Striped snakehead Channa striata, copyright Vijay Anand Ismavel.

Belongs within: Acanthomorphata.
Contains: Synbranchidae, Mastacembeloidei.

Into the labyrinth
Published 29 April 2013
Climbing perch Anabas testudineus emerging from water, as illustrated by Richard Lydekker.

Amongst the unholy mess that is the Percomorpha, one group that has long been recognised is the labyrinth fishes of the Anabantoidei. The anabantoids are a group of freshwater fishes found in southern Asia and Africa (but not Madagascar) that get their vernacular name from their possession of a distinctive respiratory organ called the labyrinth. This organ, found in a cavity above the gills, is derived from part of the first gill arch; the bone has become expanded and much-folded, and is covered with a layer of respiratory epithelium. So long as the gills do not actually dry out, the labyrinth allows these fish to take in oxygen directly from the air, and they can survive in warm, low-oxygen waters. They can even survive for limited periods entirely out of water (a feature that has helped make some of the larger species popular food fish, due to the greater ease of keeping them fresh in a tropical environment). Recent phylogenetic studies (e.g. Li et al. 2009) have agreed in placing labyrinth fishes as related to a number of other freshwater Indo-Australian fishes, such as the snakeheads of the Channidae and the swamp eels of the Synbranchidae, many of which are also tolerant of air-breathing.

Kissing gouramis Helostoma temminckii, from Peter Bus.

Labyrinth fishes can be divided between three families (Rüber et al. 2006). One of these contains a single species, the kissing gourami Helostoma temminckii of south-east Asia. Kissing gouramis are primarily specialised filter feeders, though they may also graze on algae or insects. The vernacular name refers to their enlarged lips, making them look permanently puckered up. Kissing gouramis even ‘kiss’, pressing their smackers against one another, though this is regarded as an act not of affection but of aggression (kind of like a 1930s Hollywood melodrama) as the fish push against one another.

A rather unfortunate Cape kurper Sandelia capensis, photographed by Darryl Lampert.

The climbing perches of the Anabantidae include the south Asian Anabas and the African Ctenopominae. These short-bodied carnivores have serrated edges to their gill covers that the Asian species use to pull themselves over land when travelling between water bodies (imagine lying on your stomach and pulling yourself along with your chin). You can see video of some climbing perch Anabas testudineus emerging from water here.

Giant gourami Osphronemus goramy, photographed by E. Naus.

The most diverse subgroup of the Anabantoidei is the gouramis of the Osphronemidae, another south Asian group. The largest of the Osphronemidae, the giant gourami Osphronemus goramy, grows up to 70 cm, but most species are quite a bit smaller. A number of gourami species (as well as the kissing gourami) are popular aquarium fishes; the most popular by far is the Siamese fighting fish Betta splendens, males of which have been bred to exhibit much longer and more ornamental fins than found in the wild. The gouramis are generally omnivorous, with species varying in the extent to which they prefer plant or animal food. The most specialised carnivore of the Osphronemidae is the pikehead Luciocephalus pulcher, a small but elongate species that has been described as having the most protrusible mouth of any fish (and that, by the way, is no small claim). You can see the pikehead in action below:

The pikehead is so divergent from other labyrinth fishes that past authors have regarded it as its own family, possibly the sister taxon to all other anabantoids, or even questioned whether it was a labyrinth fish at all. However, as confirmed by Rüber et al. (2006), Luciocephalus is not only a true anabantoid but nested well within the Osphronemidae as sister to the chocolate gouramis of the genus Sphaerichthys. These and two other genera, Ctenops and Parasphaerichthys, form what is known as the ‘spiral egg’ clade, named after the presence of spiraling ridges on the egg leading to the micropyle, that have been suggested to act as guides for the sperm.

Siamese fighting fish Betta splendens mating below a bubble-nest, photographed by Stephen & John Downer.

The anabantoids are also known for the bubble-nests constructed by a number of species, in which the eggs are contained within a floating nest of bubbles that is guarded by the male parent (both parents in the Ceylonese combtail Belontia signata). Bubble-nesting has evolved at least twice among the anabantoids: once in the Osphronemidae, and once in the ctenopomine genus Microctenopoma (other anabantids and Helostoma are free spawners that do not construct nests or guard their eggs; the ctenopomine Sandelia capensis digs a nest in the bottom substrate) (Rüber et al. 2006). Though bubble-nesting is probably the ancestral behaviour for Osphronemidae, it has been modified in a number of sublineages. Osphronemus species build submerged nests from vegetation, while members of the ‘spiral egg’ clade (except Parasphaerichthys) and a number of Betta species are mouthbrooders. Usually the male broods the fry in these species, but the female is the brooder in a couple of Sphaerichthys species.

Systematics of Anabantomorphariae
| |--SynbranchidaeND13
| `--+--MastacembeloideiND13
| `--Indostomus [Indostomidae, Indostomoidei]ND13
| |--I. crocodilusND13
| `--I. paradoxus Prashad & Mukerji 1929LD09
`--Anabantiformes [Channoidei, Labyrinthoidei]B-RB13
|--Nandidae [Pristolepididae]ND13
| |--Pristolepis fasciataND13
| `--+--NandusND13
| | |--N. andrewiND13
| | `--N. nandusND13
| `--+--Dario darioND13
| `--Badis [Badidae]ND13
| |--B. badisB96
| `--B. pyemaND13
`--+--Channidae [Channiformes, Ophicephalidae, Ophicephaloidei]B96
| |--ParachannaB96
| |--Eochanna chorlakkiensis Roe 1991P93
| |--OphicephalusJR10
| | |--O. maculatusJR10
| | |--O. melanopterusJR10
| | |--O. melanosomusJR10
| | `--O. vagus Peters 1868JR10
| `--ChannaB96
| | i. s.: C. argusT90
| | C. maculataT90
| | C. marulius [=Ophicephalus marulius]PH72
| | C. orientalisPH72
| | C. punctatusPP07
| |--C. luciusND13
| `--+--C. melasomaND13
| `--C. striata (Bloch 1793)ND13, LD09 [=Ophicephalus striatusPH72]
| i. s.: Osphronemus [Osphronemidae]B96
| |--O. goramy Lacépède 1802P93
| |--O. olfaxO97
| `--O. trichopterusS09
| Luciocephalus [Luciocephalidae, Luciocephaloidei]B96
| `--L. pulcher (Gray 1832) [=Diplopterus pulcher]K55
|--+--Helostoma [Helostomatidae]ND13
| | `--H. temminckiiNE12
| `--+--Trichopodus pectoralisND13
| `--Belontiidae [Polyacanthidae]B96
| |--Betta splendensND13
| |--TrichopsisB96
| |--Trichogaster trichopterusB96
| |--MacropodusB96
| | |--M. chinensisT90
| | `--M. opercularis (Linnaeus 1758)KC-L22
| |--Polyacanthus cupanusO97
| `--Belontia hasselti (Cuvier 1831)KC-L22
`--+--Microctenopoma nanumND13
|--Anabas testudineus (Bloch 1792) [incl. Perca scandens Daldorff 1797, A. scandens]JR10
|--Sphaerichthys osphronemoides Canestrini 1860K55
|--Parosphromenus deissneriK55
| |--P. d. deissneriK55
| `--P. d. sumatranus Klausewuitz 1955K55
|--C. acutirostreSC07
|--C. ctenotisB50
|--C. kingsleyaeND13
|--C. multispinusB50
|--C. mureiG74
|--C. nanumB50
`--C. pellegriniAS09

*Type species of generic name indicated


[AS09] Alfaro, M. E., F. Santini, C. Brock, H. Alamillo, A. Dornburg, D. L. Rabosky, G. Carnevale & L. J. Harmon. 2009. Nine exceptional radiations plus high turnover explain species diversity in jawed vertebrates. Proceedings of the National Academy of Sciences of the USA 106 (32): 13410–13414.

[B-RB13] Betancur-R., R., R. E. Broughton, E. O. Wiley, K. Carpenter, A. López, C. Li, N. I. Holcroft, D. Arcila, M. Sanciangco, J. C. Cureton, II, F. Zhang, T. Buser, M. A. Campbell, J. A. Ballesteros, A. Roa-Varon, S. Willis, W. C. Borden, T. Rowley, P. C. Reneau, D. J. Hough, G. Lu, T. Grande, G. Arratia & G. Ortí. 2013. The tree of life and a new classification of bony fishes. PLoS Currents Tree of Life April 18 2013. doi: 10.1371/currents.tol.53ba26640df0ccaee75bb165c8c26288.

[B96] Bond, C. E. 1996. Biology of Fishes 2nd ed. Saunders College Publishing: Fort Worth.

[B50] Brooks, J. L. 1950. Speciation in ancient lakes (concluded). Quarterly Review of Biology 25: 131–176.

[G74] Greenwood, P. H. 1974. The cichlid fishes of Lake Vistoria, East Africa: the biology and evolution of a species flock. Bulletin of the British Museum (Natural History): Zoology Suppl. 6: 1–134.

[JR10] Jordan, D. S., & R. E. Richardson. 1910. Check-list of the species of fishes known from the Philippine archipelago. Bureau of Printing: Manila.

[K55] Klausewitz, W. 1955. See- und Süßwasserfische von Sumatra und Java. Senckenbergiana Biologica 36 (5-6): 309–323.

[KC-L22] Kmentová, N., A. J. Cruz-Laufer, A. Pariselle, K. Smeets, T. Artois & M. P. M. Vanhove. 2022. Dactylogyridae 2022: a meta-analysis of phylogenetic studies and generic diagnoses of parasitic flatworms using published genetic and morphological data. International Journal for Parasitology 52: 427–457.

[LD09] Li, B., A. Dettaï, C. Cruaud, A. Couloux, M. Desoutter-Meniger & G. Lecointre. 2009. RNF213, a new nuclear marker for acanthomorph phylogeny. Molecular Phylogenetics and Evolution 50: 345–363.

[ND13] Near, T. J., A. Dornburg, R. I. Eytan, B. P. Keck, W. L. Smith, K. L. Kuhn, J. A. Moore, S. A. Price, F. T. Burbrink, M. Friedman & P. C. Wainwright. 2013. Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes. Proceedings of the National Academy of Sciences of the USA 110 (31): 12738–12743.

[NE12] Near, T. J., R. I. Eytan, A. Dornburg, K. L. Kuhn, J. A. Moore, M. P. Davis, P. C. Wainwright, M. Friedman & W. L. Smith. 2012. Resolution of ray-finned fish phylogeny and timing of diversification. Proceedings of the National Academy of Sciences of the USA 109 (34): 13698–13703.

[O97] Ogilby, J. D. 1897. On some Australian Eleotrinae. Proceedings of the Linnean Society of New South Wales 21 (4): 725–757.

[PP07] Pandey, R. P., & P. M. Padhye. 2007. Studies on phytodiversity of Arid Machia Safari Park-Kailana in Jodhpur (Rajasthan). Bulletin of the Botanical Survey of India 49: 15–78.

[P93] Patterson, C. 1993. Osteichthyes: Teleostei. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 621–656. Chapman & Hall: London.

[PH72] Pillai, R. S., & S. J. S. Hattar. 1972. Rain of fish in Shillong, Meghalaya. Journal of the Bombay Natural History Society 69 (1): 202–204.

Rüber, L., R. Britz & R. Zardoya. 2006. Molecular phylogenetics and evolutionary diversification of labyrinth fishes (Perciformes: Anabantoidei). Systematic Biology 55 (3): 374–397.

[SC07] Smith, W. L., & M. T. Craig. 2007. Casting the percomorph net widely: the importance of broad taxonomic sampling in the search for the placement of serranid and percid fishes. Copeia 2007 (1): 35–55.

[S09] Stead, D. G. 1909. Notes and exhibits. Proceedings of the Linnean Society of New South Wales 33: 797.

[T90] Taguchi, S. 1990. Nihon no Sakana. Kogakukan: Tokyo.

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