Malihkaia aligera, 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 : 85-87

Malihkaia aligera , new species

( Figs. 1 , 2 )

Holotype. MHNG 2766.051 , male, 65.7 mm SL; Myanmar: Kachin State: Mali Hka River, about 9 km upstream of Kang Mu Lon ; 402 masl; 27°25′54″N 97°27′56″E; M. Kottelat, Nyein Chan et al., 26 November 2014.

Paratypes. CMK 25508, 2 males, 64.9–73.0, 2 females, 73.1–77.2 mm SL ; ZRC 55630, 1 male, 65.9 mm SL; same data as holotype .

Diagnosis. See generic diagnosis for characters distinguishing the species from all other nemacheilids.

Description. See Figs. 1 & 2 for general appearance and Table 1 for morphometric data of holotype and paratypes. An elongate nemacheilid with body depth increasing until somewhat in front of dorsal-fin origin, then decreasing until posterior extremity of dorsal-fin base. Behind dorsal fin, body depth almost uniform until caudal-fin base. Dorsal profile with a marked hump behind head. Head strongly arched in lateral view, slightly depressed; body slightly compressed anteriorly to very compressed on caudal peduncle. Interorbital area arched. Eye below dorsal profile of head. Head deep, with high cheek. Cheeks not swollen (in both sexes). Snout rounded in dorsal and lateral view. Caudal peduncle 1.3–1.5 times longer than deep, of uniform depth. Low dorsal keel on posterior half of post-dorsal area. Low ventral keel on posterior half of caudal peduncle. Dorsal keel continuous with upper margin of caudal fin. Largest recorded size 77.2 mm SL.

Dorsal fin with 4 unbranched and 8½ branched rays; distal margin straight to slightly concave. Second branched ray longest. In first branched ray, anterior branch not branched a second time, shorter than posterior branch. Pectoral fin with 1 unbranched and 10 branched rays, falcate in males, reaching beyond pelvic-fin base, rounded in females, reaching about two thirds of distance to pelvic-fin base (see diagnosis of genus for more detailed description of pectoral fin; Fig. 4 ). Pelvic fin with 1 unbranched and 6 (1) or 7 (5*) branched rays, reaching about three-fifths of distance to anal-fin origin (not reaching anus); rounded; posterior margin straight; origin below base of branched dorsal-fin rays 1 to 2. Axillary pelvic lobe present, entirely free. Anus situated about 1.5–2 eye diameter in front of anal fin. Anal fin with 3 unbranched and 5½ branched rays; distal margin straight. Caudal fin with 9+8 branched rays; forked, lobes rounded, lower lobe slightly longer than upper one; upper lobe 1.3–1.5 times longer than median rays.

Body entirely scaled except on anterior half of predorsal area and belly in front of pelvic fins. Lateral line complete, with 89–99 pores. Cephalic lateral line system with 6 supraorbital, 4+10–11 infraorbital, 8–9 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 U-shaped, gape about 1.5 times wider than long ( Fig. 3 ). Lips thick, with numerous, closely set, deep furrows. Upper lip with a small median notch, with furrows on its whole length, edge crenulated. Processus dentiformis present. Lower lip with a median interruption; with furrows on its whole length, edge crenulated. Tip of lower jaw not exposed. No median concavity in lower jaw. Inner rostral barbel reaching beyond corner of mouth; outer one reaching vertical of middle of eye. Maxillary barbel reaching beyond posterior margin of eye. Intestine with a loop posterior to stomach ( Fig. 5 ). Air bladder without visible posterior chamber.

Sexual dimorphism. Males with suborbital flap; females with neither suborbital flap nor suborbital slit. Pectoral fin rounded in females, strongly falcate in males. In males, unbranched and first branched rays rigid, arched and curled upwards. First branched ray about 5 times wider than other branched rays, flattened dorso-ventrally, reaching beyond pelvic-fin base; without membrane between the branches and all sub-branches. Second branched ray slender, branched only at tip, membrane between branches very narrow. See diagnosis of genus for more detailed description of pectoral fin of both sexes.

Coloration. In formalin, shortly after fixation. Body background colour pale yellowish brown, throat and belly whitish; except otherwise stated, all markings blackish brown to black. Head black, cheek marmorated, lower side whitish. Irregularly set and shaped patches of black pigments on lips, but always a patch on posterior edge of lower lip and on adjacent part of throat. Body with 9–12 bars (3–4 predorsal, 3 subdorsal, 3–5 postdorsal), extending from dorsal midline to level of pectoral fin (or ventral midline on caudal peduncle), mostly continuous over back with contralaterals; bars of quite regular width and shape in front of dorsal fin, less regular posteriorly; much wider than interspaces.

A conspicuous more or less squarish black blotch at middle of caudal-fin base, depth about ⅓–¼ of depth of base of fin. A more or less triangular black blotch over dorsal procurrent rays, including dorsal midline. Fainter pigments over base of uppermost and lowermost 4–6 principal rays of caudal fin, making a slightly elongated, arched mark, variably contrasted, and variably connected with other two blotches. Space between upper triangular blotch and last bar on body somewhat reddish. Axial stripe faint, or not distinct except on caudal peduncle where darker and wider, combining with blotch at middle of caudal-fin base to make a larger and more conspicuous blotch.

Dorsal fin hyaline, no pigments on membranes, with a small black spot at base of unbranched rays and middle and distal parts of last unbranched ray black; pigments on rays at branching points and on middle of unbranched part of first branched rays (and branched rays 2–4 in largest specimens). Caudal fin hyaline, with pigments between segments of branched rays and near branching points. Anal fin hyaline, with pigments near branching points of branched rays.

Pelvic fin hyaline, with pigments along rays and near branching points of branched rays. Pectoral fin with membranes hyalines, pigments on rays, darker along posterior edge of branched rays 2–10. In males, unbranched and first branched rays more or less completely covered by pigments, on dorsal side, on whole length; identical in females, but pigments less densely set.

Notes on biology. The two females did not have ripe ovaries. The stomach contained unidentifiable insect remains.

Distribution and habitat. Malihkaia aligera has been observed only once, in the Mali Hka River near Putao. It was collected over gravel and cobble, in fast riffles, in about 60 cm depth ( Fig. 6 ). Other species collected in the same microhabitat at this locality include Bangana sp., Garra sp. ( Cyprinidae ), Psilorhynchus brachyrhynchus (Psilorhynchidae) , Homalopteroides rupicola (Balitoridae) , Acanthocobitis sp., Schistura malaisei , S. nubigena , S. sikmaiensis (Nemacheilidae) , Batasio procerus (Bagridae) , Amblyceps murraystuarti (Amblycipitidae) , Pseudecheneis brachyurus (Sisoridae) and Mastacembelus armatus (Mastacembelidae) . Schistura malaisei and Homalopteroides rupicola were the most abundant species.

Etymology. From the Latin aliger ( aligera , aligerum), winged. An adjective.

Remarks. The colour pattern of the six available specimens of M. aligera is made of very regular bars on body, with very well marked edges, on a pale background. This general pattern is rare among Southeast Asian nemacheilids. Interestingly, one of the species collected together with M. aligera is Schistura sikmaiensis , which also has a regular and contrasted colour pattern ( Fig. 7 ). A third species collected at the same locality is S. nubigena (described below), which has a sharply contrasted colour pattern of 4 bold black bars on a whitish background. Finally, S. wanlainensis , also described below, from the same area but at higher altitude and habitat with higher gradient, also has a very contrasted colour pattern of very regular bars on a pale background.

Figures

Fig. 1. Malihkaia aligera, MHNG 2766.051, holotype, male, 65.7 mm SL; Myanmar: Irrawaddy drainage; Mali Hka River near Putao.

Fig. 2. Malihkaia aligera, CMK 25508, paratypes; a, male, 73.0 mm SL; b, female, 77.2 mm SL; Myanmar: Irrawaddy drainage: Mali Hka River near Putao.

Fig. 4. Malihkaia aligera, CMK 25508, 73.0 mm SL; left pectoral fin of male; dorsal (above) and ventral (below) view. Extremity of fourth branched ray damaged.

Fig. 3. Malihkaia aligera, CMK 25508, 73.0 mm SL; ventral view of head.

Fig. 5. Malihkaia aligera, MHNG 2766.051, holotype, 65.7 mm SL; digestive tract. Scale bar = 1 mm.

Fig. 6. Type locality of Malihkaia aligera and Schistura nubigena; Myanmar: Kachin state: Mali Hka River near Kang Mu Lon; 402 masl; 26 November 2014.

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.