Speolabeo hokhanhi, Cao & Deng, 2018

Cao, Nguyen Dinh Tao Liang & Deng, Shuqing, 2018, Speolabeo hokhanhi, a new cavefish from Central Vietnam (Teleostei: Cyprinidae), Zootaxa 4476 (1), pp. 109-117 : 110-114

Speolabeo hokhanhi sp. nov.

( Figs. 1–3 )

Holotype. IHB 2016092883 , 74.6 mm SL, Hang Va Cave (17o29’29’’N, 106o17’06’’E), Phong Nha-Ke Bang National Park ( Son River basin) at Tan Trach Commune, Bo Trach District, Quang Binh Province, Central Vietnam; coll. Nguyen Dinh Tao, 21 April 2014.

Paratypes. IEBR 2884–5 , 2 specimens, 50.7–54.4 mm SL, IHB 2016092886–8 , 3 specimens, 61.8–69.0 mm SL; all other data same as holotype .

Diagnosis. Speolabeo hokhanhi can be easily distinguished from S. musaei by having a lower lip without papillae (vs. with a band of papillae along its anterior margin), no hump immediately behind the head (vs. present), a duckbilled (vs. pyramidal) snout, the pelvic fin inserted closer to the snout tip than to the caudal-fin base (vs. midway between the snout tip and caudal-fin base) and a shorter (vs. longer) caudal peduncle (length 16.8–18.6% SL vs. 19.6–22.7). All data here used for S. musaei are from Kottelat and Steiner (2011).

Description. Morphometric measurements and meristic counts of the type specimens are provided in Table 1. See Figures 1 and 2 for general appearance and Figure 3 for the ventral view of the head. Body elongate, slightly compressed laterally. Dorsal profile of head slightly concave. Predorsal profile of body slightly convex or nearly straight without distinctive hump behind head, straight along dorsal-fin base. Postdorsal profile somewhat concave or nearly straight. Ventral profile of head almost straight, slightly convex from pectoral-fin insertion to pelvic-fin insertion, then slightly concave between pelvic-fin insertion and anal-fin origin, and concave from anal-fin origin to caudal-fin base.

Head depressed anteriorly, wider than deep. Snout duckbilled in lateral view and rounded in dorsal view, with broad interorbital space. Eyes fully absent in all examined specimens. Mouth inferior and arched, close to tip of head. Rostral fold pendulous, with irregularly crenulated distal margin, connected from lips. Upper and lower lips continuous around corners of mouth. Lateral portions of upper lip in normal state, not covered by rostral fold, but with median portion greatly reduced into thin skin fold closely reflected on upper jaw behind cutting edge. Upper jaw laterally enclosed by upper lip and medially bearing thin, flexible horny sheath on cutting edge. Lower lip not papillated, laterally in normal condition and medially separated from lower jaw by shallow groove in larger specimens or adnate to it behind its cutting edge in smaller specimens. Lower jaw laterally enclosed in lower lip, medially bearing thin flexible horny sheath on cutting margin, distally not covered by lower lip. Postlabial groove deep, long, anteriorly extended, with wide median interruption. Rostral barbels rooted at anterior end of sublachrymal groove on side of snout, extending greatly beyond maxillary-barbel base; maxillary barbels positioned at corners of mouth or next to lateral extremity of rostral fold, longer than rostral barbels, extending to preoperculum.

Dorsal fin with 3 simple and 7 (6*) branched rays, last simple ray smooth or without serration along posterior edge of lower portion; distal margin slightly concave or nearly straight; origin halfway between snout tip and caudal-fin base, or slightly more anteriorly positioned, and anterior to pelvic-fin insertion. Pectoral fin short, with 1 simple and 12 (4*) or 13 (2) branched rays, tip of adpressed fin not reaching pelvic-fin insertion. Pelvic fin falcate, with 1 simple and 7 (6*) branched rays, inserted halfway between pectoral-fin insertion and anal-fin origin, tip of adpressed fin not extending to vent. Anal fin with 3 simple and 5 (6*) branched rays; origin equidistant to pelvicfin insertion and caudal-fin base; distal margin truncate. Caudal fin deeply forked.

Body scaled; scales medium-sized. Lateral line complete, extending along mid-lateral body from upper extremity of gill opening to middle of caudal fin, with 35 (1), 36 (1), 37 (2*), or 38 (2) pored scales. Scale rows above lateral line 4½ (2) or 5 (4*) and below lateral line 3½ (2) or 4 (4*); 14 (6*) circumpedunclar scales. Vertebrae 36 (5*) or 37 (1).

Coloration. In preserved specimens, body and head uniformly pale yellow; all fins white. In freshly captured individuals, body white to pinkish; all fins transparent ( Figs. 1–2 ).

Etymology. The specific epithet is named in honor of Mr. Ho Khanh who discovered many caves in Phong Nha–Ke Bang National Park. He was a local guide of the cavefish survey conducted by the first author during 2014 into the cave where the type specimens were collected and provided detailed information about the collection site. As common names, we suggest Hokhanh’s Blind-cavefish (English) and cá mù hang va hỗ-khanh (Vietnamese).

Characters S. hokhanhi S. musaei

Upper lip Laterally in normal state and uncovered by rostral cap, Separated from upper jaw and greatly reduced but with median portion greatly reduced into a thin skin into a thin skin fold closely adnate to it behind fold closely adnate to upper jaw behind cutting margin cutting margin; not covered by rostral cap

Upper jaw Bearing a thin and flexible horny sheath on cutting Bearing a thick and sharp horny sheath on margin of its median portion cutting margin of its entire length

Lower lip Laterally in normal state and anteromedially separated Fully separated from median part of lower jaw from median part of lower jaw by a shallow groove and adnate to it behind cutting edge, but from adnate to it behind its cutting margin; non-papillated lateral parts by postoral grooves; papillated

Lower jaw Distally uncovered by lower lip, bearing a thin flexible Completely exposed or uncovered by lower horny sheath on cutting edge; laterally enclosed in lower lip; laterally disconnected from lips lip

Postoral groove Absent Present, restricted to corner of mouth

Postlabial groove Deep; anteromedially extended Shallow; anteriorly extended

Distribution and habitat. Speolabeo hokhanhi is known only from the type locality ( Fig. 4 ). Hang Va Cave is roughly 35 km south of Phong Nha village, rather close to Hang Son Doong, the world’s largest known cave that is 5 km long, 200 m high and 150 m wide. A 24 km southward drive along the West Ho–Chi–Minh highway starting from the tourism center of the Phong Nha–Ke Bang National Park leads to the point closest to the cave site of the Hang Son Doong. From there, roughly 1.5 hours’ northward walk following a narrow stony track through thick forest arrives at Hang Va Cave. Its entrance is about 30 meters above the ground. A descent of 15 m from the entrance reaches a cave passage containing a subterraneous stream. Downstream for approximately 200 meters, there is a shallow water pool with many stalagmites, usually 2–3 m tall ( Fig. 5 ), where the type specimens of the new species were collected during the dry season. At this time, the pool had a muddy substrate and was 0.5–1.5 m in depth, 10 m wide, and 25 m long. More than 30 individuals of about the same size were observed in the pool; only six were captured using a hand-net. The fishes were swimming slowly and haphazardly, rather close to the water surface; when disturbed, they swam deeper, but did not seek shelter. A new shrimp species was found to sympatrically occur with the cavefish ( Do & Nguyen 2014).

Figures

FIGURE 1. Lateral view of Speolabeo hokhanhi, IHB 2016092883, holotype 74.6 mm SL; central Vietnam, Son River basin, Hang Va Cave.

FIGURE 2. Speolabeo hokhanhi sp. nov., fresh individual immediately after capture. Lateral view.

FIGURE 3. Oromandibular structures in Speolabeo hokhanhi sp. nov.; lj, lower jaw; ll, lower lip; mb, maxillary barbel; pg, postlabial groove; rb, rostral barbel; rf, rostral fold; ul, upper lip; uj, upper jaw.

FIGURE 4. Distribution of Speolabeo hokhanhi (▲).

FIGURE 5. Vietnam: Son River basin: Hang Va Cave. a) habitat of Speolabeo hokhanhi, b) the pool where type specimens were collected.