Devario laoensis

Devario: appears to be derived from a local vernacular name for the type species of the genus Cyprinus (now Devario) devario Hamilton, 1822.

laoensis: named for Lao People's Democratic Republic, more commonly referred to simply as Laos.

Type locality is 'Ban Nam Khueng' which lies in northwestern Laos and it's since been recorded from various localities within the upper Mekong watershed in Laos and Thailand (Chiang Rai and possibly Chiang Mai provinces).

Rainboth (1996) reported it to occur in the Salween River which borders western Thailand for a stretch but no other records from that drainage exist as far as we know.

This species' habitats are situated at relatively high altitude and receive a great deal of rainfall between the months of May and October.

It's likely to be restricted to hill streams and small rivers with substrates of gravel, variably-sized rocks and some marginal or over-hanging vegetation, while water flow is almost certainly variable depending on time of year.

In the River Nam Mae Lao, Chiang Rai province, northern Thailand D. laoensis was collected alongside Danio roseus.

It's also been recorded downstream of the Kuang Si (also spelled Kuang Xi) Falls in Luang Prabang Province, northern Laos.

This series of multi-tiered, travertinous falls, cascades and pools flows over a forested limestone cliff and the water is tinted a bright blue/green colour due to reflection of light from the high levels of calcium carbonate it contains.

The loach Schistura sertata was collected at the same locality.

A further collection locality was a small stream in Phôngsali Province, northern Laos located within the Nam Ou river watershed.

There it occurred sympatrically with Acheilognathus deignani, Cyprinus rubrofuscus, Mystacoleucus greenwayi, Pseudorasbora parva, and Barbodes semifasciolatus.

A tank with a base measuring 90 ∗ 30 cm36 ∗ 12 in or equivalent should be the minimum considered.

No information regarding captive care exists but presumably it won't prove difficult to keep in a well-maintained set-up as with related species.

It's likely to thrive in an environment resembling a flowing stream or river with a substrate of variably-sized, water-worn rocks, sand, fine gravel and perhaps some small boulders.

This can be further furnished with driftwood roots or branches, and while the majority of aquatic plants will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis or Anubias spp. can be grown attached to the décor.

Since it naturally occurs in pristine habitats it's likely intolerant to accumulation of organic pollutants and requires more-or-less spotless water in order to thrive.

Though very fast flow is unnecessary it should also prefer a relatively high proportion of dissolved oxygen and moderate water movement.

Weekly water changes of 30-50% volume should be considered routine, and the tank must have a very tightly-fitting cover as all Devario spp. are accomplished jumpers.

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 best colouration and conditioning.

Probably not an aggressive fish but may upset slow-moving or timid tankmates with its constant activity and vigorous feeding behaviour so is most appropriate for larger aquaria containing robust, similarly-sized fishes.

There are plenty of suitable choices including many cyprinids, loaches, cichlids, catfish and characins, although as always when selecting a compatible community of fish proper research is essential.

It's a schooling species by nature and ideally should be kept in a group of at least 8-10 specimens which will not only make the fish less nervous but will result in a more effective, natural looking display.

Any aggression will also be contained as the fish concentrate on maintaining their hierarchical position within the group, and males tend to display better colours in the presence of rivals.

Sexually mature females should be rounder-bellied, less colourful and a little larger than males.

When in breeding condition the lower half of the body is suffused with bright orange in dominant male specimens.

This species is more-or-less unheard of in the hobby at time of writing, though a handful specimens were imported to Singapore in the late 2000s.

It has a complete lateral line, well-developed infraorbital process, 8-9 branched dorsal-fin rays, 12-14 branched anal-fin rays and two rows of pharyngeal teeth.

It can be further distinguished from other species in the genus by colour pattern consisting of a dark, horizontal P stripe originating around mid-body, where it's relatively faint, this becoming thicker and darker in the posterior portion of the body and terminating at the base of the caudal-fin.

Among congeners it's most similar to D. chrysotaeniatus but that species lacks the infraorbital process, has three rows of pharyngeal teeth and the P stripe extends to the end of the caudal-fin rays.

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) Devario spp. are characterised by: possession of a P stripe extending onto the median caudal-fin rays; a short maxillary barbel (absent in some species); absence of the A stripe (a less distinct, relatively wide stripe is present in some species, e.g., D. acrostomus, D. annandalei, D. xyrops); a short, wide premaxillary process (cleft in the upper jaw) with a tiny apophysis (bony tubercule) touching the kinethmoid bone; infraorbital 5 not or slightly reduced.

The current genus name has only been in general use since 2003 prior to which members were considered to belong to the genus Danio.

Older, molecular, phylogenies tended to agree that the latter represented a monophyletic group consisting of two major clades; the 'Danio devario' grouping containing the larger, deeper-bodied species and the 'D. rerio' assemblage comprising the smaller, slimmer fish.

However in 2003 Fang 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, although following Kottelat (2013) the latter should be used only for the type species, Danio dangila, with most former members placed within the revalidated genera Brachydanio and Celestichthys.

These results have largely been supported by subsequent phylogenetic analyses (e.g. Mayden et al., 2007), although Devario has still undergone a little reshuffling, particularly following Fang et al. (2009) and Kottelat (2013).

In the former study the two species previously comprising the genus Inlecypris were brought into synonymy with Devario and three species formerly included in Microrasbora were moved into the new genus Microdevario based on possession of shared synapomorphies with Devario. The existence of a monophyletic clade consisting of the genera Devario, Chela, Laubuca, Microdevario and Microrasbora was also hypothesised, a theory upheld in the more recent study by Tang et al. (2010). The genus Betadevario (Pramod et al., 2010)[8] is also nested within this grouping and is sister to Devario and Microrasbora.

Kottelat (2013) revalidated the genus Inlecypris whilst noting that phylogenetic evidence suggests the existence of two genetic lineages within Devario. The first contains the species with prominent lateral stripes, which leaves the remaining members (D. apogon and D. chrysotaeniatus) of uncertain taxonomic placement. In addition, a number of the striped species share a colour pattern comprising a midlateral stripe on the posterior half of the body with a few bars in the anterior portion and golden patches between them. These may eventually be placed in a separate genus for which the name Parabarilius is available.