Cyclothone

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Cyclothone
Cyclothone microdon1.jpg
Veiled anglemouth (C. microdon)
Cyclothone pallida.jpg
Tan bristlemouth (C. pallida)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Stomiiformes
Family: Gonostomatidae
Genus: Cyclothone
Goode & T. H. Bean, 1883

Cyclothone is a genus containing 13 extant species of bioluminescent fish, commonly known as 'bristlemouths' or 'bristlefishes' due to their shared characteristic of sharp, bristle-like teeth. These fishes typically grow to around 1-3 inches, though some can be larger. They are most commonly found in the mesopelagic zone of the ocean, mostly at depths of over 300 meters (1,000 feet), and many species have bioluminescence. [1]

Contents

Cyclothone is believed to be the most abundant fish genus on Earth, with estimates that there are up to a quadrillion individuals (1015, or one million billion in the short scale). [2] [3] Their abundance is so large that they are also believed to be the most abundant genus of vertebrate on earth. [4]

Distribution and habitat

Cyclothone are found mostly in the open ocean at tropical to temperate latitudes. [5] [6] Within the water column, they reside in the mesopelagic zone (also sometimes called the Ocean Twilight Zone). Cyclothone fishes are found in the aphotic zone and have limited access to light and light-dependent food sources. Some species of this genus, such as Cyclothone signata, are believed to migrate towards the surface, although they do not appear to do so in a diel vertical migration pattern. Other species, such as Cyclothone acclinadens, are believed to remain at depth for their entire lives. [7]

Life in the Deep

All species in the genus Cyclothone live in the midwater range of the deep sea, and are most commonly found in the mesopelagic zone at 300–1500 meters depth (roughly 1,000-5,000 feet). [7] The deep sea is an extreme habitat, and life in the deep ocean has specialized adaptations to survive. Light is virtually absent (<1%) in the deep sea, meaning that organisms living there cannot rely on using their eyes to catch prey, avoid predators, or find mates. The deep ocean is also very cold due to the lack of light and the fact that deep waters originate (downwell) in polar regions; below 200 meters, the average temperature of the ocean is 4 °C [39F]. [8] [9] Organisms in the deep sea are also subject to immense pressure, with pressure increasing by 1 atmosphere (equivalent to the pressure we feel on land at sea level) for approximately every 10 meters depth. At 1,000 meters, the pressure of the ocean is equivalent to 100 times that of pressure experienced at sea level. [10]

In order to survive in such extreme conditions, organisms must be highly specialized to match their physiological tolerances to the physical conditions of the deep sea. For example, deep sea organisms do not possess gaseous structures such as lungs or air-pocket swim bladders, which would change size with changes in depth. [10] Specialized adaptations to deep-sea conditions have been part of the reason why Cyclothone have been wildly successful in regards to biomass, but also make them difficult to study: Cyclothone fishes cannot survive when brought to the surface, and therefore cannot be observed alive in a laboratory setting. [7] [11]

Species

Image of a preserved Cyclothone, likely Cyclothone acclinidens. Image of a preserved Cyclothone .jpg
Image of a preserved Cyclothone, likely Cyclothoneacclinidens.

There are currently 13 recognized extant species in this genus: [11]

Extinct species

There are currently 4 nominal extinct species and several unnamed extinct species in this genus: [12]

The oldest species yet to be named in the genus is discovered from the Middle Miocene deposits of Honshu Island, Japan. Other unnamed species are also known from Pliocene and Pleistocene deposits of Italy. [12]

Feeding and diet

In general, Cyclothone species appear to be opportunistic feeders and tend to feed on whatever organisms they encounter in their extreme environment. [14] Some species have been thought to migrate towards the surface to feed (though not in a diel vertical migration pattern), but some remain at depth their entire lives. [7] They have been commonly known to eat copepods and chaetognaths, [15] but they have also been known to eat Euphausiids, mysid shrimp, ostracods, and even detritus and fecal pellets. [14]

Cyclothone falls in the middle of the food web, and its main predators are slightly larger deep-sea fishes, such as dragonfish and fangtooths. [2] One adaptation that could lend a clue to our understanding of predator avoidance strategies in Cyclothone has to do with their bioluminescence. In the midwater region of the deep sea, predators cannot see below but can sometimes use the small amount of light available to see shadows above them. Cyclothone fishes have small bioluminescent spots on their ventral (bottom) side that cause them blend in with the surrounding light, allowing them to remain unseen to predators below. This adaptive strategy is known as counter-illumination. [16]

Reproduction

Little is known about reproduction in Cyclothone fishes due to the difficulty in observing individuals in situ. Cyclothone are believed to be protandrous, meaning all individuals begin life as males and some become females at reproductive age. [17] Sex determination in reproductive-age Cyclothone is typically dependent on environmental conditions. Males tend to be slightly smaller than females and appear to have a stronger sense of smell. Having a strong sense of smell is likely ecologically advantageous for males in order to find mates in the darkness. [2] [18]

Conservation status

At the present time, there are no species of Cyclothone on the ICUN Red List and they have not been thoroughly evaluated by conservation scientists. [6] Because Cyclothone is believed to be the most abundant vertebrate genus on Earth, it is not believed that any of the species are in immediate threat of extinction. [4]

Related Research Articles

<span class="mw-page-title-main">Deep-sea fish</span> Fauna found in deep sea areas

Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, viperfish, and some species of eelpout.

<span class="mw-page-title-main">Stomiiformes</span> Order of fishes

Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes, for example, dragonfishes, lightfishes, loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families with more than 50 genera and at least 410 species. As usual for deep-sea fishes, there are few common names for species of the order, but the Stomiiformes as a whole are often called dragonfishes and allies or simply stomiiforms.

The mesopelagiczone, also known as the middle pelagic or twilight zone, is the part of the pelagic zone that lies between the photic epipelagic and the aphotic bathypelagic zones. It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the depths of this zone are between approximately 200 to 1,000 meters below the ocean surface.

The bathypelagic zone or bathyal zone is the part of the open ocean that extends from a depth of 1,000 to 4,000 m below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypelagic is also known as the midnight zone because of the lack of sunlight; this feature does not allow for photosynthesis-driven primary production, preventing growth of phytoplankton or aquatic plants. Although larger by volume than the photic zone, human knowledge of the bathypelagic zone remains limited by ability to explore the deep ocean.

<span class="mw-page-title-main">Gonostomatidae</span> Family of fishes

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. The genus Cyclothone is thought to be one of the most abundant vertebrate genera in the world.

<span class="mw-page-title-main">Lanternfish</span> Family of fishes

Lanternfish are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. Lanternfishes are aptly named after their conspicuous use of bioluminescence. Their sister family, the Neoscopelidae, are much fewer in number but superficially very similar; at least one neoscopelid shares the common name "lanternfish": the large-scaled lantern fish, Neoscopelus macrolepidotus.

Telescopefish are small, deep-sea aulopiform fish comprising the small family Giganturidae. The two known species are within the genus Gigantura. Though rarely captured, they are found in cold, deep tropical to subtropical waters worldwide.

<span class="mw-page-title-main">Pelagic fish</span> Fish in the pelagic zone of ocean waters

Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs.

<span class="mw-page-title-main">Viperfish</span> Genus of fishes

A viperfish is any species of marine fish in the genus Chauliodus. Viperfishes are mostly found in the mesopelagic zone and are characterized by long, needle-like teeth and hinged lower jaws. A typical viperfish grows to lengths of 30 cm (12 in). Viperfishes undergo diel vertical migration and are found all around the world in tropical and temperate oceans. Viperfishes are capable of bioluminescence and possess photophores along the ventral side of their body, likely used to camouflage them by blending in with the less than 1% of light that reaches to below 200 meters depth.

<span class="mw-page-title-main">Deep sea</span> Lowest layer in the ocean

The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low temperatures, darkness and high pressure. The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore.

<span class="mw-page-title-main">Stoplight loosejaw</span> Genus of fishes

The stoplight loosejaws are small, deep-sea dragonfishes of the genus Malacosteus, classified either within the subfamily Malacosteinae of the family Stomiidae, or in the separate family Malacosteidae. They are found worldwide, outside of the Arctic and Subantarctic, in the mesopelagic zone below a depth of 500 meters. This genus once contained three nominal species: M. niger, M. choristodactylus, and M. danae, with the validity of the latter two species being challenged by different authors at various times. In 2007, Kenaley examined over 450 stoplight loosejaw specimens and revised the genus to contain two species, M. niger and the new M. australis.

<span class="mw-page-title-main">Phosichthyidae</span> Family of fishes

Lightfishes are small stomiiform fishes in the family Phosichthyidae

<span class="mw-page-title-main">Veiled anglemouth</span> Species of fish

The veiled anglemouth, Cyclothone microdon, is a bristlemouth of the family Gonostomatidae, abundant in all the world's oceans at depths of 300 – 2,500 meters. Its length is 10–15 cm (4–8 in) though the largest known specimen is 7.6 cm (3 in). It gets its name from its circular mouth, filled with small teeth: the name “cyclothone” means in a circle or around and “microdon” means small teeth. The International Union for Conservation of Nature (IUCN) has assessed the veiled anglemouth is of Least Concern due to its abundance in most oceans and the little effect human impact has on its population growth. Some of the veiled anglemouth's physical features include a brown to black body with a radiating, or expansive, bioluminescent pigment over its head and fins.

<span class="mw-page-title-main">Deep-sea community</span> Groups of organisms living deep below the sea surface, sharing a habitat

A deep-sea community is any community of organisms associated by a shared habitat in the deep sea. Deep sea communities remain largely unexplored, due to the technological and logistical challenges and expense involved in visiting this remote biome. Because of the unique challenges, it was long believed that little life existed in this hostile environment. Since the 19th century however, research has demonstrated that significant biodiversity exists in the deep sea.

<span class="mw-page-title-main">Oceanic zone</span> Part of the ocean beyond the continental shelf

The oceanic zone is typically defined as the area of the ocean lying beyond the continental shelf, but operationally is often referred to as beginning where the water depths drop to below 200 metres (660 ft), seaward from the coast into the open ocean with its pelagic zone.

Peter John Herring is an English marine biologist known for his work on the coloration, camouflage and bioluminescence of animals in the deep sea, and for the textbook The Biology of the Deep Ocean.

<i>Neoscopelus macrolepidotus</i> Species of fish

Neoscopelus macrolepidotus, also known as a large-scaled lantern fish, is a species of small mesopelagic or bathypelagic fish of the family Neoscopelidae, which contains six species total along three genera. The family Neoscopelidae is one of the two families of the order Myctophiformes. Neoscopelidae can be classified by the presence of an adipose fin. The presence of photophores, or light-producing organs, further classify the species into the genus Neoscopelus. N. macrolepidotus tends to be mesopelagic until the individuals become large adults, which is when they settle down to the bathypelagic zone.

Cyclothone alba, commonly known as the bristlemouth, is a species of ray-finned fish in the genus Cyclothone. It is found across the world, in the Pacific, Indian, and Atlantic Oceans.

Cyclothone signata, the showy bristlemouth, is a species of ray-finned fish in the genus Cyclothone.

A micronekton is a group of organisms of 2 to 20 cm in size which are able to swim independently of ocean currents. The word 'nekton' is derived from the Greek νήκτον, translit. nekton, meaning "to swim", and was coined by Ernst Haeckel in 1890.

References

  1. ↑ Proujan. C., (1979), SECRETS OF THE SEA, 2nd ed., London: Reader's Digest Association Limited pg.60
  2. 1 2 3 Broad, William J. (2015-06-29). "An Ocean Mystery in the Trillions". The New York Times . Retrieved 2020-09-28.
  3. ↑ "Bristlemouth dominance: How do we know? -Ocean Twilight Zone". WHOI- Ocean Twilight Zone. Retrieved 2020-09-28.
  4. 1 2 Irigoien, Xabier; Klevjer, T. A.; Røstad, A.; Martinez, U.; Boyra, G.; Acuña, J. L.; Bode, A.; Echevarria, F.; Gonzalez-Gordillo, J. I.; Hernandez-Leon, S.; Agusti, S. (2014-02-07). "Large mesopelagic fishes biomass and trophic efficiency in the open ocean". Nature Communications. 5 (1): 3271. Bibcode:2014NatCo...5.3271I. doi:10.1038/ncomms4271. ISSN   2041-1723. PMC   3926006 . PMID   24509953.
  5. ↑ McKelvie, D (September 1989). "Latitudinal variation in aspects of the biology of Cyclothone braueri and C. microdon (Pisces: Gonostomatidae) in the eastern North Atlantic Ocean". Marine Biology. 102 (3): 413–424. doi:10.1007/BF00428494. S2CID   85367773.
  6. 1 2 "Tan Bristlemouth". Oceana. Retrieved 2020-09-26.
  7. 1 2 3 4 DeWitt, Floyd A. (1972-03-08). "Bathymetric Distributions of Two Common Deep-Sea Fishes, Cyclothone acclinidens and C. signata, off Southern California". Copeia. 1972 (1): 88–96. doi:10.2307/1442785. JSTOR   1442785.
  8. ↑ National Oceanic and Atmospheric Administration. "Thermohaline Circulation - Currents: NOAA's National Ocean Service Education". oceanservice.noaa.gov. Retrieved 2022-06-07.
  9. ↑ "What conditions exist for life in the deep ocean? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research". oceanexplorer.noaa.gov. Retrieved 2020-09-28.
  10. 1 2 "How does pressure impact animals in the ocean? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research". oceanexplorer.noaa.gov. Retrieved 2020-09-28.
  11. 1 2 Froese, Rainer and Pauly, Daniel, eds. (2012). Species of Cyclothone in FishBase . February 2012 version.
  12. 1 2 3 Nam, Gi-Soo; Nazarkin, Mikhail V. (2021). "A Neogene bristlemouth of the genus Cyclothone (Stomiiformes: Gonostomatidae) from South Korea". Historical Biology. 33 (11). e1625911. doi:10.1080/08912963.2020.1820000.
  13. ↑ Nazarkin, M. V. (2015). "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. S2CID   128915597.
  14. 1 2 DeWitt, Floyd A.; Cailliet, Gregor M. (1972-12-29). "Feeding Habits of Two Bristlemouth Fishes, Cyclothone acclinidens and C. signata (Gonostomatidae)". Copeia. 1972 (4): 868. doi:10.2307/1442749. JSTOR   1442749.
  15. ↑ Collard, Sneed B. (1970-06-01). "Forage of Some Eastern Pacific Midwater Fishes". Copeia. 1970 (2): 348–354. doi:10.2307/1441657. JSTOR   1441657.
  16. ↑ Davis, Matthew P.; Holcroft, Nancy I.; Wiley, Edward O.; Sparks, John S.; Leo Smith, W. (2014-05-01). "Species-specific bioluminescence facilitates speciation in the deep sea". Marine Biology. 161 (5): 1139–1148. doi:10.1007/s00227-014-2406-x. ISSN   1432-1793. PMC   3996283 . PMID   24771948.
  17. ↑ Miya, Masaki; Nemoto, Takahisa (1987-09-01). "Reproduction, growth and vertical distribution of the meso- and bathypelagic fish Cyclothone atraria (Pisces: Gonostomatidae) in Sagami Bay, Central Japan". Deep Sea Research Part A. Oceanographic Research Papers. 34 (9): 1565–1577. Bibcode:1987DSRA...34.1565M. doi:10.1016/0198-0149(87)90109-9. ISSN   0198-0149.
  18. ↑ de Mitcheson, Yvonne Sadovy; Liu, Min (2008-03-01). "Functional hermaphroditism in teleosts". Fish and Fisheries. 9 (1): 1–43. doi:10.1111/j.1467-2979.2007.00266.x. ISSN   1467-2960.
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