Schistura geisleri 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.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

Widespread throughout much of western Thailand in the Chao Phraya river system, and has been recorded from headwaters of the Mekong in the northern province of Chiang Rai and the Tapi River basin in southern (peninsular) Surat Thani province.

It’s not been recorded from the Salween or Mae Klong river basins nor any border country meaning its range as currently understood is somewhat disjunct.

The southern population may apparently represent an undescribed species, however, and further investigation is required.

Type locality is ‘Nam Mae Taeng at Ban Mae Ta Man, 19°12’N, 98°53’E, Chiang Mai Province, Mae Nam Ping basin, Thailand’.

Habitat

Particularly associated with clear, well-oxygenated streams around watersheds 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.

The fish tend to be found in sandy areas where they can swiftly bury themselves when threatened, and normally occur in small foraging groups.

In the Mae Taeng river, Chao Phraya drainage, it was collected in a slow-moving stream modified by irrigation work with Schistura desmotes, Nemacheilus binotatus, Tuberoschistura baenzigeri, Homalopteroides smithi, Homaloptera sexmaculata, Lepidocephalichthys hasselti, Acantopsis sp., Acanthopsoides gracilis, Pangio anguillaris, Puntius orphoides, Mystacoleucus marginatus, Barilius koratensis, Rasbora aurotaenia, Garra cambodgiensis, Glyptothorax laosensis, G. lampris, Trichopodus trichopterus, Trichopsis vittata and Dermogenys pusillus.

At a locality in the Tapi basin in Khlong Sok sub-district, Surat Thani, it was found in a shallow riffle with substrate of small pebbles and clear, moderately-flowing water. Syntopic species included Acanthocobitis zonalternans, Nemacheilus ornatus, Homaloptera smithi, H. ogilviei, Amblyceps mangois and Akysis hendricksoni.

Maximum Standard Length

30 – 35 mm.

Aquarium SizeTop ↑

An aquarium with a base measuring 60 ∗ 30 cm or more is recommended.

Maintenance

Not difficult to maintain under the correct conditions meaning we recommend designing the aquarium to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel and some larger water-worn rocks or boulders.

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

Like many fishes 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 should never be introduced to biologically-immature aquaria and weekly water changes of 30-50% aquarium volume should be considered routine.

It also does best if there is a high level of dissolved oxygen and a decent level of water movement in the tank so external filters, powerheads, airstones, etc., should be employed in order to obtain the desired effect.

Water Conditions

Temperature: 21 – 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 consumed, mostly via the stomach contents of prey items.

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 ↑

Unlike many congeners this species is peaceful with conspecifics and seems to appreciate being maintained in a group so the purchase of four or more specimens is highly recommended.

In terms of tankmates fishes which inhabit similar biotopes in nature constitute the best options, especially peaceful, open water-dwelling cyprinids since the presence of one or two schools can make a visible difference to the confidence of this naturally reclusive loach.

Other possibilities include current-loving fishes such as Gastromyzon, Pseudogastromyzon, Beaufortia, Sewellia, Crossocheilus and Garra species.

Some similarly-shaped relatives, including many Schistura spp., are excessively territorial or otherwise aggressive, although a combination may work in larger aquaria.

Sexual Dimorphism

Adult males possess a prominent suborbital flap and a thickened first branched pectoral-fin ray with rows of tubercle-shaped unculi on the upper surface.

Reproduction

Has been spawned at least once in aquaria with 2 males and 4 gravid females removed to a separate tank with coarse gravel substrate and removed post-spawning.

NotesTop ↑

 S. geisleri is available in the aquarium trade from time-to-time but is by no means common.

It exhibits several anomalies compared with the majority of congeners such as its small adult size, sociable behaviour and tendency to bury itself in the substrate when threatened.

It can be distinguished from other Schistura spp. by the following combination of characters: unique colour pattern consisting of a yellowish background with 5-8 dark brown blotches along the lateral line and 6-8 irregular dark saddle-shaped markings on the dorsal surface in specimens measuring less than 25 mm SL; in larger specimens the saddles extend further down the body and may connect with the lateral line blotches, and the markings in general are less dark; top of head dark brown; a dark spot at the dorsal-fin origin; a dark, vertically-elongate blotch on the lower part of the caudal-fin base and a further spot at its upper extremity; presence of a large, hammer-shaped suborbital flap and thickened first branched pectoral-fin ray in males.

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. 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. 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., 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.
5. 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).
6. 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.