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Nemacheilus masyae SMITH, 1933

Arrow Loach

SynonymsTop ↑

Nemacheilus masyai Smith, 1933; Noemacheilus masyae (Smith, 1933); Noemacheilus masyai (Smith, 1933)


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


Order: Cypriniformes Family: Nemacheilidae


Described from the Tadi river, Nakhon Si Thammarat province, southern Thailand, and subsequently recorded from the Terengganu, Pahang and Endau drainages in Peninsular Malaysia plus parts of the Mae Klong and Chao Phraya basins in Thailand.

Type locality is given as ‘Ban Ta Yai, Tadi stream, Nakhon Sritamarat, Peninsular Thailand’.

Roberts (1996) hypothesised it might range into the Mekong system in northwestern Cambodia via the Cardamom mountain range but this appears to remain unconfirmed.


Has been recorded from both small, blackwater forest streams and turbid main river channels with variable flow and substrates of mud, sand or small rocks.

In the Sai Buri river, Pattani province, southern Thailand it was collected from a stretch less than 2 metres deep with a muddy bed and sandy margins alongside Tuberoschistura baenzigeri, Homaloptera zollingeri, Acantopsis sp., Labiobarbus lineatus, Cyclocheilichthys heteronema, Barilius bernatziki, Mystacoleucus chilopterus, Mystus nigriceps, Xenentodon cancila, Glossogobius giuris and Brachirus harmandi.

In the Tapi river it was observed in deeper pools containing moderately flowing, clear water with Nemacheilus ornatus, Acanthocobitis zonalternans, Schistura geisleri, Homaloptera smithi, H. ogilviei, Amblyceps mangois and Akysis hendricksoni collected from connecting riffles.

Maximum Standard Length

60 – 70 mm.

Aquarium SizeTop ↑

tank with base dimensions of 60 ∗ 30 cm or more is recommended.


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 MicrosorumBolbitis, 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

Temperature23 – 26 °C

pH6.0 – 7.5

Hardness36 – 215 ppm


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 DaphniaArtemiabloodworm, 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 NemacheilusAcanthocobitis, 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

Mature males possess a suborbital flap, thickened first branched pectoral-fin ray and rows of small tubercules on the second and third branched pectoral rays.

Adult females are likely to be slightly larger and heavier-bodied than males.



NotesTop ↑

The specific name has been spelled both masyae and masyai in the past but following Kottelat (2012) the latter is either a misspelling or unjustified emendation, thus the former, original spelling is correct.

It can be distinguished from the majority of congeners by body patterning comprising 14-18 short, dark vertical bars on each flank, 12-17 saddle-like markings running along the dorsal surface, a dark spot on the caudal peduncle at the termination of the lateral line and a dark blotch in the lower half of the first few dorsal-fin rays.

It can be told apart from the very similar-looking N. pallidus by its more slender body (12.6-17.6% vs. 14.8-19.1% SL), lesser interorbital width (4.9-6.8% vs. 5.7-8.0% SL) and the fact that the dark body bars and saddles are wider than the light-coloured interspaces between (vs. thinner), sometimes connecting with one another.

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.


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