Nemacheilus masyae Smith, 1933
Arrow loach
photo by Ott, G.

Family:  Nemacheilidae (Brook loaches)
Max. size:  13.5 cm SL (male/unsexed)
Environment:  benthopelagic; freshwater
Distribution:  Asia: western Malaysia, Peninsular Thailand, the Meklong and part of the Mae Nam Chao Phraya basins (Ref. 39226). Likely to occur in the Mekong basin (Ref. 12693).
Diagnosis:  Dorsal soft rays (total): 13-13; Anal soft rays: 8-8. Distinguished from all other species of nemacheilines in Indochinese area by its color pattern consisting of a light background with 14-18 dark blotches along sides and 12-17 dark saddles along the back, a black spot at posterior extremity of lateral line and a black spot on anterior dorsal rays at about one fourth of ray length. From the closely related N. pallidus, it is distinguished by a slender body (body depth 12.6-17.6% SL versus 14.8-19.1), eye situated more on the top of head (interorbital width 4.9-6.8% SL, versus 5.7-8.0; and darker and wider markings (spots and saddles usually wider than interspaces, versus thinner).
Biology:  Inhabits shallow depths of 2 m or less in rivers and streams with moderate current and muddy to sandy bottoms (Ref. 12693). Occurs in forest streams flowing clear and slightly black waters, as well as in turbid waters (Ref. 39226). Feeds on insect larvae and aquatic invertebrates (Ref. 39226).
IUCN Red List Status: Least Concern (LC); Date assessed: 09 August 2019 Ref. (130435)
Threat to humans:  harmless

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