''Comephorus'', known as the golomyankas or Baikal oilfish, are a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
comprising two
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of peculiar,
sculpin fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
es
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
to
Lake Baikal in
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
. ''Comephorus'' is the only genus in the family Comephoridae. Golomyankas are
pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...
fishes which make the main food source of the
Baikal seal
The Baikal seal, Lake Baikal seal or (''Pusa sibirica''), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seal ...
.
Description
''Comephorus'' have translucent bodies with no scales,
[Animals and plants of Lake Baikal]
from Irkutsk State University, accessed May 5, 2006 but appear dull when dead.
The big Baikal oilfish (''C. baikalensis'') can reach up to in length and the little Baikal oilfish (''C. dybowskii'') up to .
[ Males are smaller than females, only reaching about the length.] They have long pectoral fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
s, and although pelvic bones are present, they lack pelvic fins. They have a strong lateral line. The lateral line system on the head consists of large cavities linked by narrow, bony bridges with small external pores. High lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
content and porous bones result in an almost neutral buoyancy
Neutral buoyancy occurs when an object's average density is equal to the density of the fluid in which it is immersed, resulting in the buoyant force balancing the force of gravity that would otherwise cause the object to sink (if the body's densi ...
[Sideleva, V.G. (1996). Comparative character of the deep-water and inshore cottoid fishes endemic to Lake Baikal. Journal of Fish Biology 49(sA): 192–206.] and lack of swim bladder allows the fish to tolerate varying pressure extremes as they move through the water column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
. Over a third of the body weight (38.9%) of ''C. baikalensis'' is oil, but ''C. dybowskii'' contains far less (4.7%). It has been said that they decompose
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
in sunlight, leaving behind only fatty oil and bones,[ although the accuracy of this claim has been questioned.][ Unusually, their eyes only contain rod cells (not cone cells), indicating a high sensitivity to light.][ Some of the adaptions in golomyankas resemble those seen in deep sea fish.][
]
Species
There are currently two recognized species in this genus:
* ''Comephorus baikalensis'' (Pallas
Pallas may refer to:
Astronomy
* 2 Pallas asteroid
** Pallas family, a group of asteroids that includes 2 Pallas
* Pallas (crater), a crater on Earth's moon
Mythology
* Pallas (Giant), a son of Uranus and Gaia, killed and flayed by Athena
* Pa ...
, 1776) (Big Baikal oilfish)
* ''Comephorus dybowskii'' ( Korotneff, 1904) (Little Baikal oilfish)
Biology and ecology
The common name ''golomyanka'' originates from the old-Russian ''golomen'', meaning "far from the shore" in the local dialect and referring to their pelagic
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...
behavior. They are the principal ecological competitor to the omul
The omul, ''Coregonus migratorius'', also known as Baikal omul (russian: байкальский омуль), is a whitefish species of the salmon family endemic to Lake Baikal in Siberia, Russia. It is considered a delicacy and is the object o ...
, which also eat small golomyankas, and represent a primary food source for the Baikal seal
The Baikal seal, Lake Baikal seal or (''Pusa sibirica''), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seal ...
, at more than 90% of its diet.[ They are easily identifiable, and are large enough to be easily seen. Golomyankas are unusual for occurring pelagically throughout the entire ]water column
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
of Lake Baikal, ranging from depths of around to near the surface, but they primarily occur deeper than . During the night they move up the water column to feed, often occurring as shallow as , and in the winter they can occasionally be seen swimming just below the ice-covered surface. They are considered the world's most abyssal freshwater fish, together with certain Lake Baikal deep-water sculpin
The Abyssocottinae are a subfamily of ray-finned fishes in the family Cottidae, the sculpins. They are known commonly as the deep-water sculpins.Froese, R. and D. Pauly. (Eds.Abyssocottidae.FishBase. 2011. The entire family is endemic to Lake Ba ...
s (Abyssocottidae).[Hunt, D. M., et al. (1997). Molecular evolution of the cottoid fish endemic to Lake Baikal deduced from nuclear DNA evidence. ''Molecular Phylogenetics and Evolution'' 8(3), 415-22.] They move without much regard for changes in pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
, although they can exist only in cold temperatures, preferring water that is no more than and dying at .[Ichthyofauna of Lake Baikal]
from Baikal Web World, accessed May 5, 2006 (with a photo of the golomyanka).
The biomass of the golomyanka population is estimated at about 150 thousand tons, making it the most populous fish in Lake Baikal.[ It is estimated that about 70% of the fish in the lake are golomyankas.][ Their juveniles are also the most abundant pelagic ]fish larvae
Ichthyoplankton (from Greek: ἰχθύς, , "fish"; and πλαγκτός, , "drifter") are the eggs and larvae of fish. They are mostly found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epi ...
in the lake. Large shoals
In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material and rises from the bed of a body of water to near the surface. I ...
are not known for this species, although groups of up to about 20 individuals have been recorded near the lake bottom.[ Females are more common than males, which only make up about 32% of the population in the little Baikal oilfish and 17% in the big Baikal oilfish.][ The females do not lay eggs; rather, they are ]viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
, giving birth to a swarm of 2000–3000 larvae.[ Females containing developing embryos can be seen year-round,][ but there does appear to be a level of seasonality in the birth, with the largest number of larvae occurring from August to April (some differences in the peak timing between the two species).][ Most females die after giving birth.][ It has been claimed that their bellies burst open to release the young, killing the female in the process, but this is a myth.][ Golomyanka can reach an age of up to 6–8 years.][
They are sluggish fish, and have relatively large mouths with several rows of somewhat brush-like teeth, allowing them to sift out fine organisms from the water.][ They primarily feed on the planktonic copepod '']Epischura baikalensis
''Epischurella baikalensis'' (previously ''Epischura baikalensis'') is a species of copepod in family Temoridae. It is endemic to Lake Baikal, being the dominant zooplankton species there: 80%–90% of total biomass. It measures .
''Epischur ...
'', the amphipod crustacean '' Macrohectopus branickii'' and larvae of sculpins,[Miyasaka, Dzyuba, Genkai-Kato and Wada (2006). Feeding ecology of two planktonic sculpins, Comephorus baicalensis and Comephorus dybowskii (Comephoridae), in Lake Baikal. Ichthyological Research 53(4): 419-422.] including those of their own species.[
]
Relationship to humans
Despite being numerous in the lake, golomyankas are difficult to catch in large quantities as they do not gather in large schools.[ Golomyankas are not harvested commercially, although their fats and oils were used in lamps and as ]traditional medicine
Traditional medicine (also known as indigenous medicine or folk medicine) comprises medical aspects of traditional knowledge that developed over generations within the folk beliefs of various societies, including indigenous peoples, before the ...
by native Siberians when storms tossed the fish up on shore.[ They are of no value as a food source for humans, dogs or cats, but are the primary food source for the ]Baikal seal
The Baikal seal, Lake Baikal seal or (''Pusa sibirica''), is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seal ...
, and also eaten by other fish in the lake.[ They are so numerous and spawn so rapidly that they represent the largest concentration of fish biomass within the entire lake, and would seriously unbalance the ecosystem of Lake Baikal if not constantly preyed upon by ]predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s.
See also
* List of fish families
This is a list of fish families sorted alphabetically by scientific name. There are 525 families in the list.
__NOTOC__
A - B - C - D - E - F -
G - H - I - J - K -
L - M - N - O - P - R - S - T - U - V - W - X - Y - Z
--- ...
References
Lake Baikal FAQ
Irkutsk State University Lake Baikal FAQ, accessed May 5, 2006
{{Taxonbar, from=Q803775
Comephoridae
Cottoidei
Scorpaeniformes genera
Viviparous fish
Taxa named by Bernard Germain de Lacépède
Endemic fauna of Russia
Fish of Lake Baikal