Anabantoidei

Suborder of fishes

The Anabantoidei are a suborder of anabantiform ray finned freshwater fish distinguished by their possession of a lung like labyrinth organ, which enables them to breathe air. The fish in the Anabantoidei suborder are known as anabantoids or labyrinth fish, or colloquially as gouramies. Some labyrinth fish are important food fish, and many others, such as the Siamese fighting fish and paradise fish, are popular as aquarium fish.

The labyrinth organs, a defining characteristic of fish in the suborder Anabantoidei, is a much folded suprabranchial accessory breathing organ. It is formed by vascularized expansion of the epibranchial bone of the first gill arch and used for respiration in air. This organ allows labyrinth fish to take in oxygen directly from the air, instead of taking it from the water in which they reside through use of gills. The labyrinth organ helps the inhaled oxygen to be absorbed into the bloodstream. As a result, labyrinth fish can survive for a short period of time out of water, as they can inhale the air around them, provided they stay moist. Labyrinth fish are not born with functional labyrinth organs. The development of the organ is gradual; most labyrinth fish initially breathe entirely with their gills, and develop the labyrinth organs as they grow older. In these species, males hold the eggs and fry in their mouths and release the free swimming fry about a week to 10 days after spawning.

Several labyrinth fish are important food sources in their native countries. The giant gourami, in particular, is highly valued as food fish, due to its size and tender flesh with few spines. This species is farmed extensively in Thailand and other Southeast Asian countries, and was intentionally introduced in tropical and subtropical waters around the world. During the colonial period, the French attempted to introduce this fish to many of their territories. Although an attempt to introduce a population in southern France failed, the giant gourami became well established in other French colonies. Other smaller labyrinth fish, such as the climbing perch, the kissing gourami, the snakeskin gourami, and other gouramies of the genus Trichogaster, are local food fish in Southeast Asia.

The Siamese fighting fish is perhaps the most popular labyrinth fish in the aquarium trade. The paradise fish also has a long aquarium history and was one of the first aquarium fish introduced to the West. Many species of gouramies, particular the three spot gourami and the dwarf gourami, are commercially bred for the trade, and several color morphs are commonly available. Because of their capability to use atmospheric oxygen, these fish generally are not so dependent on a form of aeration in their tanks, as they can rise to the surface of the water and take a breath, or breathing apparatus. Many of the labyrinth fish are peaceful and do well in most community tanks. However, individual males, especially the Siamese fighting fish and paradise fish, are territorial towards each other. Male Siamese fighting fish cannot be kept together under any circumstances, as they have been bred for aggression and will fight to the death. In many breeding pairs, the male and female cannot be kept together for long periods of time. Males may perceive males of other species as competition if they have long and bright fins and attack them, as well. For other species of anabantoids, a large aquarium with only one male per tank is ideal to prevent aggression.