The stream catfishes comprise the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Akysidae of

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

es.

Distribution and habitat

Akysids are known from across a large area in

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

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

Malay Peninsula The Malay Peninsula is located 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 area contains Peninsular Malaysia, Southern Tha ...

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 list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

Sarawak Sarawak ( , ) is a States and federal territories of Malaysia, state of Malaysia. It is the largest among the 13 states, with an area almost equal to that of Peninsular Malaysia. Sarawak is located in East Malaysia in northwest Borneo, and is ...

, and western and southern

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

. 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 (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

; 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 parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

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 (biology), family of catfishes (order (biology), order Siluriformes) also known as the banjo catfishes, with about 43 species. Distribution Aspredinids are found throughout the major tropical ri ...

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 projectio ...

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, whisker like sensory organ near the mouth (sometimes called whiskers or tendrils). Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the z ...

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

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only b ...

is present and moderate. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

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 raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of th ...

s 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 epithelia ...

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 Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

References

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