Schistura wanlainensis, Kottelat, 2017

Kottelat, Maurice, 2017, A new genus and three new species of nemacheilid loaches from northern Irrawaddy drainage, Myanmar (Teleostei: Cypriniformes), Raffles Bulletin of Zoology 65, pp. 80-99 : 92-97

publication ID

https://doi.org/ 10.5281/zenodo.4504495

publication LSID

lsid:zoobank.org:pub:70097B8F-3EF2-4740-97D4-AD2357234011

persistent identifier

https://treatment.plazi.org/id/03F987AC-FFB4-FF92-FF2C-CC3A8A66FBB0

treatment provided by

Carolina

scientific name

Schistura wanlainensis
status

sp. nov.

Schistura wanlainensis View in CoL , new species

( Figs. 13 View Fig , 14 View Fig )

Holotype. MHNG 2766.053 View Materials , female, 84.4 mm SL; Myanmar: Kachin State: Phunganrazi Wildlife Sanctuary: area of Wa Sar Dam: Mon Lan Chaung (stream) near Wan Lain Dam village ); 27°29′10″N 97°10′29″E, 850 masl; Nyein Chan , 25 July 2015. GoogleMaps

Paratypes. CMK 26417, 5 , 79.6–91.8 mm SL; same data as holotype GoogleMaps . — CMK 26584, 1 , 81.2 mm SL ; CMK 26377, 3 , 71.2–78.2 mm SL ; ZRC 55631, 1 View Materials , 74.8 mm SL; Myanmar: Phunganrazi Wildlife Sanctuary: area of Wa Sar Dam: Mon Lan Chaung (stream); 27°28′51″N 97°10′35″E, 843 masl; Nyein Chan, 22 July 2015 GoogleMaps .

Description. See Figs. 13 View Fig & 14 View Fig for general appearance and Table 3 for morphometric data of holotype and paratypes. A moderately elongate nemacheiline with a massive appearance. Body depth increasing up to dorsal-fin origin. Behind dorsal fin, body depth decreasing slowly until above base of anal fin, then uniform until caudal-fin base.

Dorsal profile continuous between head and body. Head slightly depressed; body slightly compressed anteriorly, very compressed posteriorly. Interorbital area arched. Eye below dorsal profile of head. Cheeks not swollen. Snout rounded in lateral and dorsal views. Caudal peduncle 1.2–1.5 times longer than deep, of uniform depth. Very low dorsal crest on posterior half of post-dorsal area. Very low ventral crest along entire length of caudal peduncle. Dorsal crest continuous with upper margin of caudal fin. Largest recorded size 91.8 mm SL.

Dorsal fin with 4 unbranched and 8½ branched rays; distal margin straight to slightly concave. Second branched ray longest. Pectoral fin with 1 unbranched and 11 branched rays (two specimens with an additional small, unbranched ray), rounded, reaching about halfway of distance to pelvic-fin base; rays without filamentous extensions. No proper axillary pectoral lobe, but swelling dorsally at base of fin. Pelvic fin with 1 unbranched and 7 branched rays; reaching about two thirds of distance to anus; posterior edge rounded, second or third ray longest; origin below base of branched dorsal-fin rays 2–3. Axillary pelvic lobe present, free, conspicuous. Anus situated about 2 eye diameters in front of anal fin, hidden under a protuberant, massive genital papilla (at least in females before spawning). Anal fin with 3 unbranched and 5½ branched rays; distal margin slightly concave. Caudal fin with 9+8 branched rays; dorsal and ventral procurrent rays cannot be counted; forked, upper lobe 1.4–1.8 times longer than median rays, lobes rounded, of equal length.

Body entirely scaled, except around lateral line pores 1–5 and belly between pectoral fins. Scales deeply embedded and not densely set in anterior half of body. Lateral line complete, with 90–106 pores (difficult to count with accuracy). Many lateral line scales with 2 auxillary pores, above and below main pore. Cephalic lateral line system with 6 supraorbital, 4+11 infraorbital, 8–10 preoperculo-mandibular and 3 supratemporal pores.

Anterior nostril pierced in front side of a pointed flap-like tube. Posterior nostril adjacent to anterior one. Mouth arched, gape about two times wider than long ( Fig. 15 View Fig ). Lips thick, fleshy. Upper lip with median notch, with furrows along whole length, edge crenulated. Lower lip with narrow median interruption; median part without sulci, lateral part with numerous furrows on whole length. Processus dentiformis present, feebly marked, very wide (more than half of mouth gape); no sharp edge on upper jaw. Tip of lower jaw exposed. A median concavity in lower jaw. Inner rostral barbel not reaching corner of mouth; outer one reaching base of maxillary barbel. Maxillary barbel reaching vertical of posterior margin of eye. In single dissected specimen, intestine with a large loop behind stomach ( Fig. 16 View Fig ). No apparent posterior chamber of air bladder.

Sexual dimorphism. All specimens apparently females; presence of eggs, about 0.6 mm diameter observed in four specimens 78.2–91.8 mm SL; most slender specimen (85.6 mm SL) indeterminate, remaining specimens not checked but all with distended belly. All specimens have a short slit in a position that would correspond to posterior edge of suborbital flap in species in which males have a suborbital flap (compare Figs. 17 View Fig & 18 View Fig ); in species in which such a slit is present in females, the males usually have a suborbital flap. No tubercles or unculi observed.

Coloration. After two months in formalin. Head and body background colour pale yellowish to pale grey; throat and

belly whitish to pale yellowish; darker on back; head darker grey in most specimens. Except otherwise stated, markings blackish brown to black. Head with vermiculated pattern on top, snout, suborbital area and opercle. Body with 18–32 bars, extending from dorsal midline and reaching downwards to below level of pectoral fin (on belly in largest specimens but not reaching ventral midline); continuous over back with contralaterals in most specimens; bars of regular shape, wider than interspaces anteriorly, narrower than interspaces on caudal peduncle; some of anterior bars fused at their upper extremity.

Black pattern at base of caudal fin made of a vertically elongated blotch at middle of base, and a smaller blotch at its dorsal and ventral extremities; blotches contiguous in one specimen. Median blotch occupying about median half of fin base; with a median constriction. Upper blotch elongated, slanted forwards upwards, at base of principal unbranched ray and upper branched rays 1–3; in some specimens continued posteriorly by a band of black and red pigments on upper branched ray. Lower blotch elongated, slanted towards lower edge of caudal fin, on base of principal unbranched ray and lower branched rays 1–3, continued posteriorly by a band of black and red pigments on lower branched ray. No visible inner axial stripe.

Dorsal fin with hyaline membranes. All branched rays black except distal extremity; proximal third paler in some specimens, greyish in one (holotype). Last unbranched ray black on posterior half, orange on anterior half. Other unbranched rays black. Membrane between last unbranched and first branched ray orange in distal area; membranes between branches of first branched ray orange; distalmost part of membrane between first two branched rays yellowish.

Caudal fin with hyaline membranes in most specimens, pale orange in some. Rays blackish brown. One or two irregular and incomplete vertical rows of spots corresponding to accumulation of pigments at primary and secondary branching points. Black stripes along principal unbranched ray of each lobe (see above, black pattern at caudal-fin base), surrounded by pale-orange to reddish area.

Anal fin with hyaline membranes. Branched rays with one or two rows of black spots corresponding to accumulation of black pigments at primary and secondary branching points. Last unbranched ray orange, as well (in some specimens) as distal extremity of membrane between last unbranched and first branched rays. Blackish areas adjacent to lower extremity of flank bars.

Pelvic fin with hyaline membranes. Branched rays with one or two rows of black spots corresponding to accumulation of black pigments at primary and secondary branching points. Unbranched ray orange (and in one specimen, also distal extremity of first branched ray), as well (in some specimens) as distal extremity of membrane between unbranched and first branched rays.

Pectoral fin with hyaline membranes. Rays black; in some specimens, unbranched ray orange as well as anterior half of first branched ray. In all branched rays, posterior branch more densely pigmented than anterior branch. Membrane between unbranched and first branched rays orange, at least distally.

Notes on biology. A dissected female (CMK 26584, 81.2 mm SL) with distended belly had ovaries filled with a large number (probably> 1000) of eggs 0.6 mm in diameter. Its stomach contained unidentified green vegetal material.

Distribution and habitat. Schistura wanlainensis is presently known only from the Mon Lan Chaung in the area of Wa Sar Dam, in Phunganrazi Wildlife Sanctuary ( Fig. 19 View Fig ). The Mon Lan Chaung becomes known as Mula Chaung on Putao Plain and is a tributary of the Mali Hka, which it enters from the west on Putao Plain.

At the places of sampling, the Mon Lan Chaung is a large river about 50 m wide, with very fast water flowing over

a stone and boulders bottom. Other species collected in the same microhabitat at these localities include Garra cf. dulongensis , Garra sp., Neolissochilus compressus , Oreinus meridionalis , Semiplotus cirrhosus (Cyprinidae) , Acanthocobitis sp., Schistura malaisei (Nemacheilidae) , Amblyceps murraystuarti (Amblycipitidae) , Glyptothorax sp., Oreoglanis sp. ( Sisoridae ) and Mastacembelus armatus (Mastacembelidae) . Schistura malaisei was the most abundant species.

Etymology. Named for Wan Lain Dam village where the fish were collected, and whose inhabitants have established a fish conservation zone. An adjective. not all regularly fused in pairs dorsally (vs. much narrower and regularly fused). In S. wanlainensis , the bars are of uniform intensity of black. In S. sikmaiensis , the edge of the bars is clearly darker than the inner and this is gradually more marked from the posterior to the anterior bars, with some bars becoming vertically split and the number of bars increasing with size.

Remarks. Schistura sikmaiensis was diagnosed from all other species of Schistura in Southeast Asia by the absence of processus dentiformis ( Rendahl, 1948: 27; Kottelat, 1990: 208). Examination of additional material suggests that the processus dentiformis could also be described as present but feebly marked and very wide, as in S. wanlainensis . Schistura sikmaiensis (of which S. putaoensis is a synonym) is recorded from a few localities in the upper Irrawaddy in Myanmar, China and India ( Kottelat, 1990: 208) but it was not found in the Mon Lan Chaung and its tributaries in the hills. It was observed only on Putao Plain (see Fig. 7 View Fig ). The two species share a number of characters, including the pale background colour, the bars on the anterior part of the body narrower than those on the posterior part and often fused in pairs dorsally, a similar black pattern at the base of the caudal fin, and the presence in females of a slit in a position that corresponds to the posterior edge of suborbital flap of males.

Schistura wanlainensis is distinguished from S. sikmaiensis by its general appearance (compare Figs. 13 View Fig , 14 View Fig & 7 View Fig ). For example, the more slender caudal peduncle whose depth is 1.8–2.1 times in the depth of the body (vs. 1.3–1.6) and 1.2–1.5 times in its own length (vs. 1.3–1.7), a pointed snout (vs. rounded), a somewhat shorter head (lateral length 21.4–23.2 % SL vs. 22.3–24.6). Besides, S. wanlainensis has more (18–32 vs. 13–21) and narrower bars, the bars on the caudal peduncle narrower than the interspaces (vs. wider than the interspaces), and the bars on the anterior part of the body not much narrower than the posterior ones and Comparison material. Schistura sikmaiensis: CMK 25507, 1, 54.5 mm SL; Myanmar: Kachin state: Mali Hka River, about 9 km upstream of Kang Mu Lon. — CMK 25560, 10, 54.5–77.9 mm SL; Myanmar: Kachin state: Mula River at Lika village, about 0.8 km downriver of Mulashidi.

ZRC

Zoological Reference Collection, National University of Singapore

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