Cyclothone microdon, from Kissling (1911).

Belongs within: Stomiatii.

The Gonostomatidae, bristlemouths, are small, slender-bodied oceanic fishes that are abundant in the mesopelagic and bathypelagic zones (Harold 1999).

Ubiquitous fish
Published 15 June 2007

At this point, I would like you to consider the Gonostomatidae, commonly known as bristlemouths. If the names are not ringing any immediate bells, then shame on you. Bristlemouths are possibly the most abundant vertebrates in the world (or so every source I’ve looked at [e.g. Bond (1996), Craddock & Hartel (2002)] says, though I’ve yet to find an actual figure). They are mesopelagic or bathypelagic fish (or ‘feesh’ as they say here in Western Australia), mostly quite small (according to Craddock & Hartel [2002], some species mature at less than 20 mm) and, like oh so many mesopelagic fish, not overly attractive. Gonostomatidae have an elongate body form with relatively big mouths (according to Wikipedia, the name ‘bristlemouth’ refers to the evenly-sized bristle-like teeth, a description that appears more true for some genera [Cycothone] than others [Gonostoma]). There are one or more rows of photophores along the length of the body. Some like Triplophos have multiple rows almost covering the animal whereas others such as Bonapartia have only a single row on the lower edge of the body plus a few scattered over the head (Harold, 1999). They are micropredators of small crustaceans and such (Craddock & Hartel, 2002).

Elongated bristlemouth Gonostoma elongatum (above) and Bonapartia pedaliota, from Goode & Bean (1896).

The Gonostomatidae belong to the order Stomiiformes, sometimes known as dragonfishes (some of the other members of the order reach a reasonable size, and you may have seen illustrations of them before—they’re the elongate deep-sea fish with the mouths full of enormous teeth). As an aside, the intro for Stomiiformes in Collette & Klein-MacPhee (2002) refers to it as a ‘very large group’. Only vertebrate workers would consider a few hundred species a ‘very large group’. The Gonostomatidae itself includes seven or eight genera in two subfamilies, the Gonostomatinae (Gonostoma, Sigmops, Margrethia, Bonapartia, Cyclothone) and Diplophinae (Diplophos, Manducus, Triplophos).

Unlike many mesopelagic fish, bristlemouths do not appear to engage in daily vertical migrations (McClain et al., 2001). Their small size and deep-water habitat mean that, despite their abundance, they are rarely seen except by researchers.

Systematics of Gonostomatidae

Characters (from Harold 1999): Body moderately elongate (to about 36 cm standard length); head and body compressed. Relative size of head highly variable. Eye very small to moderately large. Nostrils high on snout, prominent in dorsal view. Mouth large, angle of jaw well posterior to eye. Premaxillary teeth usually uniserial; dentary teeth biserial near symphysis. Chin barbel absent. Gill openings very wide. Branchiostegals 12 to 16 (4 to 6 on posterior ceratohyal). Gill rakers well developed. Pseudobranchiae usually absent. Dorsal fin usually at or slightly posterior to middle of body. Anal-fin base moderately to very long. Dorsal fin with 10 to 20 rays; anal fin with 16 to 68 rays; caudal fin forked; pectoral-fin rays 8 to 16; pelvic-fin rays 5 to 9. Dorsal adipose fin present or absent; ventral adipose fin absent. Scales deciduous. One or more rows of discrete photophores on body; BR 7–16; OA 0–77; IV 11–51; VAV 3–17; AC 12–51; isthmus photophores (IP) present or absent; posterior orbital photophore (ORB 2) absent. Parietals well developed; epiocciptals separated by supraoccipital. Usually four pectoral-fin radials.

<==Gonostomatidae [Gonostomidae]
    |  i. s.: Scopeloides glarisianus (Agassiz 1839)P93
    |--Diplophinae [Diplophidae]CH02
    |    |--Triplophos Brauer 1902H98, H99
    |    |    `--T. hemingi (McArdle 1901)H99
    |    `--+--Manducus Goode & Bean 1896H98, H99
    |       |    |--M. greyi Johnson 1970H99
    |       |    `--M. maderensisCH02
    |       `--Diplophos Günther 1873H98, H99
    |            |--D. australis Ozawa, Oda & Ida 1990H99
    |            |--D. orientalis Matsubara 1940H99
    |            |--D. pacificus Günther 1889H99
    |            |--D. rebainsiH98
    |            `--D. taenia Günther 1873H99
         |  i. s.: SigmopsCH02
         |           |--S. bathyphilumCH02
         |           `--S. elongatumCH02
         |--+--Bonapartia Goode & Bean 1896H98, H99
         |  |    `--B. pedaliotaCH02
         |  `--Margrethia Jespersen & Tåning 1919H98, H99
         |       |--M. obtusirostra Jespersen & Tåning 1919H99
         |       `--M. valentinaeH98
         `--Gonostoma Rafinesque 1810H98, H99
              |--G. atlanticum Norman 1930H98, H99
              |--G. denudatumH98
              `--+--G. elongatum Günther 1878H98, H99
                 `--+--G. ebelingi Grey 1960H98, H99
                    |--G. gracile Günther 1878H98, H99
                    `--+--G. longipinnis Mukhacheva 1972H98, H99
                       `--+--G. bathyphilum (Vaillant 1888)H98, H99
                          `--Cyclothone Goode & Bean 1883H98, H99
                               |--C. acclinidensH98
                               |--C. albaH98
                               |--C. atraria Gilbert 1905H99
                               |--C. braueri Jespersen & Tåning 1926H99
                               |--C. kobayashii Miya 1994H99
                               |--C. lividaH98
                               |--C. microdon Günther 1878H99
                               |--C. obscura Brauer 1902H99
                               |--C. pallida Brauer 1902H99
                               |--C. parapallida Badcock 1982H99
                               |--C. pseudopallida Mukhacheva 1964H99
                               `--C. signata Garman 1899H99

*Type species of generic name indicated


Bond, C. E. 1996. Biology of Fishes 2nd ed. Saunders College Publishing.

Collette, B. B., & G. Klein-MacPhee (eds.) 2002. Bigelow and Schroeder’s Fishes of the Gulf of Maine 3rd ed. Smithsonian Institution Press: Washington.

[CH02] Craddock, J. E., & K. E. Hartel. 2002. Bristlemouths. Family Gonostomatidae. In: Collette, B. B., & G. Klein-MacPhee (eds) Bigelow and Schroeder’s Fishes of the Gulf of Maine 3rd ed. pp. 181–184. Smithsonian Institute Press: Washington.

[H98] Harold, A. S. 1998. Phylogenetic relationships of the Gonostomatidae (Teleostei: Stomiiformes). Bulletin of Marine Science 62: 715–741.

[H99] Harold, A. S. 1999. Gonostomatidae. Bristlemouths. 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. 1896–1899. Food and Agriculture Organization of the United Nations: Rome.

McClain, C. R., M. F. Fougerolle, M. A. Rex & J. Welch. 2001. MOCNESS estimates of the size and abundance of a pelagic gonostomatid fish Cyclothone pallida off the Bahamas. Journal of the Marine Biology Association of the United Kingdom 81: 869–871.

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

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