introducing Artemia nauplii, microworm, etc. once the fry are large enough to accept them.
Despite its official description this species continues to be traded under various names including Danio sp. ‘pantheri’, D. sp. ‘hieroglyph’ and D. sp. ‘TW03′.
The first specimens were probably collected by Sunder Lal Hora in 1937 but misidentified as D. choprae.
In the description paper Kullander and Fang list the combination of characters that define the species as follows:
Different from all other species of Danio by colour pattern comprising 6-7 brown vertical bars anteriorly on side and two horizontal rows of small brown spots posteriorly, absence of D stripe, and absence of dark stripes on caudal fin; similar to D. kerri and D. erythromicron in possession of 12 circumpeduncular scale rows vs. 14 in D. dangila and 10 in other species of Danio; by possession of 6 branched dorsal fin rays, vs. 7-8 in other species of Danio.
In recent years it’s become commonplace to refer to the stripes on the body and fins of danionins as follows:
- P stripe: or “pigment stripe” is the central, dark, lateral stripe on the body which extends into the caudal-fin in some species. Stripes above it are numbered P+1, P+2, etc. and those beneath P-1, P-2, P-3.
- A stripe: the central stripe on the anal-fin; the proximal stripe (above it) is A+1 and the distal stripe (beneath) A-1.
- D stripe: The submarginal dorsal-fin stripe.
Following Fang (2003) Danio spp. are characterised by the presence of an A stripe on the anal-fin and two or more P stripes on the caudal, plus some internal characteristics such as enlarged nasal lamellae.
The genus has undergone some significant taxonomic reshuffling in recent years following the publication of a series of phylogenetic studies.
Older, molecular, phylogenies tended to agree that it represented a monophyletic group consisting of two major clades; the ‘Danio devario‘ group containing the larger, deeper-bodied species and the ‘D. rerio‘ clade comprising the smaller, slimmer fish.
The currently invalid genus name ‘Brachydanio‘ was often adopted for members of the latter group and is seen in much of the older aquarium literature.
However in 2003 Fang conducted a more detailed study based on morphological characters which included members of other related genera, and the results suggested for the first time that the genus Danio as previously considered represents a polyphyletic grouping, i.e., not all members derived from a single common ancestor.
The genus name Devario was suggested for the larger species with Danio being applied only to the smaller fish (with the exception of the type species, D. dangila which can grow to around 89 mm SL).
Recent molecular studies by Mayden et al. (2007) and Fang et al. (2009) have resulted in further changes.
Unfortunately while these works agree in some aspects they frequently contradict each other, notably in the usage of the subfamily names Rasborinae (Weber and de Baeufort, 1916) and Danioninae (Bleeker, 1863), the positioning of D. kyathit in relation to D. rerio and the degree of relatedness between Danio and Esomus species.
The species formerly known as Microrasbora erythromicron was found to be grouped within Danio in both sets of results.
At present SF follows the results of Fang et al. (2009), thus Danio is considered to be composed of three sub-clades, i.e., groupings of closely-related species.
The first comprises D. erythromicron, D. margaritatus, D. choprae and D. flagrans.
These exhibit unique body patterning consisting of vertical bars (D. erythromicron, D. choprae, D. flagrans) or light spots (D. margaritatus) and possess either very short barbels or none at all, whereas all other Danio spp. have lateral or horizontal stripes on the body and relatively long barbels.
There’s a suggestion that D. erythromicron and D. margaritatus will be moved again in the future as the two share morphological and behavioural aspects that appear to set them apart from other danios.
The second clade contains the type species, D. dangila, separated on the basis of its larger size and the shape of the caudal-fin, which in adults is only slightly emarginate or even truncate in shape, a feature it shares only with Tinca tinca (the common tench) among other cyprinids.
The D. dangila group is also likely to contain D. meghayalensis and D. feegradei.
The remaining species, of which D. rerio is thought to be the most ancient, are included in the third sub-clade, and there is a possibility these three groups may eventually be separated into different genera.
- Kullander, S. O. and F. Fang, 2009 - Zootaxa 2164: 41-48
Danio aesculapii, a new species of danio from south-western Myanmar (Teleostei: Cyprinidae).
- Conway, K. W., W.-J. Chen and R. L. Mayden, 2008 - Zootaxa 1686: 1-28
The 'Celestial Pearl danio' is a miniature Danio (s.s) (Ostariophysi: Cyprinidae): evidence from morphology and molecules.
- Fang, F., 2003 - Copeia 2003(4): 714-728
Phylogenetic Analysis of the Asian Cyprinid Genus Danio (Teleostei, Cyprinidae).
- Fang, F., M. Norén, T. Y. Liao, M. Källersjö and S. O. Kullander, 2009 - Zoologica Scripta 38(1): 1-20
Molecular phylogenetic interrelationships of the south Asian cyprinid genera Danio, Devario and Microrasbora (Teleostei, Cyprinidae, Danioninae).
- Mayden, R. L., K. L. Tang, K. W. Conway, J. Freyhof, S. Chamberlain, M. Haskins, L. Schneider, M. Sudkamp, R. M. Wood, M. Agnew, A. Bufalino, Z. Sulaiman, M. Miya, K. Saitoh, S. He, 2007 - Journal of Experimental Zoology, Molecular Development and Evolution 308B: 642–654
Phylogenetic relationships of Danio within the order Cypriniformes: a framework for comparative and evolutionary studies of a model species.