Schistura wanlainensis, Maurice Kottelat, 2017

Maurice Kottelat, 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

Schistura wanlainensis , new species

( Figs. 13 , 14 )

Holotype. MHNG 2766.053 , 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.

Paratypes. CMK 26417, 5, 79.6–91.8 mm SL; same data as holotype. — CMK 26584, 1, 81.2 mm SL; CMK 26377, 3, 71.2–78.2 mm SL; ZRC 55631, 1 , 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.

Description. See Figs. 13 & 14 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-fn origin. Behind dorsal fn, body depth decreasing slowly until above base of anal fn, then uniform until caudal-fn base.

Dorsal profle continuous between head and body. Head slightly depressed; body slightly compressed anteriorly, very compressed posteriorly. Interorbital area arched. Eye below dorsal profle 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 fn. Largest recorded size 91.8 mm SL.

Dorsal fn with 4 unbranched and 8½ branched rays; distal margin straight to slightly concave. Second branched ray longest. Pectoral fn with 1 unbranched and 11 branched rays (two specimens with an additional small, unbranched ray), rounded, reaching about halfway of distance to pelvic-fn base; rays without flamentous extensions. No proper axillary pectoral lobe, but swelling dorsally at base of fn. Pelvic fn 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-fn rays 2–3. Axillary pelvic lobe present, free, conspicuous. Anus situated about 2 eye diameters in front of anal fn, hidden under a protuberant, massive genital papilla (at least in females before spawning). Anal fn with 3 unbranched and 5½ branched rays; distal margin slightly concave. Caudal fn 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 fns. Scales deeply embedded and not densely set in anterior half of body. Lateral line complete, with 90–106 pores (diffcult 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 fap-like tube. Posterior nostril adjacent to anterior one. Mouth arched, gape about two times wider than long ( Fig. 15 ). Lips thick, feshy. 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 ). 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 fap in species in which males have a suborbital fap (compare Figs. 17 & 18 ); in species in which such a slit is present in females, the males usually have a suborbital fap. 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 fn (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 fn 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 fn 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 fn, 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 frst branched ray orange in distal area; membranes between branches of frst branched ray orange; distalmost part of membrane between frst two branched rays yellowish.

Caudal fn 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-fn base), surrounded by pale-orange to reddish area.

Anal fn 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 frst branched rays. Blackish areas adjacent to lower extremity of fank bars.

Pelvic fn 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 frst branched ray), as well (in some specimens) as distal extremity of membrane between unbranched and frst branched rays.

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

Notes on biology. A dissected female (CMK 26584, 81.2 mm SL) with distended belly had ovaries flled with a large number (probably> 1000) of eggs 0.6 mm in diameter. Its stomach contained unidentifed 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 ). 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 fowing 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 fsh were collected, and whose inhabitants have established a fsh conservation zone. An adjective.

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 ). 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 fn, and the presence in females of a slit in a position that corresponds to the posterior edge of suborbital fap of males.

Schistura wanlainensis is distinguished from S. sikmaiensis by its general appearance (compare Figs. 13 , 14 & 7 ). 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 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.

Figures

Fig. 7. Schistura sikmaiensis, CMK 25560; Myanmar: Irrawaddy drainage: Mula River at Lika; a, female, 61.6 mm SL; b, male, 72.7 mm SL.

Fig. 13. Schistura wanlainensis, MHNG 2766.053, holotype, 84.4 mm SL; Myanmar: Irrawaddy drainage: Mon Lan Chaung near Wan Lam Dam.

Fig. 14. Schistura wanlainensis, CMK 26417, paratypes; Myanmar: Kachin state: Irrawaddy drainage: Mon Lan Chaung near Wan Lam Dam; a, 85.6 mm SL; b, 91.8 mm SL.

Fig. 15. Schistura wanlainensis, CMK 26417, 84.3 mm SL; mouth. Arrows indicate lateral extent of processus dentiformis.

Fig. 16. Schistura wanlainensis, CMK 26584, 81.2 mm SL; digestive track. Scale bar = 10 mm.

Fig. 17. Schistura wanlainensis, CMK 26417, 84.3 mm SL, female; note suborbital slit.

Fig. 18. Schistura sikmaiensis, CMK 25560; a, female, 61.6 mm SL, with suborbital slit; b, male, 72.7 mm SL, with suborbital fap.

Fig. 19. Type locality of Schistura wanlainensis; Myanmar: Kachin state: Mon Lan Chaung near Wan Lain Dam, 850 masl; 25 July 2015. Photograph by Zau Lunn.

Tables

Table 3. Morphometric data of type material of Schistura wanlainensis (n = 11). Range and mean include holotype data.

	Holotype	Range	Mean
Standard length (mm)	84.4	71.2–91.8
Total length (mm)	100.0	95.9–108.8
In percent of standard length
Total length	118.4	116.0–121.5	119.3
Head length (dorsal)	17.8	18.5–21.0	19.8
Head length (lateral)	21.4	21.4–23.2	22.1
Predorsal length	51.0	50.0–54.7	51.9
Prepelvic length	52.7	52.7–56.7	54.3
Pre-anus length	73.9	73.1–76.4	75.0
Pre-anal length	79.5	77.0–80.2	79.2
Head depth	12.4	12.4–14.2	13.0
Body depth at dorsal-fn origin	23.1	19.6–24.9	22.6
Depth of caudal peduncle	11.6	10.7–12.5	11.5
Length of caudal peduncle	14.9	14.6–17.6	15.8
Head width	14.3	14.3–16.0	15.1
Body width at dorsal-fn origin	17.2	14.7–21.0	17.3
Snout length	8.8	8.8–10.2	9.5
Eye diameter	3.1	2.4–3.7	3.1
Interorbital width	5.7	5.5–6.1	5.8
Length of dorsal fn	16.6	15.6–19.7	18.1
Length of upper caudal-fn lobe		16.8–16.8	21.1
Length of median caudal-fn rays	10.7	10.0–13.4	10.6
Length of lower caudal-fn lobe	19.9	17.5–21.4	19.8
Length of anal fn	15.1	14.1–17.7	15.8
Length of pelvic fn	16.6	15.1–17.8	16.6
Length of pectoral fn	18.1	16.4–19.8	18.6
In percent of dorsal head length
Snout length	50	46–49	48
Eye diameter	17	12–17	16
Interorbital width	32	27–33	29
In percent of lateral head length
Snout length	41	40–45	43
Eye diameter	14	11–15	14
Interorbital width	27	25–28	26