Betta smaragdina, the wild progenitor of the Siamese Fighting Fish

Betta smaragdina, the "emerald" betta, is a member of the group of species from which human selections and hybridization have created Betta splendens, the Siamese Fighting Fish. B. smaragdina is found in northeast Thailand, at low elevations of the upper Mekong watershed and in the basin of its tributaries like the Mun, among the Khorat highlands and high plateaus of the rural Isaan region; the species is also found across the Mekong in neighboring Laos, where Maurice Kottelat found it and included it in his Fishes of Laos, 2001.  The collector Dietrich Schaller, who first introduced B. smaragdina to Germany (1970), even found a fish in the water-filled hoofprint of a water buffalo in a muddy rice field. Reports of it in the Chao Phraya, the river that passes through Bangkok and empties into the Gulf of Thailand instead of the South China Sea and drains a watershed separated from the Mekong watershed of B. smaragdina's home waters by ranges of mountains, must be of escaped captives.  
 

In the Isaan region of Thailand,  from March to September each year, when the rice fields are flooded and there is a hiatus in the agricultural cycle, the village farmers capture B. smaragdina in stagnant weed-choked pools and slow-flowing rice-field ditches and competitively  pit them against one another as pla kat, "fighting fish". The fish is simply scooped up in cupped hands; even professional betta breeders rarely net their fish, but ladle them out.
 
At the end of the fighting season, the fish are returned to the nearest convenient water; in the case of successful fighters, the owner returns him to a secret inaccessible place known to him only; the following year he will capture some of his progeny there, for on their own bettas never venture far from their home territory. These returns to waters sometimes quite distant from their native haunts and matings from common stock of very similar females, have blurred the genetics of "wild" stocks of Betta smaragdina. The fish in the photos,which I imported from Bangkok, should perhaps be called Betta cf smaragdina,  or Betta of smaragdina type.
 
The species, familiar to every Isaan farmer and child,  was not described to science until the German ichthyologist Wilhelm Ladiges formally described them in DATZ, in 1972.

Betta smaragdina has a smaller head and slimmer form than the short-finned B. splendens type that's bred for fighting. The iridescent blue-green centers of the male's body scales contrast with the deep coppery red of his fin rays and the ground color of his scales. So do his iridescent blue-green gill covers, with  brilliant red spots on thebranchiostegal membrane below them, which he can also open in head-on challenging confrontation, when he spreads and shivers his finnage and generally makes himself his largest and boldest. His fin membranes are pale blue between the deep maroon red of their rays. His ventral fins are red, with iridescent blue-white tips that make them stand out in the flaring displays. The smaller female's stress coloration, the condition in whuich she's usually photographed, is a light brown, with two darker lateral bands. Well-conditioned females will flare and circle one another aggressively; their branchiostagal rays have red spots in them as the male does; they flash these aggressively. Two females alone together in a 10-gallon tank will harass one another to exhaustion: with more territory, dense patches of Java moss and a few females to spread the aggression, you might have better luck than I. 
 
Spawning is in the familiar bubble nest constructed by the male.The female may not swell visibly with eggs, but her white genital papilla, just in front of her anal fin, will show that she's ready. She will have darkened, lost her stripes, and she'll be showing some blue-green iridescence along her flanks. The pair spawn high in the water directly under the bubble nest, not lower, near the substrate, like Betta unimaculata (according to Jörge Vierke's account of unimaculata). At each embrace under the bubble nest a single, quite large opaque white egg is expelled, which drifts slowly down until either fish takes it into its mouth and spits it into the bubble nest, coated with the same salivary secretion that makes the bubbles stick together. Seeing the new eggs like grains of rice among the bubbles. in my inexperience I thought at first the eggs were sterile, until two minute dots after a day or so showed me they'd "eyed up". My males aren't violent with their females after spawning, but  they chase off the female after spawning and care for the fry until they are free-swimming, and for weeks afterwards. In my densely planted 10 gallon tanks, with surfaces thick with duckweed and full of floating Water Sprite and large tangles of Java Moss, the female is securely out of sight, but I caught her in the act of swallowing a larval fry and swiftly found her a separate accomodation. 
 
Rival males flare at each other and circle warily, but actual combat is rare, I'm told, when the tank is both spacious enough, and too densely planted to offer distant views, and when there are both sufficient females and more than two males to offer constant distractions. I haven't tested this yet myself. The fishes are less shy in a densely planted aquarium with some floating plants than they'll be in a bare jar.
 
The only way I'd hope to raise some of these extermely tiny fry is in a well-aged plant nursery, thick with skeins of Java Moss, and full of plankton. After a week or so, they'll take microworms and from there on, raising them is without problems. Keep the tank well covered with a glass sheet, to keep ther air warm and moist.
 
Bloodlines of Betta splendens have been introduced into lines of B. smaragdina bred for the local bouts, and the resulting surplus hybrid fish are commonly released into local waters, blurring the three natural populations of B. smaragdina, whose mitochondrial DNA manifests greater divergence one from another than exists between other distinct species in the B. splendens group: they may represent valid cryptic species, researchers concluded in 2010.  My two males, sent from Thailand as B. smaragdina, are distinctly different, one whose maroon body color is more overlaid on the flanks with iridescent blue-green spangles. And my females don't show the tan body color with darker streaks of female Betta smaragdina posted on the Internet and illustrating the books: they have blue-green spangles on dark maroon body color, and maroon fins.
 
Generally speaking, Betta smaragdina is not available in the US market. 
 
Links. An account of Betta smaragdina in the Isaan region of Thailand is at Siamese CyberAquarium; there is a version at BettySplendens. The International Betta Congress site has a brief description of B. smaragdina, as well as articles by Gerald Griffin,"Care and spawning of Betta smaragdina" and  Yohan Fernando, "Spawning Betta smaragdina, the 'Emerald Betta'". Pages devoted to B. smaragdina are at AquaWorld  and SeriouslyFish 
 
Betta smaragdina at FishBase. Betta smaragdina at Wikipedia.