Stream catfish

Taxobox
name = Stream catfishes
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
superfamilia = Sisoroidea
familia = Akysidae
familia_authority = Gill, 1861
subdivision_ranks = Genera
subdivision = Subfamily Akysinae
"Akysis"
"Pseudobagarius"
Subfamily Parakysinae
"Acrochordonichthys"
"Breitensteinia"
"Parakysis"
The stream catfishes are family Akysidae of catfishes.

Distribution and habitat

Akysids are known from across a large area in Southeast Asia.cite journal|url=http://www.mapress.com/zootaxa/2004f/zt00733.pdf|title=A new species of the catfish genus "Akysis" (Siluriformes: Akysidae) from southern Borneo|first=Heok Hee|last=Ng|coauthors=Siebert, Darrell J.|journal=Zootaxa|volume=733|pages=1–8|year=2004|format=PDF] They are found in the fresh waters.cite book|title=Fishes of the World|last=Nelson|first=Joseph S.|publisher=John Wiley & Sons, Inc|year=2006|isbn=0-471-25031-7] Fish of the subfamily Parakysinae are primarily found in the Malay Peninsula, Sumatra, Sarawak, and western and southern Borneo. Most species are generally found in deeper parts of relatively swift rivers and forest streams.cite journal|title=A revision of the akysid catfish genus "Acrochordonichthys" Bleeker|first=H. H.|last=Ng|coauthors=Ng, P. K. L.|journal=Journal of Fish Biology|year=2001|volume=58|pages=386–418|doi=10.1111/j.1095-8649.2001.tb02260.x]

Taxonomy

It includes at least 42 species in five genera; many species are only recently described. The family is divided into two subfamilies, Akysinae and Parakysinae. Parakysinae has previously been listed as an independent family.FishBase family|family=Parakysidae|month=Mar|year=2007]

This family is sister to a clade formed by Sisoridae, Erethistidae, and Aspredinidae.

Description

Akysids are small to minute fishes with cryptic colouration, tiny eyes, and completely covered with unculiferous plaques or tubercles. 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 there are usually four or five soft rays. There are four pairs of barbels. Unusually among catfish, they have a low principal caudal fin ray count and more rays in the upper caudal fin lobe than the lower.cite journal|title=A revision of the akysid catfish genus "Breitensteinia" Steindachner with descriptions of two new species|first=H. H.|last=Ng|coauthors=Siebert, D. J.|journal=Journal of Fish Biology|year=1998|volume=53|pages=645–657]

In Akysinae, the body is with small unculiferous tubercles arranged in longitudinal rows, a median middorsal row and usually four lateral rows. The dorsal fin with usually five soft rays. An adipose fin is present and moderate. The pectoral fin has a strong spine, and the anterior margin is with a notch visible dorsally and usually serrated posteriorly. The gill openings are relatively narrow and the eyes are small.

In Parakysinae, the dorsal fin has four soft rays. The pectoral fin spine is nonserrate. The anal fin is with 8–13 soft rays. The mandibular barbels are usually with short accessory barbels. Gill rakers and lateral line pores are absent. The head and body are covered with rounded tubercles arranged in longitudinal rows in "Acrochordontichthys" and "Breitensteinia" or evenely 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. There are 30–32 vertebrae.

References