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Shane's World Right Arrow Species Right Arrow A voracious ambush-predator not without charm • Article © Wolfgang Ros, uploaded July 07, 2007

Up-to-date information on the care and behaviour of species belonging to the genus Cephalosilurus is, at best, hard to find. But perhaps it is just this "air of mystery" that stimulates one or another aquarium enthusiast, as, ultimately, such unusual animals can become fascinating observation objects.

A portrait of a predator with the large head, the small eyes and the short barbels

Belonging to the catfish family Pseudopimelodidae, at the time of writing, the genus Cephalosilurus contains only four described species. With that in mind, it is initially surprising that even in some specialist internet forums much confusion prevails when specimens are introduced to the forum members by means of photographs.

The first part of the generic Latin name (the Greek "Cephalos") clearly relates to the fish were are discussing here: "Cephalos" means head, and how! The broad shape of the head gives the fish a massive upper body half. In particular, attention is drawn to the uncommonly large head because of the small eyes, but also to the equally enormous muzzle which is almost as broad as the head! That given, whether it is fair to state the species belonging to this genus are prime examples of so called "monster catfish" (a term used in English language predatory fish forums) is perhaps undecided. At least in this article it is shoved to the foreground. We begin with a short overview of the genus, and will then describe our own experiences with the identification and care of some species.

The two largest of the four described Cephalosilurus species are C. fowleri, resident in Brazil and C. apurensis of Venezuela. If continuing to rank by decreasing size, these are followed by C. nigricaudus of Surinam and the smallest species, C. albomarginatus of Guyana. Above all, the larger species prefer rivers with rocky substrates and the associated opportunities for good hiding places. There they mainly hunt fish by remaining motionless and very well camouflaged. Aside from C. albomarginatus, which has probably not been introduced into the hobby, the other species are imported occasionally. In the trade they cost - depending upon size and (not always correctly) identification - between €60 and €200; in most cases these imports turn out to be C. apurensis.

Species identification
On asking our local fish dealer we found that none of the species belonging to the genus Cephalosilurus had been seen so far and this gave us little hope of being able to buy these fish. However, we had more success with the on-line stock lists of specialized catfish dealers. Using one we discovered, ordered and received our first two C. apurensis. When unpacking the polystyrene box they arrived in we found that, due to unexpected cooling (despite heat packs and other precautions), the temperature of the water in the two bags was around 18°C. Although the bags had sagged and the animals did not move any longer it was obvious they were also not yet dead. After slow adapting of the temperature they were set into separate tanks. In both cases we had prepared these beforehand — according to their natural habitat - particularly with large rounded stones with the addition of bogwood and a cave as potential hide-out.

Our first specimen of C. apurensis Our first specimen of C. apurensis
Our first specimen of C. apurensis

Both fish recovered themselves rapidly from the strains of transport. They were brownish with grey-black spots, roughly arranged in bands, this colouring, that is at least at a young age, is typical for C. apurensis. Also their robust body with the large rounded caudal fin indicated this species. What, however, did perplex us somewhat was this quite dark colouring of the caudal fin which seemed to rather point to C. nigricaudus (this species’ Latin name means "black tail"). So, we sent photos of the animals to the Brazilian ichthyologist Dr. Oscar Shibatta (Londrina) who scientifically is occupied with the Pseudopimelodidae and questioned him particularly on this issue. He answered that all Cephalosilurus - at least at a the young age - have dark tail fins; so from this feature alone, no conclusion yet could be reached on a certain species’ identity. Since our specimens were 12 and 16 centimetres long and clearly young animals, their idenitfy remained unclear, particularly given the scarcity of photos which are suitable for comparison purposes and show with certainty C. nigricaudus. Some keepers report that the outer mandibular and maxillary barbels are the same length in C. nigricaudusem> and different lengths in C. apurensis, however this is, scientifically speaking, unconfirmed and we do not wish to occupy the reader with this further. The fact seems to be that C. nigricaudus is actually more darkly coloured than C. apurensis. The demarcation of the species becomes extremely difficult, and according to Dr. Shibatta, a 100% positive identification requires not only the exact collection locality but also a count of the specimens gill rakers (these are internal bony or gristly extensions of the gill arch). Their number varies with C. apurensis around 27 and with C. nigricaudus lies between eleven and 16. However, as fishkeepers, we wanted to avoid this procedure with our animals as it probably can only used with dead specimens.

Our second specimen of C. apurensis Our second specimen of C. apurensis
Our second specimen of C. apurensis

According to our importer, with whom we had got in touch with again, our catfish originated from a Colombia import, however definitely were caught in the Rio Apure in Venezuela. Therefore, because of collection locality we designated our species, C. apurensis.

Later we took delivery of a third specimen of the genus Cephalosilurus from another source and was being sold as C. fowleri. The price confused us somewhat because this species was always sold more expensively. Indeed the 20 centimetres long specimen differed in terms of colour from the two other animals, however, it was not clearly brighter, although, for C. fowleri it could have been if just a little too dark. Its shape also was not noticeably flatter — another characteristic of C. fowleri; see André Werner (2005): "New import: Cephalosilurus fowleri" together with photo in: "Die Aquarien- und Terrarienzeitschrift" (Datz) 58 (11): 29.

Cephalosilurus nigricaudus Cephalosilurus nigricaudus
Our third, at the time or writing unclassified catfish of the genus Cephalosilurus, which later turned out to be C. nigricaudus.

Was our third fish possibly an undescribed species of Cephalosilurus? Outside of the four aforementioned described species, there are at least some specimens, the photographs of which appear from time to time in predatory fish forums. Due to remarkable differences, they don’t fit exactly right in any of the four described species. Nevertheless most of them might have to be added C. apurensis in the long run as it appears there are obviously different variants of this species which look different in colour and patterning depending upon origin. When asked, the second dealer communicated that the third specimen originated from Venezuela; an exact location was not well-known. With this information we could discount any thoughts of C. fowleri as it exclusively occurs in Brazil. Perhaps our third specimen has more to do with C. nigricaudus (however its distribution area would have to be enlarged and not exclusively limited to Surinam) or around a variant of C. apurensis. After supplying photos to Dr. Shibatta, he explained that the identification problem here could only be finally clarified by scientific investigation of the animal (including counting of its gill rakers). As this third fish grew, it became darker still and also exhibited other minor differences in body form and even in behaviour. Compared with the two other animals, it altogether does not only seem to be somewhat more aggressive and attack minded, but it is also by far more glutinous. Additionally only this specimen leaves behind a kind of secretion (probably primarily under its mouth) when it vacates its regular resting place.

Deposit left on stone under mouth of resting catfish
Deposit left on stone under mouth of resting catfish.

Keeping in the aquarium
The species C. apurensis, C. fowleri und C. nigricaudus are sporadic aquarium imports and will indeed grow large, but however do have a crucial advantage over other similarly sized species. They loyally stick to their hiding place, the urge to move is only very weakly felt and, compared with some other large predatory catfish, are not good or even persistent swimmers. Even if they are able to spurt abruptly — and they only do this in exceptional cases such as escape or predation - then they prove to be, exactly as hinted at by their clumsy shape, rather slow-moving. Our animals only actually move if they expect food, then they come out from their hiding places. Therefore, for keeping these fish in aquaria, one needs a large surface area but plenty free swimming area is not a necessity. Even with lengths of over a half a meter they are still well accommodated in six foot tanks. On the one hand, the width of the tank is important. It should amount to at least 70 centimetres. Only then it is ensured that it is possible to create adequate hiding places for adult animals. On the other hand, again considering adult fish, one should aim for a tank height of at least 65 to 70 centimetres, and this is connected with full grown size and "favourite position", with which we will deal later. Keeping as such surely accommodates the fairly short barbels of these species. By comparison, similarly sized long-barbeled and actively swimming predatory species such as Leiarius pictus need far roomier tanks, in order to guarantee that their barbels don’t simultaneously touch the side walls of the aquarium thereby keeping those fish in a constant state of stress.

So that the light sensitive catfish feel secure and comfortable, the tank should only be moderately lit during the day. Adding floating plant cover, which provides in parts for darker areas, is a good idea too. The recommended weak lighting renders many plant species unsuitable. Beside undemanding floating plants, Vesicularia dubyana and Microsorum pteropus are suitable. Otherwise one can use if necessary Cryptocoryne or Anubias species. Economic use of these plants species is suggested however as they can be easily uprooted by the bulky catfish. As for substrate, a mixture of gravel of different granulation is recommended. The creation of a den for hiding in is vitally important; fortunately cave or cave-like hiding places of any kind are taken. These are necessary at least for the well-being of juvenile animals.

C. apurensis C. apurensis
C. apurensis needs hiding places for its well-being, at best they only poke out their heads as shown here.

For larger specimens, a roomy, firm shelter is recommended, it should at least give the animal the ability to retreat under or behind roots, woods or between large stones. Beware that the catfish gleefully excavate hollows so as to redesign and expand on their own hiding places. It may be obvious, but under no circumstances should the keeper create a hideout by loose stacking up of heavy stones! Even if the animals accept this initially, their increasing strength will one day make it possible for them to bring the stones crashing down with obvious and catastrophic consequences!

C. apurensis
This individual has proclaimed its "hiding place" between large stones.

Obviously C. apurensis is very durable, because diseases never arose with our animals. Even the concern that housing them could become more difficult because they originate from running waters is unfounded due to their remarkable adaptability. One should provide a gentle current nevertheless. Also recommended is the employment of high performance filtration, and as with all large fish, weekly partial water changes are an obligation. Other water parameters are of a lesser importance. The temperature should lie between 22 and 26 degrees centigrade, however at least temporarily, these animals will also stand higher temperatures.

Feeding these animals is unproblematic. In our experience with C. apurensis in the aquarium is that it initially only would eat living fish. It very soon however became accustomed to other foods. From the beginning they could be lured from their hiding places with shrimps, worms, thawed out smelt and additionally with filleted fish pieces. Even freeze dried food tablets were taken; however these should solely be offered to smaller specimens, for larger individuals such servings are much too small. Sporadically we feed our animals almost exclusively with pieces of thawed out tilapia fillet and trout. Obviously pieces of trout with bones and other components contain everything that is important for their digesting but also its growth and in addition for its well-being. Naturally predatory catfish gladly take living fish. With C. apurensis the supply of live food is, however, unnecessary. During feeding, one cannot basically go wrong as long as feeding is not too much and also not too often. With these catfish, it is best never to allow them to become completely full. So as long acclimatized specimens do not visit the area where they are fed, they should not get food. Otherwise they will easily get obese. Their large and very flexible stomach is evolved to digest giant portions whenever food is available, but in turn this is an adaptation to survive naturally occurring fasts in which for days, or even weeks, no food is available. In addition another weight factor comes in. The animals do not move frequently and then only relatively tiny distances. Since they do not burn much energy, they do not have a fast metabolism and for this reason again do not require of daily feeding. Two to three feedings per week worked satisfactorily with our specimen. In actual fact, even a single, larger meal once a the week would be completely sufficient.

Aquarium observations
If you want an interesting insight into the daily goings on of these fishes, then the keeper has to places the obligatory hiding place in such a way that it can be well seen. Then the keeper will soon state that their C. apurensis, which will take up a position in which the first third of its body is up and out of the hiding place, is officially looking after them! A well placed hideout will also allow the keeper to observe the animal, after it has snatched a food morsel from elsewhere and returned to base. It is the catfishes custom to devour and digest this completely (particularly as a young animal) only upon return to its dwelling. Safely ensconced, it turns regularly, at times rolls onto one side, and, every now and then, even lies on its back. Several times it briefly stretches its mouth wide open and seems to totally lock its body. These movements probably help digestion of larger food morsels.

C. apurensis C. apurensis
To aid digestion, C. apurensis tears its mouth wide open.

In order not to have to give up its den as it outgrows it, C. apurensis will deploy much strategy and effort to extend and adapt the hiding place. If the animal takes up its usual resting place, for example, under a bogwood root, then one is to be able to quickly observe how it moves parts of its body back and forth across the substrate, in particular the head and belly, in order to gain more space by developing a pit.

C. apurensis C. apurensis
As it gets bigger, C. apurensis must be offered roomier hiding places (in this case, a large amphora).

C. apurensis
The second opening of the same amphora is useful for observation purposes

C. apurensis releases tremendous force during these excavations and will even move larger stones by means of its tail fin. For this reason it’s best to anticipate and provide cover appropriate to the fish as it grows. The types of artificial caves found in the aquarium trade can only serve young animals as hiding places. For specimen of more than a foot body length, these caves are usually too small or limiting. From a foot onwards, we provided increasingly larger hiding places such as roots and/or large wood-pieces which also looked visually pleasing. One can also help with large sized specimens — and to some extent remain optically pleasing — by adding amphora or similar vases from garden centres. Bottlenecks appear popular and these openings were, if necessary, extended. As soon as C. apurensis accepts a newly offered hiding place, it defends it exactly the same as the old place.

C. apurensis
Unrestrained strength: Over night the animal turned the heavy amphora once

After lights out, C. apurensis usually emerges from its shelter and moves sedately once or twice around the tank, before it returns into its hiding place. Interestingly enough all our specimens have alternative resting places nearby filter outlets, in which they rest for some hours during the night. In nature, the animals probably visit places of different water flow at night depending on what and where the local food fish is. During their "tours", if obstacles stand in their way (such as bogwood) they then sometimes try, despite their heavy girth, to swim straight through. If that does not succeed, they react with a distinct change of mood. Enraged, they seem to indignantly rear up against the inanimate barricade, and with opened mouths they try to completely force it away. The unrestrained strength unleashed must not be underestimated by the keeper. In this situation, the larger the specimen, the less tolerance of aquarium kit or décor is shown. Such larger animals can abruptly bring their wrath to bear on objects besides woods and stone. Their huge mouths can also be used to destroy technical devices. The aquarist who fastened the heater/stat directly to the side glass is in trouble! Accessories such as heaters and powerheads may not be left unprotected in the tank with these strong and sometimes somewhat self-willed animals! This truculent behaviour can also be brought on by (in their view) long overdue feeding.

C. apurensis C. apurensis
This hungry specimen is in a bad mood.

All species of Cephalosilurus are primarily true lurking predators, their bonanza is being when other fish on their annual migrations swim through their patch. Similarly in the aquarium they lurk in front of their cave or between large stones and wood motionlessly awaiting fish of suitable size approaching near enough. They are not however as camouflaged as the more specialized South American lurking predator Lophiosilurus alexandri which entrenches itself almost totally in sand. When hunting, the animals can partly and gradually stalk their victims but sight is only a subordinate function. Mainly there are the barbels which signal to the catfish - via even the lightest of water movements - when the promise of success is near. It snaps open its enormous muzzle. An instant vacuum develops which sucks in the victim. Once snapped shut, the prey is help firmly tight with the help of the strong jaw and a multiplicity of smaller pointed teeth which are arranged in several rows. Then the catfish partly retreats into its hiding place, the prey not yet completely devoured. After longer involuntary fasts, to which however C. apurensis can quite attune itself, the hungry catfish will dare itself to tackle larger fish if more "suitable" food fish are not available. Then it can snatch fish of approximately equal size and gulps them down very gradually head first. During these feats, the mouth can be stretched significantly. On such a meal the catfish can live a long time with further need of food.

Relationship to the keeper
Young or newly acclimatized C. apurensis are a little shy but afterwards the confidence of particularly larger animals is impressing. They are biddable, can be properly tamed and be accustomed to a firm feeding regime. Our specimens currently swim to the front glass as soon as we approach the aquaria. At the usual feeding time, they appear even with the lights on. Although otherwise predominantly bottom dwelling, during feeding, C. apurensis does not shrink away from rising up into the top third of the water column. There, in a vertical position with the head uppermost, they stand before the food hatch. Their outgoing charm is hard to miss.

As soon as the food hits the water surface, C. apurensis tears open its mouth. In addition to this gluttony, if we immerse an algae magnet in the tank it causes the animals to heartily bite into our fingers. So, we would better like to refrain from their designation as "hand tame"! In such an inadvertent test however, they prey snatch can be closely reconstructed. From this we learn that shortly after actual snatching, the immediately second, stronger and a bit higher bite is possible making escape unlikely even for large prey fish. For the keeper of younger fish, such a gripping is not dramatic; proper bites of larger animals however are pretty painful and leave grazes as a consequence.

C. apurensis C. apurensis
During feeding, these catfish are not always as tame as appears here.

Against this background, you may find it surprising that we touch and even pet one of our specimens. Its body feels exquisitely soft probably due to the high fat content. Unfortunately, this specimen does not send gentle signals when it becomes weary of such "tender loving care". Rather abruptly it tries to snatch at the hand - one must be rather fast in order to withdraw the fingers in time.

C. apurensis C. apurensis
Once used to it, C. apurensis permits contact and enjoys it obviously - but caution is required here also.

Growth and final size
Every now and then one reads that C. apurensis is a species that, at least compared to other predatory catfish, grows rather slowly. We cannot confirm this. In their first, and also strongest, growth phase our specimens in only three months carried out jumps of 12 to 18, 16 to 25 and 20 to 28 centimetres. After a length of 30 centimetres, growth slows down somewhat, the 40-centimetres mark is reached after a further ten to twelve months. Our largest animal clearly exceeded a total length of 45 centimetres. From this size C. apurensis is adds more to its girth than to its length, bet even then length growth has not yet stopped. So is to be assumed when fed well, the animals can grow up in the aquarium slowly and constantly to around 65 centimetres of length in a decade. According to Japanese sources, even lengths of 70 centimetres and over are possible.

The growth of these animals also brings colour pattern changes. The young dress of C. apurensis loses some of its contrast, and yields brown and moderate yellow-orange to orange colour pattern. Therefore (aside from the common name "Jelly Catfish") comes the - not entirely applicable — common name of "orange catfish". These names are likewise used for C. fowleri and the latter fits this species much better because of the orange base colour of C. fowleri. As adults, these animals are even more sedate - perhaps "chilled" is a better word - and dispassionate, as if they almost know that hardly anything can harm them.

C. apurensis C. apurensis
Typical juvenile colouring of C. apurensis.
C. apurensis C. apurensis
The adult colouration is optimally adapted to an environment of stones and wood. The "begging position" assumed at the usual feeding time.

It is easy for the keeper of C. apurensis to measure their animals and so to be able to record solid data about growth. This is connected with their described "begging position", which they punctually assume at the regular feeding time at the front glass. Rapid movements, which could affect the result of measurement and which have brought some aquarists to the edge of despair if they put the measuring tape in front of their fish, are not to fear with this species. In a relaxed state of mind, the animals will remain vertical at least for long enough to be measured and then fed.

Generally the genus Cephalosilurus is considered as very territorial; particularly this applies to the intra-species-aggression. C. apurensis does not only fiercely defend its own resting place, but also acrimoniously claims the surrounding district. Weaker tank mates are tormented until they perish due to injuries and continuing stress. Even in very large aquariums the addition of other species, in addition to other Cephalosilurus species, is not possible.

At first, when the moving them was possible without larger issues, we united our animals several times in different configurations for short time. The result was always the same: Either the "long time-resident" attacked the new kid on the block immediately and directly or the newly added specimen quickly moved in on the cave in which the other one was in to similar effect. As an aside, it showed this purposefulness in seeking out the incumbent catfish even if several hiding places were provided! Probably the animals exude substances which, due to their strongly pronounced sense of smell, make direct intraspecific detection possible for them. Just before meeting, the two fish would take a threatening position. Thereafter, in each case, the smaller specimen usually could not be intimidated by its larger comrade and contact was inevitable. With their bodies pressed together, both animals tested their powers in horizontal attitude, with mouths opened wide, attempting to force the other away. Additionally the tail fins were struck against each other. These fights looked threatening, but lasted only for a short duration, and soon one of the combatants took flight, whereupon we separated the fish again.

C. apurensis
Intraspecies aggression: Two young C. apurensis quarrel over a hiding place.

Indeed, as a young animal up to a length of 20 to 30 centimetres, C. apurensis behaves rather peacefully towards tank mates but, even by then, all fish that are not larger live in constant danger of being eaten. If one would like to keep the species with other catfish, then beside the non-predatory Loricariidae, most predatory catfish of South America are applicable above all, however these should not be too territorial for their part and at least equal in size. This is because as soon as C. apurensis takes offence or if the other fish wants to dispute rights to an occupied hiding place, it proves itself rather assertive. In the context of such an argument it positions itself first before the aggressor, in the confidence of the fact that this alone presents the sight of a massive shape. If that does not help, then C. apurensis snaps at the aggressor abruptly. Thus C. apurensis terrifies the opponent so much that in future meetings, the opponent backs off. Also several large and durable cichlid species can be kept together with C. apurensis. As soon as these come into the range of its favourite place, the catfish snaps at them to make clear its requirement for possession. Soon the cichlids will figure out the fairly small radius, which they may only cross if they wish to unleash a direct attack from the catfish. If one falls back to cichlids, then a weak night lighting system is an advantage. With one tank we decided to try out "so-called" moonlight lighting. It ensured that the catfish does not disturb its co-inhabitants too much at night, in this actual case, two adolescent Astronotus ocellatus. If the lighting is completely switched off, then the danger to co-inhabitants is highest as they may come into contact with the prowling catfish, take fright and scurry up the aquarium. And thus in C. apurensis even with only a moderate appetite, the instinct to hunt is woken.

C. apurensis C. apurensis C. apurensis
"Eye in eye": Generally C. apurensis gets along with its associated cichlids if they are only large enough. "Sic tempora mutantur": Even just nudged by the Astronotus, the catfish is going to attack. Told you!

C. apurensis
This tankmate (Heros efasciatus spec. "Red Neck")remains unmolested even in the dwelling of the catfish.

In principle, social nature is affected by surroundings and habit. If a C. apurensis was fed over a long time with living fish, then other species can hardly be kept together with it. Otherwise the social function, in our experiences at least, showed that if other fishes grew up together with the catfish; then they are regarded probably less as victims and rather as co-inhabitants. Actually a Petenia splendida female of not even 20 centimetres of length was kept from the beginning in one of the C. apurensis tanks without having ever been troubled by the catfish. However a Crenicichla sp. from 25 centimetres, which a friendly aquarist gave us due to circumstances, and which we put in with one our C. apurensis, didn’t survive the first night. On the next morning all that could be seen of it was the tail fin, which hung from the muzzle of the predator while the front of this fish was already digested. The catfish, nearly motionless, sat in its hiding place breathing very heavily; its whole abdomen seemed fit to burst, so strongly had swollen. Only after a further day was the prey completely choked down. Here we learn both that new acquisitions are endangered, but also that C. apurensis possesses the ability to be able to attack and to devour even fish that other predatory catfish of comparable size (even if they could swallow these) had to release again, in order not to choke on it.

In another case, the victim, a nearly 25 centimetre long A. astronotus was added to the aquarium containing the aforementioned two somewhat smaller species due, although snapped into the catfishes jaws, it had luck yet. Just a few hours after putting it in the tank, we found it in the mouth of the catfish which at about 40cms is only 15 centimetres longer than the oscar. Even rapping on the aquarium did not impress the C. apurensis in the slightest. Only as it was gripped by hand around the head, did it release its victim. The Astronotus was immediately moved to another tank. Indeed, clearly scarred by the bite he miraculously survived the attack and just one week later, the bite wound could hardly be seen.

C. apurensis C. apurensis
Two snapshots: The catfish snapped up the Astronotus.
C. apurensis C. apurensis
The victim the next day and then only one week later - the healing process is well advanced.

C. apurensis
Cohabitation (here with Potamotrygon hystrix) is only possible with reservations.

To some extent the cohabitation with fresh water stingrays of comparable size (such as Potamotrygon leopoldi) is possible; however, this naturally requires completely different tank dimensions to those already mentioned in the housing of a single catfish! One of our animals is kept with a male P. hystrix. Our experiences related thus far speak for the fact that a peaceful co-existence is possible here. On the other hand, the aggressiveness of C. apurensis increases with age. Since Potamotrygon can, if necessary, defend themselves with their poisoned spine, separation keeping would have been required at the first sign of trouble.

C. apurensis
Spine of P. hystrix

One time, after feeding the tank housing C. apurensis and P. hystrix, a fight fraught with such consequences broke out: The stingray strayed into the Amphora which was being used by the C. apurensis as its hiding place. This was the first time at all that the ray dared go in, it was attracted there by remnants of food. Immediately the catfish snapped at the ray. The ray panicked, could not find the exit initially and probably therefore employment of its sting ray to defend itself. It hit the catfish around the caudal fin; fortunately it survived the sting. For approximately one month, it lived completely withdrawn and did not eat. After a further three weeks however, the wound was no longer to be seen and the animal behaved completely normally again. This may permit the conclusion that C. apurensis is at least partly immune to the Potamotrygon venom - "partly" because the sting hit the catfish in a comparatively insensitive place and in addition, it was obviously not "completely" unaffected by the incident. Therefore, as a precaution, we have replaced the amphora with a large clay-container with more and wider openings by which the ray can, without a doubt, swim free without problem. Since then we’ve not experienced any further incident.

For those who have an extremely large tank, cohabitation could to be considered for example with giant Characidae such as the red Pacu (Piaractus brachypomus), since the prognosis, even on a long-term basis, seems favourable here. All that said, with C. apurensis generally, keeping them alone always remains the safest path.

C. apurensis C. apurensis
C. apurensis showing injury from spine.

Sex differences
On the subject of sexual dimorphism in Cephalosilurus, there is no firm information. As far as our animals are concerned, on the basis of the entirely oblong and blunted form of the genital papilla, are obviously the same sex and males. Some suggest the fact that - as with Lophiosilurus alexandri - adult females are larger and in the front third of the body are broader and brawnier than males. Additionally, at least with C. apurensis, we can report differences in behaviour — the female is more aggressive. Again concerning the reproduction in Cephalosilurus, we have no knowledge; thus far they have not been captive bred. Since the catfish live solitary lives, a male pairing with a larger and stronger female may only be tolerated for a defined time period and only for the purpose of the mating in its area.

Those who have already kept smaller predatory catfish will be inspired by these large predators. Anyhow we are fascinated by the animals. With increasing size they - particularly due to increased confidence - gain more and more attraction.

Even if these catfish are, in our opinion, suitable to be kept in accordingly dimensioned home aquaria, their care remains something for real specialists: It must be clear that cohabitation is only conditionally possible in very large tanks. For most aquarists however, even the die-hard "Catfish freaks" among them, in the long term it might be too monotonous to fill their tank with a single giant.

C. apurensis

C. apurensisThis article was first published in May 2007 in the German publication: "Die Aquarien und Terrarienzeitschrift" (Datz) 60 (5): 38-42. Our thanks apply here for the Datz editorship and their editor-in-chief, Rainer Stawikowski, who gave us kind permission to publish this article on PlanetCatfish. Mention must also be made of our debt to Dr. Shibatta for the given details! In some places the text was supplemented, in addition further photos were added. © Copyright text and photos, Datz, published here with permission.


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