Loaches are fish of the superfamily Cobitoidea. They are
freshwater,
benthic (bottom-dwelling)
fish found in rivers and creeks throughout
Eurasia and
northern Africa.[2] Loaches are among the most diverse groups of fish; the 1249 known
species of Cobitoidea comprise about 107
genera divided among 9
families.[3][4]
Etymology
The name Cobitoidea comes from the type genus, Cobitis, described by
Carl Linnaeus in his landmark 1758
10th edition of Systema Naturae. However, its origin predates modern zoological nomenclature and derives from a term used by
Aristotle to refer to "small fishes that bury... like the
gudgeon."[2]
Description
Loaches display a wide variety of morphologies, making the group difficult to characterize as a whole using external traits. They range in adult length from the 23 mm (1 in) miniature eel-loach, Pangio longimanus, to the 50 cm (20 in) imperial flower loach, Leptobotia elongata, with the latter weighing up to 3 kg (6.6 lbs).[5][6][7] Most loaches are small, narrow-bodied and elongate, with minute
cycloid scales that are often embedded under the skin, patterns of brown-to-black pigment along the dorsal surface and sides, and three or more pairs of whisker-like
barbels at the mouth.[8] The type species of the family Cobitidae, Cobitis taenia, has a body shape and pigment pattern typical of Cobitoidea. However, many loaches are eel-like or conversely, quite stout-bodied; some
balitorids have large, visible scales.[9]
Cobitoidea is a superfamily within the order
Cypriniformes, one of the most diverse groups of vertebrates. The order is commonly known as "minnows, carps, loaches, and relatives," and it includes the suckers (
Catostomidae) and algae eaters (
Gyrinocheilidae). Fishes of the latter family, which contains only a single genus Gyrinocheilus, are sometimes referred to as sucking loaches. It is uncertain if Gyrinocheilidae, or a clade containing both Gyrinocheilidae and Catostomidae, is sister to Cobitoidea.[12]
History of classification
At the turn of the 20th century only two families of loaches had been described, and of these only Cobitidae was widely recognized by taxonomists. In the early 1900s, the American
ichthyologistFowler and the Indian ichthyologist
Hora recognized what would come to be known as Balitoridae and Gastromyzontidae.[13][14] Nemachelidae, and later Botiidae, were described as subfamilies of Cobitidae until their elevation to family status in 2002.[15][16][17] Owing to shared morphological characteristics (see osteology, below) the relationship of the botiid and cobitid loaches was particularly difficult to resolve until the advent of
molecular phylogenetics. Three of the nine families, containing only two or three species apiece, were recognized within the last ten years.[12]
Phylogeny
Reproduction of molecular phylogeny of Cobitoidea from Bohlen & Šlechtová, 2009,[18] with common names following Eschmeyer's Catalog of Fishes.[19]
Among loaches, the majority of known morphological
synapomorphies (shared characters derived from a common ancestor) are
osteological. In particular, modifications to the ethmoid and surrounding bones within the neurocranium unite Cobitoidea, in addition to certain lateral-line canal ossifications.[8] An erectile suborbital spine, a modification of the lateral ethmoid, was formerly thought to represent a synapomorphy between Cobitidae and Botiidae.[20] It is now considered a
pleisiomorphy of Cobitoidea, a character shared by the common ancestor but lost in most loach lineages.[21] The suborbital spine is also retained in the
serpent loaches, Serpenticobitidae.[10]
Habitat and distribution
Loaches are found in a wide variety of habitats throughout Europe, northern Africa, and central and Southeast Asia. Most families occur predominantly in rocky mountain streams at high elevations, but almost all have lowland representatives as well.[2] Many species of Cobitidae burrow in the sand and inhabit riverbeds in broad, flat terrain. At least three families contain blind,
troglomorphic species adapted to life in caves.
Relationship with humans
Some loaches are important food fish, especially in East and Southeast Asia where they are a common sight in markets.
Loaches are popular in the aquarium trade. Some of the most well-known examples are the
clown loach (Chromobotia macracanthus), the
kuhli loach (Pangio kuhlii), and the
dwarf chain loach (Ambastaia sidthimunki). Botiid and gastromyzontid loaches also occasionally make their way into the trade.[22]
Although loaches have a strictly Old World native distribution, the
oriental weatherfish, Misgurnus anguillicaudatus, (also known as the dojo loach) has been introduced in parts of the United States.[23][24]
^
abcKottelat, M. (2012). "Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei)". The Raffles Bulletin of Zoology. Supplement no. 26: 1–199.
^Nelson, J. S.; Grande, T. C.; Wilson, M. V. H. (2016). Fishes of the World (5th ed.). Hoboken, New Jersey: John Wiley & Sons. pp. 189–193.
ISBN978-1-118-34233-6.
^Britz, R.; Kottelat, M. (2009). "Pangio longimanus, a miniature species of eel-loach from Central Laos (Teleostei: Cypriniformes: Cobitidae)". Ichthyological Exploration of Freshwaters. 20 (4): 371–376.
ISSN0936-9902.
^Bohlen, J.; Šlechtová, V. (2009). "Phylogenetic position of the fish genus Ellopostoma (Teleostei: Cypriniformes) using molecular genetic data". Ichthyological Exploration of Freshwaters. 20 (2): 157–162.
ISSN0936-9902.
^Sawada, Y. (1982). "Phylogeny and zoogeography of the superfamily Cobitoidea (Cyprinoidei, Cypriniformes)". Memoirs of the Faculty of Fisheries Sciences, Hokkaido University. 28 (2): 65–223.
^Šlechtová, V.; Bohlen, J.; Tan, H. H. (2007). "Families of Cobitoidea (Teleostei; Cypriniformes) as revealed from nuclear genetic data and the position of the mysterious genera Barbucca, Psilorhynchus, Serpenticobitis and Vaillantella". Molecular Phylogenetics and Evolution. 44 (3): 1358–1365.
doi:
10.1016/j.ympev.2007.02.019.
PMID17433724.
^Loaches: natural history and aquarium care. Neptune City, NJ: T.F.H. Publications. 2008.
ISBN9780793806201.
^Fuller, P. L.; Nico, L. G.; Williams, J. D. (1999). Nonindigenous fishes introduced into inland waters of the United States. Bethesda, MD: American Fisheries Society, Special Publication #27. p. 176.
^Robins, R. H.; Page, L. M.; Williams, J. D.; Randall, Z. S.; Sheehy, G. E. (2018). Fishes in the fresh waters of Florida: an identification guide and atlas. Gainesville, Florida: University of Florida Press. pp. 141–142.
ISBN9781683400332.