Betta rubra PERUGIA, 1893

Etymology

rubra: from the Latin ruber, meaning ‘red’.

Classification

Order: Perciformes Family: Osphronemidae

Distribution

Known only from northwestern Sumatra, Indonesia with definitive records existing from the Singkil area in Aceh province and around Sibolga in North Sumatra (Sumatera Utara) province.

Type locality is given by Perugia as ‘Lago Toba, Siboga’, with the latter an alternative or misspelling of ‘Sibolga’, although it’s not thought to inhabit the lake itself which lies at an altitude of around 900 m AMSL.

Other former localities for B. rubra are currently considered to refer to the closely-related B. dennisyongi and it’s unclear if the two occur together naturally in some locations due to human interference (Tan, 2013).

All rivers in northwestern Sumatra drain into the Indian Ocean and the region is hydrogeographically isolated from the remainder of the island by the Barisan mountain range, resulting in it being considered a distinct ichthyofaunal province due to the high proportion of endemic species occurring there.

Much of this area has been beset by violence for many years due to an ongoing struggle between the Gerakan Aceh Merdeka (better known as the Free Sumatra Movement in the West) and the Indonesian Government resulting in B. rubra being known only from the type specimens for around 100 years.

Following a peace agreement in 2005 the area seems to have become safer as the species began to appear in the aquarium hobby during early 2007.

Habitat

Most recently collected from a highly-disturbed tract of former peat swamp forest which in 2009 had been cleared for possible planting of oil palms with much of the water drained via man-made ditches.

The fish were collected from a stagnant blackwater pool with a pH of 5.5 and no other fish species were present, while surrounding pools and a nearby river were not found to contain any specimens.

Maximum Standard Length

30 – 42 mm.

Aquarium SizeTop ↑

An  aquarium with base measurements of 45 ∗ 30 cm or equivalent is sufficient for a single pair, with something larger required for a group.

Maintenance

Can be maintained in a fully-decorated aquarium although many breeders prefer not to use a substrate for ease of maintenance.

Driftwood roots and branches can be used and placed such a way that a few shady spots are formed while clay plant pots or lengths of piping can also be included to provide further shelter.

The addition of dried leaf litter further emphasises the natural feel and as well as offering additional cover for the fish brings with it the growth of microbe colonies as decomposition occurs.

These can provide a valuable secondary food source for fry and the tannins and other chemicals released by the decaying leaves are also considered beneficial for fishes from blackwater environments.

There is no need to use natural peat, however, the collection of which is both unsustainable and environmentally-destructive.

Like others in the genus this species seems to do best under fairly dim lighting.

You could add aquatic plant species that can survive under such conditions such as Microsorum, Taxiphyllum or Cryptocoryne spp., and a few patches of floating vegetation would be useful as well.

This species should ideally be kept in acidic conditions with negligible carbonate hardness and very low general hardness so a reverse osmosis unit or other method of obtaining soft water may need to be employed, and this can be further acidified using phosphoric acid or similar if necessary.

As it naturally inhabits sluggish waters filtration should not be too strong, with an air-powered sponge filter set to turn over gently adequate.

Keep the tank well-covered and do not fill it to the top as like all Betta spp. it requires occasional access to the layer of humid air that will form above the water surface, and is an excellent jumper.

Water Conditions

Temperature: 22 – 27 °C

pH: 5.0 – 6.5

Hardness: 18 – 90 ppm

Diet

Likely to feed mostly on insects and other small invertebrates in nature.

Captive fish will normally accept dried products once they’re recognised as edible, but should be offered plenty of small live or frozen foods such as Daphnia, Artemia or bloodworm regularly to ensure development of optimal colour and condition.

Small insects such as newly-hatched crickets or Drosophila fruit flies are also suitable to use; it’s best to fill the stomachs of these by feeding them fish flakes or some kind of vegetable matter before offering them to the fish.

Take care not to overfeed as Betta spp. seem particularly prone to obesity.

Behaviour and CompatibilityTop ↑

Not recommended for the standard community set-up for reasons already touched upon.

It’s requirements and disposition mean it’s best kept alone or with very peaceful species since much bigger or more vigorous fishes are likely to intimidate and outcompete it.

Some small cyprinids and loaches that inhabit similar environments in nature are compatible, but be sure to research your choices before purchase.

Mixed reports exist as to whether it can be maintained in multiple pairs or harem-type groups comprising a single male alongside several females.

Some state that although some chasing and squabbling over territory occurs actual physical damage is rare, while others recommend keeping it in single pairs having observed sustained aggression towards conspecifics from the dominant individuals in a group.

Sexual Dimorphism

Males are more colourful and develop more-extended unpaired fins than females.

Reproduction

Paternal mouthbrooder. Ideally organise a separate tank for breeding purposes unless the fish are already being maintained alone, setting this up as suggested above.

This should have the tightest-fitting cover you can find (some breeders use clingfilm instead to ensure no gaps) as the fry need access to a layer of warm, humid air without which development of the labyrinth organ can be impaired.

Following a protracted courtship eggs and milt are released during an ’embrace’ typical of osphronemids in which the male wraps his body around that of the female, and several ‘dummy’ embraces may be required before spawning itself commences.

In contrast to the majority of mouthbrooding Betta spp. the eggs are not caught in the anal-fin of the male but that of the female as is typical in bubble-nesting congeners.

The male then collects the eggs directly in his mouth and the cycle is repeated until the female is spent of eggs, a process which can take some time.

A brooding male may swallow or release the eggs prematurely if stressed or inexperienced, so it’s preferable to leave the female in situ.

The incubation period is 10-17 days at the end of which the male will begin to release fully-formed, free-swimming fry.

At this point they can be removed or left to grow alongside the parents, with some reports suggesting they actually grow more quickly under such circumstances.

The fry are large enough to accept motile foods such as microworm and Artemia nauplii immediately, though it should be noted that there exist reports of young Betta developing health issues if fed excessive amounts of the latter.

Offer small amounts of different foods 2 -3 times per day for optimal growth rate, and don’t change too much water at once, with regular, small changes preferable to intermittent larger ones.

NotesTop ↑

This species is available in the aquarium hobby but is not traded in large numbers and may have been inadvertently hybridised with the similar-looking congener B. dennisyongi prior to the latter’s description in early 2013 since the two are typically exported mixed together.

It was previously included in the Betta foerschi group of closely-related species within the genus, but following its redescription in 2012 now lends its name to the B. rubra group.

It was first placed into its own species group by Witte and Schmidt (1992), primarily on the basis of a triangular marking that appears below the eyes of the fish, although Tan and Ng (2005a) suggested that this feature is insufficient to warrant the formation of a separate species group and placed it into the B. foerschi group on a tentative basis.

Schindler and van der Voort (2012) redescribed B. rubra and erected the B. rubra group but both were subsequently redefined by Tan (2013), the latter also describing B. dennisyongi in the same publication.

Following Tan (2013) members of the B. rubra group are defined by the following shared characters: no vertical bars on operculum; operculum pattern comprising a continuous or interrupted post-orbital stripe extending to the edge or almost to the edge of the opercle with its posterior portion enlarged to form a bar-like marking; broad suborbital stripe always present and covering 2-5 scale rows, forming a triangular marking; anal-fin with 2-4 spinous and 22–25 soft rays (total = 25–27); lateral scales 29–32; males and females both with pointed dorsal and anal fins, caudal-fin rounded with extended median rays; mature males with 4–8 broad black lateral bars; females and juveniles with longitudinal black lateral stripe ; found in lowland habitats of northwestern Sumatra; size up to 42 mm SL.

B. rubra can be told apart from B. dennisyongi, currently the only other member of the B. rubra group, by the following combination of characters: black postorbital stripe interrupted and extending from posterior of eye to mid-opercle, with a large bar-like marking on posterior half of opercle not extending to opercle edge (vs. a continuous stripe in B. dennisyongi), leaving a clear cream edge over entire opercle margin (vs. not entire opercle margin); less broad suborbital stripe below eye forming a triangular black mark (2–3 scale rows wide, vs. 4–5); more intense body colouration with smaller interspaces between the black body bars in males; more anal-fin rays (mode 27, vs. 25); fewer subdorsal scales (5–5½, vs. 6–7); fewer lateral scales (mode 30, vs. 31); fewer vertebrae (mode 29, vs. 30); shorter dorsal-fin base (11.0–13.4, vs. 13.0–18.4% SL); larger maximum size (42.1, vs. 35.4 mm SL).

The genus Betta is the most speciose within the family Osphronemidae with almost 70 recognised members and looks set to grow further with new ones continuing to be described on a regular basis since the turn of the century.

Betta species have successfully adapted to inhabit a variety of ecological niches from stagnant ditches to flowing hill streams including some extreme environments such as highly acidic peat swamp forests.

The referral of members to a number of putative groups containing closely-related species is now generally accepted but largely based on morphological and behavioural characters meaning molecular phylogenetic work may prove useful in more precisely determining relationships between these fishes.

A full list of the species groups as currently recognised can be found here.

Like others in the suborder Anabantoidei this species possesses an accessory breathing organ known as the labyrinth.

So-called due to its maze-like structure this organ allows the fish to breathe atmospheric air to a certain extent.

Comprising paired suprabranchial organs formed via expansion of the epibranchial (upper) section of the first gill arch and housed in a chamber above the gills, it contains many highly-vascularised, folded flaps of skin which function as a large respiratory surface.

Its structure varies in complexity between species, tending to be better-developed in those inhabiting harsher environments.

References

1. Perugia, A., 1893 - Annali del Museo Civico di Storia Naturale di Genova, Serie 2a v. 13: 241-247
   Di alcuni pesci raccolti in Sumatra dal Dott. Elio Modigliani.
2. Schindler, I. and J. Schmidt, 2006 - Zeitschrift für Fischkunde 8(1/2): 47-69
   Review of the mouthbrooding Betta (Teleostei, Osphronemidae) from Thailand, with descriptions of two new species.
3. Schindler, I. and S. van der Voort, 2012 - Bulletin of Fish Biology 13(1/2): 21-32
   Re-description of Betta rubra Perugia, 1893 (Teleostei: Osphronemidae), an enigmatic fighting fish from Sumatra.
4. Tan, H. H., 2013 - Raffles Bulletin of Zoology 61(1): 323-330
   The identity of Betta rubra (Teleostei: Osphronemidae) revisited, with description of a new species from Sumatra, Indonesia.
5. Tan, H. H. and P. K. L. Ng, 2005a - Raffles Bulletin of Zoology Supplement 13: 115-138
   The labyrinth fishes (Teleostei: Anabantoidei, Channoidei) of Sumatra, Indonesia.
6. Tan, H. H. and P. K. L. Ng, 2005b - Raffles Bulletin of Zoology Supplement 13: 43-99
   The fighting fishes (Teleostei: Osphronemidae: Genus Betta) of Singapore, Malaysia and Brunei.
7. Witte, K.-E. and J. Schmidt, 1992 - Ichthyological Exploration of Freshwaters 2(4): 305-330
   Betta brownorum, a new species of anabantoids (Teleostei: Belontiidae) from northwestern Borneo, with a key to the genus.