| Epalzeorhynchos | |
|---|---|
 | |
| Thered-tailed black shark (E. bicolor) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cypriniformes |
| Family: | Cyprinidae |
| Subfamily: | Labeoninae |
| Genus: | Epalzeorhynchos Bleeker, 1855 |
| Type species | |
| Barbus kalopterus Bleeker, 1851 | |
| Diversity | |
| 4 species | |
Epalzeorhynchos is a smallray-finned fishgenus of thefamilyCyprinidae. Its members are – like some other cyprinids – known as "freshwater sharks" or simply "sharks". They are, however,freshwater members of theOsteichthyes lineage which is distinct from theChondrichthyes lineage of sharks. The description of these animals as "shark" is most likely a reference to the shark-like shape of these popular cyprinids.
The genusEpalzeorhynchos may be placed in thetribeGarrini of theLabeoninae, or insubtribe Garraina of tribe Labeonini, if these are considered a tribe of subfamilyCyprininae. It is not yet resolved which is a more appropriate representation of theirphylogeny.[1]
In size and shapeEpalzeorhynchos generally resemble theIndian loaches (Botia), which, although they are alsocypriniforms, are far too distantly related to have anything other thanparallel or evenconvergent evolution be responsible for this similarity. Alternatively,Epalzeorhynchos might be considered a plumper version ofCrossocheilus, which includes the well-knownSiamese algae eater (C. siamensis) and is a very close relative. Their coloration is also reminiscent of someCrossocheilus, or of theMekong loaches (Yasuhikotakia), depending on the particularEpalzeorhynchos species.
Unlike actualsharks,Epalzeorhynchos "freshwater sharks" areOsteichthyes. Thus, they havegill covers that can actively pump water over thegills, enabling them to breathe comfortably while at rest. As typical for Garrini, they spend much time on or near the ground – though not quite as much as the related truegudgeons of the Gobioninae or theloaches of the cypriniformsuperfamilyCobitoidea. Still, they usually only move for prolonged distances duringmigration to theirspawning grounds.[2]
This genus feeds mainly onaufwuchs,detritus and smallinvertebrate andplant matter. Their mouthparts are not asapomorphic as that of many other Garrini; they do not have a pronounced rostral cap, but in addition to the twobarbels on therostrum they retain another pair of barbels at the rear edges of thelower maxilla. The upperlip carries a short bristly ridge, while the lower one has a sizeable hard edge with which they can scrape food off hardsubstrate like rocks or logs.[3]
Three species are frequent in theaquarium fish trade;E. munense is the only member of the genus that rarely (if ever) makes its way into the trade.[4] The demand for these colourful fishes is high, and breeding is almost impossible to achieve in the home aquarium. The popular species are thus bred on an industrial scale inSoutheast Asia. Today allred-tailed black sharks (E. bicolor), allflying foxes (E. kalopterus), and mostrainbow sharks (E. frenatum) seen in the aquarium trade are believed to be farm-bred.[5][6][7] The main problem for their status isdamming of rivers between the fishes' usual haunts and the breeding grounds. While otherwise a considerable take of wildEpalzeorhynchus could be sustained, dams will literally stand in the way of successful reproduction, and such isolatedsubpopulations are easily extinguished byoverfishing.Water pollution is also problematic. Due to these threats, the red-tailed black shark is very rare and was believed to beextinct in the wild, but a tiny wild population is now known, leading to its currentIUCN rating ascritically endangered.[5] Among the remaining,E. munense isvulnerable, the rainbow shark is considered safe, and the flying fox isdata deficient (its status is unclear based on 2009 knowledge).[6][7][8]
A mere fourspecies are placed in thisgenus:
In addition to these,Akrokolioplax bicornis was included inEpalzeorhynchos until 2006.[9]
