Schistura scyphovecteta, Lokeshwor & Vishwanath, 2013

Lokeshwor, Y. & Vishwanath, W., 2013, Two new species of stone loaches of the genus Schistura from the Koladyne basin, Mizoram, India (Teleostei: Cobitoidei: Nemacheilidae), Zootaxa 3731 (4), pp. 561-576 : 568-573

Schistura scyphovecteta , sp. nov.

( Fig. 7 )

Holotype. MUMF 11136 , 39.4 mm SL, female; Ka-ao River near New Serkawr village (Koladyne basin), Saiha District, Mizoram, India, 22°21'10.8"N, 92°57'49.88"E, 199 m above sea level, Y. Lokeshwor et al., 8 April 2012.

Paratypes. MUMF 11135 , 36.5 mm SL, female, and MUMF 11137 , 32.5 mm SL, male, data as for holotype ; MUMF 11138–11139 , 2 specimens, 36.6–37.8 mm SL, males, Kolchaw River near Kolchaw village (Koladyne basin), Saiha District, Mizoram, India, 22°23'89"N, 92°57'98"E, 146 m above sea level, Y. Lokeshwor et al., 1 April 2011. One paratype ( MUMF 11139 , 37.8 mm SL) was dissected for study of the intestinal coil and air bladder .

Diagnosis. Schistura scyphovecteta is distinguished from all other species of Schistura by the combination of the following characters: six dark brown saddles, each one continuing to the flank, forming globular-shaped bars overlaying a hazy brown stripe along the lateral line, a complete lateral line, two black spots at the dorsal-fin base, an incomplete black basicaudal bar, no median notch on the lower jaw, and a suborbital flap in males. The new species is similar to S. menanensis (a congener from the Mae Nam Nan drainage, Thailand) in having a longitudinal brown stripe along the lateral line superposed by the bar pattern, but distinguished from that species in having a complete (vs. incomplete) lateral line, 7½ (vs. 8½) branched dorsal-fin rays, 10 (vs. 9) branched pectoralfin rays, and the absence (vs. presence) of a median notch on the lower jaw.

Description. General appearance as in Fig. 6 . Morphometric data are listed in Table 1, meristic characters in Table 2. Body relatively small, moderately elongate, cylindrical in cross-section at dorsal-fin origin, compressed posteriorly. Dorsal profile of body elevated evenly from tip of snout to dorsal-fin origin, then slanting gently downwards towards caudal-fin base. Head slightly depressed, moderately elongate. Snout rounded in lateral aspect, about half as long as dorsal head length. Interorbital distance about two-thirds maximum head width at cheek.

Dorsal fin with 4 simple and 7½ branched rays, its origin in advance of pelvic-fin origin, midway on standard length. Anterior distal margin of dorsal fin convex, posterior distal margin concave. Second branched dorsal-fin ray longer than remaining branched rays. Anal fin with 3 simple and 5½ branched rays, almost reaching caudal-fin base, separated from it by 1.5 eye diameters. Pectoral fin sub-acuminate, with 1 simple and 10 branched rays, reaching two-thirds distance to pelvic-fin origin. Pelvic fin sub-acuminate, with 1 simple and 7 branched rays, its origin on vertical through base of dorsal-fin branched rays 2 or 3, reaching anus when adpressed. Axillary pelvicfin lobe well developed. Caudal fin with 9+8 branched rays, deeply emarginate, lobes subequal, lower lobe a little longer than upper one. Caudal peduncle 1.2–1.5 times longer than deep, with no dorsal or ventral adipose crest. Largest known size 39.4 mm SL (MUMF 11136).

Body completely covered with minute deeply embedded cycloid scales except on chest and belly anterior to anal-fin origin. Lateral line complete, with 78–84 pores. Cephalic lateralis system with 9 supraorbital, 3+9 infraorbital, 9 (3)–10 (2) preorperculo-mandibular and 3 supratemporal pores. Unculi blunt, low on outer face of both jaws but high on margin and inner face, arrange side by side like tiles ( Fig. 8 ). Taste buds pyramidal, with small opening at tip, arranged closely on lips and barbels.

Anterior nostril pierced anteriorly, a low leaf-like pointed tube. Mouth arched, 1.4–1.5 times wider than long. Lips fleshy, finely pleated. Lower lip with deep median interruption, each medial margin slightly broader than thin distal portion with 6–7 furrows on interior edge on each side ( Fig. 9 ). Upper lip with shallow median incision, medial portion broader than lateral, low regular furrows on entire lip (furrows deeper near corners of mouth). Processus dentiformis prominent, with blunt end. No median notch on lower jaw.

Barbels in three pairs, inner rostral barbel not reaching corner of mouth; outer one reaching base of maxillary barbel. Maxillary barbel reaching vertical through posterior margin of eye. Free posterior chamber of air bladder well formed, spherical, not encapsulated ( Fig. 10a ). Intestine without loop, slightly bent about 3–4 mm from posterior margin of stomach ( Fig. 10b ).

Sexual dimorphism. Males with a spoon-shaped suborbital flap ( Fig. 11), pelvic fin slightly longer, reaching anus when adpressed. Females larger than males, with deeper body.

Coloration. Body with 6 black saddles on creamy yellow background (2 each in pre-dorsal, sub-dorsal and post-dorsal regions), each continued on both flanks forming broad globular-shaped bars superimposed on a longitudinal brown stripe along lateral line. All bars extending a little distance beneath lateral line, not meeting their antimeres ventrally. Interspaces as wide as each saddle on dorsum, about half of each bar on flank. Lateral head horizontal to posterior rim of orbit light brown, much darker on dorsum, creamy yellow on ventro-lateral and ventral region of head. Two black spots at dorsal-fin base, first at bases of simple and first branched rays, second at bases of branched rays 6–7. A row of light brown spots at midway of each dorsal-fin ray, extending from fourth simple ray to last branched ray. First five pectoral-fin rays dark brown, remaining rays hyaline. Basicaudal bar black, incomplete, midlateral, leaving gaps of about half eye diameter each on both extremities of caudal-fin base. Inferior caudal-fin rays streaked dark grey, appearing as a continuation of basicaudal bar to its dorsal and ventral portion. A faint dark-grey V-shaped row at midlength of caudal-fin rays.

Distribution. Known only from the Kaoao and Kolchaw Rivers near New Serkawr and Kolchaw villages (the Koladyne basin) respectively, Saiha District, Mizoram, India ( Fig. 5 ).

Habitat. In southern Mizoram this species is a typical inhabitant of streams with swift current, among big boulders and rocks. Topotypic specimens were collected from a Kaoao River near New Serkawr village, among big boulders, in fast current ( Fig. 12 ). Two paratypes were also collected from the Kolchaw River near Kolchaw. Other species occurring with Schistura scyphovecteta were Bagridae : Olyra sp. ; Cyprinidae : Devario sp. , Pethia sp. , Garra sp. ; Nemacheilidae : Schistura nebeshwari ; and Sisoridae : Glyptothorax jayarami .

Etymology. The specific name is derived from Latin scypho meaning goblet and Latin vectes meaning bars; a compound name referring to the presence of goblet shaped bars on the body. The name is formed as an adjective.

Figures

FIGURE 5. Map showing type locality of Schistura nebeshwari and Schistura scyphovecteta.

FIGURE 6. Mizoram: stream Kolchaw at Kolchaw, collection site of Schistura nebeshwari; looking upstreams and to the east. Photo: Y. Lokeshwor.

FIGURE 7. Schistura scyphovecteta, n. sp.: a. holotype, MUMF 11136, 39.4 mm SL, female (lateral view); b. holotype (dorsal view); c. holotype (ventral view).

FIGURE 8. Oromandibular structures of Schistura scyphovecteta (MUMF 11140, 31.4 mm SL). A. Ventral surface of head. B. Magnified portion of ventral surface of head. C. Close up box i in A, showing taste bud on rostral barbel. D. Close up box ii in B, showing unculi on lower jaw. E. Close up box iii in B, showing skin fold on upper lip. F. Close up box iv in B, showing taste bud on lower lip. LJ ─ lower jaw; LL ─ lower lip; RB ─ rostral barbel; UL ─ upper lip; TB ─ taste bud; SF ─ skin fold.

FIGURE 9. Lip structure of Schistura scyphovecteta (MUMF 11136, 39.4 mm SL). Scale bar 1 mm.

FIGURE 10. Schistura scyphovecteta (MUMF 11139, 37.8 mm SL) showing a. free posterior chambers of air bladders; b. coiling patterns of intestine. pab — posterior chamber of air bladder. Scale bar 1 mm.

FIGURE 12. Mizoram: stream Ka-ao near New Serkawr, collection site of Schistura scyphovecteta; looking upstreams and to the southeast. Photo: Y. Lokeshwor.