Baryancistrus xanthellus RAPP PY-DANIEL, ZUANON & RIBEIRO DE OLIVEIRA, 2011

Gold Nugget Pleco, L018, L085, L177, LDA060

Classification

Order: Siluriformes Family: Loricariidae

Distribution

Endemic to the rio Xingu basin where it inhabits a section of the river’s main channel known as ‘Volta Grande do rio Xingu’ which lies between Belo Monte falls and the mouth of the rio Iriri in Pará state, Brazil.

Populations from this stretch of the river are known by the codes L018 and L085 in the aquarium hobby. The Iriri is a major tributary of the Xingu and B. xanthellus has also been recorded along its mid-to-lower course with that population coded L177.

Habitat

Occurs predominantly in whitewater rapids with young specimens observed to congregate under flat rocks at the bottom of shallow stretches whereas adults are found under and among submerged rocks and boulders. Other species recorded in the same habitats include Baryancistrus aff. niveatus, Ancistrus spp., Oligancistrus punctatissimus, Oligancistrus sp.Parancistrus nudiventris, Pseudancistrus sp., Scobinancistrus aureatus, S. cf. pariolispos, and Hypostomus spp.

Maximum Standard Length

The largest specimen examined for the official description measured 224.1 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: 6.0 – 8.0

Hardness: 54 – 268 ppm

Diet

Gut analyses of wild specimens 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 in order 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

The possibly conspecific L081 has been bred on a single occasion. Any successful attempt is likely to depend on providing a large tank, well-oxygenated water and an excellent diet.

NotesTop ↑

Prior to description this species was traded under the DATZ code numbers L018, L085, or L177, and ‘Das Aquarium’ code LDA060, while a very similar-looking fish, possibly from the lower rio Xingu, has been assigned the code L081 and may also represent a form of B. xanthellus but is not mentioned in the description paper.

B. xanthellus can be distinguished from congeners by a combination of the following characters: presence of a broad, light-coloured (usually yellow) distal band on the dorsal and caudal fins in juveniles, this reducing to form a small marking at the tips of those fins in adults; presence of light-coloured spots on the entire body and head; unplated, ‘naked’ abdomen.

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 individual 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 and grouped in the Panaque clade of that tribe, close to Parancistrus and Hemiancistrus.

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. 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).
2. 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).
3. 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.
4. 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.
5. 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.
6. 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).
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).