Osphronemidae

Diversity

The Belontiidae family, commonly known as gouramies, is composed of approximately 12 genera and 46 species, and is the largest and most diverse family in the Anabantoidei suborder. Gouramies are restricted to fresh water and are capable of inhabiting stagnant, low-oxygen areas due to the existence of an air-breathing organ called the labyrinthine (in Physical Description below). In addition, the Belontiidae family contains some of the most popular fish in the aquaria trade. One species, Betta splendens ( Siamese fighting fish ), has been in cultivation for over 100 years and captive individuals scarcely resemble the wild variety (see Economic Importance for Humans). Due to their pugnacious behavior, many gouramies have been used in behavioral studies as well (see Behavior).

Geographic Range

All members of the Belontiidae family inhabit freshwater and are indigenous to Africa and Southern Asia. They can be found in Pakistan, India, China, Korea to the Malay archipelago, Indonesia and Borneo. However, due to their popularity in the aquarium trade and ease of transport, belontiids are frequently shipped far beyond their natural range. Several species that now live in the Philippines and United States originally escaped from the aquarium trade (Lever 1996 from Berra 2001 pg. 480, 487).

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• palearctic palearctic
  • native native
• oriental oriental
  • introduced introduced
  • native native
• ethiopian ethiopian
  • native native

Habitat

Gouramies are uniquely adapted to the stagnant waters of tropical areas. They inhabit swift streams, the backwaters of large rivers, brackish lagoons, and potholes. They are most common in stagnant areas with dense aquatic or overhanging vegetation. With the ability to breathe air directly from the atmosphere, gouramies are able survive in marginal to anoxic waters.

• Habitat Regions
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

• Other Habitat Features
• urban urban
• suburban suburban
• agricultural agricultural
• riparian riparian

Systematic and Taxonomic History

Liem (1963) established three subfamilies, representing the major evolutionary lines of the Belontiidae family: Belontiinae (combtail gouramies), with one genus and two species, Magropodinae (Siamese fighting fishes, paradisefishes), with seven genera and approximately 32 species, and Trighogastrinae (gouramies), with four genera and about 13 species.

Gouramies are characterized by a distinct physical adaptation to stagnant waters, which is the labyrinthine organ. In this organ, located above the gill chamber, intricate, vascularized tissue stores air and allows gouramies to gulp air directly from the atmosphere. Additionally, gouramies have a long body cavity, allowing the swimbladder to extend into the tail.

Physical Description

Most gouramies are small (10 cm or less) and have elongate and cylindrical bodies. Others are deep-bodied and compressed. Gouramies have rounded tails and the anal fin base is much longer than the dorsal fin base in most species. In some gouramies, the first ray on the pelvic fin is elongated and is used as a tactile (touch-sensing) organ. After extensive breeding in captivity, the color and fin form have changed considerably in some gouramies. Sexual dimorphism has been reported for some members of this family.

One of two distinct physical features is the labyrinthine organ located above the gill chamber, which allows gouramies to breathe atmospheric air by capturing air bubbles from the surface water and holding them in the labyrinthine organ until they are expelled through the gill covers. “This unique organ is formed of highly vascularized, convoluted tissue, supported by an enlarged dorsal element of the gill arches” (Johnson, G.D. and A.C. Gill 1998). The bubbles taken in by gouramies are also important in hearing. Air bubbles are stored adjacent to membranous windows on either side of the cranium, which contains the inner ear. Slight vibrations picked up by the air bubble are easily transmitted to the inner ear through this membranous window. The second feature is a long body cavity that allows the swimbladder to extend into the caudal region. (Click here to see a fish diagram ).

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently
• sexes shaped differently

Development

After spawning, female gouramies release their eggs into the water. The eggs are gathered by the male and left in a nest near the surface until fry hatch.

Reproduction

Female gouramies use pheromones to attract males during spawning. The female deposits eggs into the water and they are collected by the male to deposit into the nest. The courting behavior of some gouramies is quite elaborate and spawning territory is maintained aggressively by the male.

Gouramies use air bubbles in constructing their nests. They create a nest of froth by expelling mucous-covered bubbles at the surface, often beneath leaves. After gathering the eggs, the male deposits them into the froth nest. The nest has a dual purpose: to keep the developing young close together for protection and to keep them near the water’s surface where it is well oxygenated.

• Key Reproductive Features
• iteroparous iteroparous
• gonochoric/gonochoristic/dioecious (sexes separate)
• fertilization fertilization
  • external external
• oviparous oviparous

Male gouramies guard the froth nest and maintain it by producing new bubbles as older ones break down. If juveniles try to leave the nest early, the male transports them back by carrying them in his mouth and spitting them back. In some genera ( Macropodus and Betta ) mouthbrooding has been reported as well.

• Parental Investment
• male parental care male parental care

Lifespan/Longevity

No specific information was found concerning lifespan or longevity for this family.

Behavior

Members of the Betta ( fighting gouramies ) genus have been used extensively in behavioral studies. Male fighting gouramies are extremely belligerent toward each other and they are often bred to fight, as with the fighting cocks. Talking gouramies use the air-breathing organ (labyrinthine) to produce a croaking sound, which is used in establishing territories and dominance hierarchies. Additionally, some gouramies use an elongated pelvic fin ray in exploratory behavior. The ray is directed forward to gather information about the fish’s surroundings or sense another individual as it approaches. Another interesting behavior of gouramies is the socially controlled synchronous air breathing. Groups of individuals in both Trichogaster and Colisa come to the surface and gulp air simultaneously in a temporary school to lessen the chance of predation while surfacing.

• Key Behaviors
• natatorial natatorial
• motile motile
• aestivation
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

Communication and Perception

Gouramies use several forms of communication: Talking gouramies use croaking to communicate, a modified pelvic fin ray is used as a tactile organ, and chemical signals are used during mating. The former two are described in more detail in the Behavior section and the latter is discussed in Reproduction.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• choruses choruses
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Members of the genera Belontia , Trichopsis , and Macropodus are omnivores, while Trichogaster is primarily herbivorous, and Betta and Colisa are carnivorous, feeding on shrimp, fish and insects in or out of water. Colisa uses the same technique as archerfishes to prey on insects just above the water. Bullets of water are created by compressing the gill covers and forming a groove using the tongue and palate. The fish “shoots” insects out of overhanging vegetation with these bullets and eats them when they hit the water.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • eats eggs
  • insectivore insectivore
  • eats non-insect arthropods
• herbivore herbivore
• omnivore omnivore

Predation

One impact of predation on gouramies is the frequency and location of atmospheric air breathing. In the presence of predatory birds or fish, some gouramies hide in mats of aquatic vegetation and surface less frequently. Other gouramies form temporary schools when they come up in order to deter predators. This “synchronous air breathing” is discussed above in Behavior.

Ecosystem Roles

Because gouramies are uniquely adapted to harsh conditions, such as hypoxia (water without oxygen) and desiccation, they are an important predator in the stagnant and intermittent waters of Asia. In addition, air breathing serves to protect gouramies from excessive water pollution so they play an important role in the biological control of insects in urban areas. This is discussed further in Economic Importance for Humans.

Economic Importance for Humans: Positive

Many gouramies are popular aquarium fishes because of their bright coloration, small size, and interesting reproductive behaviors. Members of the genus Betta , fighting fishes, have been used extensively in genetic and behavioral studies. Fighting fishes are also bred for entertainment and gambling in some countries. Finally, members of the genus Trichogaster have been cultured in ponds as food fish.

Experiments with Macropodus cupanus show that breathing air at the surface instead of consuming oxygen entirely from water lessens the absorption of toxic pollutants, which makes gouramies more effective in the biological control of insects. For example, mosquito larvae form the main diet of fish in the Betta genus. Each adult consumes approximately 10,000 to 15,000 mosquito larvae each year, significantly reducing the mosquito populations and mosquito-related illnesses.

• Positive Impacts
• pet trade pet trade
• food food
• research and education
• controls pest population

Economic Importance for Humans: Negative

No specific information was found concerning any negative impacts to humans.

Conservation Status

There are 11 species of concern within the genus Betta . Of these, three are listed as critically endangered, one is listed as endangered, and seven are listed as vulnerable. Additionally, Parosphromenus harveyi is listed as endangered, and Belontia signata and Malpulutta kretseri are listed as low risk depending on conservation efforts.

Additional Links

Encyclopedia of Life

Contributors

R. Jamil Jonna (author), Animal Diversity Web.

References

Berra, T. 2001. Freshwater Fish Distribution . San Diego, CA: Academic Press.

Froese, R., D. Pauly, D. Woodland. 2003. "Fish Base" (On-line). FishBase World Wide Web electronic publication. Accessed May 05, 2003 at http://www.fishbase.org/ .

Graham, J. 1997. Air-breathing fishes: evolution, diversity, and adaptation . San Diego, CA: Academic Press.

Helfman, G., B. Collete, D. Facey. 1997. The Diversity of Fishes . Malden, MA: Blackwell.

Johnson, G., A. Gill. 2002. Perches and Their Allies. Pp. 193 in Encyclopedia of Fishes – second edition . San Diego, CA: Academic Press.

McKinnon, J., N. Liley. 1987. Asymmetric species specificity in responses to female sexual pheromone by males of two species of Trichogaster (Pisces: Belontiidae). Can. Journal Zool. Dep. Zool., Univ. British Columbia, Vancouver, B.C. , 65 no. 5: 1129-1134.

Moyle, P., J. Cech. 2000. Fishes: An Introduction to Ichthyology – fourth edition . Upper Saddle River, NJ: Prentice-Hall.

Nelson, J. 1994. Fishes of the World – third edition . New York, NY: John Wiley and Sons.

The World Conservation Union, 2002. "IUCN 2002" (On-line). 2002 IUCN Red List of Threatened Species. Accessed July 08, 2003 at http://www.iucnredlist.org/ .

Wheeler, A. 1985. The World Encyclopedia of Fishes . London: Macdonald.