Sewellia | |
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Sewellia lineolata | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cypriniformes |
Family: | Gastromyzontidae |
Genus: | Sewellia Hora, 1932 |
Type species | |
Sewellia lineolata Valenciennes, 1846 | |
Synonyms | |
DiardichthysRoberts, 1998 |
Sewellia is a genus of fish in the family Gastromyzontidae. They are commonly called hillstream loaches (a common name shared with family Balitoridae) and are found in Laos and Vietnam. [1] According to Roberts (1998) a possible defining characteristic of the genus Sewellia is their posterior pelvic valve is highly complex and different from other rheophilic loaches (loaches adapted to fast flowing water), their posterior pelvic valve involves the overlapping of the second to last ventrally exposed rays. [2] Adapted to high velocity streams, Sewellia have depressed body shapes that are laterally expanded, thus increasing their hydrodynamical properties and allowing them to better stay attached to rocks in swift current. [2] Sewellia also have paired fins with a single simple ray and numerous branched rays allowing them to grip rocks in swift current. [2]
Fish in the genus Sewellia occur in the Sekong River, a tributary of the Mekong river. [3] The Sekong river drains large parts of central and southeast Laos as well as southern Vietnam.
Sewellia are found in the rapids and riffles of steep gradient 'hill streams', hence the common name Hillstream Loach. [4] Due to their steep gradients these streams have high current velocities, Sewellia are known to inhabit streams with current velocities exceeding m/s in some habitats. [5] Sewellia feed mainly on micro to macro sized aquatic invertebrates that inhabit the periphyton attached to submerged rocks. [4]
Sewellia are sexually dimorphic, males have soft elevated patches of fine tubercles on the anterior part of pectoral-fin rays 1-6, females do not. [5] Sewellia lineolata are common in the aquaria trade, they are sexed based on differences in shape, at sexual maturity males tend to be more streamlined while females are somewhat broad; the beginning of the pectoral fins occurs at a much sharper angle in the male than females, females have pectoral fins that begin in a more rounded fashion (softer angle). [6]
There are currently 13 recognized species in this genus: [7]
Cypriniformes is an order of ray-finned fish, which includes many families and genera of cyprinid fish, such as barbs, gobies, loaches, botias, and minnows. Cypriniformes is an “order-within-an-order”, placed under the superorder Ostariophysi—which is also made up of cyprinid, ostariophysin fishes. The order contains 11-12 families, over 400 genera, and more than 4,250 named species; new species are regularly described, and new genera are recognized frequently. Cyprinids are most diverse in South and Southeast Asia, but are entirely absent from Australia and South America. At 112 years old, the longest-lived cypriniform fish documented is the bigmouth buffalo.
Cobitidae, also known as the True loaches, is a family of Old World freshwater fish. They occur throughout Eurasia and in Morocco, and inhabit riverine ecosystems. Today, most "loaches" are placed in other families. The family includes about 260 described species. New species are being described regularly.
The hillstream loaches or river loaches are a family, the Balitoridae, of small fish from South, Southeast and East Asia. The family includes about 202 species. They are sometimes sold as "lizardfish" or "flossensaugers". Many of the species are popular for aquaria, species in the genus Sewellia are most commonly sold in the aquaria trade. They have a number of similarities with the Cobitidae, their sibling family of "loaches", such as multiple barbels around the mouth. They should not be confused with the loricariids, which look similar but are a family of catfish.
Garra is a genus of fish in the family Cyprinidae. These fish are one example of the "log suckers", sucker-mouthed barbs and other cyprinids commonly kept in aquaria to keep down algae. The doctor fish of Anatolia and the Middle East belongs in this genus. The majority of the more than 160 species of garras are native to Asia, but about one-fifth of the species are from Africa.
Schistura is a genus of fish in the stone loach family Nemacheilidae native to the streams and rivers of the southern and eastern Asia. Some of these species are troglobitic.
Maurice Kottelat is a Swiss ichthyologist specializing in Eurasian freshwater fishes.
Hemimyzon ecdyonuroides is a species of hillstream loach in the genus Hemimyzon. It is known from two tributaries of the Mekong, from Sekong River and Sesan River drainages in Vietnam and Laos.
Balitora is a genus of fish in the family Balitoridae endemic to Asia.
Loaches are fish of the superfamily Cobitoidea. They are freshwater, benthic (bottom-dwelling) fish found in rivers and creeks throughout Eurasia and northern Africa. Loaches are among the most diverse groups of fish; the 1249 known species of Cobitoidea comprise about 107 genera divided among 9 families.
Homatula is a genus of stone loaches endemic to China.
Liniparhomaloptera is a genus of fish in the family Gastromyzontidae found in China and Vietnam.
Oxynoemacheilus is a genus of fish in the family Nemacheilidae found in Europe and Western Asia.
Paracobitis is a genus of Asian stone loaches.
Paraschistura is a genus of stone loaches most of which occur in Central, South and Western Asia.
Parasewellia is a small genus of hillstream loaches endemic to Vietnam. Described in a single work by Nguyen & Nguyen, the validity of claims, as of 2012, cannot be properly analyzed due to poor descriptions and low quality of illustrations. Due to extremely restricted ranges it is possible that multiple claimed species represent a single one. Maurice Kottelat places them under Sewellia.
Physoschistura is a genus of fish in the family Nemacheilidae found mostly in Southeast Asia.
The Nemacheilidae, or stone loaches, are a family of cypriniform fishes that inhabit stream environments, mostly in Eurasia, with one genus, Afronemacheilus found in Africa. The family includes about 790 species.
Balitoropsis also known as the lizard loaches is a genus of hillstream loaches native to eastern Asia.
The Gastromyzontidae are a family of loaches native to China and Southeast Asia, where typically found in streams and rivers with a fast current. The family includes about 137 species in eighteen genera. This family was resurrected by M. Kottelat in his review and revision of the loaches in 2012. They are commonly called hillstream loaches.
Sewellia lineolata, the reticulated hillstream loach, is a species of fish from the provinces of Thua Thien-Hue, Quang Nam, Quang Ngai and Binh Dinh in Vietnam.