Schistura nicholsi (SMITH, 1933)

SynonymsTop ↑

Nemacheilus nicholsi Smith, 1933; Nemacheilus thai Fowler, 1934; Schistura thai (Fowler 1934); ? Schistura laterimaculata 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.

nicholsi: named for J. T. Nichols.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

Widespread in the Mekong basin in Laos (Xe Bangfai, Xe Don and Xe Kong rivers) and Thailand, and may also occur in Cambodia.

Type locality is ‘a small mountain stream near Pak Jong, circle of Nakon Rajasima, Siam’, which corresponds to a locality within the Mekong drainage in Nakhon Ratchasima province, central Thailand.

Chen et al. 2005 report that it’s restricted to the Chap Phraya watershed in Thailand but this is in contradiction with all other published information.

Habitat

As is typical of many Schistura it’s known only from clear, well-oxygenated tributary streams and headwaters.

These are often shaded by forest cover with the substrate invariably composed of coarse sand, gravel, rocks and boulders with no aquatic plants.

Flow rate, volume and turbidity are likely to vary somewhat depending on the time of year and weather conditions.

At one habitat in the Nam Man drainage, Loei Province, northern Thailand the river was 4-6 metres in width and was flowing moderately fast over a substrate of pebbles.

S. nicholsi was collected from shallow riffles with sympatric fish species including Nemacheilus pallidus, Homalopteroides smithi, Lepidocephalichthys hasselti, Acanthopsoides sp., Rasbora borapetensis and Amblyceps mangois.

Maximum Standard Length

The largest specimen known measured 74 mm.

Aquarium SizeTop ↑

Even a small group will need an aquarium with base dimensions of 120 ∗ 30 cm or similar.

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: 20 – 26 °C

pH: 6.0 – 7.5

Hardness: 36 – 215 ppm

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

None recorded.

Reproduction

Has been bred in an aquarium with coarse, mixed substrate in which young fish simply began to appear alongside the adults. It seems the adults consume both eggs and fry since only 7 were recovered.

NotesTop ↑

This species is sometimes traded for aquaria but its name also appears to have been widely misapplied to other fishes.

It can be identified via the following combination of characters: presence of 8-10 quite regular dark bars on body which are wider than the light interspaces; black bar at base of caudal-fin complete and projecting anteriorly and posteriorly along dorsal and ventral midlines and caudal-fin lobes; anterior base of dorsal-fin with a black spot followed by an orange blotch and an elongate black blotch; caudal-fin sometimes red, other fins hyaline; lateral line usually incomplete, tending to reach anal-fin origin at most; processus dentiformis pointed; no median incision in upper lip; axillary pelvic lobe present; cheeks never inflated; length of caudal peduncle fits 6.5-7.5 times in SL; depth of caudal peduncle fits 0.8-1.2 times in its length.

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.

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. Smith, H. M., 1933 - Journal of the Siam Society, Natural History Supplement 9(1): 53-87
   Contributions to the ichthyology of Siam. II-VI.
2. 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).
3. Chen, X.-Y., D.-P. Kong and J.-X. Yang, 2005 - The Raffles Bulletin of Zoology Supplement 13: 27-32
   Schistura cryptofasciata, a new loach (Cypriniformes: Balitoridae) from Salween drainage in Yunnan, southwestern China.
4. Freyhof, J. and D. V. Serov , 2001 - Ichthyological Exploration of Freshwaters 12(2): 133-191
   Nemacheiline loaches from Central Vietnam with descriptions of a new genus and 14 new species (Cypriniformes: Balitoridae).
5. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
6. 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.
7. Kottelat, M., 2001 - WHT Publications, Colombo: 1-198
   Fishes of Laos.
8. Kottelat, M., 2000 - Journal of South Asian Natural History 5(1): 37-82
   Diagnoses of a new genus and 64 new species of fishes from Laos (Teleostei: Cyprinidae, Balitoridae, Bagridae, Syngnathidae, Chaudhuriidae and Tetraodontidae).
9. Kottelat, M., 2013 - Raffles Bulletin of Zoology Supplement No. 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
10. 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).
11. 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.