Akysis

Taxobox
name = "Akysis"
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Siluriformes
familia = Akysidae
subfamilia = Akysinae
genus = "Akysis"
genus_authority = Bleeker, 1858
type_species = "Pimelodus variegatus"
type_species_authority = Bleeker, 1846
subdivision_ranks = Species
subdivision ="A. brachybarbatus"
"A. clavulus"
"A. clinatus"
"A. ephippifer"
"A. filifer"
"A. fuliginatus"
"A. galeatus"
"A. hendricksoni"
"A. heterurus"
"A. longifilis"
"A. maculipinnis"
"A. manipurensis"
"A. microps"
"A. pictus"
"A. prashadi"
"A. pulvinatus"
"A. recavus"
"A. scorteus"
"A. variegatus"
"A. varius"
"A. vespa"

"Akysis" is the largest genus of catfishes (order Siluriformes) of the family Akysidae.

Taxonomy

In 1996, it was determined that "Akysis" is the sister group to all other akysids, then only including "Parakysis", "Acrochordonichthys", and "Breitensteinia". However, it was acknowledged that the genus "Akysis" was poorly-sampled at the time and may be deemed non-monophyletic in the future.

In 1998, it was recognized that the large genus "Akysis" includes two species groups. The first species group was the "Akysis variegatus" group, for species more closely related to the type species; the other group was the "pseudobagarius" group for species more closely related to the formerly-named "Akysis pseudobagarius"; the authors recognized it as conceivable that the groups represented two genera, but tentatively retained the species in a single genus.cite journal|title=The catfish genus "Akysis" Bleeker (Teleostei: Akysidae) in Indochina, with descriptions of six new species|first=Heok Hee|last=Ng|coauthors=Kottelat, M.|journal=Journal of Natural History|year=1998|volume=32|pages=1057–1097|doi=10.1080/00222939800770531] Since then, the genus "Pseudobagarius" was erected for this species group, leaving only members of the "A. variegatus" group in the genus "Akysis".cite journal|url=http://silurus.acnatsci.org/ACSI/library/biblios/2007_Ferraris_Catfish_Checklist.pdf|title=Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types|first=Carl J., Jr.|last=Ferraris|journal=Zootaxa|volume=1418|pages=1–628|year=2007|format=PDF]

In 2007, "Laguvia manipurensis" was redescribed to the genus "Akysis" as part of the "A. variegatus" group.cite journal|url=http://www.zoosprint.org/viewPDFFile.asp?fname=2675-2678.pdf&typ=jnl&Imonth=5&Iyear=2007|title=Fishes of the Genus "Akysis" Bleeker from India (Teleostei: Akysidae)|first=W.|last=Vishwanath|coauthors=Linthoingambi, I.; Juliana, L.|journal=Zoos' Print Journal|volume=22|issue=5|pages=2675–2678|format=PDF]

Distribution

These fish are found in fast-flowing streams in Southeast Asia. This area is bordered by the Irrawaddy River drainage to the west, the Barito River drainage to the east, the Lancanjiang (upper Mekong) drainage to the north, and the Citarum River drainage to thesouth.cite journal|url=http://www.mapress.com/zootaxa/2006f/zt01150p030.pdf|title="Akysis longifilis", a new species of catfish (Teleostei: Akysidae) from Myanmar|first=Heok Hee|last=Ng|journal=Zootaxa|volume=1150|pages=19–30|year=2006|format=PDF] "Akysis" have been reported from Java, Sumatra, Borneo, Tenasserim, Thailand, Myanmar, and, most recently, the distribution of "Akysis" has been discovered to include India.

Description

These small catfish can be distinguished by their general colouring of yellow markings on a brown background. Fishes of the genus "Akysis" are diagnosed by having tough leathery skin covered with tubercles which are arranged in longitudinal rows along the sides, the anterior margin of the pectoral spine with a notch visible dorsally, the nasals with expansions beyond the canal-bearing teeth, and no palatal teeth. These fish are distinguished from the members of the genus "Pseudobagarius" by a number of characteristics: these species have a terminal mouth; the posterior and anterior nostrils being relatively smaller and located further apart with a distance between the base of the nasal barbel and anterior nostril; the anterior nostrils are situated at the tip of a short tube; and the caudal fin is truncate or emarginate rathern that forked.

The maximum adult size of "Akysis" species is less than 70 millimetres (2.8 in) SL.cite journal|title="Akysis hardmani" (Siluriformes: Akysidae), a new species of catfish from Thailand|first=Heok Hee|last=Ng|coauthors=Sabaj, Mark H.|journal=Ichthyol. Explor. Freshwaters|volume=16|issue=3|pages=215–222|date=September 2005]

Ecology

Catfishes of the genus "Akysis" are small cryptically-coloured species.cite journal|title="Akysis clavulus", a new species of catfish (Teleostei: Akysidae) from central Vietnam|first=Heok Hee|last=Ng|coauthors=Freyhof, Jörg|journal=Ichthyol. Explor. Freshwaters|volume=14|issue=4|pages=311–316|date=December 2003] "Akysis" are small secretive fishes that occupy a variety of habitats. Most species typically inhabit clear swift-flowing upland streams with sandy or rocky substrates. Some species are reported from the muddy side and main channels and deltas of large rivers. In smaller streams they may be found hiding in leaf litter and woody debris, in patches of live vegetation such as "Cryptocoryne affinis", or in shallow riffle areas under coarse gravel or larger stones. Species of "Akysis" also are reported from the shallow margins to the bottom depths of large rivers where they are usually taken in trawls together with decaying vegetation.

References