Schistura deansmarti VIDTHAYANON & KOTTELAT, 2003

Etymology

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

deansmarti: named for for Dean Smart, a British speleologist who ‘collected most of the specimems and a strong voice for cave conservation in Thailand’.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

Type locality is ‘Tham [=cave] Phra Sai Ngam, about 200 meters from entrance, Thung Salaeng Luang National Park, Phitsanulok Province, Thailand, 16°37’22″N, 100°39’47″E’, and this species is endemic to the Tham Phra Sai Ngam cave system.

Habitat

Tham Phra Sai Ngam is a limestone cave system about 1.7 km long and containing a subterranean stream with a seasonally-variable flow, the fish existing in stagnant pools for part of the year.

Maximum Standard Length

The largest known specimen measured 105 mm.

Aquarium SizeTop ↑

N/A

Maintenance

N/A

Water Conditions

Temperature: N/A

pH: N/A

Hardness: N/A

Diet

Unconfirmed but likely to consist largely of benthic invertebrates and zooplankton.

Sexual Dimorphism

Males have a poorly-developed suborbital flap which is missing in females.

NotesTop ↑

This species’ conservation status clearly precludes its suitability as an aquarium fish so it’s included here for reasons of interest only. It’s protected by Thai national law and illegal to remove from its habitat.

Species exhibiting morphological, physiological or behavioral adaptations to a subterranean existence are often referred to as troglomorphic.

In S. deansmarti some specimens have no externally visible eyes, while in others vestigial eyes are present in a subcutaneous pit. All individuals are entirely depigmented.

Troglomorphic fishes have been described from several familes with at least four other  blind loach species endemic to Thailand: Schistura jarutanini, S. oedipus , Nemacheilus troglocataractus ( all Nemacheilidae) and Cryptotora thamicola (Balitoridae).

Troglomorphic fish species may also be referred to as hypogean or troglobitic, and are often characterised by certain aspects of their ecology including low population size, restricted distribution, low tolerance to environmental degradation, precocial life cycle traits, a lack of environmental cues, restricted space and frequent scarcity of food (Trajano, 2001).

They’ve been found in all continents except Europe with the majority representatives of the orders Cypriniformes and Siluriformes.

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. 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).
2. 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.
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.