Baryancistrus sp. cf. xanthellus

Gold Nugget Pleco, L081

Classification

Order: Siluriformes Family: Loricariidae

Distribution

Known only from the Rio Xingu watershed, Pará state, Brazil, but conflicting reports exist as to where it originates from. While some state it’s  collected from close to the river’s confluence with the Amazon, near the town of Porto de Moz, others refer to localities ‘south of Altamira’ or at São Félix do Xingu, which places the collection points much further upstream, and overlapping the range of the very similar-looking congener B. xanthellus (see ‘Notes’).

Maximum Standard Length

150 – 180 mm.

Aquarium SizeTop ↑

Given the adult size an aquarium with base dimensions of 120 ∗ 45 cm or equivalent should be the smallest considered for long-term maintenance.

Maintenance

Not difficult to maintain under the correct conditions but largely unsuitable for the ‘general’ community aquarium. We recommend keeping it in a set-up designed to resemble a flowing river with a substrate of variably-sized rocks, gravel and some large water-worn boulders.

This can be further furnished with driftwood branches, roots and tough aquatic plants such as Microsorum, Bolbitis, or Anubias spp., which can be grown attached to the décor.

Bright lighting will promote the growth of aufwuchs upon which the fish will graze. Like many species that naturally inhabit running waters it’s intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive.

It’s also essential to provide sufficient levels of dissolved oxygen and water movement using a combination of canister filters, powerheads, etc., particularly if the aim is for the fish to breed. Weekly water changes of 40-70% should also be considered mandatory.

Water Conditions

Temperature: 27 – 32 °C; this species will not thrive in cooler water.

pH: 6.4 – 7.6

Hardness: 54 – 268 ppm

Diet

Gut analyses of wild specimens of B. xanthellus revealed the diet to be composed chiefly of algae, particularly diatoms and filamentous genera such as Spirogyra alongside smaller amounts of invertebrates such as chironomids and bryozoans.

In the aquarium aufwuchs should thus be allowed to colonise all surfaces except the viewing pane so that the fish can browse naturally although the diet should of course be supplemented with high-quality, sinking dried foods (preferably with added vegetable content), live or frozen bloodworm and similar, plus slices of fresh fruit and vegetables and the occasional defrosted prawn or shrimp.

Home-made, gelatine-bound recipes containing a mixture of puréed fish food, shellfish, fruit, and vegetables, are also proven to work well and in many ways represent the ideal staple diet since the ingredients can be altered at will, and when made well such foods contain a greater concentration and diversity of nutrients than any of the other options.

Baryancistrus spp. are often under-nourished and/or suffering from health issues post-importation and may require an extended period of quarantine and acclimatisation. They also have a relatively high metabolic rate and may initially require several meals per day.

Behaviour and CompatibilityTop ↑

Juveniles are relatively peaceful but males in particular become highly intolerant of conspecifics as they age and typically aggressive towards any other fish viewed as a territorial threat. It’s therefore best kept with species that inhabit other areas of the tank with medium-to-large sized characids particularly suitable.

In very large aquaria you may be able to combine it with other catfishes or maintain a group provided care is taken to provide sufficient territorial space and visual barriers when laying out the décor.

Sexual Dimorphism

Adult males develop a broader, slightly flatter head profile and longer pectoral-fin spines than females.

Reproduction

May only have been achieved on a single occasion, with any successful attempt likely to require a very large tank, well-oxygenated water and an excellent diet.

NotesTop ↑

It remains unconfirmed as to whether this fish represents a colour form of B. xanthellus or not since its DATZ code number of L081 is not referred to in the description paper whereas all other codes for ‘gold nugget’ plecos, i.e., L018, L085, L177, plus the ‘Das Aquarium’ code LDA060 are mentioned.

While it does appear different to the other forms, in that the spots on the body are noticeably smaller, the authors of the B. xanthellus paper note ‘considerable variation in density and size of spots’ between individuals.

In addition, one of the specimens in our images was collected at São Félix do Xingu which is significantly upstream of any B. xanthellus locality; this form possesses very fine spots on the body and has been referred to as ‘L081n’ or ‘L081 stardust’.

The genus Baryancistrus can be distinguished from all other loricariids by possession of an enlarged membrane located posteriorly to the last branched dorsal-fin ray. This membrane may or may not reach the supporting structure of the adipose fin and in this way members can be told apart from the genera Oligancistrus, Parancistrus, and Spectracanthicus, in which the dorsal and adipose fins are completely connected, and Hemiancistrus in which the membrane is not well-developed.

The family Loricariidae is the largest among catfishes with over 700 species described to date and many awaiting description. The latter are typically assigned a specific ‘L’ number by hobbyists and scientists alike in order to provide a basic means of identification, although in some cases several species have been referred to the same number, or multiple numbers have been used for different populations of a single taxon. All loricariids are also commonly referred to as ‘pleco’, ‘plecostomus’, or ‘suckermouth armoured catfishes’.

The closer relationships of member genera have long been of interest to icthyologists but in numerous cases remain unresolved. Isbrücker (1980) was the first to propose an arrangement of six subfamilies, namely Lithogeneinae, Neoplecostominae, Hypostominae, Ancistrinae, Hypoptopomatinae, and Loricariinae, and this model was generally followed until publication of Armbruster’s morphological analysis in 2004.

His phylogeny also contained six subfamiles, with Isbrücker’s (1980) Ancistrinae being included as one of five tribes comprising Hypostominae. This was later modified slightly by Reis et al. (2006) and an adapted version of their key is reproduced here:

1a. No lateral and dorsal plates anterior to the dorsal fin: Lithogeneinae
1b. Possession of lateral plates anterior to the dorsal fin (except in Pareioraphis nudulus): 2
2a. Ventral surface of the pectoral girdle exposed (i.e. supporting odontodes) towards the centre of the coracoid strut: Hypoptopomatinae
2b. Ventral surface of the pectoral girdle covered in skin or plates towards the centre of the coracoid strut (odontodes supported by the plates rather than the girdle): 3
3a. Caudal peduncle flattened dorsoventrally; no adipose fin: Loricariinae
3b. Caudal peduncle oval, round, or triangular in cross-section; adipose fin usually present: 4
4a. Postdorsal ridge formed from several preadipose plates arranged singly. Teeth almost symmetrically bifid (divided into two equal parts): Delturinae
4b. Usually no postdorsal ridge. Teeth asymmetrical or unicuspid: 5
5a. Dorsal–fin spinelet V-shaped, dorsal–fin spine can be locked: Hypostominae
5b. Dorsal–fin spinelet rectangular or absent, dorsal–fin spine cannot be locked: Neoplecostominae

Subsequent papers attempting to resolve relationships within the Hypoptopomatinae and Neoplecostominae by Cramer et al. (2008, 2011) have revealed both subfamiles to be polyphyletic arrangements alongside several genera, e.g., Pareiorhaphis, Pareiorhina, Hisonotus, and Parotocinclus, so there is evidently a great deal of work still to be done. At any rate Baryancistrus is currently considered a member of the tribe Ancistrini within Hypostominae.

The sucking disc formed by the mouthparts is common to all representatives but both oral and dental morphology are highly variable depending on a given species‘ ecological adaptation(s), and some even practice xylophagy (wood-eating). Many are also facultative air-breathers, i.e., they possess the ability to respire atmospheric air if necessary.

References

1. Armbruster, J. W., 2008 - Zootaxa 1822: 1-76
   The genus Peckoltia with the description of two new species and a reanalysis of the phylogeny of the genera of the Hypostominae (Siluriformes: Loricariidae).
2. Armbruster, J. W. , 2004 - Zoological Journal of the Linnean Society 141: 1-80
   Phylogenetic relationships of the suckermouth armoured catfishes (Loricariidae) with emphasis on the Hypostominae and the Ancistrinae.
3. Cramer, C. A., A. M. R. Liedke, S. L. Bonatto, and R. E. Reis, 2008 - Bulletin of Fish Biology 9: 51-59
   The phylogenetic relationships of the Hypoptopomatinae and Neoplecostominae (Siluriformes: 725 Loricariidae) as inferred from mitochondrial cytochrome c oxidase I sequences.
4. Cramer, C. A., S. L. Bonatto, and R. E. Reis, 2011 - Molecular Phylogenetics and Evolution 59(1): 43-52
   Molecular phylogeny of the Neoplecostominae and Hypoptopomatinae (Siluriformes: Loricariidae) using multiple genes.
5. Lujan, N. K., M. Arce, and J. W. Armbruster, 2009 - Copeia 2009(1): 50-56
   A new black Baryancistrus with blue sheen from the upper Orinoco (Siluriformes: Loricariidae).
6. Rapp Py-Daniel, L. , J. Zuanon, and R. Ribeiro de Oliveira, 2011 - Neotropical Ichthyology 9(2): 241-252
   Two new ornamental loricariid catfishes of Baryancistrus from rio Xingu drainage (Siluriformes: Hypostominae).
7. Reis, R. E., E. H. L. Pereira, and J. W. Armbruster, 2006 - Zoological Journal of the Linnean Society 147(2): 277-299
   Delturinae, a new loricariid catfish subfamily (Teleostei, Siluriformes), with revisions of Delturus and Hemipsilichthys.
8. Werneke, D. C. , M. H. Sabaj Pérez, N. K. Lujan and J. W. Armbruster, 2005 - Neotropical Ichthyology 3(4): 533-542
   Baryancistrus demantoides and Hemiancistrus subviridis, two new uniquely colored species of catfishes from Venezuela (Siluriformes: Loricariidae).