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Research Article
A new species of freshwater crab of the genus Mediapotamon Türkay & Dai, 1997 (Crustacea, Decapoda, Brachyura, Potamidae) from Guizhou, China
expand article infoSong-bo Wang‡, Xian-min Zhou‡, Jie-xin Zou‡
‡ Nanchang University, Nanchang, China

Corresponding author: Jie-xin Zou ( jxzou@ncu.edu.cn )

Academic editor: Sammy De Grave
© 2019 Song-bo Wang, Xian-min Zhou, Jie-xin Zou.
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: Wang S-b, Zhou X-m, Zou J-x (2019) A new species of freshwater crab of the genus Mediapotamon Türkay & Dai, 1997 (Crustacea, Decapoda, Brachyura, Potamidae) from Guizhou, China. ZooKeys 873: 9-23. https://doi.org/10.3897/zookeys.873.36702
ZooBank: urn:lsid:zoobank.org:pub:3E20828E-F1D7-41E9-BA12-0D5F2BD93ED9
Open Access

Abstract

A new species of Mediapotamon Türkay & Dai, 1997 from a karst system in southwest China is described. The new species can be separated from congeners by the combination of a sharp and distinct epibranchial tooth, the anterolateral region lined with few scattered granules, the terminal segment of the male first gonopod distinctly bent with a constant diameter, and the position of the female vulvae. Mitochondrial 16S rDNA genetic data was used to investigate the systematic position of the new species, which is supported as a new taxon.

Keywords

freshwater crab, Mediapotamon liboense, systematics, taxonomy, 16S rDNA

Introduction

China has the highest number of freshwater crab species in the world, with more than 300 species (Dai 1999, Cumberlidge et al. 2011). There are unique karst landforms in Guizhou, China where numerous caves are distributed (Han et al. 2010), and researchers have discovered a number of new freshwater crab species in these caves (Ng and Trontelj 1996, Ng 2017, Huang et al. 2017). To investigate the species diversity of freshwater crabs in this area, the authors conducted scientific investigations twice in 2010 and 2017 to collect specimens of Chinapotamon Dai & Naiyanetr, 1994, Mediapotamon Türkay & Dai, 1997, Daipotamon Ng & Trontelj, 1996, and Longpotamon Shih, Huang & Ng, 2016, some of which have already been published (Shih et al. 2016). After morphological comparison of the collected specimens, the specimen from Yaozhai village, Dongtang town, Libo County, Qiannan Buyei and Miao Autonomous Prefecture, was found to be a new species of Mediapotamon. This new species is described in this paper, and although also distributed in the karst landforms, is found not in caves but in a hill stream between densely populated mountains. Individuals of this species do not have the characteristics of cave crabs, which determined it as not a karst species but also living in a surrounding karst system. We sequenced the mitochondrial 16S rDNA gene of a specimen and combined the sequence with related reference sequences in GenBank to establish a phylogenetic tree based on Bayesian Inference (BI) and Maximum Likelihood (ML) methods. The molecular data analysis was consistent with the morphological identification results, confirming that it is a new species.

Materials and methods

Specimens were collected from Banzhai Hill, Yaozhai village (25.2128°N, 108.0041°E), Dongtang town, Lino County, Qiannan Buyei and Miao Autonomous Prefecture, Guizhou Province; preserved in 95% ethanol; and deposited at the Department of Parasitology of the Medical College of Nanchang University, Jiangxi, China (NCU MCP). Comparative materials were deposited at the Sun Yat-sen Museum of Biology, Sun Yat-sen University, Guangzhou, China (SYSBM) and the Institute of Zoology, Chinese Academy of Sciences, Beijing, China (IZCAS CB). Carapace width and length were measured in millimetres. The abbreviations G1 and G2 refer to the first and second gonopods, respectively. The terminology used herein primarily follows that of Dai (1999) and Davie et al. (2015).

Pereiopod muscle tissue was extracted from specimens of the new species with a DP1902 Tissue Kit (BioTeke Inc., Beijing). The mitochondrial 16S rDNA gene was obtained by PCR amplification with the primers 1471 (5’-CCTGTTTANCAAAAACAT-3’) and 1472 (5’-AGATAGAAACCAACCTGG-3’) (Shih et al. 2004). The PCR extension procedure is as follows: denaturation for 50 s at 94 °C, 33 cycles of annealing for 40 s at 52 °C and extension for 1 min at 72 °C and a final extension for 10 min at 72 °C. The PCR products were sequenced on an ABI 3730 automatic sequencer.

For molecular data analysis, the mitochondrial 16S rDNA from 52 species in 41 genera was used to construct a phylogenetic tree (Table 1). Sequences were aligned using MAFFT ver. 7.215 (Katoh and Standley 2013) based on the G-INS-I method. The best model for BI analysis was GTR+ I + G, which was determined by ModelGenerator ver. 8.5.1 (Katoh and Standley 2013) and the Bayesian information criterion (BIC). The BI tree was constructed by MrBayes ver. 3.2.6 (Ronquist et al. 2012). Four Markov chain Monte Carlo (MCMC) chains were run for 2000000 generations, with samples stored every 1000 generations, and the first 25% were discarded as burn-in. The effective sample size (ESS) values were checked by TRACER ver. 1.6 (Rambaut and Drummond 2013) (all ESSs were greater than 200). The best evolutionary model for ML analysis was HKY+I+G, as determined by MEGA 7.0 (Kumar et al. 2016) and ModelTest ver. 3.7 (David 2003) based on the Akaike information criterion (AIC) standard. A ML tree was built based on 1000 bootstrap replicates in MEGA 7.0 (Kumar et al. 2016).

Table 1.
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The 16S rDNA of 52 species from 41 genera of the family Potamidae from Asia. All sequences retrieved from GenBank except for the new species described herein.

Species Museum catalogue number Locality GenBank number
Amamiku amamense (Minei, 1973) NCHUZOOL 13125 Amami, the Ryukyus AB428457
Aparapotamon grahami (Rathbun, 1929) ZRC YCM 0334(II) Yunnan, China AB428489
Apotamonautes hainanensis (Parisi, 1916) ZRC Hainan, China AB428459
Beccumon jarujini (Ng & Naiyanetr, 1993) ZRC 1991.1865 (paratype) Chiangma, Thailand AB428479
Candidiopotamon rathbunae (De Man, 1914) NCHUZOOL Nantou, Taiwan AB208598
Chinapotamon glabrum (Dai, Song, Li & Liang, 1980) CAS Guangxi, China AB428451
Chinapotamon maolanense Zou, Bai & Zhou, 2018 NCU MCP 196101 Guizhou, China 11280060
Cryptopotamon anacoluthon (Kemp, 1918) NCHUZOOL 13122 Hong Kong AB428453
Daipotamon minos Ng & Trontelj, 1996 ZRC Guizhou, China LC198524
Demanietta renongensis (Rathbun, 1905) ZRC 1998.146 Ranong, Thailand AB428475
Diyutamon cereum Huang, Shih & Ng, 2017 SYSBM Guizhou, China LC198520
Eosamon boonyaratae (Naiyanetr, 1987) ZRC 1991.1861 Trat, Thailand AB428487
Eosamon smithianum (Kemp, 1923) ZRC Chantaburi, Thailand AB428486B428486
Eosamon yotdomense (Naiyanetr, 1984) ZRC 1991.1851 Ubon Ratchathani, Thailand AB428485
Esanpotamon namsom Naiyanetr & Ng, 1997 ZRC 1997.776 (paratype) Udon Thani, Thailand AB428463
Flabellamon sp. ZRC Mae Sot, Thailand AB428472
Geothelphusa albogilva Shy, Ng & Yu, 1994 NCHUZOOL Pingtung, Taiwan AB127366
Geothelphusa marginata fulva Naruse, Shokita & Shy, 2004 NCHUZOOL 13124 Iriomote, the Ryukyus AB428456
Geothelphusa olea Shy, Ng & Yu, 1994 NCHUZOOL 13123 Taichung, Taiwan AB428455
Hainanpotamon fuchengense Dai, 1995 NCHUZOOL 13128 Hainan, China AB428461
Huananpotamon angulatum (Dai & Lin, 1979) ZRC Fujian, China AB428454
Indochinamon ou (Yeo & Ng, 1998) ZRC Phongsali, Laos AB428481
Indochinamon tannanti (Rathbun, 1904) ZRC 1998.264 Yunnan, China AB428482
Johora johorensis (Roux, 1936) ZRC 1990.576 Gunung Pulai, Johor, Malaysia AB290620
Johora murphyi Ng, 1986 ZRC 2001.2267 Kota Tinggi, Johor, Malaysia AB290621
Kanpotamon duangkhaei Ng & Naiyanetr, 1993 ZRC Kanchanaburi, Thailand AB428471
Kukrimon cucphuongense (Dang, 1975) ZRC NHH9729 160997 Ninh Binh, Vietnam AB428483
Longpotamon baiyanense Ng & Dai, 1997 ZRC Hunan, China AB428470
Longpotamon planum Dai, 1992 ZRC 1998.1178 Anhui, China AB428469
Mediapotamon leishanense Dai, 1995 SYSBM001094 Guizhou, China LC155164
Mediapotamon liboense sp. nov. NCU MCP 343004 Guizhou, China MK820377
Mediapotamon liboense sp. nov. NCU MCP 343008 Guizhou, China MK820376
Mediapotamon sp. nov., leg. Chao Huang SYSBM001259 Guizhou, China LC155165
Megacephalomon kittikooni (Yeo & Naiyanetr, 1999) ZRC 1998.22 (holotype) Xieng Khuang, Laos AB428462
Mindoron balssi (Bott, 1968) ZRC Mindoro, the Philippines AB428464
Minpotamon nasicum (Dai & Chen, 1979) NCHUZOOL 13121 Fujian, China AB428450
Nanhaipotamon formosensis (Parisi, 1916) NCHUZOOL 13144 Tainan, Taiwan AB212867
Nanhaipotamon nanriense Dai, 1997 CAS CB05103 Fujian, China AB212868
Neotiwaripotamon jianfengense Dai & Naiyanetr, 1994 NCHUZOOL 13127 Hainan, China AB428460
Ovitamon artifrons (Bürger, 1894) ZRC Luzon, the Philippines AB428466
Parapotamon spinescens (Calman, 1905) NCUDP Yunnan, China AB428467
Pararanguna semilunatum Dai & Chen, 1985 ZRC Yunnan, China AB428490
Potamiscus yiwuensis Dai & Cai, 1998 ZRC Yunnan, China AB428476
Potamiscus yongshengense Dai & Chen, 1985 NNU150951 Yunnan, China KY963597
Pudaengon sakonnakorn Ng & Naiyanetr, 1995 ZRC Thailand AB428484
Pupamon nayung (Naiyanetr, 1993) ZRC 1995.558 (paratype) Udon Thani, Thailand AB428477
Ryukyum yaeyamense (Minei, 1973) NCHUZOOL 13126 Iriomote, the Ryukyus AB428458
Shanphusa curtobates (Kemp, 1918) NRM 13920 Taunggyi, Shan State, Myanmar AB428478
Socotrapotamon nojidensis Apel & Brandis, 2000 ZRC 2000.2232 Socotra, Yemen AB428493
Tenuipotamon huaningense Dai & Bo, 1994 CAS CB05175 Yunnan, China AB428491
Thaiphusa sp. ZRC 1997.656 Thailand AB428474
Tomaculamon pygmaeus Yeo & Ng, 1997 ZRC 1997.326‐330 (paratype) Phitsanulok, Thailand AB428473
Trichopotamon daliense Dai & Chen, 1985 NCHUZOOL 13130 Yunnan, China AB428492
Yarepotamon gracilipa (Dai, Song, Li & Liang, 1980) ZRC Guangxi, China AB428452

Key to institutional abbreviations: CAS, The Chinese Academy of Sciences, Beijing, China; NCHUZOOL, Zoological Collections of the Department of Life Science, National Chung Hsing University, Taichung, Taiwan; NCUDP, Department of Parasitology, Nanchang University, Jiangxi, China; NRM, Swedish Museum of Natural History, Stockholm, Sweden; ZRC, Zoological Reference Collection of the Raffles Museum of Biodiversity Research, National University of Singapore, Singapore.

Taxonomy

Family Potamidae Ortmann, 1896

Mediapotamon Türkay & Dai, 1997

Mediapotamon liboense sp. nov.

http://zoobank.org/69B0792B-F233-403A-ADC2-6666B007F093
Figs 1, 2, 3, 4, 5

Type locality

China, Guizhou Province: Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, Dongtang Town, Yaozhai Village, Banzhai Hill, 25.2128°N, 108.0041°E, under rock in small hill stream.

Type specimen

Holotype male, with gonopods in a separate microvial. Original label: “China, Guizhou Province: Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, Dongtang Town, Yaozhai Village, Banzhai Hill, 25.2128°N, 108.0041°E, 10 Oct. 2010, Xian-min Zhou”, “NCU MCP 343001”. Paratypes, male, same collection data as for holotype, “NCU MCP 343002”; female, same collection data as for holotype, “NCU MCP 343003”.

Material examined

Holotype. CHINA • ♂, NCU MCP 343001, 24.2 × 19.6 mm, Guizhou Province, Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, Dongtang Town, Yaozhai Village, Banzhai Hill, under rock in small hill stream, catch by hand, 10 Oct 2010, Xian-min Zhou leg.

Paratypes. ♂, NCU MCP 343002,19.4 × 15.6 mm • ♀, NCU MCP 343003, 23.4 × 19.0 mm, same collection data as for holotype.

Other material

♂, NCU MCP 343004, 30.9 × 24.7 mm • 4 ♀♀; NCU MCP 343005, 21.5 × 16.8mm; NCU MCP 343006, 19.2 × 14.6 mm; NCU MCP 343007, 25.0 × 20.0 mm; NCU MCP 343008, 20.0 × 15.8 mm; same collection data as for holotype.

Comparative material

Mediapotamon angustipedum (Dai & Song, 1982): 2 ♂♂; IZCAS CB 00995, 15.3 × 13.1 mm; IZCAS CB 00988, 18.4 × 16.0 mm; Guangxi Zhuang Autonomous Region, Baise City, Jingxi County, Hurun Town, Xinxing Village, 7 Oct 1978. Mediapotamon leishanense (Dai, 1995): 1♂, IZCAS CB 05181, 14.8 × 11.5 mm, Guizhou Province, Qiandongnan Miao and Dong Autonomous Prefecture, Leishan County, Leigong Mountain, 23 Apr. 1988; 1♂, SYSBM 001094, 15.5 × 12.4 mm, Guizhou Province, Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, coll. C. Huang, Jul 2013. Mediapotamon sp. nov. (sequence number LC155165 in Fig. 8): 1♂, SYSBM 001255, 26.7 × 21.4 mm, 1 ♀, SYSBM 001259, 17.5 × 13.6 mm, Guizhou Province, Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, coll. C. Huang, Jul 2013. Daipotamon minos (Ng & Trontelj, 1996): 1♂, NCU MCP 195501, 20.1 × 16.3 mm, 1 ♀, NCU MCP 195502, 18.8 × 15.1 mm, Guizhou Province, Qiannan Bouyei and Miao Autonomous Prefecture, Lino County, Chaoyang Town, Buyong Village, coll. L. J. Yang, 17 Jul 2010.

Diagnosis

Carapace trapezoidal, regions indistinct, dorsal surface flat, epigastric cristae indistinct, postorbital cristae convex, cervical groove indistinct, H-shaped groove inconspicuous (Figs 1A, B, 3A). External orbital angle triangular, epibranchial tooth sharp, anterolateral margin lined with scattered granules, posterolateral surface smooth (Figs 1A, B, 3A). Third maxilliped exopod with slender flagellum, extending equal to width of merus (Fig. 1C). Male pleon narrow triangular, telson with arc-shaped apex in male (Fig. 2B). G1 slender, terminal segment bend inwards obviously in sub-proximal portion with constant diameter, G1 terminal segment oblique toward dorsal in mesial view in the demarcation between G1/G2 (Figs 4A, F, 7A). Proximal part of G2 sub-ovate (Fig. 4C). Female vulva large-sized, not reaching suture sternites 5/6, vulval membrane extending outward (Fig. 3B).

Figure 1. 

Mediapotamon liboense sp. nov. Holotype male (24.2 × 19.6 mm) (NCU MCP 343001). A overall habitus B dorsal view of carapace C frontal view of cephalothorax.

Figure 2. 

Mediapotamon liboense sp. nov. Holotype male (24.2 × 19.6 mm) (NCU MCP 343001). A outer view of chelipeds B ventral view of anterior thoracic sternum and pleon C left third maxilliped D ventral view of sterno-pleonal cavity with left G1 in situ E right fourth ambulatory leg, low view.

Description

Carapace: outline trapezoidal, width 1.2–1.3 × length (n = 8); dorsal surface flat with numerous pits, anterolateral region wrinkled (Figs 1A, B, 3A). Epigastric cristae indistinct; cervical groove shallow, indistinct; H shaped groove between gastric and cardiac regions inconspicuous (Figs 1A, B, 3A). Postorbital cristae slightly convex, not fused with epigastric cristae, separate with epibranchial tooth (Figs 1A, B, 3A). External orbital angle bluntly triangular, separate with anterolateral margin by conspicuous gap (Figs 1A, C, 3A). Epibranchial tooth sharp, distinct; anterolateral margin convex laterally, cristae, lined with approximately 9 or10 scattered granules (Figs 1A, B, 3A). Posterolateral surface smooth, with inconspicuous oblique striae, posterolateral margins converging posteriorly (Figs 1A, B, 3A). Orbits medium-size; supraorbital margin cristate and lateral portion, infraorbital margins lined with scattered inconspicuous granules (Fig. 1C). Sub-orbital, sub-hepatic and pterygostomial regions covered with low round granules (Fig. 1C). Epistome posterior margin slightly oblique laterally, with broadly triangular median lobe (Fig. 1C).

Third maxilliped: exopod reaching proximal 1/3 of merus length, with slender flagellum extending equal to width of merus (Figs 1C, 2C). Merus subquadrate, 1.3 times as broad as long, generally flat (Figs 1C, 2C). Ischium trapezoidal, 1.4 times as long as broad, with distinct median sulcus (Fig. 2C).

Chelipeds (pereiopod 1): slightly unequal (Fig. 2A). Merus surface smooth; carpus surface with pits and a sharp spine at inner-distal angle (Figs 1A, 3A). Palm of larger chela length 1.4 × height in males (n = 3), 1.5–1.6 × in females (n = 5); dactylus 1 × palm length in males (n = 3), 0.9–1 × in females (n = 5); dactylus as long as pollex (Figs 1A, 2A, 3A). Inner margin of fingers with few round blunt teeth, with little gap when fingers closed (Fig. 2A).

Figure 3. 

Mediapotamon liboense sp. nov. Paratype female (23.4 × 19.0 mm) (NCU MCP 343003). A overall habitus B ventral view of thoracic sternum and vulvae.

Figure 4. 

Mediapotamon liboense sp. nov. Holotype male (24.2 × 19.6 mm) (NCU MCP 343001). A ventral view of the left G1 B dorsal view of the left G1 C ventral view of the left G2 D ventral view of the terminal segment of left G1 E dorsal view of the terminal segment of left G1 F mesial view of the terminal segment of left G1. Scale bars: 1 mm (A–F).

Ambulatory legs (pereiopods 2–5): slender; pereiopod 3 merus 0.5 × carapace length in males (n = 3), 0.4 × carapace length in females (n = 5) (Figs 1A, 3A). Pereiopods 5 propodus 1.9 × as long as broad in males (n = 3), 1.9–2.1 × as long as broad in females (n = 5) (Fig. 2E); shorter than dactylus (n = 8) (Figs 1A, 2E, 3A).

Male thoracic sternum: flat and covered with pits; sternites 2-4 broad, width ca. 2 × length; sternites 2 very broad triangular with sharp apex; suture between sternites 2/3 transverse, clear; sternites 3/4 fused but with slight oblique demarcation superficially (Fig. 2B). Male sterno-pleonal cavity deep and narrow, barely reaching anteriorly to level of mid-length of cheliped coxae base; median longitudinal groove present between sternites 7 and 8 medium in length; male pleonal locking tubercle position at middle of sternite 5 (Fig. 2D).

Male pleon: narrow triangular (Fig. 2B); somites 4-6 progressively narrowed distally, lateral margins oblique; telson width 1.3 × length with arc-shaped apex in males (n = 3); somite 6 width 2.4 × length in males (n = 3) (Fig. 2B).

G1: slender (Figs 4A, 7A); terminal segment bend inwards obviously in the sub-proximal portion with constant diameter, distal end reaching but not beyond pleonal locking tubercle in situ (Fig. 2D); subterminal segment length 2.9 × length of terminal segment (Figs 4A, 7A). The mesial view of G1 terminal segment not straight but oblique toward dorsal in the demarcation between G1/G2 (Fig. 4F). Basal segment of G2 sub-ovate, subterminal segment length 1.8 × length of distal segment, the distal segment is slender and sharp (Fig. 4C).

Female vulva: large, not reaching sternites 5/6 in situ, with the opening outward and the outer membrane extending outward (Fig. 3B). Reaching approximate three-fifths width of sternite 6 and the position generally distantly each other (Fig. 3B).

Etymology

The species is named after the type locality, Libo County, Qiannan Bouyei and Miao Autonomous Prefecture, Guizhou Province.

Colour in life

The overall colour is brownish black, which is similar to the colour of the surrounding environment (Fig. 5).

Figure 5. 

Mediapotamon liboense sp. nov. Colour in life, not collected (photograph by Chao Huang).

Distribution

The new species is presently known only from the type locality: Libo County, Qiannan Bouyei and Miao Autonomous Prefecture, Guizhou Province.

Ecology

This species lives in karst mountain locations surrounded by low crests and covered with diverse vegetation (Figs 6A, B). The species lives along the stream flowing down the mountain and remains hidden under rocks during the day.

Figure 6. 

Karst terrain of Libo County (photographs by Chao Huang).

Remarks

The new species fits the characteristics of Mediapotamon Türkay & Dai, 1997, viz., carapace intermediate or small in size (15–20 mm), surface smooth without a conspicuous bulge or depression, anterolateral margin lined with granules, male telson triangular, and G1 slender without any projection and reaching the pleonal locking tubercle in situ (Türkay and Dai 1997). Mediapotamon liboense sp. nov. is similar to M. angustipedum (Dai & Song, 1982), M. leishanense Dai, 1995, and Daipotamon minos, Ng & Trontelj, 1996, but the new species can be differentiated from its congeners by some distinct characters: epibranchial tooth sharp and distinct, anterolateral margin lined with a few scattered granules [versus sharp and distinct in M. angustipedum but blunt and indistinct in M. leishanense, both lined with numerous inseparable granules (cf. Table 2)]; shape of the male telson narrow triangular [versus broad triangular in congeners (cf. Table 2, Fig. 7)]; and shape of G1 slender, terminal segment distinctly bent with a constant diameter [versus very slender, terminal segment straight and thinner gradually in M. angustipedum and very slender, terminal segment bent obviously and thinner gradually in M. leishanense (cf. Table 2, Fig. 7)]. Its differences compared to D. minos can be found in Table 2 and Figure 7.

Figure 7. 

Left G1s. A Mediapotamon liboense sp. nov. NCU MCP, 24.2 × 19.6 mm B M. angustipedum (Dai & Song, 1982), IZCAS CB 00995, 15.3 × 13.1 mm C M. leishanense Dai, 1995, IZCAS CB 05181,14.8 × 11.5 mm D Daipotamon minos, Ng & Trontelj, 1996, NCU MCP 195501, 20.1 × 16.3 mm.

DNA analyses and discussion

We used the mitochondrial 16S rDNA gene sequence for phylogenetic analyses, and 52 species from 41 potamid genera were included (Table 1), using BI and ML analyses to construct phylogenetic trees with support values. The results are shown in Figure 8, and both analysis methods support most of the clades (Shih et al. 2009). The new species clusters with the same species as M. liboense and M. leishanense (specimen collected by Chao Huang in the Maolan Nature Reserve of Libo County in July 2013). After discussion with Huang, we think that the other new species of Mediapotamon with sequence number is LC155165 and M. liboense sp. nov. are the same species, although the two specimens were collected separately. In the phylogenetic tree, Daipotamon is clustered with Mediapotamon in two separate branches, and the phylogenetic relationships between the new species and Chinapotamon maolanense, which was also collected in Libo County, are distant (Fig. 8)

Figure 8. 

A Bayesian inference (BI) tree based on 16S rDNA with the sequences and accession numbers from Shih et al. (2009) with some additional species from Guizhou. The species collected from the type locality and its surroundings are highlighted in grey. The probability values at the nodes represent support values for BI and maximum likelihood (ML). Only values > 50% are displayed.

Despite the new species clustering with congeners and Daipotamon in the larger clade, the genetic distance suggests that the congeners are closer, while Daipotamon is farther away. For the habitat, Daipotamon lives in limestone formations and collected from one of karst caves and was determined as a karst species (Ng and Trontelj 1996), while the new species lives in hill streams, which is consistent with congeners, so the new species can be separated from Daipotamon in morphology, phylogenetic analyses, and ecology (Table 2, Fig. 8). Mediapotamon contains M. leishanense and M. angustipedum (Dai 1999), but we were unable to obtain molecular data for the latter, so its phylogenetic relationship with the new species is unclear. From molecular and morphological data, it is distinct from M. leishanense. Although there is no molecular data for M. angustipedum, the distinct morphological differences and more than 400 kilometres geographical distance separate the new species from M. angustipedum clearly. Morphological differences among the three Mediapotamon species, including the new species described in this study, are described in detail (Table 2).

Table 2.
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Differences between Mediapotamon liboense sp. nov., M. angustipedum (Dai & Song, 1982), M. leishanense Dai, 1995 and Daipotamon minos, Ng & Trontelj, 1996.

Character/ Species M. liboense sp. nov. M. angustipedum M. leishanense Daipotamon minos
Carapace Flat, cervical groove indistinct Swollen, cervical groove indistinct Flat, cervical groove distinct Slightly swollen, cervical groove distinct
Epibranchial tooth Sharp, distinct Sharp, distinct Blunt, indistinct Blunt, indistinct
Anterolateral margin Lined with scattered granules Lined with numerous inseparable granules Lined with numerous inseparable granules Lined with numerous inseparable granules
Shape of male telson Narrow triangular Broad triangular Broad triangular Tongue-shape
G1 in situ Reaching pleonal locking tubercle Reaching pleonal locking tubercle Reaching pleonal locking tubercle Not reaching pleonal locking tubercle
Shape of G1 Slender, terminal segment obviously bent with constant diameter Very slender, terminal segment straight and gradually narrowing Very slender, terminal segment obviously bent and gradually narrowing Stout, terminal segment slightly bent with constant diameter
Female vulvae Large-sized, not reaching sternites 5/6 in situ Medium-sized, reaching sternites 5/6 in situ Large-sized, reaching sternites 5/6 in situ Medium-sized, not reaching sternites 5/6 in situ

Before our study, only three new species, namely Diyutamon cereum, Qianguimon elongatum, and Chinapotamon maolanense, collected in Guizhou had been published in the past 20 years (Huang et al. 2017, Huang 2018, Zou et al. 2018), implying that the freshwater crabs in this area still have high taxonomic research value. With the new species presently described, there are now 31 species of 13 potamid genera in Guizhou (Shih and Ng 2011).

Acknowledgements

The present study is supported by the National Sharing Service Platform for Parasite Resources (TDRC-22), the National Natural Science Foundation of China (No. 31560179, 31460156), the Natural Science Foundation of Jiangxi Province (No. 20171BAB205108), Nanchang University College Students’ Innovation and Entrepreneurship Training Program (No. 2018388). Thanks are due to Chao Huang, who also collected a specimen, for providing several original materials for the images and for appraising the new species when we identified it. We also thank Ya-Nan Zhang and Meng-Jun Zhao for their help in the molecular work and Xin-Nan Jia and Shu-Xin Xu for their help in constructing the phylogenetic tree.

References

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