Bristlemouths
Temporal range:
Elongated bristlemouth, Gonostoma elongatum (top) and Bonapartia pedaliota (bottom)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Stomiiformes
Suborder: Gonostomatoidei
Family: Gonostomatidae
Genera

Bonapartia
Cyclothone
Diplophos
Gonostoma
Manducus
Margrethia
Sigmops
Triplophos

The Gonostomatidae are a family of mesopelagic marine fish, commonly named bristlemouths, lightfishes, or anglemouths. It is a relatively small family, containing only eight known genera and 32 species. However, bristlemouths make up for their lack of diversity with relative abundance, numbering in the hundreds of trillions to quadrillions.[1] The genus Cyclothone (with 13 species) is thought to be one of the most abundant vertebrate genera in the world.

The fossil record of this family dates back to the Miocene epoch. Living bristlemouths were discovered by William Beebe in the early 1930s and described by L. S. Berg in 1958. The fish are mostly found in the Atlantic, Indian, and Pacific Oceans, although the species Cyclothone microdon may be found in Arctic waters. They have elongated bodies from 2 to 30 cm (0.79 to 11.81 in) in length.[2] They have a number of green or red light-producing photophores aligned along the undersides of their heads or bodies.[1] Their chief common name, bristlemouth, comes from their odd, equally sized, and bristle-like teeth. They are typically black in color which provides camouflage from predators in deep, dark waters. They mainly feed on zooplankton and small crustaceans due to their small size.[3]

Morphology

Bristlemouths are protandrous, therefore a male first hermaphrodite. They begin their lives as males and some of them switch to female. Male bristlemouths are smaller than females.[4]

Bristlemouths have large jaws that are capable of catching prey larger than themselves. The length of the S. glarisianus's (a species of Bristlemouth) lower jaw is equaled to 70% of the entire length of their head.[5] The lower jaw of the Bristlemouths is not functional in terms of masticating their prey. It is therefore hypothesized that they swallow their prey tail first.[5]

Bristlemouths are extremely small, measuring on average 75 mm. Bristlemouths have elongated bodies, small eyes, short snouts, large mouths, and large jaws. The position of the dorsal fin begins in line with the anal fin. The difference between bristlemouths species is found in the intensity of their pigmentation and photophore size. For the majority of the species, the morphology remains the same.[6]

Bristlemouths are mostly dark in pigmentation but at times can display translucently.[4] Bristlemouths contain a pineal organ which functions to detect slow changing ambient light. This allows the Bristlemouth to have control over its circadian clock and seasonal behavior.[7]

Due to the small size of the fish, they are easy prey to dragonfish and fangtooths.[4]

Taxonomy

Some classifications include the genera Pollichthys and Vinciguerria, but this article follows FishBase in placing them in the family Phosichthyidae.

Some classifications include species in the genus Zaphotias, but these are junior synonyms of the species Bonapartia pedaliota.

Genus Image Species Description
Bonapartia 1 There is only one described species in this genus. It grows to a length of 7.2 centimetres (2.8 in) SL.[8]
Cyclothone 13[9] Cyclothone is a genus of bioluminescent bristlemouths. They are typically about 3 inches long and found usually at depths exceeding 1000 feet.[10] This genus is thought to contain more individuals than any other vertebrate genus.
Diplophos 5 [11]
Gonostoma 3 [12]
Manducus 2 [13]
Margrethia 2 [14]
Sigmops 4 [15]
Triplophos 1 There is only one described species in this genus. It grows to a length of 36 centimetres (14 in) SL.[16]

Feeding habits

Bristlemouth specimen showing jaw length.

Brislemouths feed mostly on zooplankton and small crustaceans. Their diet is composed of a range from 92 to 98% of Crustacea.[3] A minor part of their diet is made up of opportunistic encounters with smaller fish. Brislemouths that consume fish prey are found in individuals ranging from 70 mm to 75 mm.[5] Bristlemouths do not have seasonal trends when it comes to their feeding habits.

Bristlemouths are diel vertical migrators, therefore migrating closer to the surface waters in the nighttime in order to find more food.[3] Out of the thirteen bristlemouth species, eight have been found near the surface therefore explaining their DVM behaviors.[17]

Bristlemouths are able to efficiently capture their prey due to their bioluminescent nature.[18]

Bioluminescence

Bristlemouths are light emitting fish. Bristlemouths rely on their bioluminescence for different outcomes. Some rely on it to find prey while others use it to avoid predation. However, the most common way that their bioluminescence is used is to signal between fish in the same way people "dance or wear bright colors at the nightclub."[18]

References

  1. 1 2 Broad, William J. (June 29, 2015). "An Ocean Mystery in the Trillions". The New York Times. Retrieved August 1, 2015.
  2. ↑ Fink, William L. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 121. ISBN 0-12-547665-5.
  3. 1 2 3 Lancraft, Thomas (November 10, 1988). "Aspects of the ecology of the mesopelagic fish Gonostoma elongatum(Gonostomatidae, Stomiiformes) in the eastern Gulf of Mexico" (PDF). Department of Marine Ecology, University of South Florida. 49: 27–40.
  4. 1 2 3 Broad, William J. (2015-06-29). "An Ocean Mystery in the Trillions (Published 2015)". The New York Times. ISSN 0362-4331. Retrieved 2020-10-22.
  5. 1 2 3 Přikryl, Tomáš; Prokofiev, Artém M.; Krzemiński, Wiesław (2012-07-01). "Feeding habits of the Oligocene bristlemouth fish Scopeloides glarisianus (Teleostei: Stomiiformes: Gonostomatidae)". Geobios. 45 (4): 377–386. doi:10.1016/j.geobios.2011.10.012. ISSN 0016-6995.
  6. ↑ Nazarkin, M. V. (2015-03-01). "Fossil bristlemouth Cyclothone mukhachevae sp. nov. (Stomiiformes: Gonostomatidae) from the Neogene of western Sakhalin, Russia". Paleontological Journal. 49 (2): 162–175. doi:10.1134/S0031030115020045. ISSN 1555-6174. S2CID 128915597.
  7. ↑ Bowmaker, J. K. (2004-06-15). "Pineal organs of deep-sea fish: photopigments and structure". Journal of Experimental Biology. 207 (14): 2379–2387. doi:10.1242/jeb.01033. ISSN 0022-0949. PMID 15184510.
  8. ↑ Froese, Rainer; Pauly, Daniel (eds.) (2012). "Bonapartia pedaliota" in FishBase. February 2012 version.
  9. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Cyclothone in FishBase. February 2012 version.
  10. ↑ Proujan, C. (1979). Secrets of the Sea (2nd ed.). London: Reader's Digest Association. p. 60. OCLC 30992870.
  11. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Diplophos in FishBase. February 2012 version.
  12. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Gonostoma in FishBase. February 2012 version.
  13. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Manducus in FishBase. February 2012 version.
  14. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Margrethia in FishBase. February 2012 version.
  15. ↑ Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Sigmops in FishBase. February 2012 version.
  16. ↑ Froese, Rainer; Pauly, Daniel (eds.) (2012). "Triplophos hemingi" in FishBase. February 2012 version.
  17. ↑ Gaither, Michelle R; Bowen, Brian W; Rocha, Luiz A; Briggs, John C (September 2016). "Fishes that rule the world: circumtropical distributions revisited". Fish and Fisheries. 17 (3): 664–679. doi:10.1111/faf.12136.
  18. 1 2 "The world's oceans have way more light producing fish than we imagined". ZME Science. 2016-06-09. Retrieved 2020-10-22.
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