Schistura robertsi KOTTELAT, 1990

Etymology

Schistura: from the Greek schizein, meaning ‘to divide’, and oura, meaning ‘tail’, in reference to the caudal-fin shape of many species.

robertsi: named for Tyson R. Roberts, who collected the majority of the type series.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

This species is known from the western slope of the Malay Peninsula with distribution extending south from Tennasserim province, Myanmar to Trang province southern (peninsular) Thailand. It’s also been recorded on the islands of Phuket Thailand and Langkawi (Malaysia).

Type locality is ‘Tributary of Khlong Khao Thalu at Ban Bang Kan, 8°33’N, 98°28’E, road from Phangnga to Kapong, Phangnga Province, Thailand’.

Habitat

Inhabits shallow, narrow branches of streams with substrates of sand, gravel or stone.

At the type locality of Schistura udomritthiruji in Ranong Province, southern Thailand S. robertsi was collected from a stream with wider, slow-moving stretches broken up by narrower, fast-flowing riffles.

The substrate was composed of gravel and rocks and the water transparent with a pH value of 8.0 and temperature 84.7°F/29.3°C.

Other fish species were Homalopteroides smithi, Hara filamentosa, Mastacembelus armatus and an unidentified gobiid.

At Ban Bang Kan in southern Thailand it was collected alongside Acanthocobitis zonalternans, Homaloptera sp., Pangio myersi, Lepidocephalichthys berdmorei, Rasbora sumatrana, R. caudimaculata, ‘Puntius‘ binotatus, ‘P.‘ lateristriga, Hampala macrolepidota, Devario peninsulae, Clarias sp., Aplocheilus panchax, Badis sp., Pseudogobiopsis siamensis, Channa sp., and Mastacembelus unicolor.

Maximum Standard Length

The largest specimen known measured 56 mm.

Aquarium SizeTop ↑

Base dimensions of 80 ∗ 30 cm or equivalent should be the smallest considered.

Maintenance

Should not prove difficult to maintain under the correct conditions. We strongly recommend keeping it in a tank designed to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel, and some water-worn boulders.

This can be further furnished with driftwood branches arranged to form a network of nooks, crannies, and shaded spots, thus providing broken lines of sight. While the majority of aquatic plants will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis, or Anubias spp. can be grown attached to the décor.

Though torrent-like conditions are unnecessary it does best if there is a high proportion of dissolved oxygen and some water movement in the tank meaning power filter(s), additional powerhead(s), or airstone(s) should be employed as necessary.

Like many fishes that naturally inhabit running water it’s intolerant to accumulation of organic pollutants and requires spotless water in order to thrive, meaning weekly water changes of 30-50% tank volume should be considered routine.

Water Conditions

Temperature: 18 – 30 °C

pH: 6.0 – 8.0

Diet

Schistura species are omnivorous although the bulk of their diet consists of small insects, worms, crustaceans, and other zooplankton with only relatively small amounts of plant matter and other organic detritus consumed.

In the aquarium they will accept dried foods of a suitable size but should not be fed these exclusively. Daily meals of small live and frozen fare such as Daphnia, Artemia, bloodworm, etc., will result in the best colouration and condition.

Behaviour and CompatibilityTop ↑

Not especially aggressive compared with some members of the genus but remains largely unsuitable for the ‘general’ community aquarium due to its somewhat specialised requirements.

This is not to say it must be kept alone, rather that tankmates must be selected with care and proper research. .

Slow-moving or long-finned species should certainly be omitted because they’re likely to struggle with the necessary level of water movement and may end up with nipped fins.

Placid bottom-dwellers such as Corydoras or Pangio spp. also tend to be easy targets for territorial Schistura and are best avoided.

Fishes which inhabit similar biotopes in nature, especially those which swim in open water such as Danio, Devario, Mystacoleucus, smaller Barilius, Pethia, Puntius, and Rasbora spp. constitute the best options, and one or two schools can make a visible difference to the confidence of this naturally reclusive loach.

Other possibilities include current-loving loaches from genera such as Pseudogastromyzon, Beaufortia, or Sewellia plus benthic cyprinids such as Crossocheilus and Garra spp.

Similarly-shaped relatives like Nemacheilus, Acanthocobitis, and other Schistura spp. aren’t recommended under most circumstances although a combination may work in larger aquaria.

While it can’t be described as gregarious a group can be maintained together provided the set-up contains plenty of rocky structures and broken lines of sight.

Occasional skirmishes may occur, however, and in small or sparsely-decorated tanks conspecific aggression may escalate to an unacceptable level.

Sexual Dimorphism

Unknown, although sexually-mature females should appear rounder-shaped than males, especially when gravid.

Reproduction

Unrecorded.

NotesTop ↑

This species may not yet have appeared in the aquarium hobby although possibly exported alongside similar-looking relatives such as S. cf. balteata.

It can be told apart from congeners by the following characters: processus dentiformis present; 8-10 regular dark body bars, wider than pale interspaces in adults; males without a suborbital flap; lateral line incomplete with 9-15 visible pores, and reaching at most to base of pectoral-fin; lower lip with a black marking on either side of a median interruption; 7 pelvic-fin rays; 9 pectoral-fin rays; 8-9 + 8 branched caudal-fin rays; caudal-fin emarginate; a black bar at the base of the caudal-fin; axillary pelvic lobe absent; anus 1.5-2.0 times eye diameter in front of anal-fin.

In young specimens the barred colour pattern is often irregular, whereas in adults the bars are well-defined but may be fused laterally except on the dorsal surface.

Kottelat (1990) two, possibly non-monophyletic groups of Indochinese Schistura species and S. robertsi is included in his group B which currently includes S. acuticephalus, S. cincticauda, S. daubentoni, S. diminuta, S. kangjupkhulensis, S. malaisei, S. paucicincta, S. paucifasciata, S. robertsi and possibly S. aurantiaca, these sharing certain morphological similarities (see below).

Schistura is the most species-rich genus among nemacheilid loaches with some 190 members and it continues to grow with over 100 having been described since 1990.

It may represent a polyphyletic lineage and is often arranged into a number of loosely-defined species ‘groups’, some of which are quite dissimilar to one another.

Among these are an assemblage in which some or all of the body bars are vertically split and another which exhibit reductions in body size (adult size <50 mm SL), the number of pelvic and pectoral-fin rays and often the number of caudal-fin rays and lateral line length, for example (the latter is the group ‘B’ mentioned above).

Some species, such as S. geisleri, also appear to be unrelated to any of the others.

Most inhabit flowing streams or areas close to waterfalls where there naturally exist high concentrations of dissolved oxygen, and a handful are troglobytic, i.e., cave-dwelling, in existence. The latter have reduced pigmentation and are completely blind in many cases.

Schistura spp. are distinguished from other nemacheilids by a combination of morphological characters which include: a moderately arched mouth which is 2-3.5 times wider than it is long; a median ‘interruption’ in the lower lip which does not form two lateral triangular pads and can vary from smooth to furrowed in texture; diverse colour pattern but usually dark with relatively regular bars; usually a black bar at the caudal-fin base which can be broken into two spots or smaller bars; one or two black markings along the base of the dorsal-fin; lack of acuminate scales on the caudal peduncle; caudal-fin shape variable from truncate to forked but usually emarginate; presence or absence of a median notch in the lower jaw; clear sexual dimorphism in some species.

The family Nemacheilidae is widely-distributed across most of Eurasia with the Indian subcontinent, Southeast Asia and China representing particular centres of species diversity.

References

1. Kottelat, M., 1990 - Verlag Dr. Friedrich Pfeil, München: 1-262
   Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of Thailand, Burma, Laos, Cambodia and southern Viet Nam.
2. Bohlen, J. and V. Ŝlechtová , 2010 - Ichthyological Exploration of Freshwaters 20(4): 319-324
   Schistura udomritthiruji, a new loach from southern Thailand (Cypriniformes: Nemacheilidae).
3. Bănărescu, P. M. and T. T. Nalbant, 1995 - Travaux du Muséum d'Histoire Naturelle 'Grigore Antipa' 35: 429-495
   A generical classification of Nemacheilinae with description of two new genera (Teleostei: Cypriniformes: Cobitidae).
4. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
5. Ou, C., C. G. Montaña, K. O. Winemiller and K. W. Conway, 2011 - Ichthyological Exploration of Freshwaters 22(3): 193-200
   Schistura diminuta, a new minature loach from the Mekong River drainage of Cambodia (Teleostei: Nemacheilidae).
6. Plongsesthee, R., L. M. Page, and W. Beamish, 2011 - Ichthyological Exploration of Freshwaters 22(2): 169-178
   Schistura aurantiaca, a new species from the Mae Khlong basin, Thailand (Teleostei: Nemacheilidae).
7. Tang, Q., H. Liu, R. Mayden, and B. Xiong, 2006 - Molecular Phylogenetics and Evolution 39(2): 347-357
   Comparison of evolutionary rates in the mitochondrial DNA cytochrome b gene and control region and their implications for phylogeny of the Cobitoidea (Teleostei: Cypriniformes).
8. Šlechtová, V., J. Bohlen and H. H. Tan, 2007 - Molecular Phylogenetics and Evolution 44(3): 1358-1365
   Families of Cobitoidea (Teleostei; Cypriniformes) as revealed from nuclear genetic data and the position of the mysterious genera Barbucca, Psilorhynchus, Serpenticobitis and Vaillantella.