Microphysogobio luhensis, Huang & Chen & Zhao & Shao, 2018

Huang, Shih-Pin, Chen, I-Shiung, Zhao, Yahui & Shao, Kwang-Tsao, 2018, Description of A New Species of the Gudgeon Genus Microphysogobio Mori 1934 (Cypriniformes: Cyprinidae) from Guangdong Province, Southern China, Zoological Studies 57 (58), pp. 1-14 : 4-9

Microphysogobio luhensis n. sp.

( Figs. 2; 3a b ; 4a )

urn:lsid:zoobank.org:act:855FE0C8-8BF1-48E8-B29E-56C39F68863C

Material examined: Holotype: NTOUP 2013- 10 - 119 , 56.2 mm SL, Rong River (Rongjiang), Dongkeng Town, Luhe County, Guangdong Province, China (23°18'15.4"N, 115°42'51.4"E), coll. S.P. Huang, 2 April 2009 . Paratypes: ASIZP 0080740, 2 specimens, 48.3-60.8 mm SL. NTOUP 2010-11-545, 1 specimen, 52.7 mm SL. ASIZB 204717, 1 specimen, 57.3 mm SL. Paratypes were collected with holotype. Non-types: NTOUP 2013- 10-116, 3 specimens, 46.7-53.7 mm SL, collected with holotype.

Diagnosis: This new species can be distinguished from other congeners by the following unique combination of features: (1) meristic accounts: anal fin rays 3, 6; pectoral fin rays 1, 12-13 (modally 13); lateral-line scales 37-38 (modally 37); transverse scales 7; predorsal scales 10-11 (modally 10); gill rakers 16; vertebral counts 4 + 33-34; inside papillae lobes covered with clusters of 20-26 well-developed pearl-like papillae; (2) lip papillae: A pair of barbels flat and slightly short, 16.2-18.4% of head length, maximum barbel diameter was measured as 27.0-29.8% of barbel length; the medial pad on lower lip divided; (3) color patterns: Body with five distinct black crossbars; Two horizontally aligned black dashes above and below each lateral-line scale; caudal fin membrane with two rows of distinct verticallyaligned black lines.

Description: Body elongated and compressed laterally. Snout pointed. Eye moderately large and located in dorsal half of head, eye diameter was measured as 25.2-27.9% of head length. Belly flatted in males, and slightly rounded in females. Body covered with moderately small cycloid scales which are larger posteriorly. The morphometric measurements of this new species are provided in table 2.

Inter-pectoral fin basal region always naked, but rear margin of which, backward extending to anal fin anterior base always covered with cycloid scales. Lateral line complete and running slightly downward abruptly above pectoral fin and along the ventral profile into middle of caudal fin base.

Vertebral counts 4 + 33 (in 1 individual)-4 + 34 (1). Gill rakers 16 (1). Dorsal fin rays 3, 7 (8), anal fin rays 3, 6 (8), pectoral fin rays 1, 12 (2)-1, 13 (11), pelvic fin rays 1, 7 (15). Lateral line scales 37 (11)-38 (5), transverse scales 7(8), predorsal scales 10 (6)-11 (2). Pectoral fin maximum reach anterior margin of pelvic fin when compressed in both sexes. Pelvic fin rounded. Anterior margin of pelvic fin inserted below second branched ray of dorsal fin. Caudal fin deeply forked and rear margin of caudal fin lobe rounded. Snout is prominent, 40.2-45.0% of head length.

Lip papillae: Mouth horseshoe-shaped. Upper and lower lip thick, covered with pearl papillae. Lip papillae consists of three parts: a pair of papillae on upper lip, and backward extending to the base of barbel; a pair of inside papillae lobes on lower lip; and a heart-shaped medial pad on lower lip. On upper lip, anterior papillae covered with one row of large pearl-like papillae, both posterior lobes covered with clusters of well-developed, small pearl-like papillae. Posterior margin of both inside papillae lobes rounded, and covered with clusters of 20-26 well-developed, small pearl-like papillae ( Table 1). The medial pad on lower lip completely divided. The lip papillae of M. luhensis is shown in figure 4.

The morphometric measurements of papillae and barbell were shown in table 1. Entire papillae lobe was measured as 26.5-29.8% of head length. A pair of posterior lobes and inside papillae lobes were measured as 15.1-19.7% and 10.5-13.6% of head length, respectively. Medial pad was measured as 10.4-11.0% of head length. A pair of barbels flat and slightly short, located at corners of mouth and rooted at posterior edge of lower jaw, 16.2-18.4% of head length. Maximum barbel diameter was measured as 27.0-29.8% of barbel length.

Coloration in fresh specimen: Head and body generally pale yellowish brown ( Fig. 2). Belly pale grayish white. Body with five distinct black crossbars (four bars on trunk and one bar on neck) ( Fig. 3 ). Cheek and lower opercular regions bright sliver-white, and with a few indistinct small black spots. Upper opercular region grayish brown. A distinct bar is present on anterior margin of eye and extending to upper lip. Two horizontally aligned black dashes above and below each lateral-line scale. Dorsal fin membrane with two rows of indistinct, longitudinally-aligned black lines. Pectoral fin and pelvic fin membranes having some tiny black spots. Anal fin membrane clean. Caudal fin base with a distinct small black mark. Caudal fin membrane with two rows of distinct verticallyaligned black lines.

Distribution: Known only from the upper reaches of the Rongjiang River (Rong River), a river located in eastern Guangdong Province, southern China ( Fig. 1 ).

Etymology: The Latinized specific name, “ luhensis ” is refers to “Luhe County”, located in northeastern Guangdong Province, China, wherein lies the type locality.

Remarks: On the aspect of morphological feature, compared to all 22 valid Microphysogobio species from related areas, M. luhensis can be immediately distinguished from five valid species ( M. chenhsienensis , M. chinssuensis , M. exilicauda , M. tafangensis and M. wulonghensis ) by the different types of medial pad on lower lip (centrally divided vs. undivided).

As to the remaining 17 species, M. luhensis can be discriminated from M. hsinglungshanensis , M. liaohensis , M. linghensis and M. nudiventris by the different pattern of scale distribution (midventral region covered with scales vs. midventral region naked).

Out of the remaining 13 species, this new species can be distinguished from M. tungtingensis and M. zhangi by having more anal fin rays (3, 6 vs. 3, 5). Compared to the remaining 11 species, M. luhensis can be distinguished from M. alticorpus , M. amurensis , M. microstomus , M. kiatingensis and M. xianyouensis by having different frequency distribution of lateral-line scale series (37-38 vs. 39-42 for M. amurensis , 35-36 for M. alticorpus , M. kiatingensis and M. xianyouensis ; 34 for M. microstomus ).

As to the remaining five species, M. luhensis can be discriminated from M. yunnanensis by having fewer pearl-like papillae on inside papillae (20-26 vs. 30-41), and this new species can be distinguished from M. elongatus by having more vertebral counts (4 + 33-34 vs. 4 + 32).

Compared to the remaining four species, M. luhensis can be distinguished from M. brevirostris , M. fukiensis , and M. pseudoelongatus by having different type of medial pad (heart-shaped for M. luhensis vs. rectangular form for the rest) ( Fig. 4 ).

Of all the valid species of Microphysogobio , the new species appears to be most closely related to M. kachekensis based on molecular evidence and some morphological features. Both species share similar anal fin rays (3, 6), predorsal scale series (10-11), spotted dorsal fin and caudal fin, and these two species with two horizontally aligned black dashes above and below each lateral-line scale. However, M. luhensis still can be distinguished from M. kachekensis based on following morphological difference: (1) M. luhensis has shorter and broader barbel (16.2-18.4% of head length and 27.0-29.8% of barbel length, respectively) when compared to M. kachekensis (21.0-23.8% of head length and 15.0-18.8% of barbel length, respectively); (2) M. luhensis has fewer pearl-like papillae on inside papillae (20-26 vs. 32-40); (3) the rear margin of posterior papillae lobe always in arc-shaped for M. luhensis , and in tassel-shaped for M. kachekensis ; (4) different color patterns (presence vs. absence of five distinct black crossbars at body); and (5) fewer lateral-line scale series (modally 37 vs. 38).

Pseudogobio labeoides Nichols and Pope, 1927 which was described from Nodoa, Hainan Island, China, was previously regarded as a junior synonym of Microphysogobio kachekensis ( Kottelat 2001b) . In order to confirm the taxonomic status of P. labeoides , its holotype specimen was examined. The result revealed that P. labeoides should be conspecific with M. kachekensis , both share the same type of medial pad on lower lip, the rear margin of medial pads always in arc-shaped ( Fig. 4b ). In addition, P. labeoides and M. kachekensis share the longer and slender barbel. P. labeoides can be immediately distinguished from M. luhensis by the latter species having an acuminate rear margin and having shorter and broader barbel ( Fig. 4a ). Our result was consistent with Kottelat’s taxonomic treatment, suggesting the P. labeoides should be treated as a junior synonym of M. kachekensis . Under the subfamily Gobioninae , both Microphysogobio and Pseudogobio are common benthic gudgeon distributed in East Asia. In addition, these two genera share similar characters, including have a pair of barbels and lip covered with pearl papillae. However, Pseudogobio can be distinguished from Microphysogobio by having flatter snout and longer snout (longer than two times of eye diameter) ( Pan 1991).

Otherwise, Microphysogobio luhensis is further compared with several nominal species of Microphysogobio distributed in Vietnam, Mongolia, and the Yalu River, which forms the border between China and North Korea. The results are discussed as follows. When compared to the M. yaluensis ( Mori, 1928) known from the Yalu River, M. luhensis can be distinguished by having more pectoral fin rays (1, 12-13 vs. 1, 11).

Microphysogobio luhensis differs from M. anudarini Holcík and Pivnička, 1969 , a species known from Mongolia, by having significantly shorter distance between the anus and anal fin origin (17.2-17.6% of SL, averaged 17.4%, measured from five individuals including holotype versus 19.0-20.8% of SL, using previous data from the literature reported by Kottelat in 2006). M. luhensis has two irregular lines on caudal fin membrane, but it is rather regular in M. anudarini (based on its detailed specimen photograph from the literature reported by Kottelat in 2006).

Microphysogobio luhensis can also be discriminated from two nominal species of Microphysogobio known from Vietnam. At the first, it differs from M. nikolskii ( Dao and Mai, 1959) by having fewer lateral-line scales (37- 38 vs. 43). Kottelat (2001b) reported that the taxonomic assignment of M. vietnamica Mai, 1978 , another nominal species from Vietnam still remains unclear. Nevertheless, M. luhensis can be discriminated from M. vietnamica by having smaller dorsal fin and longer pectoral fin (versus a dorsal fin reaching backward almost to the anal fin base, and pectoral fin never reach base of pelvic fin in M. vietnamica ).

Molecular phylogenetic analysis: The code of each species and GenBank accession numbers used in this study were given in table 3. Carassius auratus langsdorfi was used as outgroup species. The Cyt b and partial COI sequences from M. luhensis and 10 species of Microphysogobio were analyzed. A total of 20 haplotypes from 42 individuals for Cyt b gene, and 15 haplotypes from 26 individuals for COI gene were included in this analysis. The length of Cyt b and COI sequence are 1141 bp and 636 bp in total, respectively. The alignment contains 390 and 232 total mutations, and 329 and 177 polymorphic (segregating) sites for Cyt b and COI genes, respectively. The phylogenetic analysis using the Bayesian inference (BI) was provided. The phylogenetic trees were reconstructed by the BI method based on the HKY + G model.

The Cyt b phylogenetic tree ( Fig. 5 ) revealed that M. luhensis - M. kachekensis - M. yunnanensis clade is the earliest offshoot. Out of all taxa, M. alticorpus and M. zhangi formed respective clades. M. tafangensis and M. chenhsienensis formed a related sister group, which is sister to M. brevirostris - M. xianyouensis + M. elongatus - M. fukiensis clade. Inter-specific nodes between M. luhensis and the closely related species M. kachekensis and M. yunnanensis with high posterior probability reach to 1.00. All inter-specific nodes were supported by high bootstrap values (as high as 0.95-1.00). However, an inter-clades node between two clades (clade M. brevirostris + M. xianyouensis + M. elongatus + M. fukiensis , and clade M. tafangensis + M. chenhsienensis ) had a lower posterior probability of 0.67. The genetic distances of relationships among M. luhensis and ten valid species of Microphysogobio were analyzed based on Kimura 2 parameter model (K2P), ranged from 1.2-16.1% for Cyt b gene, and ranged from 2.9-20.2% for COI gene.

Although the COI phylogenetic tree ( Fig. 6 ) revealed clades different from those on the Cyt b tree, the COI tree also strongly supported that the M. luhensis can be discriminated from M. kachekensis and M. yunnanensis , and that this phylogenetic tree had high posterior probability reaching 1.00.

Figures

Fig. 3. The dorsal view of Microphysogobio luhensis n. sp. (a, b) and Microphysogobio kachekensis (c, d), standard length was measured as 56.2, 57.3, 50.3 and 68.2 mm SL for individual a, b, c and d, respectively.

Fig. 4. Lip papillae of a, Microphysogobio luhensis n. sp., holotype; b, Microphysogobio kachekensis, NTOUP 2013-10-117, 64.4 mm SL; c, an illustration for morphometric measurements of lip papillae. Scale bar = 1 mm. © 2018 Academia Sinica, Taiwan

Fig. 1. The Sampling localities of Microphysogobio luhensis n. sp., and comparative materials. ✚, M. luhensis n. sp.; u, M. alticorpus; l, M. brevirostris; N, M. chenhsienensis; △, M. elongatus; ◇, M. exilicauda; ▼, M. fukiensis; ¨, M. kachekensis; ▽, M. kiatingensis; ▲, M. microstomus; ¢, M. pseudoelongatus; ★, M. tafangensis; ◎, M. tungtingensis; ¤, M. xianyouensis; ☆, M. yunnanensis; ✱, M. zhangi.

Fig. 5. Molecular phylogenetic tree of Microphysogobio luhensis n. sp. and other comparative materials based on Cyt b sequence reconstructed by Bayesian analysis method (values above the branch: posterior probabilities). The sample size of each haplotype is shown behind the OTU.

Fig. 6. Molecular phylogenetic tree of Microphysogobio luhensis n. sp. and other comparative materials based on partial COI sequence reconstructed by Bayesian analysis method (values above the branch: posterior probabilities). The sample size of each haplotype is shown behind the OTU.