 ©
Copyright text and photos,
Aquaristik
Fachmagazin/Tetra Verlag GmbH,
published here with permission.
 
n the last years under the designated name "Pseudopimelodus
nigricaudus" there have been repeated introductions
of broad shaped catfish. Those have been 15 to 25 centimetres
long animals with the extra large head and the enormous muzzle
and assigned to four species so far in the genus Cephalosilurus,
which today is the valid name for the earlier genus name
Pseudopimelodus.
Striking are the similarities of C.
nigricaudus with C. apurensis which is the most
frequently imported species of this genus. Can distinguishes
be crystallized out?.
Probably because they are so dark and frowning, these plump,
little catfish every now and then are assigned to C. fowleri
which is notorious for its aggressiveness and is a third Cephalosilurus
species apart from C. albomarginatus, which has not
been introduced to aquarists yet.
Primarily here however no mistake is possible, because apart
from the brighter colouring, C. fowleri is to be identified
clearly by its slimmer shape and the flatter head.
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C. nigricaudus of 15 cm length with its typical juvenile
colouring. |
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C. nigricaudus
of 35 cm length: Caudal fin and tail
are still nearly black. |
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The Latin name “nigricaudus”
means “black tail”, and indeed already with young
specimen of C. nigricaudus the very dark colouring of
the caudal fin is remarkable. On the other hand according to personal
information from the Brazilian ichthyologist Dr. Oscar Shibatta
(Londrina) who is scientifically occupied with the Pseudopimelodidae,
and also with young specimens of C. apurensis, the caudal
is quite dark. So from this conclusion, one of the two species
can be told apart.
At present I keep two with the figuration and colouring nearly
similar in both specimens, of which one came from a private sale
and the other one was acquired from Tropic-Aquaristik as C.
nigricaudus. A comparison with one from Aquarium Glaser GmbH
bought by another aquarist approximately two years before as,
Pseudopimelodus nigricaudus which agreed was complete
in form, colouring and behaviour. At first sight they are quite
similar to my C. apurensis. By the way with regard to
price there’s not much of a difference; as young animals
they both can be bought starting from approximately 60 euro upward.
So what now is common with both species and which is much more
important for the enthusiastic keeper of these catfish, what are
the differences? Here are some beginning possibilities:
Habitat: Already the name
of C. apurensis shows that this species is to be found
in the Rio Apure of Venezuela. The habitat of C. nigricaudus
is limited to Surinam. If asking the dealers the exact origin
of these animals one mostly gets the answer that they were imported
from Colombia or Venezuela. The exact habitat can only rarely
be determined. If one comes to speak on Surinam then it is pointed
out that at least at the questionable time no exports from there
have taken place. A contradiction? Not necessarily, as a dealer
confirmed, because catfish also from Surinam were imported from
Venezuela. Besides it is questionable whether the actual area
of circulation of C. nigricaudus is really limited to
Surinam.
Gill rakers: According to Dr. Shibatta the number
of gill rakers (these are internal bony or gristly extensions
of the gill arch) varies with C. apurensis to around
27 and with C. nigricaudus lies between eleven and 16.
Since such a counting can be made only with dead animals, it does
not really help the aquarist with the identification of his specimen.
Colouring: Obviously there
are differences in the colouring. Both species indeed have a remarkable
juvenile dress by their black, partly in the form of stripes,
arranged marks. The juvenile dress of C. nigricaudus however
is altogether clearly more dark than of C. apurensis
especially in the head area which is light brownish. The stripes
are more on C. nigricaudus than with C. apurensis
which are less clearly pronounced and are replaced later by points
of different sizes and also with adult specimens of C. nigricaudus
there remains by the multiplicity of the affect of marks something
like a great big ribbon which drags on over the whole rear body
region. With C. apurensis at 30 centimetres in length,
the caudal fin and the tail are not so dark.
C. nigricaudus (left)
and C. apurensis in direct comparison.
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Figure: Compared with
its genus comrade, the body of C. nigricaudus is somewhat
flatter and the rear third seems to be longer. C. apurensis
particularly in old age seems so massive with its brawny head.
Both species also have a little bit different muzzle form.
Growth and final length:
At the 40 centimetres mark C. nigricaudus as C. apurensis,
bought as young fish of 15 centimetres in length, exceed to this
size not later than in 18 months, afterwards growth slows down
with both. Against the data of Fishbase one must assume with C.
nigricaudus from a minimum length which is with half a meter,
and the smaller of the two (according to Fishbase), C. apurensis,
really reaches even 65 to 75 centimetres (cf. Fishbase-website
of May 4th, 2008, where the maximal length of C. apurensis is
indicated with 29 centimetres and for C. nigricaudus - in both
cases male specimen - with 35 centimetres).
Behaviour: Actually as
to the behaviour of my specimen of C. nigricaudus one
could hit the nail squarely on the head in such a way that they
they love to hide itself and they eat wholeheartedly for their
life. Basically both  these
attributes also applies to C. apurensis. Nevertheless,
when keeping both species you will soon determine that C.
nigricaudus is a bit more nocturnal, otherwise however it
is more greedy. This is to be considered with its keeping, best
in a tank with a capacity of approximately 800 litres upward.
So it must be suggested that absorbed light and the supply of
a hiding place which is appropriate to the body size. One is not
dependent on giving live fish, the ambush-predator devours worms,
shell meat and after habituation also fillet of fish in enormous
portions. Therefore if at all one should socialise it only as
a young animal with larger and in addition high-backed fish. At
a temperature from 23 to 26° Celsius and otherwise "normal"
water equivalents these species prove very durable.
Blow the co-inhabitant, who comes too close for this, a good 45
cm long C. nigricaudus!
Also in the behaviour for the keeper there
are characteristics: C. nigricaudus needs more time for
its acclimatizing and cannot as rapidly be tamed as C. apurensis,
and if the food is given by hand, it shows itself as the more self-willed,
more incalculable and thus in the long run also more snappy, with
which one should act out with special caution.
In relation to species and other genus comrades
C. nigricaudus gives itself out as much more aggressive
than C apurensis. With the entrance of sexual maturity
it becomes feisty also in relation to other socialised fish of every
species and size. If it cannot overwhelm and devour these, it becomes
dangerous for them by its strong biting. Some observers would describe
this behaviour as bad and mean, however it serves exclusively the
purpose to drive away all further, and even if they are only potential
one, food competitors out from their own territory. The species
is even capable of attacking anything which is unprotected in the
tank like heaters or pumps. I could observe with my larger, in the
meantime nearly half a meter-long specimen, how it refused the right
to exist to an additionally installed interior filter and how it
struck out at it with such madness with its head against it until
I had to remove it.
All in all C. nigricaudus from
the colouring is more attractive. It does not grow as large as
its genus comrade but adjusts this however by its aggressive approach
to its keeper and potential socialised fishes. So who is looking
after the mysterious and incalculable and also fascinating should
decide for this species. Who however enjoys a calm, to some extent
reliable giant overeater, which is sensitive also towards heaters
and pumps, C. apurensis is to be recommended.
Literature:
Arendt,
K. (2004): Cephalosilurus apurensis (Mees, 1978), ein Raubwels
aus den Llanos Venezuelas, AF 178: 26.
Ros,
C. und W. Ros (2007): Cephalosilurus apurensis - Ein gefräßiger
Lauerräuber, aber nicht ohne Charme, Datz 60 (5): 38-42.
Werner,
André (2005): Neu importiert - Cephalosilurus fowleri,
Datz 58 (11): 29.
This article was published in February/March
2008 in the German publication:
Aquaristik
Fachmagazin & Aquarium heute (AF) 40 (1), Nr. 199: 34-36.
 Our
thanks apply here for the AF-editorship and the Tetra Verlag GmbH
(Dr. Hans-Joachim Herrmann and Eckhard Grell-Herrmann), who gave
us kind permission to publish this article on Scotcat. Mention must
also be made of our debt to Dr. Shibatta for the given details.
© Copyright text and photos, Aquaristik
Fachmagazin/Tetra Verlag GmbH, published here with permission.
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