Schistura kohchangensis (SMITH, 1933)

Ornate Tiger Sand Loach

SynonymsTop ↑

Nemacheilus kohchangensis Smith, 1933; Noemacheilus deignani Smith, 1945; Nemacheilus deignani (Smith, 1945); Schistura deignani (Smith, 1945)

Etymology

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

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

Known from Koh Chang island plus Chon Buri, Rayong, Chanthaburi and Trat provinces, southeastern Thailand, and the northern end of the Cardamon mountain range, southwestern Cambodia.

Type locality is ‘Waterfall stream on Koh Chang, Gulf of Thailand’.

It’s also expected to occur in tributaries of the lower Mekong drainage in both Thailand and Cambodia.

Habitat

Inhabits shallow, often high gradient, streams with moderate to fast-flowing water and substrates of gravel, rocks and boulders.

During the dryer months of the year it survives in isolated, stagnant pools at some localities.

On Koh Chang one habitat consisted of a stream flowing from the waterfall Nam Tok Mai Yom which empties into the Gulf of Thailand after less than 1 km.

The stream was dry in its lower reaches and had a substrate of boulders and pebbles. Sympatric fish species included Danio albolineatus, ‘Puntius‘ binotatus, Rasbora sumatrana and an unidentified gobiid.

Maximum Standard Length

65 – 75 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 90 ∗ 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: 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

Males possess a suborbital flap, plus branched pectoral-fin rays 1-7 are thickened and possess rows of tiny tubercules on the upper surface.

Females should be slightly thicker-bodied, especially when gravid.

Reproduction

Unreported.

NotesTop ↑

This species appears in the aquarium trade from time-to-time but is not well-known in the hobby.

It can be told apart from congeners by the following combination of characters as per Kottelat (1990): colour pattern comprising 10-12 dark brown vertical bars which are usually split vertically; 8+8 branched caudal-fin rays; 8½ branched dorsal-fin rays; males with a suborbital flap; no median notch in lower jaw; black caudal peduncle bar interrupted on lateral line; caudal-fin with 5-7 irregular rows of spots.

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. Kottelat, M., 2012 - Raffles Bulletin of Zoology Supplement 26: 1-199
   Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei).
4. 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.
5. 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.
6. 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).
7. 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.