Zoological Studies 59:24 (2020) doi:10.6620/ZS.2020.59-24 Open Access A New Genus and Two New Species of Freshwater Crab (Crustacea: Brachyura: Potamidae) with Unusual Coiled Tip of Male Second Gonopods from Yunnan, Southwestern China Chao Huang1,2, Jian Wang3, and Hsi-Te Shih4,* 1School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China. E-mail: [email protected] (Huang) 2Australian Museum, 1 William St, Sydney NSW 2010, Australia 3College of Life Science and Technology, Honghe University, Mengzi, Yunnan 661199, China. E-mail: [email protected] (Wang) 4Department of Life Science, National Chung Hsing University, 250, Kuo Kuang Road, Taichung 402, Taiwan. *Correspondence: E-mail: [email protected] (Shih) Received 28 March 2020 / Accepted 13 May 2020 / Published 6 July 2020 Communicated by Benny K.K. Chan Two new species of a new genus, Tortomon puer n. gen. n. sp. and T. gejiu n. gen. n. sp. are described from southern Yunnan, southwestern China, based on the morphology and mitochondrial 16S rDNA sequences. The new genus resembles Tenuipotamon Dai, 1990 and Parvuspotamon Dai & Bo, 1994, but can be separated by characters of the male thoracic sternum, male pleon, male first gonopod, and especially the coiled tip of the male second gonopod. The latter character easily separates Tortomon n. gen. from known potamid genera. Notes on the general biology of the two new species are also included. Key words: Freshwater crabs, Yunnan, Tortomon n. gen., New species, Potamidae, Systematics, Morphology, Mitochondrial 16S rDNA. BACKGROUND In 2013, herpetologist Mian Hou and the second author of this study collected several miniature freshwater China has the richest fauna of freshwater crabs crabs from Gejiu City, Yunnan, and gave them to the in the world (Dai 1999; Liang 2004; Li et al. 2007; first author. The male second gonopods of these crabs Cumberlidge et al. 2011; Shih and Ng 2011; Chu et al. were distinct as the tips were corkscrew shaped and it 2018), and the full extent of this biodiversity is yet to was evident that the crabs were not only an unknown be realized (De Graves et al. 2008; Yeo et al. 2008). species but also from an undescribed genus. Efforts to Situated in southwestern China, the mountainous collect additional material and record the habitat were Yunnan Province is a global freshwater crab hotspot made by the first and second authors in 2018. On one and has the highest freshwater crab genus and species of these collection trips, ichthyologist Zhuo-Cheng diversity in China (Cumberlidge et al. 2011; Shih and Zhou, who was accompanying the first author, recalls Ng 2011; Chu et al. 2018). The southern areas are collecting several small purple crabs with Jia-Jun Zhou relatively low (around 1,500 m a.s.l.) compared to the in a locality in Pu’er City, Yunnan, some years ago. rest of Yunnan and belong to the Diannan Highlands We relocated the locality and successfully collected freshwater zoogeographic province (Huang et al. 2020). more specimens. These crabs also had the corkscrew- Citation: Huang C, Wang J, Shih HT. 2020. A new genus and two new species of freshwater crab (Crustacea: Brachyura: Potamidae) with unusual coiled tip of male second gonopods from Yunnan, southwestern China. Zool Stud 59:24. doi:10.6620/ZS.2020.59-24. © 2020 Academia Sinica, Taiwan 1 Zoological Studies 59:24 (2020) page 2 of 14 shaped shaped male second gonopod tip, but differed position of the taxa, 48 additional, related sequences of from the Gejiu new species in the male first gonopod the 16S sequences of genera from East Asia, Indochina morphology, suggesting the two are different species. and Southeast Asia in Shih et al. (2009), Huang et al. A single male specimen of a third species of this genus (2014 2016 2017a b 2018), and Wang et al. (2019) were was found by Jin Chen from Xishuangbanna Prefecture, included for comparison. The variable regions in loop Yunnan. The morphology of this specimen is very regions of the 16S that could not be aligned adequately close to that of the Pu’er new species. We therefore for phylogenetic analyses were excluded (Shih et al. refrained from describing this third new species until 2009). more specimens can be obtained to assess intraspecific The best-fitting model for sequence evolution variation. A genetic study of the 16S rDNA supports of 16S was determined by jModelTest (vers. 2.1.4; the uniqueness of these species as they are not clustered Darriba et al. 2012), selected by the Bayesian with other known Chinese or Indochinese genera in the information criterion (BIC). The best model obtained phylogenetic tree. We herein describe two new species was HKY+I+G, which was subsequently applied of a new genus, Tortomon puer n. gen. n. sp. and for Bayesian inference (BI) and minimum evolution Tortomon gejiu n. gen. n. sp., from southern Yunnan. (ME) analyses. The BI analysis was performed with MrBayes (vers. 3.2.2; Ronquist et al. 2012) and the search was run with four chains for 10 million MATERIALS AND METHODS generations, with trees sampled every 1000 generations. The convergence of chains was determined by the Specimens were collected by hand and preserved average standard deviation of split frequency values in 75% ethanol from 2013 onwards from southern below the recommended 0.01 (Ronquist et al. 2005) Yunnan, China. They are deposited in the Sun Yat- and the first 1500 trees were discarded as the burnin sen Museum of Biology, Sun Yat-sen University, accordingly. The ME tree was constructed on MEGA Guangzhou, China (SYSBM); the Australian Museum, with the gamma correction obtained from jModeltest, Sydney, Australia (AM); and the Zoology Collection the Kimura (1980) two-parameter model (CNI level = 2, of the National Chung Hsing University, Taichung, initial tree = NJ, and maximum number of trees to retain Taiwan (NCHUZOOL). Measurements, in millimetres, = 1) and 2,000 replicates by the interior-branch method are of the carapace width and length, respectively. Other (Sitnikova et al. 1995). The pairwise estimates of K2P abbreviations are as follows: G1, male first gonopod; distances for genetic diversities between haplotypes, G2, male second gonopod; CW, carapace width; P2– and the basepair (bp) differences (by treating the gaps as P5, pereiopods 2–5, respectively. The terminology used a fifth character state) were calculated with PAUP* (vers. primarily follows that of Dai (1999) and Davie et al. 4.0b10; Swofford 2003). (2015). Specimens used in the molecular study include Tortomon puer (SYSBM 001837, 001839), T. gejiu RESULTS (SYSBM 001246, 001834), T. sp. (AM P.104576 Xishuangbanna, Yunnan, coll. J. Chen, March, 2015) SYSTEMATICS and Parvuspotamon dixuense Naruse, Chia & Zhou, 2018 (NCHUZOOL 16428, 16429, Zhetu, Guangnan, Family Potamidae Ortmann, 1896 Yunnan, coll. H.-T. Shih, 2 November 2002). 16S Subfamily Potamiscinae Bott, 1970 (sensu Yeo sequences were obtained following Shih et al. (2009), & Ng 2003) using the primers 16H10 and 16L29 (Schubart 2009), and aligned with the MUSCLE function of MEGA Genus Tortomon n. gen. (vers. 10.0.5; Kumar et al. 2018), after verification (Figs. 1–8) with the complimentary strand. Sequences of different urn:lsid:zoobank.org:act:06743881-BA7C-4DB9-9AC1- haplotypes were deposited in the DNA Data Bank of D7E5E55D79FE Japan (DDBJ) under accession numbers LC548635 for Type species: Tortomon puer n. gen. n. sp., by Parvuspotamon dixuense, LC548634 and LC548635 for current designation. Tortomon puer, LC548633 for T. gejiu and LC548636 Diagnosis. Small sized (CW < 25 mm). Carapace for T. sp. A preliminary analysis showed that this genus broader than long, smooth all over, convex; regions belongs to the “Eastern-Asia Subclade” of the subfamily indistinct (Figs. 1, 4); epigastric cristae and postfrontal Potamiscinae and not related directly with the groups cristae smooth, low, inconspicuous (Figs. 1, 4); of “Socotra”, “SW China” and “Malay Peninsula” external orbital tooth inconspicuous; external orbital (Shih et al. 2009). As a result, to confirm the systematic © 2020 Academia Sinica, Taiwan Zoological Studies 59:24 (2020) page 3 of 14 angle fused with anterolateral margin (Figs. 1, 2A, 4, (Figs. 3C–E, 6C–E, 7A–D). G2 terminal segment short, 5A). Anterolateral margin smooth to weakly cristate with thin coiled tip (Fig. 3B, 6B, 7E). Female vulva (Figs. 1, 4). Orbits small (Figs. 1, 2A, 4, 5A). Median with relatively wide space between one another, ovate; lobe of epistome broadly triangular (Figs. 2A, 5A). medium-sized, mainly situated on sternite 6, reaching to Maxilliped 3 with relatively broad ischium, exopod sternite 5 but not sternite 7 (Figs. 2F, 5F). Female pleon strongly tapering, reaching beyond anterior edge of ovate (Figs. 2E, 5E). ischium, flagellum absent (Figs. 3A, 6A). Cheliped Etymology: The genus name is an arbitrary merus margins smooth, palm surface smooth (Figs. 1, combination of Latin tortus and the type genus of 3F–G, 4, 6F–G). Ambulatory legs slender (Figs. 1, 4). Potamidae, Potamon. It alludes to the coiled tip of Male anterior thoracic sternum relatively wide, width the G2 of the new genus, which is its most distinctive around 1.7 times length (Figs. 2B, 5B). Male pleon character. Gender: neuter. See the Supplementary narrowly triangular, telson with blunt apex and concave Material for its proposed Chinese name. lateral margins (Figs. 2C, 5C). G1 generally straight Distribution: Yunnan, China. and slender; terminal segment short, tapering, with Remarks: Tortomon n. gen. is included in the blunt tip; pointing upwards to slightly bent outwards Potamiscinae due to the absence of a transverse Fig. 1. Dorsal habitus of Tortomon puer n. sp. (A) male holotype (21.8 × 16.1 mm), SYSBM 001836; (B) female paratype (19.5 × 14.6 mm), SYSBM 001839. © 2020 Academia Sinica, Taiwan Zoological Studies 59:24 (2020) page 4 of 14 ridge on the eighth thoracic sternite (Yeo and Ng potamid.