Lucifuga subterraneus, from Eigenmann (1904).

Belongs within: Ophidiiformes.

The live-bearing brotulas
Published 17 December 2012
Black brotula Stygnobrotula latebricola, photographed by Thomas W. Doeppner.

The subject of today’s post is the Bythitidae, a family of mostly marine fishes referred to as the live-bearing brotulas. Bythitids belong to the Ophidiiformes, a group of more or less elongate fishes with long soft dorsal and anal fins. They differ from most other ophidiiforms in that the males have an external intromittent organ and they are mostly live-bearers rather than egg-layers (though at least one species, Didymothallus criniceps, is potentially an egg-layer: Schwarzhans & Møller 2007). Bythitids do share these features with the deep-water Aphyonidae, which are however particularly elongate, lack scales and a swim bladder, and have loose translucent skin in contrast to the firm skin of bythitids (Nielsen et al. 1999).

Bahamian cave fish Lucifuga spelaeotes, photographed by Joe Dougherty.

Bythitids are often thought of as deep-water fishes, but there is also a reasonable diversity of them in shallower habitats such as coral reefs. The shallower-living species are mostly very cryptic in their habits and may be only rarely encountered; deeper-water species may occupy more open habitats or be found in association with hydrothermal vents. Some species of the genera Lucifuga and Ogilbia are found in freshwater caves in the Caribbean (Lucifuga species), the Yucatan (Ogilbia pearsei) and the Galapagos (O. galapagosensis); other species are found in marine caves such as the ‘blue holes’ of the Bahamas. New species of bythitid continue to be described at a reasonable rate of knots (over 100 species have been described in the last ten years alone). They vary in size from small (Microbrotula species are about four centimetres in length) to very large (Cataetyx laticeps reaches over 75 cmm; the Fishes of Australia website states that bythitids grow up to 2 m, but I haven’t been able to find which species this refers to).

Yellow cuskeel Dinematichthys iluocoeteoides, from here.

Because of their cryptic habits, the lifestyles of most bythitids remain poorly known. They are predators of invertebrates and other fish. The few identified larvae have been collected in the epipelagic zone (Nielsen et al. 1999) but bythitids are believed to have relatively low fecundity rates (presumably as only small numbers of embryos have been found in gravid females). Reef-dwelling species, as far as is known, have only small ranges, and many may be endangered by habitat degradation.

Systematics of Bythitidae
    |    |  i. s.: StygnobrotulaB96
    |    |         Oligopus robustus Smith & Radcliffe 1913N99a
    |    |         Bellottia armiger Smith & Radcliffe 1913N99a
    |    |         Bythites lepidogenys Smith & Radcliffe 1913N99a
    |    |         Hastatobythites arafurensis Machida 1997N99a
    |    |         Hephthocara crassiceps Smith & Radcliffe 1913N99a
    |    |         MicrobrotulaN99a
    |    |           |--M. andersoni Schwarzhans & Nielsen 2011JG19
    |    |           `--M. randalli Cohen & Wourms 1976N99a
    |    |         Pseudonus platycephalus (Smith & Radcliffe 1913)N99a
    |    |         Saccogaster tuberculata (Chan 1966)N99a
    |    |--Diplacanthopoma brunnea Smith & Radcliffe 1913ND13, N99a
    |    `--+--CataetyxND13
    |       |    |--C. laticeps Koefoed 1927LD09
    |       |    |--C. lepidogenysNE12
    |       |    `--C. rubirostrisT09
    |       `--AphyonidaeN99b
    |            |--Parasciadonus pauciradiatus Nielsen 1997N99b
    |            |--BarathronusND13
    |            |    |--B. diaphanus Brauer 1906N99b
    |            |    `--B. maculatusND13
    |            `--AphyonusN99b
    |                 |--A. bolini Nielsen 1974N99b
    |                 `--A. gelatinosus Günther 1878 [incl. A. gracilis Günther 1887]M58
         |--Brosmophycis marginataND13
         |    |--B. bleekeri Schwarzhans & Møller 2007MM14
         |    `--B. macrophthalmus Machida 1993N99a
         |--Brosmolus longicaudus Machida 1993N99a
         |--Brosmophyciops pautzkei Schultz 1960N99a
         |    |--D. alleni Schwarzhans, Møller & Nielsen 2005MM14
         |    |--D. beateae Schwarzhans, Møller & Nielsen 2005MM14
         |    |--D. jeffjohnsoni Schwarzhans, Møller & Nielsen 2005MM14
         |    |--D. longifilis Ogilby 1898N99a
         |    `--D. novaeguineae (Machida 1996)MM14
         |--Parabrosmolus novaeguinae Machida 1996N99a
         |--Dermatopsis Ogilby 1896N99a, TP86
         |    `--*D. macrodon Ogilby 1896O96
         |--Monothrix Ogilby 1897N99a, TP86
         |    |--M. mizolepis (Günther 1867)N99a
         |    `--M. polylepis Ogilby 1897TP86
         |--Ogilbia Jordan & Evermann in Evermann & Kendall 1898B96, TP86
         |    |--O. deroyi [=Caecogilbia deroyi]TP86
         |    |--O. galapagosensis (Poll & Leleup 1965) [=Caecogilbia galapagosensis]TP86
         |    `--O. pearsei (Hubbs 1938) [=Typhliasina pearsei]TP86
         |    |--D. iluocoeteoides Bleeker 1855MM14
         |    |--D. megasoma Machida 1994N99a
         |    |--D. randalli Machida 1994N99a
         |    |--D. trilobatus Møller & Schwarzhans 2008MM14
         |    `--D. ventralisO96
         `--Lucifuga Poey 1858B96, TP86
              |--L. (Lucifuga) subterraneus Poey 1858TP86
              `--L. (Stygicola Gill 1863)TP86
                   |--L. (S.) dentatus Poey 1858TP86
                   |--L. (S.) simile Nalbant 1981TP86
                   `--L. (S.) spelaeotes Cohen & Robins 1970TP86
Bythitidae incertae sedis:
  Dipulus Waite 1905TP86
    `--D. caecus Waite 1905TP86
  Dinematichthyinorum crepidatus (Voigt 1926)P93
    |--A. piger (Alcock 1890)MM14
    `--A. riukiuensis (Aoyagi 1954)MM14
    |--D. criniceps Schwarzhans & Møller 2007MM14
    `--D. mizolepis (Günther 1867)MM14
  Eusurculus pistillum Schwarzhans & Møller 2007MM14
  Paradiancistrus christmasensis Schwarzhans & Møller 2011JG19

*Type species of generic name indicated


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

[JG19] James, D. J., P. T. Green, W. F. Humphreys & J. C. Z. Woinarski. 2019. Endemic species of Christmas Island, Indian Ocean. Records of the Western Australian Museum 34 (2): 55–114.

[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.

[MM14] Moore, G. I., S. M. Morrison, J. B. Hutchins, G. R. Allen & A. Sampey. 2014. Kimberley marine biota. Historical data: fishes. Records of the Western Australian Museum Supplement 84: 161–206.

[M58] Munro, I. S. R. 1958. The fishes of the New Guinea region: a check-list of the fishes of New Guinea incorporating records of species collected by the Fisheries Survey Vessel “Fairwind” during the years 1948 to 1950. Papua and New Guinea Agricultural Journal 10 (4): 97–369 (reprinted: 1958. Territory of Papua and New Guinea Fisheries Bulletin no. 1).

[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.

[N99a] Nielsen, J. G. 1999a. Bythitidae. Brotulas. In: Carpenter, K. E., & V. H. Niem (eds) The Living Marine Resources of the Western Central Pacific vol. 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae) pp. 1983–1984. FAO: Rome.

[N99b] Nielsen, J. G. 1999b. Aphyonidae. Aphyonids. In: Carpenter, K. E., & V. H. Niem (eds) The Living Marine Resources of the Western Central Pacific vol. 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae) pp. 1985. FAO: Rome.

Nielsen, J. G., D. M. Cohen, D. F. Markle & C. R. Robins. 1999. FAO species catalogue. Volume 18. Ophidiiform fishes of the world. An annotated and illustrated catalogue of pearl-fishes, cusk-eels, brotulas and other ophidiiform fishes known to date. FAO Fisheries Synopsis 125 (18): i–xi + 1–178.

[O96] Ogilby, J. D. 1896. Descriptions of two new genera and species of Australian fishes. Proceedings of the Linnean Society of New South Wales 21 (2): 136–142.

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

Schwarzhans, W., & P. R. Møller. 2007. Review of the Dinematichthyini (Teleostei: Bythitidae) of the Indo-west Pacific. Part III. Beaglichthys, Brosmolus, Monothrix and eight new genera with description of 20 new species. The Beagle, Records of the Museums and Art Galleries of the Northern Territory 23: 29–110.

[T09] Thacker, C. E. 2009. Phylogeny of Gobioidei and placement within Acanthomorpha, with a new classification and investigation of diversification and character evolution. Copeia 2009 (1): 93–104.

[TP86] Thinès, G., & G. Proudlove. 1986. Pisces. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 709–733. E. J. Brill/Dr W. Backhuys: Leiden.

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