Oreonectes shuilongensis, Deng, Huaiqing, Xiao, Ning, Hou, Xiufa & Zhou, Jiang, 2016

Deng, Huaiqing, Xiao, Ning, Hou, Xiufa & Zhou, Jiang, 2016, A new species of the genus Oreonectes (Cypriniformes: Nemacheilidae) from Guizhou, China, Zootaxa 4132 (1), pp. 143-150 : 145-149

Oreonectes shuilongensis , new species

Figures 1–3

Holotype: GNUG 20100618010, 66.0 mm TL (Total length), 54.1 mm SL ( Fig. 1); China: Guizhou Province: Sandu County: Shuilong Township: unnamed stream in Liujiang River basin, 25°50′44.4″ N, 107°52′54.3″ E; June 2010.

Paratypes: GNUG 20090723001– GNUG 20090723003, 54.58–62.29 mm TL, 48.12–50.86 mm SL; data as for holotype; July 2009. GNUG 20100618001– GNUG 20100618009, 40.62–63.64 mm TL, 34.34–51.40 mm SL; data as for holotype; June 2010.

Diagnosis. The combination of the following characteristics place this species in Oreonectes : the head is wide and flat; the anterior and posterior nostrils are well separated by a short distance, with the anterior nostril located in a short tube that extends into a relatively long barbel; the anterior portion of the body is slightly dorsoventrally flattened, and the posterior portion is more laterally compressed; the stomach is U-shaped ( Zhu, 1989; Du et al., 2008).

Du et al. (2008) divided the genus Oreonectes into two subgroups: the furcocaudalis group (which has a forked caudal fin) and the platycephalus group (which has a rounded, truncated, or slightly concave caudal fin). Among the 16 species of Oreonectes , 10 belong to the furcocaudalis group ( O. furcocaudalis , O. microphthalmus , O. macrolepis , Oreonectes sp. nov. ( Chen et al. 2011), O. elongatus , O. acridorsalis , O. barbatus , O. duanensis , O. translucens , and O. donglanensis ), and six belong to the platycephalus group ( O. platycephalus , O. anophthalmus , O. polystigmus , O. retrodorsalis , O. guananensis , and O. luochengensis ). The caudal fin of O. shuilongensis is truncated or slightly concave, indicating that the species belongs to the platycephalus group.

The new species has eyes (distinguishing it from O. anophthalmus ) and a unique color pattern consisting of fine black marks on the body except on the abdomen (distinguishing it from O. luochengensis [pink in live specimens], O. guananensis [irregular dark brown stains dorsally and laterally, with a brown stripe along the lateral line], and O. polystigmus [fine black marks on the body including the abdomen]). Also, it lacks scales (distinguishing it from O. guananensis [scales on the body] and O. luochengensis [small scales on the sides of the body]) ( Table 2 ).

Notes: * In Zhu (1989); ** In Lan et al. (1995).

Oreonectes shuilongensis can be distinguished from O. platycephalus on the basis of the following characteristics ( Table 2 ): 6 vs. 5 branched anal rays; ratio of body length to body height 7.0–7.9 vs. 5.6–7.0; ratio of head length to distance between eyes 3.5–4.9 vs. 2.0–2.4; naked vs. scaly body; densely distributed fine black stains except on abdomen; and semitransparent body. In fresh condition, dorsal region of head and dorsal region of body in O. shuilongensis gray and black. Upon preservation in alcohol, these regions become grayish, and fins become transparent. Back and upper side of body have irregular grey black markings in O. platycephalus .

Distinctions between the new species and O. retrodorsalis include: iii vs. iv unbranched rays in both dorsal and anal fins; 10–12 vs. 13–14 gill rakers on first gill arch; ratio of body length to body depth 7.1–7.9 vs. 5.3–6.5; ratio of head length to distance between eyes 3.5–4.9 vs. 2.6–3.2; anterior nostril, a short tubular process extending into long barbel vs. short tube with rear edge extending into short barbel; nasal barbels, when pressed directed rearward, may surpass anterior edge of eye vs. middle of posterior edge of nostrils and anterior edge of eye; head width greater than vs. equal to head depth; body lacking scales vs. densely distributed fine scales on body; lateral line with 8–10 pores terminating above pectoral fin vs. lateral line with 3–4 pores behind head; and rear edge of caudal fin truncated or slightly concave vs. deeply concave.

Description. Standard length 7.0- to 7.9-fold greater than body depth; 3.6 to 4.3-fold greater than head length; 7.0- to 9.2-fold greater than caudal peduncle length; and 9.5- to 11.8-fold greater than narrowest portion of caudal peduncle. Head length 2.5- to 2.9-fold greater than snout length; 6.6- to 8.6-fold greater than eye diameter; and 3.5- to 4.9-fold greater than interorbital width. Body depth 1.0- to 1.2-fold greater than body width. Caudal peduncle lengt 1.0- to 1.5-fold greater than height ( Table 2 ).

Body naked, elongated, slightly compressed anteriorly, and more laterally compressed posteriorly; lateral line incomplete, with 8–10 lateral pores behind head; lateral-line system pores present on head; snout length less than postorbital length ( Fig. 2); eyes positioned dorsolaterally on head; mouth inferior, mouth gape and upper jaw arched; lower jaw spoon-like with obtuse edge; three pairs of barbels, including medial rostral barbel extending to posterior margin of anterior or posterior nostrils, lateral rostral barbel extending beyond posterior margin of eye, and maxillary barbel (mean length 6.1 mm); dorsal-fin origin posterior to pelvic-fin origin, closer to caudal-fin base than to snout tip; dorsal fin little emarginated, with first branched ray longest; pectoral fin longer than pelvic fin, not reaching pelvic-fin origin when extended horizontally; the pelvic fin not reaching anus when extended; caudal fin emarginated or truncated. Stomach: U-shaped; intestine: straight ( Fig. 3).

Bladder divided into two compartments; anterior compartment wrapped in bony swim bladder, with posterior wall of side sac membranous. Air bladder well developed, separated into two cavities, dissociated from abdominal cavity, connected to front compartment by short tube. End of posterior compartment near pelvic-fin origin.

Color. In fresh conditions, dorsum gray and black, covered with many flecks; excluding abdomen, body semitransparent, becoming grayish after preservation in alcohol.

Phylogenetic results. Mitochondrial cytb sequences (1140 bp) were obtained for five specimens of O. shuilongensis . The overall transition/transversion bias: R = 1.206. In the ML tree, O. shuilongensis was closest genetically to O. platycephalus ( Fig. 4 ) with a high bootstrap value (BP = 80), supporting the inclusion of O. shuilongensis in Oreonectes . The genetic distance between O. shuilongensis and O. platycephalus was 0.657– 0.789.

Habitat. The species inhabits an underground river flowing in a cave. The cave, which opens near a hilltop, is approximately 150–200 m in length. The underground river is near the bottom of the cave and is approximately 15 m long and 0.15–0.85 m wide. Its flow is gentle and clear, and the average depth of the water is 0.40 m. This new species was observed at depths of 0.01–0.40 m. In the underground river, the only other aquatic organisms found were small shrimps.

Etymology. The specific epithet is based on the Chinese name “Shuilong,” which is the name of the township where the specimens were collected.

Figures

FIGURE 4. The ML phylogenetic tree of Oreonectes shuilongensis and related fish species. Numbers at nodes are confidence coefficients.

Tables

TABLE 2. Comparison of traits of Oreonectes shuilongensis sp. nov., O. platycephalus, and O. retrodorsalis.

Traits	O. shuilongensis , sp. nov.	O. platycephalus *	O. retrodorsalis **
No. of specimens	16	14	7
Location	Sandu, Guizhou	Zhaoping, Guangxi	Guangxi
Dorsal-fin rays	Iii, 7–8	Iii, 7	Iv, 7
Anal-fin rays	Iii, 6	Iii, 5	Iv, 5
Gill rakers	10–12	11–14	13–14
Body length/body depth	7.0–7.9	5.6–7.0	5.3–6.5
Head width/distance between eyes	3.5–4.9	2.0–2.4	2.6–3.2
Head width/eye diameter	6.6–8.6	5.7–8.5	5.0–6.8
Anterior nostril	Anterior nostril in short tube extending into relatively long barbel, beyond posterior edge of eye	Anterior nostril in short tube extending into relatively long barbel, beyond edge of posterior nostril	Anterior nostril in short tube extending into barbel
Scales on body	Body without scales	Body covered with fine scales	Body densely covered with fine scales
Lateral line	Lateral line incomplete, terminates above pectoral fin; 8–10 pores	Lateral line incomplete, terminates above pectoral fin	Lateral line incomplete, 3–4 pores
Caudal-fin rays	Truncated or slightly concave	Rounded	Apparently concave
Body color	Top of head and body gray and black in fresh condition; grayish in dorsum and body light brown after preservation in alcohol; fins transparent	In formaldehyde, body light brown; dorsum and side of body with irregular dark gray; dark brown horizontal stripe at end of caudal fin; fins without stains	In preserved specimens, body and top of head brownish gray; ventral yellowish gray; light black vertical stripe along axis of body; no clear blotches on fins