We are delighted to present the first in an occasional series of Catfish of the Month articles by Heok Hee Ng. Heok Hee is currently completing his doctoral dissertation in ichthyology, but he has already emerged as a leading authority on siluriform systematics and taxonomy.
Marine aquarists have their live rocks and freshwater aquarists have their "live driftwood", which is the subject of this month's review. Looking very much like a piece of driftwood, Acrochordonichthys rugosus (the Asian banjo cat) is one of the most lethargic of catfishes. The fish spends all of its time lying on the substrate, sometimes out in the open (one fish I kept stayed at the exact spot in the corner of the tank for two weeks), and even looking for food seems to be an onerous task that the fish would happily forego. Catching an Asian banjo is as simple as picking it out of the water (the fish will not put up much of a struggle). Release it, and it will make no attempt to swim, drifting with the current until hitting the bottom.
The Asian banjo bears an uncanny resemblance to the real banjo catfishes (family Aspredinidae) of South America, and this resemblance is not simply due to convergence, as a close relationship between akysids and aspredinids has been shown in recent studies. Like the banjo cats, Acrochordonichthys occasionally molts and sheds its old skin (during this process, the old skin peels off in large patches, which are usually promptly gobbled up by hungry tankmates), although the reasons for doing so are not clear. There is a conspicuous axillary pore at the base of each pectoral spine, which produces a milky-coloured substance when the fish is greatly disturbed. This mucus is poisonous to other fishes and personal experience has shown that it is capable of killing other fishes in the vicinity within seconds. Out in the field, we learnt very quickly to bag Asian banjos we caught separately, as the very predictable outcome of placing a highly stressed fish into a bag of other fish left us with a still very stressed catfish in a bag full of dead fish. On another occasion, a large Asian banjo I kept decided to die and take out my entire tank with it in a massive apocalyptic fit (note to self: do not keep Asian banjos in the same tanks as my prize fish).
Acrochordonichthys species are difficult to identify due to the great variability shown in color and many other external characters. A recent revision by Ng & Ng (2001) recognized nine species. The species most commonly encountered in the aquarium trade is A. rugosus, as many of these imports hail from southern Thailand (where only one species occurs). They readily feed on bloodworms in the aquarium, although their lethargy means that the only possible way to ensure that they get enough food is to drop the food right in front of their mouths. In the wild, Asian banjos are ambush predators and a large (ca. 100 mm SL) specimen captured in northern Peninsular Malaysia regurgitated three loaches (Nemacheilus) and a catfish (Glyptothorax).
In the wild, Asian banjos are found only in clear, swiftly flowing forested streams with sandy or rocky bottoms, the fish preferring to rest against tree stumps and fallen logs in deeper parts of the stream. As such, the fish is not easy to catch with nets, although the aquarium collectors in southern Thailand catch large numbers by simply sinking lengths of hollow bamboo rods into the river bed and harvesting the fish from within the rods a few days later.
Its gill openings include an unusual spout-like structure found immediately below the base of the pectoral fin. The water leaving the gills is apparently channeled through this spout, and the fish may be able to use this to jet-propel itself through the water in the same manner as aspredinids.
With the personality of a rock and fairly demanding needs, this occasional import is not for the beginner. Most aquarists are not enamored of keeping a fish that barely moves and has the potential to wipe out the entire tank in seconds, but the Asian banjo certainly possesses enough interesting traits to make it a worthwhile addition to the catfish enthusiast's tank.
Ng, H. H. & P. K. L. Ng, 2001. A revision of the akysid catfish genus Acrochordonichthys Bleeker. J. Fish Biol. 58: 386-418.
Copyright information for the images used in this article can be found on the species' full Cat-eLog page.
|Cat-eLog Data Sheet|
|Scientific Name||Acrochordonichthys rugosus (Bleeker, 1847)|
|Common Name||Asian Banjo Catfish|
|Type Locality||Java, Indonesia.|
|Synonym(s)||Acrochordonichthys buettikoferi, Acrochordonichthys platycephalus, Acrochordonichthys varius, Acrochordonichthys zonatus, Pimelodus rugosus, Pimelodus zonatus|
|Pronunciation||ack roe KOR don ick thees - rue GO suss|
|Etymology||Acrochordonichthys: From the Greek akrochordon, meaning wart, and ichthys, meaning fish; in reference to the tuberculate skin. rugosus alludes to the rough textured skin of this species.|
|Size||110mm or 4.3" SL. Find near, nearer or same sized spp.|
|Identification||Catfish of the genus Acrochordonichthys are cryptically coloured species generally found at the bottoms of rivers throughout Southeast Asia. They have a highly rugose skin with tubercles arranged in longitudinal rows along the side of the body, a long low adipose fin and an emarginate caudal fin. |
Generally dark brown with many irregular light brown patches.
|Sexing||Difficult to sex. Males have a more slender genital papilla immediately in front of anus. Females tend to be larger and fuller-bodied.|
|Distribution||Asia: Peninsular Malaysia and the Greater Sunda Islands (except northeast Borneo).|
Pacific, Greater Sunda Island Rivers, Borneo Waters, Western Borneo Waters, Kapuas (click on these areas to find other species found there)
Indonesian Waters, Citarum (click on these areas to find other species found there)
Pacific, Greater Sunda Island Rivers, Borneo Waters, Barito (click on these areas to find other species found there)
Pacific, Greater Sunda Island Rivers, Sumatra Waters, Musi (click on these areas to find other species found there)
Pacific, Malaysia Waters, Peninsular Malaysia Waters, Pahang (click on these areas to find other species found there)
Pacific, Malaysia Waters, Peninsular Malaysia Waters, Selangor (click on these areas to find other species found there)
Pacific, Malaysia Waters, Peninsular Malaysia Waters, Terengganu (click on these areas to find other species found there) (Click the map-icon to show/hide map of species distribution)
|pH||5.0 - 7.0|
|Temperature||18.0-25.0°C or 64.4-77°F (Show species within this range)|
|Other Parameters||Requires fairly well-oxygenated water and a strong current is preferred.|
|Feeding||Ambush predator. Easily adapts to a diet of frozen food and pellets in the aquarium. May eat small bottom dwellers.|
|Furniture||Inhabits clear, swiftly flowing forested streams with sandy or rocky bottoms; hides under submerged logs or rocks with some leaf litter in the swifter parts of the stream. The fish does appear to move about after dark, as it is often found wedged under cover during the day. Driftwood and rocks seem to be their favorite cover, so provide plenty of these.|
|Compatibility||Ambush predator. Avoid small bottom dwelling tankmates (see Feeding).|
|Suggested Tankmates||Suitable for a community tank. Ideal tankmates are active mid-water fish such as barbs and rasboras. Will not do well in a tank with many bottom dwellers, as they tend to be outcompeted for food due to their lethargy.|
|References||Verh. Batav. Genootsch. Kunst. Wet.v. 21 - pp11|
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|More on Acrochordonichthys rugosus|
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|Last Update||2010 Oct 02 04:52 (species record created: 2003 Mar 01 11:22)|
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