Siamese fighting fish: see betta.

Freshwater tropical fish (Betta splendens; family Belontiidae or Anabantidae), noted for the males' pugnacity toward one another. A native of Thailand, it was domesticated there for use in contests. Combat consists mainly of fin nipping and is accompanied by a display of extended gill covers, spread fins, and intensified colouring. This slender fish grows to about 2.5 in. (6.5 cm) long. In the wild it is predominantly greenish or brown, with red fins; domesticated, it has been bred with long, flowing fins and in a variety of colours, such as red, green, blue, and lavender.

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See Betta