Badis khwae KULLANDER & BRITZ, 2002

Classification

Order: Perciformes Family: Badidae

Distribution

Appears to be endemic to the Khwae Noi River basin in western Thailand, close to the border with Myanmar, where it can be found in small streams feeding the main river. Further south the Khwae Noi joins the Khwae Yai at the town of Kanchanaburi to form the Mae Klong. The localities furthest upriver lie close to the headwaters of the Ataran River which flows to the west through Myanmar.

Habitat

This species has been mostly collected from sluggish to moderately-flowing streams with turbid or clear water. These are usually shallow and surrounded by forest with trees and other vegetation growing into the riparian zone. The clear water habitats tend to have sandy substrates with patches of submersed vegetation but in both cases the fish are usually found in marginal areas or still pools. One population was found living in a reservoir with “very clear, cold water, and dense aquatic vegetation” (Kullander and Britz, 2002).

Maximum Standard Length

Around 55 – 60 mm for males, with females a little smaller.

Aquarium SizeTop ↑

A single pair or small group can be housed in a tank with a base measuring 60 ∗ 30 cm or more.

Maintenance

B. khwae will thrive in a well-structured set-up with a sand or gravel substrate plus plenty of water-worn rocks and pebbles to provide cover. Plant species that can be grown attached to the decor such as Microsorum, Taxiphyllum or Anubias species can be added if you wish but aren’t essential.

Driftwood twigs, branches, floating plants and leaf litter can also be used to lend a more natural feel while filtration and lighting need not be too strong. Some cave-like structures should be included to act as potential spawning sites; many breeders use half-coconut shells or up-turned clay plant pots with drilled holes or parts of the rim removed to allow the fish access.

Water Conditions

Temperature: Prefers slightly warmer and more constant temperatures than most badids within the range 22 – 26 °C.

pH: 6.5 – 7.5

Hardness: 36 – 215 ppm

Diet

Badis species are micropredators feeding on small aquatic crustaceans, worms, insect larvae and other zooplankton. They can be a little picky in the aquarium and may not accept dried foods although in some cases they will learn to take them over time. At any rate they should always be offered regular meals of small live or frozen fare such as Artemia, Daphnia or bloodworm in order to develop ideal colour and conditioning.

They’re somewhat shy, deliberate feeders (see ‘compatibility’) and it’s also important to note that all species develop issues with obesity and become more susceptible to disease when fed chironomid larvae (bloodworm) and/or Tubifex so these should be omitted from the diet.

Behaviour and CompatibilityTop ↑

Given its rarity in the hobby the emphasis should be on captive reproduction and we strongly recommend maintaining it alone. It is not a gregarious fish as such and rival males can be very aggressive towards one another, especially in smaller tanks. In these cases only a single pair or one male and several females should be purchased but in roomier surroundings a group can coexist provided there is space for each male to establish a territory and plenty of broken lines of sight. The clever placement of caves can help enormously in this respect; do not be tempted to cluster all the available spawning sites in one area of the tank, for example.

If you do intend to house it in a community tankmates must be chosen with care. It is slow-moving with a retiring nature and may be intimidated or outcompeted for food by larger/more boisterous tankmates. Peaceful, schooling cyprinids are likely to make good choices as are gouramis and other surface-dwelling species. Accommodating it in a biotope-style community of fish from the Khwae Noi is trickier although suitable species found in the region include Acanthocobitis zonalternans, Rasbora borapetensis, Pethia stoliczkana, and ‘Puntius‘ partipentazona.

Certainly do not combine it with similar-looking, territorial bottom dwellers such as dwarf cichlids unless the tank is very large and never house it with other Badis species as hybridisation might occur. Also note that freshwater shrimp of the popular genera Caridina and Neocaridina, and certainly their young, may be preyed upon.

Sexual Dimorphism

Males are slimmer, considerably more colourful than females when in spawning condition and possess a white edge to the dorsal fin.

Reproduction

Members of this genus are cave spawners that form temporary pair bonds and are not usually too difficult to breed provided the tank is arranged correctly (see ‘tank set-up’). Other species are best omitted if you want to raise good numbers of fry although in a mature, well-furnished community a few may survive to adulthood. Either a single pair or a group of adults can be used but if using multiple males be sure to provide each with a cave to defend. Water parameters should be within the values suggested above. Feed the fish with plenty of live and frozen foods and spawning should not present too many problems.

As they come into breeding condition rival males will become increasingly combative and begin to display courtship behaviour towards females entering their chosen territory. During this process they display some wonderful changes in patterning with the body intensifying in colour. The locking of mouths is also common; the male literally attempting to drag his partner into the cave. A receptive female will enter and spawning takes place with usually 30-100 eggs being laid.

Post-spawning the female is ejected and the male takes sole responsibility for the eggs and fry, defending the territory against intruders and fanning the brood with his fins. If you wish the other adult fish can be removed at this point although it is not absolutely necessary yet. The eggs usually hatch in 2-3 days but the fry do not become free swimming until they are 6-8 days old and may not leave the vicinity of the cave for another week or so after that.

From then the adults (parent male included) may begin to regard them as food and are best transferred to a separate tank. The young fish are quite sedentary for the first few days meaning microworm is the ideal initial food but once they are visibly swimming in the water column Artemia nauplii can be introduced to the diet.

NotesTop ↑

Like most badids this species is poorly documented and has yet to find significant popularity in the aquarium hobby, though given its restricted natural distribution it is unlikely ever to be available in large numbers. Within the genus it is most easily confused with B. ruber and B. siamensis but both these species have rows of dark spot-like markings on the flanks which are lacking in B. khwae. The three also differ in the shape of the dark marking on the caudal peduncle; in B. ruber it is relatively large and extends over the dorsal surface of the peduncle, in B. khwae it is noticeably smaller and in B. siamensis even further reduced or absent altogether in some cases.

Prior to 2002 the family Badidae included just five species of which only B. badis and, to a lesser extent, Badis dario (referred to as B. bengalensis by some sources) were popular in the aquarium hobby. However an extensive revision paper by Kullander and Britz released that year resulted in the erection of no less than ten new species along with the genus Dario into which B. dario was moved and designated the type species. Dario currently contains only three members which are most easily distinguished from Badis by their small adult size (usually less than 1″/2.5cm), predominantly red colouration, extended first few dorsal rays/pectoral fins in males, straight-edged (vs. rounded) caudal fin, lack of visible lateral line and less involved parental behaviour. Badis species now number fifteen with several new ones described recently and others awaiting description.

Some of them are not always easy to identify correctly. For example B. badis, B. chittagongis, B. ferrarisi, B. kanabos, B. khwae, B. ruber, B. siamensis and B. tuivaiei all exhibit a dark cleithral spot just above the base of the pectoral fin. However B. khwae, B. ruber and B. siamensis all have an additional blotch on the caudal peduncle, and B. badis can be told apart from B. kanabos by possessing a series of dark markings in the dorsal fin and/or at its base (vs. a single marking at the front of the fin) and only faint or indistinct vertical bars on the flanks (vs. a series of dark narrow bars). B. badis, B. chittagongis, B. dibruensis, B. tuivaiei and B. ferrarisi only differ in some morphological counts although the latter has very distinctive patterning, displaying a series of black vertical bars along the centre of the flanks.

Badids have historically been considered members of the families Nandidae or Pristolepididae and it was not until 1968 that Barlow proposed a separate grouping for them. They share some characteristics with anabantoids, nandids and channids; most notably for aquarists the typical spawning embrace in which the male wraps his body around that of the female. More recent studies have concluded that this procedure is an ancient trait inherited from a common ancestor to all these families.

In the 2002 revision paper all Badis, Dario and Nandus species were found to share a uniquely bifurcated (split) hemal spine on the penultimate vertebra and the authors hypothesise that this may represent evidence of the monophyly of this group. They further propose that the family Nandidae should be restricted to include only Nandus species with the other genera (Polycentrus, Monocirrhus, Afronandus and Polycentropsis) grouped together in Polycentridae. Following this system the Nandidae and Badidae are only separated by differences in morphology and egg structure although the phylogenetic relationships between them are yet to be fully-studied.

These recent studies have also shown that there exist several groups/clades within the genus, each containing species that are most closely-related to one another. The B. badis group is distinguished only by the cleithral spot and contains B. badis, B. chittagongis, B. dubruensis, B. ferrarisi, B. kanabos and B. tuivaiei. B. ruber, B. siamensis and B. khwae comprise the B. ruber group and are most easily identified by the combination of cleithral spot plus caudal peduncle blotch.

The B. assamensis group consists of B. assamensis and B. blosyrus with a unique body pattern of light and dark striping while the B. corycaeus group includes B. corycaeus and B. pyema which possess an ocellated marking at the base of the caudal fin along with a reduction in the number of sensory pores on the head.

There are two unique species which don’t fit into any of these groups; B. kyar is separated by its relatively elongated body shape, pattern of vertical barring and band-like caudal fin marking; B. juergenschmidti is similar to B. kyar in some respects but the first vertical body bar is straight (vs. curved), vertical bars 5, 6 and 7 are solid (vs. vertically split) and the dorsal and lower caudal fin lobe are edged in white in males (vs. no white patterning). In the phylogenetic study B. kyar was found to represent the sister group to either the B. ruber or B. badis/B. assamensis clades depending on the test performed and further studies are required to determine the exact placement of these two within the genus.

References

1. Kullander, S.O. and R. Britz. 2002 - Ichthyological Exploration of Freshwaters 13(4): 295-372
   Revision of the family Badidae (Teleostei: Perciformes), with description of a new genus and ten new species.
2. Geetakumari, K.H. and W. Vishwanath. 2010 - Journal of Threatened Taxa 2(1): 644-647
   Badis dilbruensis, a new species (Teleostei: Badidaae) from northeastern India.
3. Rüber, L., R. Britz, S. O. Kullander and R. Zardoya. 2004 - Molecular Phylogenetics and Evolution 32(3): 1010-1022
   Evolutionary and biogeographic patterns of the Badidae (Teleostei: Perciformes) inferred from mitochondrial and nuclear DNA sequence data.
4. Schindler, I. and H. Linke. 2010 - Vertebrate Zoology 60(3): 209-216
   Badis juergenschmidti - a new species of the Indo-Burmese fish family Badidae (Teleostei: Perciformes) from Myanmar.
5. Vishwanath, W. and K. Shanta. 2004 - Zoos' Print Journal 19(9): 1619-1621
   A new fish species of the Indo-Burmese genus Badis Bleeker (Teleostei: Perciformes) from Manipur, India.