Classification and Conservation of a Rare Betta Species. Betta Macrostoma: The Jewel of Borneo

Betta macrostoma: The Jewel of Borneo

Introduction to Betta macrostoma

Betta macrostoma, a species that fascinates both aquarists and biologists, is a remarkable member of the Osphronemidae family within the Perciformes order. Known for its vibrant coloration and unique reproductive behavior, Betta macrostoma is also a species of significant conservation concern. This stunning fish is endemic to the island of Borneo, where it inhabits the pristine waters of rainforests that are increasingly threatened by human activities.

Distribution: A Species Endemic to Borneo

Betta macrostoma is found exclusively on the island of Borneo, with its distribution limited to Brunei Darussalam and the northern part of Sarawak in Malaysia. Within Brunei, this species inhabits several known locations along the Mendarem River and within the dense Labi rainforest, primarily in the Labi administrative region, which borders Sarawak to the south. In Sarawak, the species is restricted to the Baram district near the town of Marudi.

Interestingly, Betta macrostoma populations from different localities display variations in coloration and patterning, underscoring the importance of maintaining these groups separately in captivity to preserve their unique genetic traits.

Conservation Status: The Fight for Survival

Due to its highly limited range, Betta macrostoma has been classified as Vulnerable on the IUCN Red List of Threatened Species under criterion D2. This designation highlights the species’ acute restriction in its area of occupancy, indicating that it is at risk of becoming critically endangered or extinct in a short time if its habitat faces further threats.

To protect this vulnerable species, the Sultan of Brunei has implemented a ban on its export. However, many Betta macrostoma in the aquarium trade are believed to originate from Sarawak, where the species is not protected by law. The legality of these exports from Brunei remains unclear, with some reports suggesting that the ban might apply only to wild-caught specimens, leaving room for the legal export of captive-bred fish. Unfortunately, there are also concerns about the future of the Sarawak populations, as their habitat is under threat from potential conversion into oil palm plantations.

Natural Habitat: The Rainforest Pools of Borneo

In the wild, Betta macrostoma has been collected from still, shaded pools located near the tops of rainforest waterfalls in both Brunei and Sarawak. These pools are typically characterized by substrates composed of gravel and rocks of various sizes, often covered with leaf litter from the surrounding vegetation. In some areas of Brunei, the substrate is described as more clayey, further illustrating the diverse microhabitats this species occupies.

Aquarium Maintenance: Mimicking Nature

Betta macrostoma can thrive in a well-decorated aquarium that closely replicates its natural environment. While some breeders prefer a bare-bottom setup for ease of cleaning, a more naturalistic approach involves the use of driftwood roots and branches arranged to create shaded areas. If driftwood is not available, dried and bark-free beech or oak branches can be used as alternatives. Additional shelter can be provided by including clay plant pots or lengths of piping.

Incorporating dried leaf litter, such as beech, oak, or Ketapang almond leaves, can enhance the tank's natural feel while providing additional cover for the fish. As the leaves decompose, they foster the growth of microbial colonies that offer a valuable secondary food source for fry. Moreover, the tannins and other compounds released during decomposition can improve water quality by mimicking the soft, acidic conditions of the species’ native habitat.

Betta macrostoma, like other species in its genus, thrives under dim lighting. Aquatic plants that can tolerate low light, such as Microsorum pteropus (Java fern), Taxiphyllum barbieri (Java moss), or Cryptocoryne species, are ideal for such setups. Adding patches of floating vegetation can help diffuse the light entering the aquarium, further simulating the dappled sunlight of a rainforest pool.

Regarding filtration, a gentle flow is preferred, with an air-powered sponge filter being an adequate choice. It’s crucial to keep the aquarium well-covered, as Betta macrostoma, like all Betta species, requires access to the humid air layer above the water surface to breathe properly. Additionally, they are known to be excellent jumpers, so a secure lid is essential to prevent escapes.

Water Parameters: Ensuring a Healthy Environment

To replicate Betta macrostoma’s natural environment, maintain water temperatures between 20°C and 25°C. The pH should remain within a range of 4.0 to 6.0, closely reflecting the soft, acidic conditions typical of its native rainforest pools.

Behavior and Compatibility: A Fish with Specific Needs

Betta macrostoma is not suited for a traditional community aquarium. Its specific environmental requirements and relatively peaceful nature make it best suited for a species-only setup or with very docile tankmates. More active or larger fish are likely to outcompete or intimidate Betta macrostoma, making it difficult for this species to thrive. Small, peaceful cyprinids or loaches that share similar environmental preferences can be considered compatible tankmates.

When it comes to social interactions, Betta macrostoma is best kept as a pair. However, it may be necessary to temporarily house a group to allow the fish to select their partners naturally. Males are known for their territorial aggression, often engaging in persistent fights when kept together. Even females may engage in squabbles until a dominance hierarchy is established.

Sexual Dimorphism: Identifying Males and Females

In Betta macrostoma, sexual dimorphism is pronounced. Males are typically larger, more vibrantly colored, and have broader heads and more elongated fins compared to females. These differences become more apparent as the fish mature, making it relatively easy to distinguish between the sexes.

Reproduction: The Art of Paternal Mouthbrooding

Betta macrostoma is a paternal mouthbrooder, with the male taking on the responsibility of incubating the eggs in his mouth until they hatch. To facilitate successful breeding, it’s advisable to set up a separate breeding tank, unless the pair is already housed alone. The breeding tank should be prepared according to the same guidelines for general maintenance, with particular attention given to ensuring a tight-fitting cover. Some breeders use clingfilm to eliminate any gaps, as the fry require access to a warm, humid air layer for proper development of their labyrinth organ.

When breeding Betta macrostoma, it is often best to allow a compatible pair to form naturally from a group. Randomly selected pairs may not always coexist peacefully, with the risk of aggression sometimes leading to the death of one partner. Once a pair is established, they usually coexist peacefully, provided they have adequate space.

Courtship is a prolonged process in this species. The vividly colored male initiates the interaction by approaching the female with his mouth agape and fins fully extended. The female typically positions herself so that the male is facing one of her flanks and may respond by flaring her fins and gaping in return. Spawning involves the typical “embrace” seen in osphronemids, where the male wraps his body around the female’s. This process may include several practice runs before actual spawning occurs.

During spawning, the male and female release eggs and milt in small batches. Both parents collect the fertilized eggs, but the male ultimately assumes the responsibility of mouthbrooding. The spawning process is repeated until the female has released all her eggs, a cycle that can take some time.

After spawning, it is crucial to minimize disturbances to the male. Males of this species are notorious for consuming their broods if stressed, with the likelihood of this occurring increasing as the incubation period progresses. To avoid disturbing the male, some breeders choose to leave the female in the tank. However, in smaller tanks, the female may need to be removed if she harasses the male or poses a threat to the fry.

The incubation period can vary significantly, with reports suggesting a range of 14 to 35 days. Once the fry are ready to be released, the male will begin to free them from his mouth. The fry are large enough at birth (approximately 5mm) to immediately consume live foods such as microworms and Artemia nauplii. For optimal growth, feed the fry small amounts of a variety of foods multiple times a day, but be cautious not to overfeed, as this species’ young are prone to developing intestinal issues.

Daily water changes of 5% to 10% of the tank volume are recommended to maintain water quality and prevent the accumulation of organic waste.

Conclusion: The Fragile Future of Betta macrostoma

Betta macrostoma is not only a species of aesthetic beauty but also of ecological significance. Its limited range and specific habitat requirements make it highly susceptible to environmental changes, particularly those driven by human activities. Conservation efforts must focus on preserving its natural habitat while promoting responsible breeding practices in captivity. As the forests of Borneo face increasing pressure, the survival of Betta macrostoma hangs in the balance, serving as a reminder of the delicate interplay between species and their ecosystems.

FAQs

What is Betta macrostoma?
Betta macrostoma is a species of Betta fish endemic to Borneo, known for its vibrant colors and unique reproductive behavior.

Where is Betta macrostoma found?
It is found exclusively in Brunei Darussalam and the northern part of Sarawak, Malaysia, in Borneo.

Why is Betta macrostoma considered vulnerable?
Betta macrostoma is listed as Vulnerable due to its restricted distribution and the threat of habitat loss, particularly from deforestation and agricultural development.

How can Betta macrostoma be cared for in captivity?
Betta macrostoma requires a well-maintained aquarium that mimics its natural environment, with soft, acidic water, dim lighting, and plenty of shelter.

Is Betta macrostoma a good choice for a community tank?
Due to its specific environmental needs and peaceful nature, Betta macrostoma is not recommended for a typical community tank and does best in a species-specific setup.

What is the breeding behavior of Betta macrostoma?
Betta macrostoma is a paternal mouthbrooder, with the male incubating the eggs in his mouth until they hatch. Successful breeding requires careful management and a peaceful environment.

References:

Exploring Betta Macrostoma Habitat in Brunei Darussalam

Regan, C. T., 1910 – Proceedings of the Zoological Society of London 1909(4) : 767-787

The Asiatic fishes of the family Anabantidae.
Tan, H. H. and P. K. L. Ng, 2005 – Raffles Bulletin of Zoology Supplement (13): 43-99

The fighting fishes (Teleostei: Osphronemidae: Genus Betta) of Singapore, Malaysia and Brunei.