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B. Macrostoma - General Information

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Introduction
Naming - "Big Mouth"
Labyrinth Fish (Anabantids)
Mouth Brooding
Further Information

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Introduction

The Betta Macrostoma is probably one of the most sought after of the Bettas. This is not only due to the beautiful and striking coloration of the males, but also because numbers in the wild have been steadily dwindling. The International Union for Conservation of Nature and Natural Recourses (IUCN) (http://www.iucnredlist.org/details/2782) has classified the Betta Macrostoma as Vulnerable (VU) and has further sub classified them as D2, in which the following applies:

“Population is characterized by an acute restriction in its area of occupancy (typically less than 100 km2) or in the number of locations (typically less than five). Such a taxon would thus be prone to the effects of human activities (or stochastic events whose impact is increased by human activities) within a very short period of time in an unforeseeable future, and is thus capable of becoming Critically Endangered or even Extinct in a very short period.”
(http://www.redlist.org/info/categories_criteria1994#categories)

betta macrostoma

Adding the scarcity issue, the Sultan of Brunei has decreed that the Macrostoma be a protected species and exporting from their native country of Brunei is illegal. However they occationally may be smuggled across the Temburong border to the Malaysian territory of Sarawak where export is legal. I have personally seen the "border" between Temburong and Sarawak and well.... for all intensive purposes... there really isn't one......

Because of this very precarious situation, this is not a fish for just any aquarist. I firmly believe that only experienced aquarists who are committed to the rehabilitation of the species should attempt to keep this species.

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Naming - "Big Mouth"

Big Mouth betta macrostoma

Yes… that’s exactly what its name means… “Big-Mouthed”. “Macrostoma” comes from 2 greek root words “Macro” (as in macro vs. micro) meaning “Big”, and “Stoma” (as in stomata) meaning “Mouth”. One would debate the different evolutionary purposes for the huge gaping mouth, but the main purpose is for mouth brooding (see Mouthbrooders below).

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Labyrinth Fish (Anabantids)

Taxonomically, B. Macrostoma belongs to the order PERCIFORMES, which includes other fishes such as Paradise fishes and Gouramis.

What makes anabantids unique is that they have an organ called the labyrinth (located in a cavity inside their head, above the roof of the mouth) that enables them to “breathe” air directly through the organ. This allows them to live in water where there is poor circulation or where there is low oxygen content. This is why people are able to house bettas in a little cup when most other fish would quickly die in the same situation.

(Disclaimer: I do not in any way support the idea of keeping bettas in a tiny cup! I’m sure you wouldn’t want to be stuck in a little cubicle all your life either! Even pet store bettas (splendens) should be kept in at least 1 gal of water each with frequent water changes.)

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Mouth Brooding

After successfully mating, the male incubate the eggs in his mouth for over a month. During this time the male does not eat. (Imagine going on a 30 day fast while holding a boiled egg in your mouth! Can’t be fun...). The fry emerge after hatching and brooding and vary in size from about ¼ inch to slightly under ½ inch. (About 0.5 – 1 cm). After which the male will (if all goes well) begin to start eating again. Upon emerging, the fry are independent and are large enough to ingest Baby Brine Shrimp (BBS) and microworms.

Here's a vid of one of my males holding eggs. Note the bulge under the "chin" area along the centerline of the fish. Once in a while he will "gulp". I'm not sure what this "gulp" is all about but i'm guessing it may be to move the eggs around or perhaps to create circulation around the eggs.

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Further Information

Displaying Male:
Male betta macrostoma

Pregnant Female:
Female betta macrostoma

Physical Appearance	Adult males are characterized by red/pink body coloration with dark blue/black markings around the mouth and gill plate (flanking a red spot), and the fringes of both the anal and tail fin. There is also a vertical black bar at the base of the tail fin and one large (or sometimes two) black spot on the middle of the trailing edge of the dorsal fin. Sometimes an iridescent blue /white fringe is present on the tail and dorsal trailing edges. Females and juveniles tend to be silver with very slight coloration. Main identifying feature is the double horizontal black lines running the entire length of the body and two black spots just under the lower jaw. There may be a black spot present where the two black lines terminate at the tail. Females may show some iridescent spotting and fringes on the dorsal and tail fin. In some cases, females may have very faint colorings that are similar to males, but nowhere near the intensity of the male.
Other Names	Peacock Mouthbrooder, Brunei Beauty
Size	Typically 9cm – 11cm (about 3.5 – 4.5 inches) Females typically smaller than males
Taxonomy	ANIMALIA > CHORDATA > ACTINOPTERYGII > PERCIFORMES > BELONTIIDAE
Distribution	Brunei Darussalam and surrounding North Eastern Borneo areas including Sarawak. See IBC page for further occurrences http://smp.ibcbettas.org/species/macrostoma.html
Diet	Omnivorous
Natural Habitat	Tropical rainforest. Tributaries of acidic freshwater rivers and pools.
Further References	Baensch, H.A. and R. Riehl, 1985 Aquarien atlas. Bd. 2. Melle: Mergus, Verlag für Natur- und Heimtierkunde, Germany. Baillie, J. and B. Groombridge (eds.), 1996 1996 IUCN red list of threatened animals. IUCN, Gland, Switzerland. 378 p. Hilton-Taylor, C., 2000 2000 IUCN red list of threatened species. IUCN, Gland, Switzerland and Cambridge, UK. xviii + 61 p. (with 1 CD-ROM) Kottelat, M., A.J. Whitten, S.N. Kartikasari and S. Wirjoatmodjo, 1993 Freshwater fishes of Western Indonesia and Sulawesi. Periplus Editions, Hong Kong. 221 p. Regan, C. T. 1909. The Asiatic fishes of the family Anabantidae. Proc. Zool. Soc. Lond. 767-78

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PLUG

On the urging of my friends, I started this website by putting together the original (and quite successful) B. Macrostoma pages. Since then it has grown by quite a bit. All this time I've provided all this info and lots of free e-mail support to anyone who needed help. The advertising on this page helps out a little to offset the cost of webhosting. So if you see something that you may be interested in listed within the Google Ads banners, then please don't hesitate to check it out.

I thank you all for your great interest in my articles and I hope to keep hearing from you guys, even if it is just dropping me a note to say hi. God Bless!

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