Schistura stala, Endruweit, 2017

Endruweit, Marco, 2017, A new Schistura from an upper Mekong affluent in Yunnan (Teleostei: Nemacheilidae), Zootaxa 4341 (4), pp. 585-592 : 586-589

Schistura stala , new species

Figs. 1–3

Holotype. KIZ 2009005397 , 84.3 mm SL; China: Yunnan Prov.: Dali Pref.: Yangbi Cty.: Xu village; Mekong : Yangbijiang River ; about 25°40' N, 99°58' E, coll. Ren, Q., 14 Dec. 2009 .

Paratypes. KIZ 2009005391–5396, 5398, 7 specimens, 81.4–86.7 mm SL; data as for holotype.

Diagnosis. Schistura stala is distinguished from its congeners in the upper Mekong and adjacent drainages by having the basicaudal bar reduced stretching over the median ⅓. Further characters useful to diagnose the species are: 37–39 [38] vertebrae; body depth 5.6–5.8 times in SL; TL 116–118% SL; head length 19–20% SL dorsally, 22–24% SL laterally; pelvic fin not reaching anus; 9–12 faint irregular bars, often anastomotic or dissolved; few scales scattered on body anterior to dorsal fin; and a naked breast.

Description. See Figures 1 and 2 for general appearance and Table 1 for morphometric data. Body moderately elongate, depth 5.6–5.8 times in SL; predorsal region cylindrical, bulbous; postdorsal region laterally compressed. Maximum body depth slightly anterior to dorsal fin. Caudal peduncle moderate in depth, depth 1.1–1.3 times in its length; crests absent. Axillary pelvic lobe present, free. Anus located 1.2–2.2 times eye diameter in front of anal-fin origin. Snout blunt. Cheek not inflated. Head width constantly increasing from nostril to about edge of preoperculum. Eye moderate in diameter; located dorsolaterally, not reaching dorsal profile when viewed laterally. Interorbital space convex, wide. Anterior nostril with flap-like tube, unpierced, not reaching orbit. Suborbital lobe absent. Mouth inferior, gape 1.2–1.5 times wider than long ( Fig.3 ). Lips thick, fleshy, smooth; lower lip slightly notched medially. Upper jaw with rounded processus dentiformis; lower jaw spoon-like, deeply notched medially. Medial rostral barbel not reaching rictus, lateral reaching rictus. Maxillary barbel reaching past vertical through posterior rim of orbit. Few tubercles on dorsal and ventral side of pectoral and pelvic fins in some specimens.

Vertebrae 37–39 [38] (n=8); 21 abdominal and 16–18 [17] caudal. Gas bladder in ossified capsule; dumbbellshaped; no secondary gas bladder chamber (n=1). Gastrointestinal tract with simple, U-shaped stomach; intestines with 2 coiling loops after stomach. Largest recorded length 86.7 mm SL, 101.7 mm TL (KIZ 2009005392, paratype).

Scales small, few scattered on body anterior to dorsal fin; breast naked. Lateral line complete, reaching caudalfin base, with 95–108 pores. Cephalic lateralis system with 9 supraorbital, 4 otic, 10 infraorbital, 10 preoperculomandibular, and 3 supratemporal pores.

Dorsal fin with 4 simple and 7½–8½ [8½] branched rays; distal margin convex. Anal fin with 3 simple and 5½ branched rays; distal margin convex; not reaching caudal-fin base. Caudal fin slightly emarginate, with 9+8 branched rays; lower lobe slightly longer, lobes widely rounded. Pelvic fin 8–9 [9] rays, not reaching anus, inserted opposite of first branched dorsal-fin ray; fourth ray longest; distal margin convex. Pectoral fin with 11–13 [12] rays, reaching midway to pelvic-fin origin; fifth ray longest; distal margin convex.

Coloration of preserved specimens. Body beige, dorsum brown, with 9–12 faint gray bars, as wide as interspaces; intensity of bars decreasing towards head, often with dark gray hue over the flanks. Bars irregular in width and shape, often anastomotic or dissolved, number on both sides not always symmetrical, interconnected over dorsum or forming saddles, not reaching ventral midline, often reduced to rectangular blotches along midlateral portion of flank. A faint, gray humeral spot. Bar at caudal-fin base faint, dark gray, straight, short, wide, Stretching over median ⅓ of fin baSe. Head brown, top mottled gray; operculum with gray-ruSSet hue. DorSal fin with a basal, black spot anterior to first branched ray and with a broad, transverse, median black band on light gray ground. Other fins plain light gray.

Distribution. Schistura stala is only known from the type locality in Yangbi County, which is drained by the Yangbijiang River, an affluent of the upper Mekong ( Fig. 4 ).

Ecology. Schistura stala occurs sympatrically with Homatula pycnolepis Hu & Zhang 2010 . Female specimen KIZ 2009005395, 84.2 mm SL, was dissected. The ovary contained about 300 eggs, each 1.2 mm in diameter; the stomach was empty.

Etymology. From the Greek στάλα ( stala ), meaning drop of a liquid; in reference to the species’ appearance: anteriorly quite bulbous the body gradually tapers to the caudal fin. A noun in apposition.

Figures

FIGURE 1. Schistura stala, KIZ 2009005397, holotype, 84.3 mm SL, reverSed; Yunnan: YanGbi; YanGbijianG River.

FIGURE 2. Schistura stala, KIZ 2009005396, paratype, 84.0 mm SL; Yunnan: YanGbi; YanGbijianG River.

FIGURE 3. Schistura stala, KIZ 2009005394, paratype, 83.3 mm SL; mouth.

FIGURE 4. Map of the Upper MekonG drainaGe; 1, MekonG; 2, YanGbijianG River; 3, Erhai Lake; 4, YanGZte. Symbol indicateS the type locality of Schistura stala.