The fish commonly known as the Betta is a staple in the aquarium trade, instantly recognizable for its aggressive behavior and dramatically flowing fins. This popular title, which earned the species the moniker “Siamese Fighting Fish,” represents a widespread misperception of its true biological diversity. The brilliant colors and territorial nature seen in pet stores have made this single fish an international icon, but it is only one member of a vast genus.
The Wide World of the Genus Betta
The number of species within the genus Betta is far greater than generally assumed, with over 76 scientifically recognized species and more being discovered regularly. This genus belongs to the family Osphronemidae, which is more broadly known as the Gourami family. These small, freshwater fish are native exclusively to Southeast Asia, inhabiting a range of environments across countries like Thailand, Malaysia, and Indonesia.
All members of the genus possess a specialized respiratory organ called the labyrinth, an adaptation that allows them to breathe atmospheric air. This unique biological feature enables them to survive in low-oxygen habitats, such as stagnant pools, rice paddies, and slow-moving streams, which would be lethal to most other fish.
The Familiar Face: Betta splendens
The single species that dominates the global pet trade is the Siamese Fighting Fish, Betta splendens. This fish is by far the most commercially significant member of the genus, largely due to centuries of selective breeding. Domesticated varieties have been line-bred to display exaggerated finnage, such as the full, flowing tails of the halfmoon or crowntail types, alongside a spectrum of intense colors that are rarely found in the wild.
Historically, B. splendens originated in Thailand and surrounding regions, where it was domesticated at least a thousand years ago. Early breeding efforts focused on aggression for organized gambling matches, which cemented its reputation as a “fighting fish.” In contrast to the elaborate domestic strains, wild B. splendens are generally smaller, possess shorter, more streamlined fins, and exhibit much duller, more natural coloration.
Classifying the Wild Bettas
The classification of wild Betta species is based on their distinct reproductive strategies, which divide the genus into two primary groups. The first group, which includes B. splendens, consists of bubble nesters. In this strategy, the male builds a nest of mucus-coated air bubbles at the water’s surface to house the fertilized eggs. The second, and more numerous, group comprises the mouthbrooders, where the male incubates the eggs entirely within his mouth for weeks until they hatch.
Mouthbrooding species, like those in the picta complex, are found in moving water habitats where a surface bubble nest would be unstable. These fish exhibit a more subdued, spotted or barred pattern and are usually smaller than their domesticated cousins.
Other Bubble Nesters
Species from the coccina complex, like Betta coccina, are bubble nesters known for their deep wine-red color. They require highly acidic, blackwater habitats common in peat swamp forests.