Schistura sirindhornae Suvarnaraksha, 2015
Crown Scaly Stream Loach

Family:  Nemacheilidae (Brook loaches)
Max. size:  7.89 cm SL (male/unsexed); 7.86 cm SL (female)
Environment:  benthopelagic; freshwater; pH range: 6.5,
Distribution:  Asia: tributaries of the upper Nan River basin in Nan Province, Thailand.
Diagnosis:  Anal soft rays: 8-8; Vertebrae: -30. Schistura sirindhornae is distinguished from all other congeners in having overlapping scales on the entire body similar to the scales of balitorids, transparent scales on the belly and thorax, a lateral-line canal that is similar to that of most cyprinids and balitorids in being present across the entire lateral-line surface of the scale instead of being represented only by a pore, and a unique color pattern of irregular brown bars on the back and side of the faint yellow-orange body, a bright triangular orange mark on the occiput, an orange crown-shaped mark between the eyes, an uninterrupted black mark along the base of the dorsal fin, a crescent-shaped bar on the base of the caudal fin, and bright iridescent orange areas on the upper and lower extremities of the caudal-fin base. Scales are generally larger than those of other nemacheilids with a larger focal area (Ref. 102608). Description: large nemacheilid with moderately elongated, robust body; body anteriorly rounded in cross section, body depth/ width at dorsal-fin origin 1.2±0.10 times, slightly compressed posteriorly; body depth/ width at anal-fin origin 2.0±0.55 times, caudal peduncle slightly compressed; maximum body depth between pectoral-fin base and dorsal-fin origin; dorsal-fin origin slightly posterior to pelvic-fin origin; dorsal fin with 3 simple and 6½-7½ branched rays; distal margin of dorsal fin straight or slightly convex; anal fin with 3 simple, 5½ branched rays, with tip nearly reaching caudal-fin base; pelvic fin with 1 simple ray, 7-8 branched rays, not reaching beyond anus; axillary pelvic lobe present; pectoral fin rounded, reaching half distance to pelvic-fin base, with 1 simple ray, 8-10 (rarely 8) branched rays, reaching half-way between its origin and pelvic-fin origin; anus closer to anal fin than to pelvic-fin; caudal fin with 8+8 branched rays, deeply emarginated, lobes rounded; 19 trunk- and 11 caudal-vertebrae; caudal peduncle length/depth 1.0±0.08 times; head moderately large 4.3±0.65 times in SL; eye relatively small, 0.4±0.04 times in interorbital space, 14.4±0.74% HL; mouth moderately large, width 39.5±3.78% HL; anterior nostril with flap-like tube with low anterior rim; mouth arched, width 1.8±0.26 times in mouth length; processus dentiformis present on upper jaw, broadly rounded, none on lower jaw; lips thick, upper lip with well-marked median incision, small furrows on entire length; lower lip with broad median interruption with prominent pad on each side, and thin flap of lip on corner of mouth, occasionally including 3-5 furrows; sometimes smooth in fresh specimens, with black spot on pads; inner rostral barbel reaching beyond vertical to nostril, length 1.0±0.13 times in snout length (33.9±3.02% HL); outer rostral barbel reaching beyond vertical through posterior rim of eye, length 0.8±0.10 times in snout length, 48.0±4.50% HL; maxillary barbel 45.7±2.93% HL, 0.8±0.07 times in snout length; largest individual 78.9 mm SL; body completely covered with exposed, non-embedded scales, including between belly and thorax; scales larger than in other nemacheilids, closely resembling those of balitorids, with large focal area; lateral line complete to hypural plate, ends slightly before posterior margin of caudal peduncle with 118-123 scales; lateral-line canal similar to that of cyprinids and balitorids in being present across entire lateral-line surface of scale instead of being represented only by pore; scales absent on head; cephalic lateral line system with 7 supraorbital, 4+10-12 infraorbital, 8-10 preoperculo-mandibular, and 3 supratemporal pores; stomach syphonal, intestine straight with single bend; gas bladder with 2 encapsuled chambers united by short encapsuled duct; lips and barbels covered with unculi (Ref. 102608). Coloration: live specimens: golden brown on back and side of body, venter white; numerous irregular dark brown bars punctuated by bright, luminous orange vertical bars across back and side of body similar to the tiger, Pantera tigris; dark longitudinal stripe on side of body posterior to dorsal fin; pelvic and anal-fin rays hyaline; head with orange crown-like mark between eyes, triangular-shaped bright orange mark on occiput; underside of head uniformly light gray, slightly paler on gular region; numerous minute chromatophores on median incision of lower lip; all barbels bright orange with becoming darker proximally and lighter distally; dark crescent-shaped bar on caudal-fin base; color variation not correlated with size or sex in specimens examined. Freshly preserved specimens in alcohol ranged from light to dark brown, becoming lighter on venter; dorsal portion of head with crown-shaped mark; upper lip and rostral barbels with black pigment of varying density, being lighter distally; black pigment on lower lip usually present and concentrated medially; lateral pattern varying substantially among individuals; side of body usually with dark brown bars reaching ventrally to lower level of pectoral-fin base; most specimens with black stripe with indistinct outline along posterior half of body; no dark pigment on fins (Ref. 102608).
Biology:  Found in upland areas on the bottoms of cool, clear, flowing streams with pools and forest canopy. Collected between 721-1,155 m above sea level in steep streams in Huay Nampan and tributaries of the Nan River basin. At the time of sampling during the start of the hot-dry season, Huay Nampan was about 2-4 m wide and 0.2-0.5 m deep; water volume might be higher during the rainy season. Encountered only in shaded areas and was absent from light-exposed open areas and lowlands. Substrate was composed mainly of stones, bedrock, and some sand and gravel in small pools. The upper stream bank was covered by large native trees with more than 90% canopy cover and at the time of sampling, the water was clear, and the temperature was 18.4°C (air temperature 22.5°C), conductivity 2.6 S/ m, and pH 6.5. Collected together with Schistura menanensis (Nemacheilidae) and Oreoglanis suraswadii (Sisoridae). Gut content analysis indicated that this species feeds mainly on aquatic insect larvae (Ref. 102608).
IUCN Red List Status: Not Evaluated (N.E.) Ref. (130435)
Threat to humans:  harmless


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