Sawbwa resplendens

Cyprindae

Endemic to the isolated mountain lake of Inle and surrounding watershed in Shan State, eastern Myanmar. The lake lies in a karstic valley almost 900m above sea level in the Shan Plateau region and is home to many endemic animals including nine species of fish and numerous gastropods.

The water in Lake Inle is clear, shallow (2-3 metres deep in most places) and has a very fertile, loamy substrate. It is famous for its stilted villages and local fishermen who have the ability to row their boats using only one leg. These tribes have also constructed floating gardens from aquatic vegetation and bamboo poles where they grow fruit, vegetables and flowers. The gardens are designed to rise and fall with the water level and have come to form the habitats of many fish which take shelter among the tangle of roots and plant stems at their base. From images we've seen submerged aquatic plants also grow densely and include Ceratophyllum and Elodea-like species. Sawbwa resplendens has also been collected around the margins of the lake where grass and reed-like plants grow thickly, in open, clear water among dense submerged vegetation and from pools and slower-flowing sections of streams within its extended basin.

Around 1"/2.5cm.

Males of this species are quite combative among themselves (see 'compatibility') so a group will require a tank measuring at least 24" x 12" x 12"/60cm x 30cm x 30cm/56 litres.

Best kept in a densely-planted tank and is an excellent choice for the carefully-aquascaped set-up. The addition of some floating plants to diffuse the light entering the tank also seems to be appreciated and adds a more natural feel. Filtration does not need to be particularly strong as it mostly hails from sluggish waters and may struggle if there is a fast current in the tank. Do not add this fish to a biologically immature tank as it can be susceptible to swings in water chemistry.

Temperatures in Lake Inle have been recorded to vary between 68 - 75°F/20 - 24°C.

Will tolerate slightly acidic conditions but a value of 7.0 - 8.0 is preferable.

Best kept in slightly harder water of 12 - 20°H.

Likely to feed on small invertebrates, algae and other zooplankton in nature. In the aquarium it will accept dried foods of a suitable size but should not be fed these exclusively. Daily meals of small live and frozen fare such as Daphnia, Artemia and suchlike will result in the best colouration and encourage the fish to come into breeding condition. Newly-imported specimens are often in poor condition and can be difficult to acclimatise to aquarium life. Small live foods are therefore recommended as an initial diet, with dry and frozen products being introduced as the fish become settled.

Very peaceful towards other species but is not an ideal community fish due to its small size and aggressive interactions between rival males. It will do best when maintained alone or with active, similarly-sized tankmates that enjoy comparable water conditions. A community based around species from Lake Inle would make an interesting project with suitable species available in the trade including Danio erythromicron , Devario auropurpurea, D. jayarami, Parambassis lala and Yunnanilus brevis.

Although it is gregarious by nature it is a shoaling rather than schooling species which develops a distinct pecking order. Males tend to be engaged in a continual battle for dominance, particularly when maintained in small numbers or in the presence of few females. The best way to minimise this behaviour is to purchase more females than males; a ratio of 4:1 or more is ideal. Unfortunately females can be hard to find in aquatic shops because exporters often prefer to ship only the more marketable males. At the very least try to purchase it in sexed pairs or use a larger tank arranged in such a way that many broken lines of sight are provided.

Males are much the more colourful fish possessing red tips to the snout and caudal fin plus a blue sheen on the flanks which is visible only when the fish is lit in a particular way. Females are much plainer with a uniformly olive/pale brownish colouration and appear noticeably rounder in the belly when in spawning condition.

Like many small cyprinids this species is an egg-scattering, continuous spawner that exhibits zero parental care. That is to say when in good condition and in the presence of both males and females relatively small numbers of eggs will be laid daily. In a well-furnished, mature aquarium it is therefore possible that small numbers of fry may start to appear without human intervention.

However if you want to increase the yield a slightly more controlled approach is required. The adult group can still be conditioned together but one or more small, say 16" x 8" x 8"/40cm x 20cm x 20cm/16.8 litre, containers should also be set up. Water chemistry parameters ought to be within the values suggested above, the most important factor being that they remain stable. Decor can be very simple; a couple of good-sized clumps Anubias, Echinodorus will give the fish somewhere to deposit their eggs. These should be positioned in such a way that they reach the water surface as the fish show a preference for depositing the eggs on the underside of the uppermost leaves. Floating mopsFiltration is not absolutely necessary although you may wish to include a small air-powered sponge filter bubbling away gently.

One or two pairs of well-conditioned adult fish should then be introduced to each container. It is wise to make the transfer slowly in order to avoid excessive levels of stress but if conditions are to their liking they should begin to spawn almost immediately. While this species will eat its eggs it appears not to actively hunt for them as is the case with many small Puntius and other related species. Once spawning has commenced it should continue on a daily basis.

The pair(s) can be left in situ for a couple of days then removed as the first eggs should hatch by the second or third day after the initial spawning. The tiny young will survive on their yolk sacs for another 3-5 days after which they will require microscopic food for the initial period. German aquarist Michael Schlüter reported that they are tricky to raise if fed Paramecium as a first food because they grow slowly and it may be a month until they are large enough to take Artemia nauplii/microworm etc. However when offered rotifers (wheel animalcules) their growth rate improved significantly and Artemia was accepted after only eight days. It's best to wait a week or two before starting to perform small water changes in order to avoid unduly shocking the young fish as they are also sensitive to changes in water chemistry.

Sawbwa resplendens may be seen on sale under several trade names including 'Asian rummynose', 'rummynose Rasbora' and 'naked Microrasbora'. These can give the false impression that it is related to members of the genera Rasbora and Microrasbora but phylogenetic studies have shown to be more closely-affiliated with Puntius and other barbs. The genus is currently monotypic and is likely to remain that way.

The small adult size evolved via a process known as miniaturisation characterised by sexually mature adults with a significantly reduced size of less than 20mm SL. Among bony fishes cyprinids are one of the few groups in which this phenomenon occurs repeatedly with all Barboides, Danionella, Microdevario, Microrasbora, Horadandia, Boraras, Paedocypris, Sawbwa and Sundadanio species representing miniaturised taxa along with a few members of Danio, Laubuca and Rasbora. All show a preference for still or slow-moving waters, often in nutrient-poor habitats such as forest peat swamps.

The anatomical structure of miniaturised cyprinids can vary greatly; there are two principle 'groupings' with some species possessing intermediate features to some degree. The first contains those fishes which though small are essentially proportionally dwarfed versions of their larger relatives e.g. Barboides, Microdevario, Microrasbora, Horadandia, Boraras, Sawbwa, Sundadanio, Danio, Laubuca and Rasbora.

The other includes those in which anatomical development stops at a point where adult still resemble a larval form of their larger ancestor i.e. Danionella and Paedocypris. The latter are usually referred to as 'developmentally truncated' or 'paedomorphic' and are thought to have evolved via a process known as 'progenetic paedomorphosis' i.e. paedomorphosis brought about by accelerated maturation. They typically exhibit a simplified skeletal structure along with species-specific morphological peculiarities such as the tooth-like projections in male Danionella dracula . Britz et al. (2009) consider that developmental truncation may have facilitated the development of such novelties "by freeing large parts of the skeleton from developmental constraints, dissociating developmentally linked pathways and creating a greater potential for more dramatic changes".

Literature cited

1. 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).
2. Liao, T. Y., Kullander, S. O. and F. Fang. 2009 - Zoologica Scripta Early View (Articles online in advance of print).
   Phylogenetic analysis of the genus Rasbora (Teleostei: Cyprinidae).
3. Rüber, L. , M. Kottelat, H. H. Tan, P. K. L. Ng and R. Britz. 2007 - BMC Evol. Biol. London. 7: [1-10].
   Evolution of miniaturization and the phylogenetic position of Paedocypris, comprising the world's smallest vertebrate.