Research Article |
Corresponding author: E Zhang ( zhange@ihb.ac.cn ) Academic editor: Sven Kullander
© 2020 Dinh Tao Nguyen, Anh Tuan Ho, Ngoc Thao Hoang, Hua Wu, E Zhang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Nguyen DT, Ho AT, Hoang NT, Wu H, Zhang E (2020) ‘Henicorhynchus’ thaitui, a new species of cavefish from Central Vietnam (Teleostei, Cyprinidae). ZooKeys 965: 85-101. https://doi.org/10.3897/zookeys.965.52751
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‘Henicorhynchus’ thaitui sp. nov. is described from a subterranean stream in a karst cave in Phong Nha Ke Bang National Park, Quang Binh Province, Central Vietnam. It differs from all congeners in having a pale pink body in life, smaller eyes with diameter less than the maxillary barbel length, and two pairs of barbels, the maxillary barbel being much longer than the rostral barbel.
Cypriniformes, karst system, morphology, Southeast Asia, taxonomy
Vietnam is rich in karst caves, and there are many magnificent caves throughout the country. The Son Dong Cave is the largest in the world (
Cavefishes are adapted to hypogean aquatic ecosystems. During the past decade, many cavefishes were discovered in Vietnam as a result of ongoing cave explorations (
The Phong Nha-Ke Bang National Park is located in the middle of the Annamite Range in the Quang Binh Province. The park, with approximately 104 km of subterranean tunnels and rivers, is among the most outstanding limestone karst ecosystems in the world (
Henicorhynchus comprises species widespread in freshwater habitats throughout tropical and subtropical regions of Southeast and South Asia. This genus has a complex taxonomic history. Its included species were previously placed under various genera, such as Cirrhinus Oken (Roberts, 1997), and Gymnostomus Heckel (Kottelat, 2013). In the absence of a stable classification of parts of the Labeonini we here follow
All measurements were taken point to point with a pair of dial calipers and data were recorded to the nearest 0.1 mm. Counts and measurements were made on the left side of specimens whenever possible, following the methods of
Abbreviations in the text include: IHB, Institute of Hydrobiology, Chinese Academy of Sciences in Wuhan City, Hubei Province, China; IEBR, Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology in Hanoi City, Vietnam; RIA1, Research Institute for Aquaculture No. 1, Bac Ninh Province, Vietnam; RIA2, Research Institute for Aquaculture No. 2, Khanh Hoa Province, Vietnam; VU, Vinh University in Nghe An Province, Vietnam; CTU, Can Tho University in Can Tho City, Vietnam; CAS, California Academy of Sciences; USNM, National Museum of Natural History, Washington, DC, USA.
IEBR 105901, 74.3 mm SL; Vietnam: Quang Binh Prov.: Phong Nha-Ke Bang National Park: Khe Lanh Cave (in Son River system in the Gianh River basin): 17°25'41"N, 106°18'31"E, altitude 185 m; collectors: A.T. Ho and N.T. Hoang, 12 August 2011 (deposited in IEBR).
IHB 2016105895–9, 5 specimens, 80.9–99.5 mm SL; IEBR 105900–04, 4 specimens, 68.8–75.6 mm SL; VU 5905–08, 4 specimens, 76.8–83.4 mm SL; all other data same as holotype (deposited in IHB and IEBR, VU).
‘Henicorhynchus’ thaitui sp. nov. can be distinguished from all congeners by having a whitish pink body in life (vs. white or silvery body with a humeral mark or some longitudinal stripes), smaller (vs. larger) eyes (diameter less than vs. greater than maxillary barbel length) and maxillary barbel longer (vs. shorter) than rostral barbel. ‘Henicorhynchus’ thaitui, along with H. horai (Bănărescu, 1986) and H. inornatus (Roberts, 1997), is further distinct from all other congeners in having 9 (vs. 8) branched dorsal-fin rays. Along with H. horai, it differs from all other congeners in the presence of rostral barbels (vs. absent) and 39–41 (vs. 34–36) lateral-line scales. ‘Henicorhynchus’ thaitui differs from H. horai and H. inornatus in the presence of two (vs. one) pairs of maxillary and rostral barbels (vs. only the maxillary barbel in H. inornatus and only the rostral barbel in H. horai); from H. horai in having fewer vertebrae (34 vs. 38–41), and a laterally compressed body (vs. cylindrical in H. horai); and from H. inornatus in having 39–40 (vs. 35 in H. inornatus) lateral-line pored scales, and in the absence of a humeral mark (vs. present in H. inornatus).
Measurements and meristics of the type series are provided in Table
Morphometric data and meristic counts for type specimens of ‘Henicorhynchus’ thaitui sp. nov. (n = 14).
Holotype | Paratypes (N=13) | ||||
---|---|---|---|---|---|
Min | Max | Average | SD | ||
SL | 74.3 | 68.8 | 99.5 | 80.9 | 8.5 |
In percent of SL | |||||
Head length | 24.1 | 20.3 | 24.1 | 22.2 | 0.9 |
Predorsal length | 53.3 | 47.8 | 53.3 | 49.9 | 1.6 |
Preanal length | 74.2 | 72.8 | 77.9 | 74.6 | 1.4 |
Prepelvic length | 49.0 | 49.0 | 54.4 | 50.9 | 1.5 |
Body depth at dorsal-fin origin | 30.0 | 23.3 | 30.0 | 26.9 | 2.2 |
Body depth at anus | 20.2 | 16.0 | 20.2 | 18.0 | 1.3 |
Depth of caudal peduncle | 14.2 | 10.6 | 14.2 | 12.7 | 0.9 |
Length of caudal peduncle | 22.1 | 13.6 | 22.1 | 17.8 | 2.4 |
Head depth | 11.8 | 10.9 | 12.8 | 11.8 | 0.6 |
Head width | 11.6 | 10.4 | 11.9 | 11.1 | 0.6 |
Snout length | 8.8 | 6.7 | 9.6 | 8.4 | 0.8 |
Dorsal-fin length | 26.3 | 20.1 | 29.6 | 25.7 | 2.7 |
Pectoral-fin length | 21.9 | 18.4 | 25.7 | 22.6 | 1.7 |
Pelvic-fin length | 20.6 | 16.9 | 23.7 | 20.8 | 1.9 |
Anal-fin length | 19.1 | 14.0 | 22.7 | 19.1 | 2.2 |
In percent of HL | |||||
Head depth | 48.9 | 48.9 | 57.6 | 53.1 | 2.7 |
Head width | 48.4 | 44.6 | 54.9 | 50.0 | 3.0 |
Snout length | 36.7 | 32.9 | 42.5 | 38.0 | 3.0 |
Eye diameter | 17.7 | 10.9 | 17.7 | 13.6 | 1.8 |
Interorbital width | 48.4 | 44.6 | 54.9 | 50.0 | 3.0 |
Counts | |||||
Lateral line scales | 39 | 39 (11), 40 (2) | |||
Transverse scale rows | 5/1/4 | 6/1/4(11), 5/1/4 (2) | |||
Predorsal scales | 14 | 14 (10) –15 (3) | |||
Cicumpeduncular scales | 16 | 16 (13) | |||
Dorsal-fin branched rays | 9 | 9 (13) | |||
Pectoral-fin branched rays | 11 | 11 (13) | |||
Pelvic-fin branched rays | 8 | 8 (13) | |||
Anal-fin branched rays | 5 | 5 (13) | |||
Caudal-fin branched rays | 9+8 | 9+8 (13) | |||
Gill rakers on lower arm of 1st arch | 37–39 (2) | ||||
Vertebrae | 34–35 (2) |
Head small, conical, longer than deep, deeper than wide. Eye relatively small, positioned laterodorsally in anterior half of head and considerably behind or above rictus, not visible when head viewed ventrally; diameter less than maxillary-barbel length. Interorbital space slightly convex. Snout slightly pointed in lateral view and broadly rounded in ventral view (Fig.
Rostral cap well-developed, overhanging, but covering median part of upper lip base; slightly crenulated, laterally attached to root of maxillary barbel and separated from lower lip. Upper lip well-developed, greatly enlarged, separated from upper jaw, covered with papillae; laterally continuous with lower lip around corners of mouth. Upper jaw bearing a thin, flexible horny sheath on cutting margin. Lower lip anteriorly separated from lower jaw by a deep, transversally arched groove; posteriorly confluent with mental region and covered with papillae. Post-labial groove extended anteromedially, but not meeting its counterpart at midline. Lower jaw bearing a thin horny sheath on cutting margin (Fig.
Dorsal fin with 3 unbranched and 9 branched rays, last one split to base; last unbranched ray flexible, without serrations along posterior border; distal margin strongly concave; origin midway between snout tip and caudal-fin base or anterior to pelvic-fin insertion. Pectoral fin short, with 1 unbranched and 11 branched rays; tip of adpressed fin not reaching pelvic-fin insertion. Pelvic fin falcate, with 1 unbranched and 8 branched rays; inserted halfway from pectoral-fin insertion to anal-fin origin; tip of adpressed fin extending to vent. Anal fin with 3 unbranched and 5 branched rays; distal margin slightly concave; origin equidistant between pelvic-fin insertion and caudal-fin base. Caudal fin with 9/8 principal rays, deeply forked; upper and lower lobes nearly equal in length.
Scales moderately large. Lateral line complete with 39 (12*) or 40 (2) pored scales, extending along mid-lateral body from upper gill-opening extremity to middle of caudal fin. Predorsal scales 14 (10*) or 15 (3). Scales in transverse row before pelvic fin 5 (3) or 6 (12*) above lateral line and 4 (14*) below. Circumpeduncular scales 16 (14*). Gill rakers on left side of first gill arch 37–39 (2) (Fig.
In freshly caught-individuals, body white to pinkish or pale pink with all fins translucent (Fig.
The specific name is a noun in the genitive case, honoring Nguyen Thai Tu, ichthyologist from Vinh University, who has contributed considerably to the taxonomy of freshwater fishes in Vietnam.
‘Henicorhynchus’ thaitui sp. nov. presents a mixture of characters characterizing hypogean and epigean fish species. The absence of pigmentation, reduced eye size, and well-developed barbels are troglomorphic characters observed in ‘H.’ thaitui. The pale pink or white to pinkish body is shared with hypogean fish species. The eyes are smaller than in congeneric epigean species, but not vestigial or absent as is common in hypogean fish species. The barbels are longer and thicker compared with all congeneric epigean species, but in this regard similar to hypogean fish species.
‘Henicorhynchus’ thaitui sp. nov. is known only from the Khe Lanh Cave where it inhabits shallow to deep (0.2–0.8 m) cave streams and pools about 800–1000 m from the cave entrance (Figs
Main diagnostic characters for ‘Henicorhynchus’ thaitui sp. nov. and its congeneric species.
Characters | H. thaitui | H. horai | H. inornatus | H. siamensis | H. lineatus | H. lobatus | H. caudiguttatus | H. cryptopogon | H. ornatipinnis | H. caudimaculatus |
Branched dorsal-fin rays | 9 | 9 | 9 | 8 | 8 | 8 | 8 | 8 | 8 | 8 |
Rostral barbels | present | present | absent | absent | absent | absent | absent | absent | absent | absent |
Maxillary barbels | present, long and well developed | absent | absent | present, very tiny | present, tiny | present, tiny | present, tiny | present, tiny | absent | absent |
Lateral line scales | 39–40 | 39–41 | 35 | 34–36 | 34–35 | 32–33 | 35 | 34–35 | 34–35 | 35–36 |
Transverse scales rows | 5–6/1/4 | 6/1/4 | 7/1/5 | 6/1/4 | 6/1/5 | 5/1/4 | 6/1/5 | 6/1/5 | 6/1/4 | 6/1/5 |
Vertebrae | 34–35 | 38–41 | 35–37 | 33–34 | 32–33 | 32 | 32 | 32–33 | 33–35 | 32 |
Dark state color distal dorsal-fin edge | absent | absent | absent | present | absent | absent | absent | present | absent | absent |
Reddish-orange pectoral fins | absent | absent | absent | absent | absent | absent | absent | absent | present | absent |
Longitudinal stripes on body | absent | absent | absent | absent | present | absent | absent | present | absent | absent |
Humeral mark color | absent | absent | present | absent | absent | absent | absent | absent | absent | absent |
Strongly projected snout | absent | absent | absent | absent | absent | present | absent | absent | absent | present |
Dark state color precaudal blotch | absent | absent | absent | absent | absent | absent | present | absent | absent | present |
Sources of data | this study |
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Species most closely related to ‘Henicorhynchus’ thaitui sp. nov.: a Henicorhynchus lineatus b H. lobatus c H. ornatipinnis d H. siamensis e Cirrhinus jullieni f C. microlepis g C. molitorella; and h Speolabeo hokhanhi. Photos b, d, e, f and g from Vietnam, by D.D. Tran (Can Tho University, Vietnam); a and c from Laos, by Bounthob Praxaysombath (National University of Laos, Laos) (from
‘Henicorhynchus’ thaitui sp. nov. is referred to the genus Henicorhynchus with hesitation. It can be distinguished from all other species of this genus by the troglomorphic characters, and would be the only species of Henicorhynchus recorded from a cave biotope.
The karst region of Central Vietnam extends into the central part of Laos from where the labeonine cavefish Speolabeo musaei is known. The second species of the genus, also troglobitic, is S. hokhanhi (Fig.
The Labeonini are characterized by a high degree of morphological modification of their oromandibular structures, variation in which is the basis for the diagnosis of the majority of included genera. The well-developed, greatly enlarged upper lip separated from the upper jaw in ‘H.’ thaitui is shared only with some species of the labeonine genera Osteochilus Günther, Labiobarbus van Hasselt, Labeo Cuvier, Cirrhinus and Henicorhynchus (
‘Henicorhynchus’ thaitui sp. nov. can be distinguished by its troglomorphic characters from all other species of Henicorhynchus and closely related genera like Cirrhinus and Gymnostomus. Except for the two species of Speolabeo (
The generic placement of ‘H.’ thaitui is not straightforward, however. Compared with species of Henicorhynchus or closely related genera which have relatively simple oromandibular structures (see
The taxonomy of Henicorhynchus and closely allied genera is poorly understood. Their generic delineation is not based on the morphology of the oromandibular structures, which are widely used for the diagnosis of genera of the Labeonini. The major character used to distinguish among Henicorhynchus and closely allied genera (Cirrhinus and Gymnostomus) is the number of branched dorsal-fin rays; their current generic definition still remains controversial, however. The focus of this controversy is on the generic assignment of species with 9 branched dorsal-fin rays. According to
Taxonomic confusion regarding Henicorhynchus, Gymnostomus, and Cirrhinus was clarified in recent molecular phylogenetic analyses of the Labeonini (
Henicorhynchus siamensis: RIA2, uncataloged, 30, 62–184 mm SL, South Vietnam (Lower Mekong basin); CAS 91751, 109 mm, Pak Mun; CAS 91749, 4, 57.4–65.2 mm, Menam Bangpakong at Ban Khao Cha-chan, 19 km South of Sa Kaeo on highway 317.
H. caudimaculatus: CTU, uncataloged, 11, 40–80 mm SL, South of Vietnam (Lower Mekong basin); USNM 117769, 27, 45.0–78.5 mm, upper Nan River at Ban Khwang, northern Siam; USNM 119493, 2, 59. 6–60.5 mm, Chao Phraya at Bangsai, central Thailand; CAS 91781, 55.2 mm, Menam Wang, 79 km by road North of Lampang and 6 km E of highway 1035.
H. cryptopogon: RIA2, uncataloged, 1, 145 mm SL, Can Tho province.
H. inornatus: CAS 91772, 115 mm, Myanmar, Mandalay market; CAS 88903, 106 mm, Pagan market; CAS 91775, 122 mm, Myitkyina market (Irrawaddy basin); CAS 91773, 6: 94.6–116 mm, Taungoo market (Sittang River).
H. lineatus: CAS 79169, 5, 64.9–95.2 mm, mouth of Huay Ngao where it flows into Mekong River 1 km South of Ban Chaem Pong (about 30 km South of Chiang Khong); CAS 91766, 9, 54.5–106 mm, Mekong mainstream from Pak Ing to Jom Paeng (about 4–5 km downstream from Pak Ing).
H. lobatus: CAS 91769, 8, 56.9–102 mm, Menam Kok at Tha Ton and up to 5 km downstream; CAS 91767, 4, 43.4–50.5 mm, Se Khone at Stung Treng.
H. horai: CAS 81548, 24, 95.9–155 mm, Inle Lake.
H. ornatipinnis: CAS 91756, 69.7 mm, roadside ditch on highway 24 at km 150, market, 179 km by road E of Nakom Ratchasima, Thailand; CAS 91760, 9, 55.7–90.5 mm, roadside ditch 5–30 km South of Phibun Mangsahan, Thailand.
Cirrhinus molitorella: RIA1 H01930101–7, 7, 105–387 mm SL, Red river. IHB 201808027404, 1, Lam river, Nghe An province, Central Vietnam; CAS 79175, 2, 82.8–93.7 mm, Huay Sangkalia, 7 km North of Sangklaburi on road to Chedi Sam Ong.
C. microlepis: RIA1 H01930201–3, 3, 65–148 mm SL, south of Vietnam; USNM 104935, 2, 122–146 mm, Chao Phraya at Nontaburi; CAS 79173, 2: 107–113 mm, rapids in mainstream of Mekong River about 12 km South of That Phanom.
C. mrigala (Hamilton, 1822): RIA1 H01930301–5, 5, 150–258 mm SL, aquaculture. IHB 201808018201–5, 5, Lam river, Nghe An province, Central Vietnam.
C. prosemion: CTU, uncataloged, 11, 71–95 mm SL, Can Tho province.
C. jullieni: CAS 91748, 104 mm, Sawankhalok market (Menam Yom), 36 km North of Sukhothai; CAS 91610, 13: 94.7–104 mm, Phnom Penh market.
Speolabeo hokhanhi: IHB 2016092883, 76.4 mm, Hang Va cave, Phong Nha-Ke Bang National Park; IEBR 2884–5, 50.7–54.4 mm, IHB 206092886–8, 61.8–69.0 mm.
Data for Cirrhinus reba (Hamilton, 1822) from
We thank the board and staff of Phong Nha-Ke Bang National Park for facilitating surveys and issuing permissions. This research work was funded by the National Sciences Foundation of China (NSFC No. 31801959), the Ministry of Education and Training of Vietnam (B2019–TDV–02) and the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 106.05–2017.321. Field survey was funded by KFW, and the equipment used was supported by Idea Wild (2012, 2014 and 2018) to Dinh Tao Nguyen.