English: Swamp eels.
Genera: 15; 99 species; 3 families.
Region: tropical America, tropical Africa, southeastern and eastern Asia, East Indies, Australia.
Use: as food, sometimes are kept in ponds or rice fields; rarely seen in home aquaria.
Ray-finned fishes, eel-like; premaxillae are present as distinct bones, nonprotrusible; lack a swim bladder.
Size: 20 to 150 cm.
Gills: poorly developed, their openings are usually single, small, confluent across the breast, and restricted to the lower half of the body; Oxygen is absorbed through the membranes of the throat or intestine.
Fins: spiny rays.; dorsal and anal fins are low, continuous around the tail tip, numerous, sharp spines; pelvic fins are absent; scales are either absent or very small; belly thorns.
Food: benthic invertebrates, larvae, fishes.
Habitat: fresh water, swamps, pools, caves, sluggish fresh and brackish waters; associated with leaf litter and mats of fine tree roots along the banks; capable of overland excursions, some can live out of water for extended periods of time; some species are burrowers; 4 species are found exclusively in caves.
Reproduction: some are sexually dimorphic; adult males grow a head hump; males are larger than females; they lay about 40 spherical eggs per clutch; eggs measure between 1 to 2 mm, with a pair of long filaments for adhesion to the substrate; reproduction takes place during the wet season; short-lived species that matures during the first year, with few individuals surviving to the second breeding season.
No synbrachiform fossil is known. Mastacembeloidei were removed from the Perciformes. Synbranchiformes are considered to be part of a monophyletic group called Smegmamorpha, also containing Mugilimorpha, Atherinomorpha, Gasterosteiformes, and Elassomatidae. Synbranchiformes are close to Anabantiformes, Carangiformes, Istiophoriformes and Pleuronectiformes, forming a sister clade to the Ovalentaria.
• Synbranchidae: 4 genera; 17 species; Mexico, Central and South America, West Africa (Liberia), Asia, Hawaii, and the Indo-Australian Archipelago.
Suborder Mastacembeloidei, or Opisthomi.
• Chaudhuriidae: genera and 5 species; Africa and through Syria to Maritime Southeast Asia, China, and Korea.
• Mastacembelidae: 3 genera; ± 26 species; northeastern India through Thailand to Korea, Malaysia, Borneo.