Dwarf Wood Cat - Helogenes marmoratus Günther, 1863
by Lee Finley, uploaded November 01, 2006
There is a British saying which is a good example of Murphy's Law in action. Perhaps it's not just limited to UK usage but anyway, it goes along the lines of, "You wait half an hour for a bus and then two come along at once!". It's amazing how often actually this happens, the phenomenon is indeed unrestricted to public transport and this month's featured catfish is another good example. Despite a decade of articles, we've yet to feature the cetopsidae or whale catfish family. Just because I can (and perhaps because we've never done it before), I'm running this months' article from Lee Finley and next month we'll look at another species from the same family albiet with a different historical classification. Over now to Lee for a long overdue whale cat CotM Part I.
When one thinks of South American cetopsid catfishes the first thing that may come to mind is the thought of an eight to 10 inch Canero, or Candiru, gnawing its way into the body of some unfortunate fish. Such is the image (not without justification) that many of these catfishes have attached to them.
For this CotM entry I would like to offer some coverage of a cetopsid catfish. But the fish to be considered, Helogenes marmoratus, is about as far as possible from the image of the "ravager" that is noted above.
Helogenes marmoratus and the three other species in the genus (H. castaneus, H. uruyensis and H. gouldingi) have historically been placed in their own family, Helogenidae. In 1995 this situation changed when these fishes were incorporated into the family Cetopsidae. Granted this required some redefinition of the family and the Helogenes species were placed in the sub-family Helogeninae with all other cetopdids going to the sub-family Cetopsinae.
Of the four species of Helogenes, it appears that H. marmoratus is the only one that is commercially imported. H. uruyensis, which is only known from Southern Venezuela, has been pictured in the aquarium literature, but these photos are based on specimens personally collected by a German aquarist (Ingo Schindler). The other two species, H. castaneus and H. gouldingi, which are respectively from Rio Meta basin (Colombia) and the Rio Madeira basin (Brazil), appear to have not been imported into the hobby.
H. marmoratus is a small species with the largest known specimen measuring 7.3 cm (2.87 inches) in standard length. It has an elongate body with a noticeably rounded head. The color pattern can show considerable variation but is typically a darker mottled brown throughout. This species is basically nocturnal in behavior, but as with many catfishes this is open for modification in captive held specimens who will readily feed under lit conditions once they are settled in. The activity pattern in this species is seemingly one of all or nothing. When feeding, or looking for food, they are very fast movers spending time dashing around at their main feeding area - just beneath the surface of the water. But, when this passes they head for their favorite hiding place - plants.
H. marmoratus has the widest distribution of all the species and is known from Guyana, Surinam, French Guiana, Venezuela (Rio Orinoco and Rio Negro basins), and the Amazon basin of Brazil, Peru, Ecuador and Southern Colombia. It is typically found in flowing forest streams which may consist of clear or black water. They may be found living over a variety of substrates, but typically they are found in areas containing aquatic vegetation and/or leaf litter. It is these areas that are used as hiding / resting places. H. marmoratus will lie on its side among leaves on the bottom where its mottled coloration serves as great camouflage. In a more or less bare aquarium this fish will go and lie on its side on the bottom. This is natural behavior, but lacking leaves it does seem out of place. When there are plants, or there are roots, in the waterway H. marmoratus will wedge itself into these. If these go all the way to the surface the catfish takes advantage of this and will often go as high as it can. In fact, some recent work has shown that they can often be found resting / hiding at least partially above the surface of the water in such plant/root groupings. This hiding among plants behavior can be readily observed in the aquarium and it should be considered a necessity that floating or tall rooted bunch plants be a part of their home. Floating plastic "bunch plants" can also be used if you prefer. I had used a large group of these in a tank containing about eight H. marmoratus, and they seemed very comfortable wedging in amongst the plastic stems and leaves. Whatever your preference, do use such floating "plants" for this species. If they are lacking plants these are potentially very unhappy fishes.
General maintenance of this species is not difficult as they are not overly fussy. In that they are small in size a large tank is not needed and a group of six or so can be comfortably housed in a 10 gallon tank - although I would personally prefer, and recommend, one of 20 gallons. I would also suggest keeping them in a species only tank. This will let you really get to know and appreciate them. Moderately soft slightly acidic water with a temperature range of 72 to 78° F is fine. Couple this with good mechanical and biological filtration and regular partial water changes and you’ll have happy fish. Oh yes, don’t forget the plants!
Feeding H. marmoratus presents no particular problems and they will adjust to a wide variety of prepared and live, frozen and/or freeze dried foods. In the wild their diet consists entirely of terrestrial type (including flying) insects. Ants seem to be a particularly favorite food, but small beetles and other insects are also eaten. From what is known, all of these are taken from the surface of the water. The surface type feeding used by this fish is easily observed in the aquarium utilizing the varied diet noted above. I think that this little species is ripe for some experimentation using some various live insect foods…and I hope to shortly obtain another group of them to work in this area.
Nothing is known regarding reproduction in this species. This can be considered a plus for the catfish aquarist looking for a challenge.
So, if the generally bad PR on cetopsids has put you off, here is one that you might consider. I think that if you can locate some you will be pleasantly surprised - and very pleased.
This article has had 6562 hits. Photo credits for the images used in this article can be found on the Cat-eLog page.
|Cat-eLog Data Sheet|
|Scientific Name||Helogenes marmoratus Günther, 1863|
|Common Name(s)||Dwarf Wood Cat|
|Type Locality||Essequibo R., Guyana.|
|Synonym(s)||Helogenes amazonae, Helogenes unidorsalis|
|Pronunciation||hell LODGE en ease|
|Etymology||Helogenes: From the Greek helos, meaning marsh and the Greek genes, meaning birth; in reference to the habitat.|
|Size||73mm (2.9") SL. Find near, nearer or same sized spp.|
|Distribution||South America: Atlantic drainages of Guyana, Suriname, and French Guiana, upper Río Orinoco and Río Negro systems in Venezuela, Amazonas Basin in Brazil, Peru, and Ecuador.
Orinoco, Upper Orinoco (click on these areas to find other species found there)
Amazon, Middle Amazon (Solimoes), Negro (click on these areas to find other species found there) (Click the map-icon to show/hide map of species distribution)
|Temperature||22.0-26.0°C or 71.6-78.8°F (Show others within this range)|
|References||Ann. Mag. Nat. Hist. (Ser. 3)v. 12 (no. 72) - pp443|
|Registered Keepers||(1) amiidae, (2) Yann (k: 6), (3) T4FR (k: 3).
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|Last Update||2007 Nov 12 02:25 (species record created: 2001 Apr 21 00:00)|
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