Catfish of the Month Right January 2013

Pseudolithoxus dumus
L244, Black Spotted Orinoco-Ancistrus (Germany), Sortplettet Flyversugemalle (Denmark) - Pseudolithoxus dumus   (Armbruster & Provenzano, 2000)

Article © Elko Kinlechner, uploaded January 07, 2013.

Happy New Year to the faithful! The year 2013 is off to a flyer with a splendid "from river to reproduction" article, the type of which I am especially fond of reading in relation to any particular species. The original German article ("Und es klappt doch — Pseudolithoxus dumus (L244)"), or, "It goes nevertheless — Pseudolithoxus dumus (L244) was translated into English by its author, Elko Kinlechner, with minimal editing from me. Over now to Elko, to describe his lengthly involvement with this featured species.

Pseudolithoxus are most readily distinguished from other plecos by their extremely long pectoral fins. On the basis of this feature they are also called flyer plecos. Much time has passed between their initial introductions as l-numbers by DATZ magazine in 1996 and the first breeding success one of the species in genus Pseudolithoxus. At the end of 2011 I was delighted to discover fry after much futile effort.

The genus Pseudolithoxus was created by Isbrücker and Werner in 2001. The following four species, which Armbruster had originally described as Lasiancistrus in 2000, were transferred to the new genus:

Pseudolithoxus anthraxPseudolithoxus anthrax (L235)

Pseudolithoxus dumusPseudolithoxus dumus (L244)

Pseudolithoxus nicoiPseudolithoxus nicoi

Pseudolithoxus tigrisPseudolithoxus tigris (L259)

Pseudolithoxus anthrax is the type species of the genus. Considerably later in 2011 Lujan & Birindelli described another attractive species and they placed it in the genus Pseudolithoxus naming it P. kelsorum (L189). In addition, three undescribed congeners are known: P. sp. L328, P. sp. L385 and Pseudolithoxus sp. "Rio Guapore". Pseudolithoxus anthrax, P. dumus and P. tigris are the best known in the aquarium hobby as these three species are regularly exported from Venezuela. P. kelsorum is rare in the trade. The first import of P. nicoi to Germany was few months ago (near the end of 2012). Pseudolithoxus anthrax, P. tigris and P. dumus we find mainly in the upper Orinoco basin, especially in the Rio Ventuari. This river is mostly clear water but can be variously clear water mixed with black water or clear water mixed with white water. P. nicoi comes from the black waters in the vicinity of the Rio Casiquare and the Rio Atabapo.

Rio Orinoco near Santa BarbaraThe Rio Orinoco near Santa Barbara.

Upper Rio Orinoco and Rio Ventuari
Temperature of water 26 — 34 °C
pH ~ 6 — 7
Conductivity ~ 20 µS/cm

About four years ago I was able to buy a group (six plecos, most likely three males and females) of Pseudolithoxus dumus in Welsladen, Chemnitz. I kept only these plecos in an aquarium that is 100 cm x 40 cm x 40 cm (160 L) [or approximately 39" x 16" x 16" (35 imp. gal.)]. This aquarium has an external JBL Eco filter and an internal Eheim 2212 filter. I heat the aquarium with a 100 watt heater. The tank has no plants, therefore it is possible to dispense with lighting. The day-night cycle is ensured by the incidental daylight. For this step-up I used catfish caves and slate, and fine, blunt gravel. I soon noticed that the Pseudolithoxus are very similar to the behaviour of Zonancistrus brachyurus (L 168), but these Pseudolithoxus live very much more withdrawn.

Behaviour is very similar - Zonancistrus guarding eggsBehaviour is very similar - Zonancistrus guarding eggs

Slate pipes instead of catfish caves!
My experience with Zonancistrus brachyurus is that they avoid standard single entrance pleco caves and prefer open ended slate pipes. Also the breeding male Zonancistrus chose such a "pipe". I decided, because of the similarity of behaviour with Zonancistrus, and even in a Pseudolithoxus aquarium, to replace standard pleco caves with such slate pipes. Additionally, I noticed that the Pseudolithoxus tried to dig holes in the gravel. Thus, the plan for the redesign of the Pseudolithoxus colony was decided; sand instead of gravel and slate pipes instead of regular pleco caves. In terms of water changes, I used mostly RO water or rain water that was supplemented with tap water to achieve the desired water parameters. In most cases I perform a water change after one or two weeks. Occasionally I waited a little longer for purpose of breeding stimulation. On that subject, during the following years I tried to stimulate the animals to spawn by, in particular, changing various water parameters. During this time, these parameters varied in the aquarium in the areas and valuesdetailed in the table below. Parenthesis are used to show minimum and maximum ranges.

Slate pipesSlate pipes

Spawning tank parameters
Temperature 27 — 32 °C
pH (4,3 - ) 5 ( - 7,0)
GH < 1 (- 7,0) °dH
KH < 1 (- 4) °dH
Nitrite < 0,025 mg/l
Nitrate < 10 mg/l
Conductivity (50 -) 100 (- 300) µS/cm

Aquarium after redesignAquarium after redesign

Mouth of Pseudolithoxus dumusMouth of Pseudolithoxus dumus

A look into the mouth of Pseudolithoxus dumus reveals that it is omnivorous, taking mainly vegetarian foods, however, it is not averse to carnivore food either. I feed mainly DuplaRin G. as well as other pleco-chips from JBL and Tetra for variety. Frozen food was barely taken, vegetables are rejected.

Gender is easily distinguishable because adult Pseudolithoxus dumus show several clear sexual dimorphisms. From the dorsal view males appear much slimmer; the odontodes on the first ray of pectoral-fin are much more numerous, thicker and longer. To a trained eye, the ventral fin appears slightly larger. Furthermore, the distinction based on the genital papilla, which appears in the female more tubular, is also possible.

Male Female

Over time I have bred several different plecos. In this time I have come to believe that the following factors play, or may play, an essential role in spawning:

  • • Male and female (long term)
  • • Size of tank (long term)
  • • establishment (long term)
  • • flow (long and short term)
  • • oxygen concentration (long term)
  • • quiet (long and short term)
  • • feed (long and short term)
  • • water values (long and short term)
  • • water change (frequency) (long and short term)
  • • water temperature (long and short term)
  • • air pressure (change of this) (short term)



3Longer ventral fins, pointed genital papillae

4Regular ventral fins, blunt genital papillae

5More, thicker spines

6Fewer spines

After four years of intensive efforts to reproduce Pseudolithoxus dumus, I had exhausted all realizable ideas in relation to probably all of these factors. In resignation, I changed the aquarium water with only with tap water on and only on occasion. About six months later, one Sunday evening, I examined the aquarium. There I discovered small Pseudolithoxus. Its yolk sac was completely consumed, therefore it had to be several days old. Based on larvae discovered a few weeks later from a following hatch and their speed to grow up, the initially discovered fry must been about four weeks old. Based on my notes, I had determined that about a fortnight before the initial fry was a change of aquarium water with RO water. Considering the fact that I had been doing water changes with tap water for a long time, the pH had fallen relatively quickly within the 14 days between water change and spawn. Over around two and a half months came five spawns, each of which produced more than 20 fry.

Water values after the initial fry
Temperature 29 °C
pH 5
GH < 1 °dH
KH < 1 °dH
Conductivity ~ 250 µS/cm

The rearing of the fry was very easy. The fry graze around the aquarium glass and aquarium equipment on algae and detritus. Soon the fry accept sera PlecoChips and DuplaRin G. Up to a size of four to five centimetres. The fry they grew rapidly within a few weeks but, thereafter, the growth was much slower. Unfortunately it was not possible to observe the male during breeding. In the hope of taking pictures of the male and the egg clutch, I have probably prevented a spawn. If you approach the aquarium, the adult Pseudolithoxus normally flee to the farthest corner. But this evening the largest male was resolutely clamped in his slate column. Unfortunately, also after I turned the cave, I saw no eggs. The next morning I saw that the slate column was abandonded. A chronological presentation of fry and juvenile development is shown in the images below.

Pseudolithoxus dumus I got to know as a very secretive species. It's a species for fans of empty looking aquaria. Nevertheless, Pseudolithoxus dumus are not an everyday species in the fishkeeping world and it is a pleasure to study the animals. It is especially nice if it is possible that a species of which was considered hard to breed, now is bred. This gives hope and inspiration to many new fishkeeping challenges!

1The first fry

2Newly hatched

3Newly hatched

4Newly hatched

5Four weeks old

6Four weeks old

7Five weeks old

8Five weeks old

9Seven weeks old

10Seven weeks old

11Four months old

12In profile

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 Pseudolithoxus dumus  (Armbruster & Provenzano, 2000)
Common Names L244, Black Spotted Orinoco-Ancistrus (Germany)
Sortplettet Flyversugemalle (Denmark)
Type Locality Río Orinoco, backwater behind sand playa about 0.5 hr upstream from Isla Temblador, 3°04'N, 66°28'W, Amazonas State, Venezuela.
Pronunciation sue doh lith ox uss.
Etymology Greek, pseudes = false + Greek, lithos = stone + Greek, oxys = sharp. 
Down Species Information
Size 101mm or 4" SL. Find near, nearer or same sized spp.
Identification Body color light with large, black spots at least anteriorly; spots may combine posteriorly to form bars. Tips of dorsal and caudal spines with light orange to cream-colored spots. Lateral line plates 24-25; dorsal plates 6-9; interdorsal plates 6-7; adipose-caudal plates 6-7; folded dorsal fin plates 11-14; and postanal plates 11-13
Down Habitat Information
Distribution South America: Upper Orinoco, upper Negro and Casiquiare River basins in Venezuela.
Orinoco, Upper Orinoco (click on these areas to find other species found there)
Amazon, Middle Amazon (Solimoes), Negro, Upper Negro, Casiquiare (click on these areas to find other species found there)

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IUCN Red List Category Not Evaluated
Temperature 23.0-26.0°C or 73.4-78.8°F (Show species within this range)
Down Husbandry Information
Breeding The first species in the genus to be bred in captivity (2011). Is a square pipe spawner, preferring open ended narrow spaces to a closed-end cave. Male guards egg clutch, free swimming fry are straightforward to feed on prepared foods as soon as their yolk sac is completely consumed.
Breeding Reports There is but a single breeding report, read it here.
Down Further Information
Reference Ichthyological Exploration of Freshwaters v. 11 (no. 3), pp 246, Fig. 3.
Registered Keepers There are 25 registered keepers, view all "my cats" data.
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Spotters Spotted this species somewhere? Click the binoculars!
There are 12 records of this fish being seen, view them all.
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Last Update 2022 Jan 19 11:09 (species record created: 2013 Jan 07 14:49)

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