Siamese fighting fish, Betta splendens, are small (about 7.5 cm long) fish in the gourami family (Osphronemidae) native to slow moving and stagnant, overgrown waters in Thailand, Viet Nam, Cambodia and Laos. Characteristic of the suborder Anabantoidei to which they belong, Betta splendens have an accessory breathing organ called the labyrinth organ that allows them to survive in waters with low oxygen content, by breathing air from the surface. These fish have been introduced to Brazil, Columbia, Indonesian and Malaysia, Singapore, the Philippines, Canada, the Dominican Republic and the USA and populations are thought to be established in many of these places. Now one of the most common species in the world-wide aquarium trade, domestication of Betta splendens began in Thailand in the 1800s, where these aggressively territorial fish were bred for competitive fighting. When agitated, wild Siamese fighting fish turn bright colors, and over years of captivity, strains have been bred to take on these colors permanently, as well as varieties with different fin and scale morphologies. In the wild, B. splendens are omnivores, and eat frequently, generally from the surface of the water, such as insects that have fallen in. They also eat algae. Like many gouramis, Siamese fighting fish are bubble breeders, and the males build bubble nests at the surface of the water. After intense courtship displays, the male wraps himself around the female in a nuptial embrace during which he fertilizes eggs released by the female. He then gathers up the eggs in his mouth as they sink and blows them into the nest. This nuptial egg release repeats until the female has no more eggs. The male then tends the eggs until they hatch about 36 hours later. Siamese fighting fish can survive periods in the dry season when water is scarce by aestivating in moist mud.
(Froese Pauly 2010. Betta splendens in FishBase. Retrieved March 6, 2012 from Froese Pauly 2010; Sturgeon 2001; Wikipedia 2012)
Their mating is a fascinating moment when the male, involving the female in a sort of embrace bridal force extrusion of eggs, which are then fertilized by the male, then this fund rescues and relocates the bubble nest that he built to house creates. After fertilization, it is the male who will take care of the offspring, remaking the nest and aerating the fertilized eggs until the birth of the fry.