Nemacheilus longistriatus KOTTELAT, 1990

Laos Blackline Torpedo Loach

Etymology

Nemacheilus: from the Greek nēma, meaning ‘thread’ or ‘filament’ and cheilos, meaning ‘lip’ in reference to the furrowed lip in members of this genus.

Classification

Order: Cypriniformes Family: Nemacheilidae

Distribution

Described from the mainstream of the Mekong River in Loei and Chiang Mai provinces, Thailand but since recorded further south from the Khorat Plateau and below the Khone Phapheng waterfalls in Laos.

The full type locality is ‘Mekong River mainstream between Chiang Khan, 17°50’N, 101°45’E, to 70 kilometers downstream by road, Loei Province, Thailand’.

Habitat

Has been collected from the Mekong main river channel as well as backwaters with substrates of bedrock or sand.

Little else is known about its ecology but it may enter temporarily flooded regions when water levels rise.

Maximum Standard Length

Rainboth (1996) suggest it can reach 125 mm but based on field and aquarium observations 60 – 70 mm seems more likely.

Aquarium SizeTop ↑

An aquarium with a base measuring 90 ∗ 30 cm or more is recommended.

Maintenance

Not 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: 23 – 26 °C

pH: Prefers weakly acidic to neutral water within the range 6.5 – 7.5.

Hardness: 36 – 215 ppm

Diet

Nemacheilus 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 ↑

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 rheophilic loaches from genera such as Gastromyzon, Pseudogastromyzon, Beaufortia, and Sewellia, plus benthic cyprinids like Crossocheilus and Garra species.

Some similarly-shaped relatives such as other Nemacheilus, Acanthocobitis, and Schistura spp. are excessively territorial or otherwise aggressive, although a combination may work in larger aquaria.

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.

Sexual Dimorphism

No external characters have been observed but adult females are likely to be slightly larger and heavier-bodied than males.

Male individuals of Nemacheilus spp. are supposed to possess some thickened pectoral-fin rays but no mention of these is made in the description.

Reproduction

Unrecorded.

NotesTop ↑

N. longistriatus is occasionally exported for the aquarium hobby.

It can be distinguished from congeners by the following combination of characters: 9-13 dark, variably-shaped, saddle-like markings along the dorsal surface; a row of 9-11 roundish dark blotches along the flanks, usually connected by a dark stripe ending in a further roundish blotch at the caudal fin base; hyaline dorsal fin.

N. binotatus is similar-looking but lacks dark saddles on the back.

Kottelat (1990) mentions a handful of other similar-looking species from Yunnan province, China but these are unlikely to have been traded.

Following Kottelat (1990) the genus Nemacheilus is characterised by a combination of characters as follows: elongate body; complete lateral line; presence of enlarged scales above and below the lateral line in some species; caudal-fin forked to deeply forked with enlarged upper lobe; large eye; small, strongly arched mouth; lips usually thin; usually no median interruption in upper lip; upper jaw with processus dentiformis (a tooth-like projection); no median notch in lower jaw; long barbels; males usually with suborbital flap, pectoral-fin rays 2-6 thickened and with rows of tubercules.

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, Germany: 1-262
   Indochinese nemacheilines. A revision of nemacheiline loaches (Pisces: Cypriniformes) of Thailand, Burma, Laos, Cambodia and southern Viet Nam.
2. Bănărescu, P. M. and T. T. Nalbant, 1995 - Travaux du Museum d'Histoire Naturelle 'Grigore Antipa' 35: 429-495
   A generical classification of Nemacheilinae with description of two new genera (Teleostei: Cypriniformes: Cobitidae).
3. 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).
4. Kottelat, M., 2001 - WHT Publications Ltd., Colombo 5, Sri Lanka: 1-198
   Fishes of Laos.
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., 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.
7. Rainboth, W. J., 1996 - FAO, Rome: 1-265
   Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes.
8. 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).
9. Šlechtová, V., J. Bohlena 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.