Catfish of the Month Right November 2002

Platystacus cotylephorus
Eel-tail Banjo Catfish, Banded Banjo, Båndet Banjomalle (Denmark), Maulbruetender Hexenwels (Germany), Mottled Eel-tail Banjo Catfish, Whiptail Banjo Catfish - Platystacus cotylephorus   Bloch, 1794

Article © Julian Dignall, uploaded November 01, 2002.

Eel tailed Banjo Catfish are uncommonly but reliably occurring imports. Chief among imports of this small but fascinating group of catfish is the Mottled Eel-Tail Banjo Catfish,Platystacus cotylephorus. The fish, at least for a Banjo Catfish (or Asprenidid), displays attractive patterning and an intriguing shape. Striking features include the random mottling colouration which - especially on mature males - gives the fish the appearance of rusting flaky paint work and a very long, curling, eel tail. In rare fits of exercise, the rays of the anal fin - which runs along the entire underside of this tail - become erect, giving the fish a menacing profile.

Raised parallel lines run along the fishes tail and this feature is most useful in distinguishing this species from the similar Aspredo aspredo. It is perhaps the variance of colouration both between individuals and the sexes in Platystacus which has led to several attempts to synonymize the two genera. Aspredo does not exhibit these rows of tubercules along the tail (you can just see them in the picture below).

Platystacus cotylephorusClose-up of row of tubercules

P. cotylephorus can be found in coastal areas of north eastern South American rivers that spill into the Atlantic - so is best considered a brackish water fish. It is so adaptable however that it can easily be accommodated in a more traditional amazon style aquarium, though a central requirement from its wild habitat is a soft or light substrate within which it can bury itself. This master of disguise can convincingly disappear from view in such a tank but will not always do so, especially when many other fish are present above it in the water column.

Reproduction is this catfishes main talking point. Females are sometimes (although very rarely) imported with eggs still attached to the underbelly - see picture to the right. These eggs are attached by minute hair-like threads. Whether these are purely for mechanical attachment or provide some form of nutrient or gas exchange remains to be fully explored. More recently it has been suggested that oxygen is supplied to the eggs via these threads during the term of attachment. Perhaps this would allow the female to continue to bury in the muddy, oxygen starved substrate of a silt laden river mouth. Here the river is wide and flows at a slow pace, allowing some silt to drop out of the water column and provide a perfect home for burying fish.

Platystacus cotylephporusEggs attached to belly of female

Other, earlier theories suggest that the threads merely provide a method of keeping the eggs attached to the female as she shields them during migration upstream into purer freshwater. These Banjo catfish are the most adept swimmers in their family and a migratory lifecycle is not unfeasible. However, whether the females migrate into freshwaters with eggs or the young fish do so on their own later, is unreported.

The young hatch and are replicas of their parents at under a week old and less than 8mm long. Microworms appear the best food at this stage. Nothing regarding fully captive reproduction is recorded; solely the hatching of eggs attached to females at import.

Copyright information for the images used in this article can be found on the species' full Cat-eLog page.

Down Cat-eLog Data Sheet
Scientific Name Platystacus cotylephorus  Bloch, 1794
Common Names Eel-tail Banjo Catfish
Banded Banjo, Båndet Banjomalle (Denmark), Maulbruetender Hexenwels (Germany), Mottled Eel-tail Banjo Catfish, Whiptail Banjo Catfish
Type Locality No locality.
Synonym(s) Aspredo cotylephorus, Cotylephorus blochii, Silurus hexadactylus
Pronunciation plat ee STAK uss - coat ee LEFF or uss
Etymology Platystacus: From the Greek platys, meaning broad or flat and the Latin acus, meaning needle; in reference to the shape. Cotylephorus: meaning sites for the attachment of developing embryos, which in this case refers to the ventral area.
Article Link - Shane's World Right Catfishology Right The Eel-tail banjo catfish Platystacus cotylephorus
Down Species Information
Size 318mm or 12.5" SL. Find near, nearer or same sized spp.
Identification The fishes mottled colouration is very variable - almost to the point of no two individuals looking exactly the same.
Sexing Females appear more brown than black with very little or no mottling. Males by contrast are darker and show high contrast mottling. Mature males have larger pectoral fins than equally aged females.
General Remarks This species is able to produce bark-like sounds by quickly moving the pectorals. These sounds are probably used to locate each other during mating periods and certainly when being attacked.
Down Habitat Information
Distribution Central and South America: Venezuela to northern Brazil (including the lower portions of coastal rivers).
Atlantic, Western Central Atlantic (click on these areas to find other species found there)

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IUCN Red List Category Least Concern, range map and more is available on the IUCN species page. Last assessed 2020.
pH 6.0 - 8.2
Temperature 22.0-25.0°C or 71.6-77°F (Show species within this range)
Other Parameters Although the fish tolerates lower, the fish should really be kept at as near to a neutral pH as possible. Water should be medium hard.
Down Husbandry Information
Feeding A nocturnal scavenger. Will eat most food after lights our. Can be tempted to eat frozen foods during the day. User data.
Furniture A large sandy bottom with leaf cover is ideal, fish of all ages will bury in the sand. Larger fish will bury in gravel.
Compatibility Will eat small fish and shrimps but otherwise entirely docile.
Suggested Tankmates Small to medium sized hardy, preferably Amazon, fish that do not mind the higher pH and hardness this species prefers. Care should be taken to avoid fish that will pick away at the unmoving partly buried catfish.
Breeding Not reported in the home aquarium, but evidence exists of the method of reproduction. See catfish of the month article.
Breeding Reports There is no breeding report.
Down Further Information
Reference Naturgeschichte der ausländischen Fische v. 8, pp 54, Pl. 372.
Registered Keepers There are 35 registered keepers, view all "my cats" data.
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Last Update 2020 Oct 23 04:10 (species record created: 2002 Nov 01 11:22)

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