The stream catfishes comprise the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Akysidae of

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

es.

Distribution and habitat

Akysids are known from across a large area in

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...

. They are found in fresh water. Fish of the subfamily Parakysinae are primarily found in the

Malay Peninsula The Malay Peninsula ( Malay: ''Semenanjung Tanah Melayu'') is a peninsula in Mainland Southeast Asia. The landmass runs approximately north–south, and at its terminus, it is the southernmost point of the Asian continental mainland. The ar ...

Sumatra Sumatra is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 473,481 km2 (182,812 mi.2), not including adjacent i ...

Sarawak Sarawak (; ) is a state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the Malaysian state of Sabah to the northeast, ...

, and western and southern

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and e ...

. Most species are generally found in deeper parts of relatively swift rivers and forest streams.

Taxonomy

It includes at least 57 species in five

genera 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 nomenclat ...

; many species are only recently described. The family is divided into two subfamilies, Akysinae and Parakysinae. The Parakysinae had previously been listed as an independent family. This family is

sister A sister is a woman or a girl who shares one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a family, familial relationship, it is sometimes used endearingly to r ...

to a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

formed by

Sisoridae Sisoridae is a family of catfishes. These Asian catfishes live in fast-moving waters and often have adaptations that allow them to adhere to objects in their habitats. The family includes about 235 species. Taxonomy The family Sisoridae is recog ...

Erethistidae Erethistidae are a family of catfishes that originate from southern Asia. It includes about 45 species. Taxonomy This family includes species previously placed in Sisoridae. They were removed because they were thought to be more closely related ...

, and

Aspredinidae The Aspredinidae are a small South American family of catfishes (order Siluriformes) also known as the banjo catfishes, with about 43 species. Distribution Aspredinids are found throughout the major tropical rivers of South America (e.g., Magda ...

Description

Akysids are small to minute fishes with

cryptic colouration Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

, tiny eyes, and completely covered with unculiferous plaques or

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

s. In some genera, some of the tubercles on the body are enlarged and arranged in distinctive longitudinal rows, the number of which may be diagnostic. The dorsal fin has a strong spine and a short base, and usually four or five soft rays and four pairs of

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some s ...

are found. Unusually among catfish, they have a low principal

caudal 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 se ...

ray count and more rays in the upper caudal fin lobe than the lower. In the Akysinae, the body has small unculiferous tubercles arranged in longitudinal rows, a median mid-dorsal row, usually in four lateral rows. The dorsal fin usually has five soft rays. An

adipose 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 se ...

is present and moderate. The

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 se ...

has a strong spine, and the anterior margin has a notch visible dorsally and usually serrated posteriorly. The gill openings are relatively narrow and the eyes are small. In the Parakysinae, the dorsal fin has four soft rays. The pectoral fin spine is not serrated. The anal fin has eight to 13 soft rays. The mandibular barbels usually have short accessory barbels. Gill rakers and

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

pores are absent. The head and body are covered with rounded tubercles arranged in longitudinal rows in ''Acrochordontichthys'' and ''Breitensteinia'' or evenly distributed in ''Parakysis''. The adipose fin is absent in ''Breitensteinia'' and ''Parakysis'' and is present as an adipose ridge; the fin is present and long in ''Acrochordontichthys''. The eyes are minute. They have 30–32

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

References

{{DEFAULTSORT:Stream Catfish Fish of Southeast Asia Taxa named by Theodore Gill