Diversity and Distribution of Fiddler Crabs (Crustacea: Brachyura: Ocypodidae) in Vietnam

© 2022 Academia Sinica, Taiwan Open Access Special issue: Systematics and Biogeography of Fiddler Crabs Diversity and Distribution of Fiddler Crabs (Crustacea: Brachyura: Ocypodidae) in Vietnam Hsi-Te Shih1, Kingsley J. H. Wong2, Benny K. K. Chan2,* , Thanh Son Nguyen3, Van Tu Do4,5 , Xuan Quang Ngo5,6 , and Pei-Yi Hsu1 1Department of Life Science and Research Center for Global Change Biology, National Chung Hsing University, Taichung 402, Taiwan. E-mail: [email protected] (Shih); [email protected] (Hsu) 2Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan. *Correspondence: E-mail: [email protected] (Chan). E-mail: [email protected] (Wong) 3Department of Applied Zoology, Faculty of Biology, VNU University of Science, Vietnam National University, Ha Noi, Vietnam. E-mail: [email protected] (Nguyen) 4Institute of Ecology and Biological Resources (IEBR), Vietnam Academy of Science and Technology (VAST), Ha Noi, Vietnam. E-mail: [email protected] (Do) 5Graduate University of Science and Technology (GUST), Vietnam Academy of Science and Technology (VAST), Ha Noi, Vietnam 6Department of Environmental Management and Technology, Institute of Tropical Biology, Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam. E-mail: [email protected] (Ngo) Received 6 January 2022 / Accepted 7 April 2022 / Published 16 November 2022 Communicated by Ryuji Machida Special issue: Systematics and Biogeography of Fiddler Crabs (articles 64–71). Editors: Hsi-Te Shih and Benny K. K. Chan Based on recently collected material and records in the literature, 14 species of fiddler crabs (Crustacea: Ocypodidae: Gelasiminae) are reported from Vietnam. DNA barcoding analyses using the mitochondrial gene COI (cytochrome c oxidase subunit I) was performed to identify examined materials and their precise distributional range. Thirteen species-level taxa are identified and, with the exception of Galsimus borealis and G. vocans, have minimum interspcific divergences of at least 7.27%. The identified species include seven species of Tubuca Bott, 1973, three of Austruca Bott, 1973 and three of Gelasimus Latreille, 1817, and one Paraleptuca Bott, 1973. Two new records of Vietnam are herein reported: Tubuca rhizophorae and T. dussumieri. The southernmost distribution limits of East Asian G. borealis, T. acuta and T. arcuata are in northern Vietnam, A. lactea in central Vietnam, whereas northernmost limit of Southeast Asian T. rhizophorae and T. forcipata in southern Vietnam. A dichotomous key to identify the 14 Vietnamese species is provided. Key words: Fiddler crabs, New records, Austruca, Gelasimus, Paraleptuca, Tubuca, Mitochondrial cytochrome c oxidase subunit I (COI), Barcodes. BACKGROUND Fiddler crabs (Ocypodidae) are a group of brachyurans dominant along intertidal zones of tropical and subtropical coasts (Crane 1975). Since the revision of the Ocypodidae by Shih et al. (2016b), several new species of fiddler crabs have been reported, and the group currently contains 11 genera with 107 species (Shih et al. 2018 2019; Shih and Poupin 2020). In the Indo-West Pacific region (IWP), 49 species have been reported. While the East Asian fiddler crab fauna has been relatively well studied in recent years (Shih et al. 2010b 2015 2016a), that in Southeast Asia has received relatively less attention. Vietnam is located on the western shores of the South China Sea (SCS), between latitudes 8° and 21.5°N, and its coastline longitudinally spans across subtropical and tropical zones. The earliest record of the fiddler crab fauna of Vietnam can be traced back to a “Uca latreillei” (= Paraleptuca splendida) from “Phuc Son and Tourane, Annam” (the latter locality now Da Nang; Balss 1922). Serène (1937) reported Uca arcuatus Citation: Shih HT, Wong KJH, Chan BKK, Nguyen TS, Do VT, Ngo XQ, Hsu PY. 2022. Diversity and distribution of fiddler crabs (Crustacea: Brachyura: Ocypodidae) in Vietnam. Zool Stud 61:66. doi:10.6620/ZS.2022.61-66. Zoological Studies 61:66 (2022) doi:10.6620/ZS.2022.61-66 1 © 2022 Academia Sinica, Taiwan from Tonkin, northern Vietnam. Dawydoff (1952) added U. annulipes, U. arcuata and U. tetragonon from French Indochina (including Vietnam and Cambodia), with “U. manii” (probably Tubuca forcipata) from Ca Mau (southernmost of Vietnam) and Cambodia, U. lactea from Ha Long Bay, northern Vietnam, and “U. dubia” (probably Tubuca dussumieri or T. paradussumieri) from the Paracels (= Xisha Islands or Hoang Sa Archipelago). Later, Crane (1975) only cited Serène’s (1937) record of Uca arcuatus, missing Dawydoff’s (1952) report. In recent decades, Do (1996) listed “Uca arcuata”, “U. lactea” and Uca sp. from Can Gio mangrove forest, southern Vietnam, but the identification was problematic. Kosuge et al. (1997) identified U. acuta, U. arcuata, U. borealis, U. lactea and U. paradussumieri from Hai Phong, northern Vietnam—results cited by Shih et al. (2010b) when revising Chinese records. Several species were listed in preliminary reports on the brachyuran fauna from northern Vietnam (Do and Hoang 2002 2004 2006; Hoang et al. 2010) and southern Vietnam (Do 2003; Hoang et al. 2012), yet the lack of illustrations or schematic descriptions make further verifications difficult. In resurrecting Paraleptuca splendida (then as Uca (Paraleptuca)), Shih et al. (2012) included specimens from Nha Trang, southern Vietnam. From the same area, detailed investigations by Chertoprud et al. (2012) revealed 10 fiddler species in vicinity of the Bay of Nha Trang, viz. U. annulipes, “U. arcuata” (probably T. dussumieri or T. paradussumieri), “U. borealis” (should be G. vocans), “U. crassipes” (= P. splendida), “U. flammula” (probably juveniles of T. forcipata), U. forcipata, U. paradussumieri, “U. rosea” (= U. vocans), U. tetragonon, and U. vocans. Kostina et al. (2016) identified four species from the Red River Delta, viz. A. lactea, T. arcuata, “T. forcipata” (probably T. arcuata) and “T. dussumieri” (probably T. paradussumieri); as well as three species from Nha Trang, viz. A. annulipes, Gelasimus vocans and “T. urvillei” (probably T. paradussumieri). As a summary of brachyuran material collected from Vietnam for over a decade, Wada (2019) listed A. lactea, G. borealis, G. vocans, P. splendida, T. acuta, T. arcuata, T. paradussumieri from northern Vietnam, and A. perplexa from southern Vietnam. In recent reports on brachyurans from southern Vietnam, Le et al. (2018) recorded U. borealis, U. annulipes, U. crassipes, U. dussumieri, U. flammula, U. lactea and U. paradussumieri from Tra Vinh Province; and Le et al. (2020) listed Uca borealis, U. arcuata, U. dussumieri, U. flammula, U. urvillei, U. annulipes, U. crassipes and U. paradussumieri from Soc Trang Province. No figures or diagnoses were appended in the latter report. From northern Vietnam, Do et al. (2021), Hoang et al. (2021) and Nguyen et al. (2022) identified Uca arcuata, U. borealis, U. lactea and U. paradussumieri. We have reservations about some of the above listed records—several probably do not occur in northern nor southern Vietnam, or in various cases judged from attached illustrations, are nearly certainly misidentifications. Based on material amassed through years of surveys along the coasts of Vietnam, as well as examining past records in the literature, using an integrated approach of morphological analyses, and molecular evidence generated by DNA analyses on sequences from the mitochondrial gene COI (cytochrome oxidase subunit I), we revised records of fiddler crabs from Vietnam. Each species is illustrated and elaborated in detail. A key to the genus and species found is also provided. MATERIALS AND METHODS Material of fiddler crabs collected from the coastal regions in Vietnam (Table 1, Fig. 1) were preserved in 70% to 95% ethanol, and deposited into the Zoological Collections of the Department of Life Science, National Chung Hsing University, Taichung, Taiwan (NCHUZOOL); the Zoological Reference Collection, Raffles Museum of Biodiversity Research, National University of Singapore (ZRC); and the Zoology collection of the Biological Museum, VNU University of Science, Vietnam National University, Hanoi, Vietnam (ZVNU). The following abbreviations are used: CW = carapace width and G1 = male first gonopod. In the synonym list of each species, for simplicity, only the publications of original description of species, taxonomic revisions, and those including Vietnamese fauna are included. Dimensions of specimens are denoted by CW, in millimeters (mm). Genomic DNA was isolated from muscle tissue using kits (see Shih et al. 2016b for details). A portion of the COI gene was amplified with a polymerase chain reaction (PCR) using the primers LCO1490, HCO2198 (Folmer et al. 1994), COL14 (Roman and Palumbi 2004), COL6, COH6 (Schubart 2009), ICOUB (Huang et al. 2021), and LCOB, HCOex, HCOex2 and HCOex3 (see Shih et al. 2022). PCR conditions for the above primers were 40 cycles of denaturation for 50 s at 94°C, annealing for 70 s at 45–47°C, and extension for 60 s at 72°C, followed by extension for 10 min at 72°C. Sequences were obtained by automated sequencing (Applied Biosystems 3730, USA). Sequences of the different haplotypes were deposited into GenBank (accession numbers given in Table 1). A neighbor-joining (NJ) tree for COI sequences was established using the Kimura (1980) 2-parameter page 2 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan 110oE105oE 15oN 10oN 20oN 120oE115oE 25oN 4 5 78 1 2 3 6 Nha Trang Hai Phong (Cat Ba Island) Nam Dinh Ha Tinh Binh Thuan Kien Giang (Phu Quoc Island) Ho Chi Minh City (Can Gio) Quang Ninh (Dong Rui) LAOS Dongsha (Pratas) Island Paracel Islands Palawan THAILAND Gulf of Thailand VIETNAM Hainan Island CHINA HONG KONG TAIWAN Spratly Islands South China Sea PHILIPPINES CAMBODIA (K2P) model with the complete deletion option using the program MEGA (vers. 11, Tamura et al. 2021). Basepair (bp) differences and pairwise estimates of K2P distances for genetic diversities between specimens were also calculated in MEGA. RESULTS Molecular analyses of COI The COI sequences from 50 specimens of fiddler crabs collected from Vietnam (Table 1, Figs. 1, 7) correspond to 13 species with good support (Fig. 2). The mean pairwise nucleotide divergences of K2P distances and bp differences of haplotypes are shown in table 2. The intraspecific nucleotide divergences (and bp differences) are all ≤ 1.70% (≤ 11 bp), with Paraleptuca splendida and Tubuca arcuata possessing the highest intraspecific divergence. The interspecific divergences are ≥ 7.27% (45 bp) (except Gelasimus borealis and G. vocans), with the lowest interspecific divergence being between T. arcuata and T. forcipata. Fig. 1. Collection sites for specimens of fiddler crabs from Vietnam examined in this study (see Table 1). page 3 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan TAXONOMY Family Ocypodidae Rafinesque, 1815 Subfamily Gelasiminae Miers, 1886 (sensu Shih et al. 2016b) Genus Austruca Bott, 1973 Austruca annulipes (H. Milne Edwards, 1837) (Fig. 3A, B) Cancer vocans minor Herbst, 1782: 81, pl. 1(10) [nomen oblitum]; Shih et al. 2021: 208, fig. 1A. Gelasimus annulipes H. Milne Edwards, 1837: 55, pl. 18(10–13) (type locality: mer des Indes (= Indian Ocean)) [nomen protectum]; Kingsley 1880: 148, pl. 10(22) [part]. Gelasimus lacteus – Kingsley 1880: 149 [part]. Uca (Celuca) lactea annulipes – Crane 1975: 298, 611, figs. 18A–C, 19I–N, 20D–F, 24N, O, 27I–J, 29D, 32L, M, 41A, 54I, II, 69D, pls. 39A–D, 40C, D [part]; Dai et al. 1986: 426, pl. 59(3), fig. 236(2). Uca (Celuca) annulipes – Dai and Yang 1991: 467, pl. 59(3), fig. 236(2). ? Uca lactea – Do 1996: 36. Uca (Paraleptuca) annulipes – Ng et al. 2008: 241. Uca lactea annulipes – Trivedi et al. 2018: 17, 20, fig. 3c. Uca annulipes – Dawydoff 1952: 141; Yamaguchi 1994: 153, 183; S-L Yang et al. 2008: 807; Shih et al. 2009: 376; Shih et al. 2010b: 6; Chertoprud et al. 2012: 266, pl. 44C, D; Hoang et al. 2012: 75; Shih et al. 2013: 643; Saher et al. 2014: 67; Le et al. 2018: 41, fig. 5D; Le et al. 2020: 15. Uca (Austruca) annulipes – Naderloo et al. 2010: 7, figs. 2a–h, 3a–e, 4b, 12a–c; Kostina et al. 2016: 196, 257. Austruca annulipes – Shih et al. 2016b: 153, 168, fig. 8A; Sasaki 2019: 12424; Shih et al. 2021: 212, fig. 2. Austruca (Austruca) annulipes – Rosenberg 2019: 734. Material examined: Nha Trang: 4 ♂ ♂ (15.3–17.4 mm), 1 ♀ (13.3 mm) (NCHUZOOL 15111), mangrove I, coll. K. J. H. Wong and I-H. Chen, 24 Nov. 2010; 7 ♂♂ (13.2–21.7 mm), 3 ♀♀ (14.7–18.6 mm) (NCHUZOOL 15112), mangrove II, coll. I-H. Chen and K. J. H. Wong, 24 Nov. 2010. Binh Thuan: 20 ♂♂ (11.6–19.6 mm), 1 ♀ (14.0 mm) (NCHUZOOL 15110), Nguyen Thong, Phu Hai, Phan Thiet, coll. I-H. Chen et al., 26 Nov. 2010. Kien Giang: 2 ♂♂ (12.8, 13.4 mm) Table 1. Specimens and COI haplotypes of the fiddler crabs from Vietnam and adjacent waters. The numbers within brackets following localities correspond to those in figure 1. See MATERIALS AND METHODS for abbreviations of museums and universities Species Locality in Vietnam (unless indicated) Sample size Catalogue no. of NCHUZOOL (unless indicated) Haplotype Access. no. Austruca annulipes Nha Trang [5] 2 15112 Aan1, Aan2 ON193445, ON193446 Binh Thuan: Nguyen Thong, Phu Hai, Phan Thiet [6] 3 15110 Aan3, Aan4, Aan5 ON193447, ON193448, ON193449 Kien Giang: Phu Quoc Island [8] 1 15113 Aan2 ON193450 China: Sanya, Hainan 1 13244 Aan2 AB471907 Malaysia: Tioman 1 13243 Aan2 AB471907 Thailand: Phuket 1 13257 Aan3 AB491160 A. lactea Hai Phong: Xuan Dam, Cat Ba Island [2] 3 15114 Ala1, Ala2, Ala3 ON193451, ON193452, ON193453 Nam Dinh [3] 2 15115 Ala4, Ala5 ON193454, ON193455 Taiwan: Siangshan, Hsinchu City 1 13249 Ala1 AB471912 Hong Kong 1 13250 Ala1 ON193456 A. perplexa Binh Thuan: Nguyen Thong, Phu Hai, Phan Thiet [6] 2 15116 Ape1 ON193457, ON193458 Ho Chi Minh: Giong Ao, Can Thanh Town, Can Gio [7] 1 15117 Ape1 ON193459 Kien Giang: Phu Quoc Island [8] 1 15119 Ape2 ON193460 Malaysia: Jeram 1 15052 Ape1 ON193461 Singapore 1 ZRC 2020.0288 Ape1 ON193462 Gelasimus borealis Quang Ninh: Dong Rui [1] 2 15121, 15122 Gbo1, Gbo2 ON193463, ON193464 Hai Phong: Cat Ba Island: Xuan Dam [2] 1 15120 Gbo3 ON193465 page 4 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Species Locality in Vietnam (unless indicated) Sample size Catalogue no. of NCHUZOOL (unless indicated) Haplotype Access. no. Taiwan: Shengang, Changhua 1 13259 Gbo2 AB491163 Hong Kong 1 13207 Gbo4 LC053376 G. tetragonon Nha Trang: Luong Son, Vinh Luong [5] 2 15124 Gte ON193466, ON193467 Taiwan: Chitou, Penghu 1 13304 Gte AB535431 Egypt: Sinai: El Monqata 1 15096 Gte AB535431 G. vocans Nha Trang [5] 1 14913 Gvo1 ON193468 Binh Thuan: Nguyen Thong, Phu Hai, Phan Thiet [6] 2 15125 Gvo2, Gvo3 ON193469, ON193470 Singapore: Lim Chu Kang 1 13189 Gvo4 AB535425 Philippines: Bohol 1 13205 Gvo5 AB813683 Paraleptuca splendida Nha Trang [5] 1 15132 Psp1 ON193471 Nha Trang [5] 2 13448 Psp2, Psp3 AB734654, ON193472 Nha Trang: Luong Son, Vinh Luong [5] 1 13459 Psp4 AB734655 Taiwan: Chitou, Penghu 1 13453 Psp5 AB734645 Taiwan: Chitou, Penghu 1 13450 Psp3 AB734646 Hong Kong: Tai Tam 1 13368 Psp6 AB734648 T. acuta Haiphong: Cat Ba Island: Xuan Dam [2] 2 15134 Tac ON193473, ON193474 Nam Dinh: Xuan Thuy National Park [3] 2 15104, 15105 Tac ON193475, ON193476 Nam Dinh [3] 1 15133 Tac ON193477 Taiwan: Kinmen 1 13650 Tac LC053369 China: Hainan: Dongzhai 1 13351 Tac LC150429 T. arcuata Hai Phong: Cat Ba Island: Xuan Dam [2] 1 15140 Tar1 ON193478 Nam Dinh: Xuan Thuy National Park [3] 1 15100 Tar1 ON193479 Nam Dinh [3] 3 15144 Tar1 ON193480, ON193481, ON193482 Ha Tinh: Cam Ha, Cam Xuyen District [4] 1 15141 Tar2 ON193483 Japan: Kaeda River, Miyazaki 1 14610 Tar1 ON193484 Taiwan: Cigu, Tainan 1 13260 Tar3 AB491165 T. forcipata Ho Chi Minh: Giong Ao, Can Thanh Town, Can Gio [7] 1 15145 Tfo1 ON193485 Ho Chi Minh: Giong Ao, Can Thanh Town, Can Gio [7] 2 15146 Tfo1, Tfo2 ON193486, ON193487 Ho Chi Minh: Giong Ao, Can Thanh Town, Can Gio [7] 1 15147 Tfo1 ON193488 Malaysia: Johor 1 NTOU Tfo1 LC053372 T. paradussumieri Quang Ninh: Dong Rui [1] 2 ZVNU.2019.010, ZVNU.2019.011 Tpa2 ON193489, ON193490 Ho Chi Minh: Rung Sac, Long Hoa, Can Gio [7] 1 15157 Tpa1 ON193491 South Vietnam 1 ZRC Tpa1 ON193492 China: Dongzhai, Hainan 1 13381 Tpa2 LC053373 Malaysia: Kuching, Sarawak 1 ZRC 1965.12.8.72-81 Tpa2 ON193493 T. rhizophorae Ho Chi Minh: Can Gio: Can Thanh Town: Giong Ao [7] 1 15148 Trh1 ON193494 Ho Chi Minh: Rung Sac, Long Hoa, Can Gio [7] 1 15149 Trh2 ON193495 Malaysia: Mersing 1 14923 Trh3 LC150442 Malaysia: Kuching, Sarawak 1 14924 Trh4 LC150443 T. typhoni Binh Thuan: Nguyen Thong, Phu Hai, Phan Thiet [6] 1 15150 Tty1 ON193496 Ho Chi Minh: Rung Sac, Long Hoa, Can Gio [7] 1 15151 Tty2 ON193497 China: Sanya, Hainan 1 13371 Tty3 LC150444 Total 76 Table 1. (Continued) page 5 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan (NCHUZOOL 15113), Phu Quoc Island, coll. H.-T. Shih, 2 Dec. 2012. Distribution: Pakistan, India, Myanmar, Thailand, Malay Peninsula, Singapore, Indonesia, Borneo, Vietnam, and South China (Hainan). Remarks: Austruca annulipes, widely distributed in IWP, is a common species in Southeast Asia (Crane 1975; Shih et al. 2009 2022; Naderloo et al. 2010; Trivedi et al. 2018). In the region of the SCS, it has been reported from southern coast of Hainan Island (ca. 18°N; Figs. 1, 7), and northern part of the SCS (Dai et al. 1986; Dai and Yang 1991; Shih et al. 2010b), which is the northernmost distribution of this species in the West Pacific. However, the current records show it is only limited to the southern parts of Vietnam (ca. 12°N; Figs. 1, 7). Fig. 2. A neighbor-joining (NJ) tree for species of the fiddler crabs from Vietnam based on the cytochrome c oxidase subunit I (COI) gene. Probability values at the nodes represent support values. Only values > 50% are shown. For haplotype names, see Table 1. NVN, northern Vietnam; SVN, southern Vietnam. Tar1 (Cat Ba I., NVN) Tar1(XuanThuy, NVN) Tar1(NamDinh,NVN) Tar1(NamDinh,NVN) Tar1(NamDinh,NVN) Tar1(Miyazaki,Japan) Tar2(HaTinh,NVN) Tar3(Tainan,Taiwan) Tfo2(CanGio,SVN) Tfo1(CanGio,SVN) Tfo1 (Can Gio, SVN) Tfo1(CanGio, SVN) Tfo1(Johor,Malaysia) Tty2(CanGio,SVN) Tty3(Hainan,China) Tty1(BinhThuan,SVN) Tpa2 (Dong Rui,NVN) Tpa2 (DongRui,NVN) Tpa2(Hainan,China) Tpa2(Sarawak, Malaysia) Tpa1 (Can Gio, SVN) Tpa1(SVN) Trh1(Can Gio,SVN) Trh2 (Can Gio,SVN) Trh3 (Mersing,Malaysia) Trh4(Sarawak,Malaysia) Tac(CatBaI.,NVN) Tac(CatBaI.,NVN) Tac(XuanThuy, NVN) Tac(XuanThuy,NVN) Tac(NamDinh,NVN) Tac(Kinmen,Taiwan) Tac(Hainan,China) Psp3(NhaTrang,SVN) Psp3 (Penghu,Taiwan) Psp1(NhaTrang,SVN) Psp5(Penghu,Taiwan) Psp4(NhaTrang,SVN) Psp2(NhaTrang,SVN) Psp6(Hong Kong) Gte(Sinan,Egypt) Gte(Penghu,Taiwan) Gte(NhaTrang,SVN) Gte(NhaTrang,SVN) Gvo5(Bohol,Philippines) Gbo3 (CatBaI., NVN) Gvo3(BinhThuan,SVN) Gvo4(Singapore) Gvo2 (BinhThuan,SVN) Gbo4(HongKong) Gvo1(NhaTrang,SVN) Gbo1(DongRui,NVN) Gbo2(Changhua,Taiwan) Gbo2(DongRui,NVN) Aan1(NhaTrang) Aan2(NhaTrang,SVN) Aan2(PhuQuoc,SVN) Aan2 (Hainan,China) A an2(Phuket, Thailand) Aan3(Phuket,Thailand) Aan3(BinhThuan, SVN) Aan5(BinhThuan,SVN) Aan4(BinhThuan, SVN) Ape1(Singapore) Ape1(Jeram,Malaysia) Ape1(CanGio, SVN) Ape1(BinhThuan,SVN) Ape1(BinhThuan,SVN) Ape2(PhuQuoc,SVN) Ala4(NamDinh,NVN) Ala5(NamDinh,NVN) Ala2(CatBaI.,NVN) Ala3(CatBaI.,NVN) Ala1(HongKong) Ala1(Hsinchu,Taiwan) Ala1(CatBaI.,NVN) 99 99 99 99 99 99 99 99 99 99 99 63 99 72 56 65 99 62 0.02 Tubuca arcuata Austruca perplexa Gelasimus borealis /vocans Austruca annulipes Austruca lactea Gelasimus tetragonon Paraleptuca splendida Tubuca paradussumieri Tubuca typhoni Tubuca rhizophorae Tubuca acuta Tubuca forcipata 99 page 6 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Table 2. Matrix of percentage pairwise nucleotide divergence with Kimura 2-parameter (K2P) distances (lower left) and mean numbers of differences (upper right) based on cytochrome c oxidase subunit I (COI) within and between species of fiddler crabs from Vietnam (see Table 1). Values of the range are shown in parentheses Intraspecific Interspecific Nucleotide divergence mean nucleotide difference A. annulipes A. lactea A. perplexa G. borealis G. vocans G. tetragonon Austruca annulipes 0.44 (0–1.08) 2.89 (0–7) 85.92 (82–89) 92.22 (90–95) 98.27 (94–103) 98.44 (94–102) 103.33 (102–105) Austruca lactea 0.41 (0–0.92) 2.67 (0–6) 14.47 (13.7–15.06) 85.29 (84–88) 100.89 (98–104) 101.49 (98–103) 105.86 (104–108) Austruca perplexa 0.1 (0–0.3) 0.67 (0–2) 15.67 (15.23–16.21) 14.38 (14.14–14.89) 94.53 (94–97) 94.53 (93–96) 106.67 (105–107) Gelasimus borealis 0.37 (0–0.77) 2.4 (0–5) 16.8 (15.96–17.75) 17.26 (16.69–17.88) 16.1 (15.99–16.59) 3.24 (1–6) 68.2 (68–69) Gelasimus vocans 0.37 (0.3–0.46) 2.4 (2–3) 16.84 (15.96–17.55) 17.38 (16.69–17.68) 16.1 (15.8–16.39) 0.5 (0.15–0.92) 67.4 (66–68) Gelasimus tetragonon 0 (0–0) 0 (0–0) 17.85 (17.57–18.19) 18.23 (17.86–18.66) 18.45 (18.11–18.52) 11.3 (11.26–11.45) 11.15 (10.9–11.26) Paraleptuca splendida 0.79 (0–1.7) 5.14 (0–11) 15.67 (14.86–16.4) 15.78 (15.02–16.36) 17.98 (17.03–18.65) 15.8 (15.02–16.77) 15.88 (15.02–16.77) 14.72 (14.36–14.95) Tubuca acuta 0 (0–0) 0 (0–0) 17.43 (17.32–17.72) 17.42 (16.93–17.53) 15.14 (14.98–15.17) 18.64 (17.28–18.98) 18.61 (18.36–18.77) 16.57 (16.57–16.57) Tubuca arcuata 0.42 (0–1.7) 2.75 (0–11) 15.93 (15.58–16.55) 17.53 (17.11–18.11) 17.67 (16.98–17.81) 17.43 (17.26–17.9) 17.51 (17.26–17.9) 17.44 (17.39–17.59) Tubuca forcipata 0.06 (0–0.15) 0.4 (0–1) 16.19 (15.53–16.7) 18.33 (17.88–18.49) 17.73 (17.56–17.76) 16.56 (16.4–17) 16.56 (16.4–16.8) 16.93 (16.77–16.97) Tubuca paradussumieri 0.08 (0–0.15) 0.53 (0–1) 16.6 (16.36–16.96) 17.28 (16.68–17.67) 16.7 (16.31–16.9) 16.72 (16.41–17.21) 16.52 (16.21–16.81) 16.71 (16.64–16.84) Tubuca rhizophorae 0.56 (0.3–0.92) 3.67 (2–6) 14.7 (14.25–15.18) 15.86 (15.19–16.17) 15.2 (15.02–15.6) 15.6 (15.25–16.06) 15.59 (15.05–15.86) 16.33 (16.23–16.43) Tubuca typhoni 1.02 (0.77–1.39) 6.67 (5–9) 16.17 (15.58–16.76) 14.56 (13.68–15.01) 16.38 (16.15–16.94) 14.45 (13.76–15.51) 14.39 (13.57–15.31) 14.94 (14.1–15.65) Interspecific P. splendida T. acuta T. arcuata T. forcipata T. paradussumieri T. rhizophorae T. typhoni Austruca annulipes 92.24 (88–96) 101.56 (101–103) 93.82 (92–97) 95.4 (92–98) 97.22 (96–99) 87.44 (85–90) 95 (92–98) Austruca lactea 93 (89–96) 101.43 (99–102) 102.05 (100–105) 106.23 (104–107) 101.05 (98–103) 93 (89–95) 86.67 (82–89) Austruca perplexa 103.67 (99–107) 89.83 (89–90) 102.33 (99–103) 102.83 (102–103) 98 (96–99) 89.92 (89–92) 96.17 (95–99) Gelasimus borealis 93.03 (89–98) 108.2 (108–109) 100.73 (100–103) 96.8 (96–99) 97.53 (96–100) 91.75 (90–94) 85.53 (82–91) Gelasimus vocans 93.43 (89–98) 107.2 (106–108) 101.13 (100–103) 96.8 (96–98) 96.53 (95–98) 91.75 (89–93) 85.27 (81–90) Gelasimus tetragonon 86.86 (85–88) 97 (97–97) 101.25 (101–102) 98.8 (98–99) 97.33 (97–98) 95.5 (95–96) 88.33 (84–92) Paraleptuca splendida 93.71 (92–95) 94.91 (92–97) 91.86 (90–95) 95.9 (94–98) 79.43 (76–82) 89.33 (87–95) Tubuca acuta 16.02 (15.66–16.27) 86.13 (85–88) 83.8 (83–84) 75.33 (75–76) 71.25 (70–73) 82 (81–83) Tubuca arcuata 16.27 (15.68–16.69) 14.64 (14.42–14.99) 47.08 (45–49) 71.71 (71–74) 77.63 (74–79) 71.92 (69–74) Tubuca forcipata 15.62 (15.26–16.23) 14.2 (14.05–14.24) 7.64 (7.27–7.98) 74.13 (73–75) 77.45 (77–79) 69.13 (68–70) Tubuca paradussumieri 16.47 (16.1–16.87) 12.62 (12.56–12.75) 11.88 (11.76–12.3) 12.3 (12.12–12.49) 76.58 (76–78) 65.67 (61–70) Tubuca rhizophorae 13.29 (12.66–13.76) 11.95 (11.72–12.28) 13.09 (12.38–13.35) 13 (12.93–13.28) 12.89 (12.78–13.16) 73 (69–76) Tubuca typhoni 15.23 (14.77–16.34) 13.9 (13.71–14.1) 11.99 (11.45–12.38) 11.44 (11.23–11.6) 10.84 (9.99–11.64) 12.27 (11.51–12.84) page 7 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Fig. 3. Dorsal view of carapace and frontal view of major cheliped. Austruca annulipes (A, B, specimens not catalogued, Phu Quoc Island, Kien Giang); A. lactea (C, D, NCHUZOOL 15115, CW 13.1 mm, Nam Dinh); A. perplexa (E, F, NCHUZOOL 15117, CW 10.3 mm, Can Gio, Ho Chi Minh City); Gelasimus borealis (G, H, NCHUZOOL 15121, CW 21.1 mm, Dong Rui, Quang Ninh). page 8 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Austruca lactea (De Haan, 1835) (Fig. 3C, D) Ocypode (Gelasimus) lactea De Haan, 1835: 54, pl. 15(5) (type locality: Japan). Gelasimus lacteus – Kingsley 1880: 149, pl. 10(28) [part]. Uca lactea – Dawydoff 1952: 141; Jones and Morton 1994: 28, fig. 6, pls. 2G, H, 3E, F; Yamaguchi 1994: 165; Kosuge et al. 1997: 182; Do and Hoang 2002: 128; Do and Hoang 2004: 15; Do and Hoang 2006: 36; S-L Yang et al. 2008: 807; Shih et al. 2009: 376; Shih et al. 2010b: 6, 10; Shih et al. 2013: 643; Le et al. 2018: 41; Do et al. 2021: 102. Uca (Celuca) lactea lactea – Crane 1975: 298, 300, 612, figs. 19A, 54J–JJ, 69E, pl. 40A, B; Dai et al. 1986: 425, pl. 59(2), fig. 236(1). Uca (Celuca) lactea – Dai and Yang 1991: 466, pl. 59(2), fig. 236(1). ? Uca lacté – Do 2003: 8. Uca (Paraleptuca) lactea – Ng et al. 2008: 241. Uca (Austruca) lactea – Naderloo et al. 2010: 19, figs. 10a–f, 11a–c, 14a, 15a, 18a, b; Kostina et al. 2016: 210, 211, 257; Shih et al. 2016a: 59, fig. 2A, B. Austruca lactea – Shih et al. 2015: 182, figs. 146–151; Shih et al. 2016b: 153, 168, fig. 8D; Ng et al. 2017: 123; Sasaki 2019: 12430; Wada 2019: e142. Austruca (Austruca) lactea – Rosenberg 2019: 734. Material examined: Hai Phong: 4 ♂ ♂ (9.7–13.3 mm), 5 ♀♀ (9.8–12.3 mm) (NCHUZOOL 15114), Xuan Dam, Cat Ba Island, coll. B. K. K. Chan, 23 Nov. 2011. Nam Dinh: 3 ♂♂ (11.8–13.1 mm), 1 ♀ (11.2 mm) (NCHUZOOL 15115), coll. V. T. Do, Aug. 2013. Distribution: Northern Vietnam, shores of China (including Hainan), Taiwan (including Penghu), Korea and main islands of Japan. Remarks: Austruca lactea has been considered as a continental species (Shih 2012a), distributed from northern Vietnam, coasts of China, western Taiwan, to Korea and main islands of Japan (Crane 1975; Shih et al. 2010b 2015). The current southernmost records of this species in South China (the northern coast of Hainan Island) and Vietnam (Huong Phong, Thua Thien Province) are around the latitude of 20°N and 16°N, respectively (Figs. 1, 7; Shih et al. 2010b; Wada 2019). Austruca perplexa (H. Milne Edwards, 1852) (Fig. 3E, F) Gelasimus perplexus H. Milne Edwards, 1852: 150, pl. 4(18) (type locality: Java). Gelasimus annulipes – Kingsley 1880: 148 [part]. Gelasimus chlorophthalmus – Kingsley 1880: 151 [part]. Uca (Celuca) lactea perplexa – Crane 1975: 298, 300, 612, 613, figs. 18D–F, 19C–H, 26D, 31E, 54K, KK, 69C (part). Uca perplexa – Yamaguchi 1994: 165; S-L Yang et al. 2008: 807; Shih et al. 2009: 376; Shih et al. 2013: 643. Uca perplesca – Do 2003: 8. Uca (Paraleptuca) perplexa – Ng et al. 2008: 241. Uca (Austruca) perplexa – Naderloo et al. 2010: 24, figs. 16a–g, 17a, b, 18c–f; Shih et al. 2016a: 62, fig. 2C–E. Austruca perplexa – Shih et al. 2015: 189, figs. 152–156; Shih et al. 2016b: 153, 168, fig. 8F; Ng et al. 2017: 123; Sasaki 2019: 12436; Wada 2019: e142. Austruca (Austruca) perplexa – Rosenberg 2019: 734. Material examined: Binh Thuan: 14 ♂♂ (8.2–17.4 mm), 3 ♀♀ (12.9–15.7 mm) (NCHUZOOL 15116), Nguyen Thong, Phu Hai, Phan Thiet, coll. I-H. Chen et al. 26 Nov. 2010. Ho Chi Minh: 6 ♂♂ (7.4– 10.3 mm), 1 ♀ (7.0 mm) (NCHUZOOL 15117), 1 ♂ (9.8 mm), 1 ♀ (7.1 mm) (NCHUZOOL 15118), Giong Ao, Can Thanh Town, Can Gio, coll. H.-T. Shih and P.-Y. Hsu, 13 Oct. 2017. Kien Giang: 4 ♂♂ (11.1–12.4 mm), 1 ♀ (13.3 mm) (NCHUZOOL 15119), Phu Quoc Island, coll. H.-T. Shih, 2 Dec. 2012. Southern Vietnam: 2 ♂♂ (14.2, 18.7 mm) (ZRC), coll. V. T. Nguyen, 2010. Distribution: Nicobar Islands, Indonesia, Australia, New Caledonia, New Guinea, Philippines, Borneo, Malay Peninsula, Thailand, Cambodia, Vietnam, Taiwan and Ryukyus. Remarks: Austruca perplexa is widely distributed in the IWP, from the western part of the eastern Indian Ocean to the West Pacific, including the Ryukyus (and probably in main islands of Japan) and Taiwan (including Penghu and Dongsha Island) in the East Asia. Recently, Shih and Poupin (2020) recognized a new allied species, A. citrus Shih & Poupin, 2020, from Fiji and eastwards (see also Crane 1975; Shih et al. 2009; Naderloo et al. 2010; Trivedi et al. 2018; Shih and Poupin 2020). Austruca perplexa was often misidentified as A. annulipes and A. lactea (see Shih and Poupin 2020), but can be distinguished by the characters of the anterolateral angles, fingers in the male major cheliped and the G1 (see dichotomous key provided below in this study). Genus Gelasimus Latreille, 1817 Gelasimus borealis (Crane, 1975) (Fig. 3G, H) Uca (Thalassuca) vocans borealis Crane, 1975: 89, 597, fig. 64A (type locality: Hong Kong); Dai et al. 1986: 424, pl. 58(8). Uca (Thalassuca) borealis – Dai and Yang 1991: 464, pl. 58(8). Uca borealis – Jones and Morton 1994: 22, fig. 4, pls. 2E, F, 3A, B; Kosuge et al. 1997: 182; Do and Hoang 2002: 128; Do and Hoang 2004: 15; Do and Hoang 2006: 37; Hoang et al. 2010: 156; S-L Yang et al. 2008: 807; Shih et al. 2010b: 6, 8; Do et al. 2021: 102, fig. 4(3); Hoang et al. 2021: 116. Uca vocans – Do and Hoang 2002: 128; Do and Hoang 2004: 15; Do and Hoang 2006: 36. Uca (Gelasimus) borealis – Ng et al. 2008: 240; Shih et al. 2016a: 63, fig. 3A–D; Le et al. 2018: 41. Gelasimus borealis – Shih et al. 2015: 200, figs. 162–167; Shih et al. 2016b: 151, 169, fig. 7A; Ng et al. 2017: 125; Sasaki 2019: 12445; Wada 2019: e142; Nguyen et al. 2022: 39. page 9 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Tubuca rhizophorae (Tweedie, 1950) (Fig. 6A, B) Uca rhizophorae Tweedie, 1950: 357, fig. 7a–c (type locality: Kuching, Malaysia). Uca (Deltuca) acuta rhizophorae – Crane 1975: 27, 592, figs. 61A, 90A, B, pl. 1A–D. Uca acuta rhizophorae – Yamaguchi 1994: 153, 183. Uca (Tubuca) rhizophorae – Ng et al. 2008: 242. Tubuca rhizophorae – Shih et al. 2016b: 159, 174, fig. 11F; Sasaki 2019: 12523. Tubuca (Angustuca) rhizophorae – Rosenberg 2019: 735. Material examined: Ho Chi Minh: 1 ♂ (11.8 mm), 1 ♀ (12.2 mm), 1 ovig. ♀ (13.2 mm) (NCHUZOOL 15149), Rung Sac, Long Hoa, Can Gio, coll. H.-T. Shih and P.-Y. Hsu, 12 Oct. 2017; 1 ♂ (15.4 mm) (NCHUZOOL 15148), Giong Ao, Can Thanh Town, Can Gio, coll. H.-T. Shih and P.-Y. Hsu, 13 Oct. 2017. Distribution: Borneo, Malay Peninsula and southern Vietnam. Remarks: Tubuca rhizophorae is a less-known species, with a limited distribution in eastern Malay Peninsula and northwestern Borneo (Crane 1975). In our study, this species is confirmed from the Mekong Delta, southern Vietnam, which is a new record to Vietnam and Indochina. Tubuca typhoni (Crane, 1975) (Fig. 6C, D) Uca (Deltuca) demani typhoni Crane, 1975: 41, 593, fig. 61C, pl. 4E– H (type locality: Manila, Luzon). Uca typhoni – Do 2003: 8; Shih et al. 2010b: 13, figs. 4A, B, 5A, C. Uca (Tubuca) typhoni – Ng et al. 2008: 242. Tubuca typhoni – Shih et al. 2016b: 159, 174; Sasaki 2019: 12525. Tubuca (Tubuca) typhoni – Rosenberg 2019: 735. Material examined: Binh Thuan: 1 ♂ (23.0 mm) (NCHUZOOL 15150), Nguyen Thong, Phu Hai, Phan Thiet, coll. I-H. Chen et al. 26 Nov. 2010. Ho Chi Minh: 1 ♂ (17.5 mm) (NCHUZOOL 15151), Rung Sac, Long Hoa, Can Gio, coll. H.-T. Shih and P.-Y. Hsu, 12 Oct. 2017. Distribution: Northern Philippines, South China (Hainan) and southern Vietnam. Remarks: Tubuca typhoni is distributed sporadically in northern Philippines, southern Hainan in China and the Mekong Delta in southern Vietnam (Crane 1975; Shih et al. 2010b; this study). This species has Fig. 6. Dorsal view of carapace and frontal view of major cheliped. Tubuca rhizophorae (A, B, NCHUZOOL 15148, CW 15.4 mm, Can Gio, Ho Chi Minh City); T. typhoni (C, D, NCHUZOOL 15151, CW 17.5 mm, Can Gio, Ho Chi Minh City). page 16 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan been included in the list of brachyuran fauna collected from southern Vietnam, albeit the lack of illustrations (Do 2003). With both morphological and molecular evidence, our report confirms the presence of this species from southern Vietnam. A key to the genera and species of fiddler crabs in Vietnam 1. Front narrow; outer major manus tubercular .............................. 2 - Front wide; outer major manus smooth .................................... 11 2. Outer major dactylus without groove; major carpus without delimited anterodorsal area flattened; more than 90% of males with major chela on the right; orbital floor without any elevations ................................................................................. 3 (Gelasimus) - Outer major dactylus with 1 to 2 grooves; major carpus with delimited anterodorsal area flattened; roughly 50% of males with major chela on either side; orbital floor often with tubercles, ridge or mound ..................................................................... 5 (Tubuca) 3. Outer major manus with small tubercles; fingers narrow and thick; outer pollex without groove; female with pile posteriorly on carapace sides .................................................... G. tetragonon - Outer surface of major manus with large tubercles; fingers broad and flat; outer pollex with one groove; female without pile posteriorly on carapace sides ...................................................... 4 4. Major pollex with shallow or without distal depression in gape, dactyl deeper than pollex only in young; oblique ridge of inner major manus low ........................................................ G. borealis - Major pollex with both deep proximal and distal depressions in gape, dactyl not deeper than pollex; oblique ridge of inner major manus high ................................................................... G. vocans 5. Meri of first 3 ambulatory legs broad ......................................... 6 - Meri of first 3 ambulatory legs slender .................................... 10 6. Floor of orbit with a row of tubercles; anterolateral margin shorter ........................................................................... T. typhoni - Floor of orbit without a row of tubercles; anterolateral margin longer .......................................................................................... 7 7. Carapace strongly arched; large size (up to CW ~37 mm); major manus with large tubercles, fingers with a series of slightly enlarged predistal teeth (< 1/4 length of inner margins of fingers) in pollex and dactyl, or absent; young male with short fingers .. 8 - Carapace not strongly arched; small size (up to CW ~20 mm); major manus with small tubercles, fingers slender, with a series of slightly enlarged predistal teeth (near 1/2 length of inner margins of fingers) in pollex and dactyl ..................................... 9 8. Ambulatory legs broader; major manus with large tubercles covering entire surface; G1 with relatively narrower genital opening and broad posterior flanges ............................. T. arcuata - Ambulatory legs narrower; major manus with large tubercles covering upper surface; G1 with relatively wider genital opening and vestigial flanges ................................................... T. forcipata 9. Groove of front broader, with sides not convergent distally; suborbital granules detectable; tubercles on outer manus larger ... .......................................................................................... T. acuta - Groove of front narrower, with sides convergent distally; suborbital granules absent; tubercles on outer manus smaller ...... ................................................................................ T. rhizophorae 10. Front with distinct narrow median groove; G1 with distal tuberculate chitinous process; female without large tooth on either finger in gape; large size (up to CW ~38 mm) .................... .......................................................................... T. paradussumieri - Front almost without discernible median groove, but clearly separated; G1 with distal blunt chitinous process; female always with a large tooth on both fingers in gape; medium size (up to CW ~27 mm) ........................................................... T. dussumieri 11. A shallow, triangular depression outside major pollex base; fourth ambulatory merus broad, its dorsal margin convex ...................... ............................................................ Paraleptuca (P. splendida) - No triangular depression outside major pollex base; fourth ambulatory merus slender, its dorsal margin straight .................... ................................................................................. 12 (Austruca) 12. Anterolateral angles triangular; major pollex without or with small predistal triangular tooth in gape; major dactyl arched throughout; G1 with thumb long, reaching well beyond flange base, flange wider than long ........................................... A. lactea - Anterolateral angles moderately acute; major pollex with moderate to large predistal triangular tooth in gape; major dactyl arched only distally; G1 with thumb moderately long, reaching flange base, flange wider than long ............................ A. perplexa - Anterolateral angles strongly acute; major pollex with small to moderate predistal triangular tooth in gape; major dactyl arched throughout; G1 with thumb short, not reaching flange base, flange remarkably long ........................................................ A. annulipes DISCUSSION Molecular analyses Of the 14 species reported in this study, DNA analyses on mtDNA COI sequences support recognition of 13 species-level taxa, with the exception of two members of the Gelasimus vocans species complex. Among the taxa recognized by the molecular data, the minimum interspecific divergence is observed between Tubuca arcuata and T. forcipata at 7.27% (Table 2). This interspecific distinction is substantial in considering values from published studies of various closely related allopatric species pairs of fiddler crabs, including: Austruca citrus Shih & Poupin, 2020 and A. perplexa (H. Milne Edwards, 1852) (≥ 1.29%, Shih and Poupin 2020); Gelasimus excisus (Nobili, 1906) (= G. neocultrimanus (Bott, 1973)) and G. jocelynae Shih, Naruse & Ng, 2010 (≥ 4.77%, recalculated from Shih et al. 2010a); Minuca rapax (Smith, 1870) and M. virens (Salmon & Atsaides, 1968) (≥ 3.29%, Thurman et al. 2018); Paraleptuca splendida (Stimpson, 1858) and P. crassipes (White, 1847) (≥ 2.49%, Shih et al. 2012); and Tubuca alcocki Shih, Chan & Ng, 2018 and T. urvillei (H. Milne Edwards, 1852) (3.78%, Shih et al. 2018). On the other hand, despite well-defined morphological differences among members of the Gelasimus vocans species complex, the minimum interspecific divergence between G. borealis and G. vocans is substantially lower at 0.15% (Table 2), agreeing with results published in the literature (Shih et al. 2010a; Chu et al. 2015). In any case, the considerable interspecific divergences among most of the species reported in this study (Table 2) indicate these species are genetically well differentiated in Vietnam. page 17 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan With regard to the intraspecific divergences, the highest values are observed among Paraleptuca splendida and Tubuca arcuata at 1.70%. Some species, however, show low values of intraspecific variation. For example, no divergence was found in Gelasimus tetragonon and Tubuca acuta; and 0.15% in Tubuca forcipata and T. paradussumieri (Table 2). This low haplotype and nucleotide diversity has been reported in Austruca occidentalis (Naderloo, Schubart & Shih, 2016) from eastern Africa, implying involved species might have experienced strong bottlenecks due to founder effects, low lineage-specific mutations rates or natural selection (García-Merchán et al. 2012; Fratini et al. 2016). Comparison of fiddler crab faunae within Vietnam and adjacent regions While the fiddler crab faunae between northern and southern Vietnam are quite distinct, Paraleptuca splendida and Tubuca paradussumieri occur in both regions (Table 3). For the remaining species, a northsouth pattern of segregation is apparent: A. lactea, G. borealis, T. acuta and T. arcuata are only distributed in northern Vietnam, whereas A. annulipes, A. perplexa, G. tetragonon, G. vocans, T. dussumieri, T. forcipata, T. rhizophorae and T. typhoni are only found in the south. This segregation is particularly interesting as pairs of sister species (or members of species complex) (Shih et al. 2016b) are involved, showing allopatric distributions, namely A. lactea vs. A. perplexa, G. borealis vs. G. vocans, T. acuta vs. T. rhizophorae and T. arcuata vs. T. forcipata, respectively from northern and southern Vietnam. The different faunae in northern and southern Vietnam are assumed to be caused by (1) variation along the temperature (and climatic) gradient in the two regions (Jian et al. 2006); (2) the lack of vast intertidal zones with soft sediment in central Vietnam, which has been described as having “no mangroves along the entire seashore” only “[narrow] strips of brackish water mangroves... along river banks” (Phan and Hoang 1993), and as a region in which mangroves “are limited to a narrow strip within estuaries” for current condition (Veettil et al. 2019); (3) the southward and northward ocean currents along Vietnamese coasts merged to form an eastward current at around 12°N (southeastern Vietnam) in summer (Quan et al. 2016), the reproduction season, which probably serves as a strong north-south barrier, preventing the planktonic larvae of most fiddler species in either region from dispersing further. The two species which occur in both northern and southern Vietnam, P. splendida and T. paradussumieri, have a broader of distribution in comparison with other species – for P. splendida spanning from coasts of Vietnam, southern Hainan, Dongsha Island and southern Ryukyus, and for the Table 3. Distribution of fiddler crabs in northern Vietnam and southern Vietnam (including the Gulf of Thailand ecoregion in Fig. 7), and adjacent areas of China, Malay Peninsula and Borneo Species Continental China (incl. N Hainan) N Vietnam S Vietnam S Hainan E Malay Peninsula (incl. Singapore) Malaysian Borneo Austruca annulipes **** Austruca lactea ** Austruca perplexa ** * Austruca triangularis * Gelasimus borealis ** Gelasimus hesperiae * Gelasimus tetragonon ** * Gelasimus vocans *?a**** Paraleptuca splendida **** Tubuca acuta ** Tubuca arcuata ** Tubuca bellator * Tubuca dussumieri *?a** Tubuca forcipata ** * Tubuca paradussumieri ** * * * Tubuca rhizophorae ** * Tubuca typhoni ** species number 8 (6) 6 10 5 9 8 a see Shih et al. 2010b. page 18 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan latter, an extensive distribution from the Bay of Bengal, Malay Peninsula, Borneo to South China (Crane 1975; Shih 2012b 2020; Shih et al. 2010b 2012 2015 2016a). The broad distributional range of both species implies stronger dispersal abilities of their larvae against eastward currents around southeast Vietnam, as well as their broader ecological tolerances. Comparing fiddler crab faunae with the adjacent areas (Table 3), the species composition of northern Vietnam bears a similarity with that of continental China (including northern Hainan) and other East Asian regions (Shih et al. 2010b 2015 2016a), with overlapping species including A. lactea, G. borealis, P. splendida, T. acuta, T. arcuata and T. paradussumieri. That of southern Vietnam is more similar with eastern Malay Peninsula and northern Borneo (Crane 1975; Tan and Ng 1994), sharing the below species: A. annulipes, A. perplexa, G. tetragonon, G. vocans, T. forcipata, T. paradussumieri and T. rhizophorae. However, three species from eastern Malay Peninsula and northern Borneo, viz. A. triangularis (A. Milne-Edwards, 1873), G. hesperiae (Crane, 1975) and T. bellator (White, 1847), have not been recorded from Vietnam so far. Based on the current data, the shore of Vietnam is biogeographically significant, where the northern part is located as the southernmost limit of G. borealis, T. acuta and T. arcuata; and A. lactea is extended to the central part (cf. Wada 2019); and the southern part is the northernmost limit of T. rhizophorae and T. forcipata (at least in continental eastern Asia). On records of Tubuca dussumieri from Vietnam and the continental coasts of the SCS Sister species Tubuca dussumieri and T. paradussumieri share a marked morphological resemblance and are discernible only by minor differences (Crane 1975; Shih et al. 2016b). Geographically, their distributions are more or less separated, with T. paradussumieri appearing to be limited to vicinity of the SCS and the Andaman Sea (i.e., continental coasts from eastern Indian Ocean, via Peninsular Malaysia and Borneo, to East Asia), and T. dussumieri appearing to be more widely distributed in oceanic islands (Crane 1975: map 18). This segregation is also reflected in their required habitat, with T. paradussumieri present on intertidal mudflats composed of finer sediments, and T. dussumieri preferring intertidal mudflats with coarser sediments (Jones and Morton 1994; Kwok and Tang 2006; Shih et al. 2015 2021). Even so, there were still reports of T. dussumieri from the SCS and adjacent regions from localities such as Guangdong in South China (Dai et al. 1986; Dai and Yang 1991; S-L Yang et al. 2008), Gulf of Thailand and southwestern Borneo (Crane 1975: map 18), Koh Surin Island in western Thailand (Frith and Frith 1977 1978), and Singapore (Tan and Ng 1994). However, the following records require verification: the Paracels in western SCS (as “U. dubia” in Dawydoff 1952) and southern Vietnam (as “U. arcuata” in Chertoprud et al. 2012). Reports of T. dussumieri from Tioman Island (southeastern Peninsular Malaysia) and Pawai Island (Singapore), both oceanic islands with coarse sediments, have been confirmed by morphological and molecular evidence (HT Shih unpublished). Because T. dussumieri generally inhabits oceanic islands, the record presented by Chertoprud et al. (2012) from the oceanic Hon Tre Island in Nha Trang Bay (as “Uca arcuata”) is reliable. Biogeography of fiddler crabs in Vietnam in relation to ecoregions and oceanographic currents In the present study, the distribution of the 14 species of fiddler crabs in Vietnam follows the ecoregions (Fig. 7) as defined in Spalding et al. (2007). The coastline of Vietnam is divided into three ecoregions: the Gulf of Tonkin ecoregion (GTo), which includes the northern coastline; the Southern Vietnam ecoregion (SV), which includes the southern coastline (Spalding et al. 2007); and the Gulf of Thailand ecoregion, which includes the Gulf of Thailand and is separated from the SV by a boundary at the region around Nha Trang. The division of these three regions is supported by the oceanographic currents around the Vietnam coastline. Climatic conditions of Vietnam are heavily influenced by the East Asian Monsoon, characterized by seasonally opposite patterns in atmospheric and oceanic circulations (see Lau et al. 1998). The northern Vietnam coastline is affected by several currents. The Gulf of Tonkin Surface Current flows southward along the coastline of northern Vietnam (Liu et al. 2016; Fig. 7). The northern coastline is also affected by a buoyancy-driven river plume originating from the runoff of the Red River (Hong River) in the north, flowing southeastwards towards the central reaches of the shore. There is an intrusion of the South China Sea Branch of Kuroshio Current, which enters from the Luzon Strait and hits the middle region of Vietnam from May to September, close to Nha Trang (Xue et al. 2004; J Yang et al. 2008; Fig. 7). The southern part of the Vietnam coastline is affected by the Southeast Vietnam Offshore Current flowing northward and mixing with the South China Sea Branch of Kuroshio Current (J Yang et al. 2008; Tsang et al. 2012; Quan et al. 2016; Fig. 7). There is a runoff from the Mekong River along the southern coastline towards the northeast (Chen et al. 2012). The page 19 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan mixing of different currents at around latitude 11–12°N, immediately south of Nha Trang, forms an upwelling zone with sea surface temperatures of approximately 24 to 25°C, some 3 to 5°C lower than surrounding seas, accompanied with enhanced chlorophyll concentration (“cold filament”; Xie et al. 2003; Doan et al. 2010). This upwelling shows inter-annual variations, contributing to a differing extent of cooling of sea surface temperatures Fig. 7. Oceanographic currents (summer) around Vietnamese waters and the distribution of fiddler crabs. Oceanographic current map is adopted from figure 5D in Xue et al. (2004) (Lincence number: 5380661146310, offered by JOHN WILEY AND SONS LICENSE). Marine ecoregions are indicated by bold dashed lines. Abbreviations: Ocean currents: GTONC – Gulf of Tonkin Current, SCSWC – South China Sea Warm Current, SCSKB – South China Sea Branch of Kuroshio, SEVOC – Southeast Vietnam Offshore Current; marine ecoregions (with numbers as listed in Spalding et al. 2007): GTo – Gulf of Tonkin (112), SC – Southern China (113), SCSOI - South China Sea Oceanic Islands (114), GTh – Gulf of Thailand (115), SV – Southern Vietnam (116), SS – Sunda Shelf (117), SK – South Kuroshio (121). Colorations depicted on marine areas represent sea surface elevation in centimeters. The record of Paraleptuca splendida in Da Nang was reported in Balss (1922) and Austruca lactea in Huong Phong, Thua Thien was recorded by Wada (2019). page 20 of 24 Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan (Xie et al. 2003). The Gulf of Thailand is affected by the monsoonal currents with anticyclonic gyre in summer (March to August) and cyclonic in winter (September to November) (Liu et al. 2016). The two sets of currents probably help explain the northern and southern Vietnamese species assemblages of fiddler crabs. The northern Vietnamese assemblage (Table 3, Fig. 7) found in the Bay of Tonkin ecoregion includes Austruca lactea, Gelasimus borealis, Paraleptuca splendida, Tubuca acuta, T arcuata and T. paradussumieri. The southern Vietnamese species assemblage (Table 3, Fig. 7) distributed in the Southern Vietnam ecoregion includes A. annulipes, A. perplexa, G. tetragonon, G. vocans, P. splendida, T. dussumieri, T. forcipata, T. paradussumieri, T. rhizophorae and T typhoni; and the Gulf of Thailand assemblage is so far composed of A. annulipes, A. perplexa and G. vocans. The distinct distributions of fiddler crab assemblages between northern Vietnam and southern Vietnam (and Gulf of Thailand) correspond well with the oceanographic currents (Fig. 7) suggesting the larval pools of these assemblages are separated by the current patterns. CONCLUSIONS 14 species of fiddler crabs were reported from Vietnam, including the newly recorded Tubuca rhizophorae and T. dussumieri. Based on DNA barcoding analyses, we show the mitochondrial COI marker can successfully distinguish most specieslevel taxa (13; with the exception of G. borealis and G. vocans), with the minimum interspecific divergences at least 7.27%. Species compositions of fiddler crabs in northern and southern Vietnam are different, with only Paraleptuca splendida and Tubuca paradussumieri being common in both regions. The fauna of northern Vietnam bears a similarity with China and other East Asian regions, whereas that of southern Vietnam is closer to that of the Malay Peninsula and Borneo. Acknowledgments: This study was supported by grants from the Ministry of Science and Technology (MOST 108-2621-B-005-002-MY3; 111-2621-B-005003), Executive Yuan, Taiwan, to HTS. We wish to express thanks to Peter K. L. Ng (ZRC) for providing specimens used in this study; I-Han Chen, Pei-Chen Tsai for assistance in fieldwork; Van Nhuong Do for providing references; and Min-Wan Chen for measuring specimens and performing part of the molecular work. We also acknowledge the reviewers Peter K. L. Ng and one anonymous referee who helped improve the manuscript. Authors’ contributions: HTS conceived this study, performed the molecular analysis, and drafted the manuscript. KJHW, BKKC, TSN, VTD, XQN and PYH collected and processed the samples, participated in the discussion and drafted the manuscript. All authors read and approved the final manuscript. Competing interests: The authors declare that they have no conflict of interest. Availability of data and materials: Sequences generated in the study were deposited into the GenBank database (accession numbers in Table 1). Consent for publication: Not applicable. Ethics approval consent to participate: Not applicable. REFERENCES Adams A. 1847. Notes from a journal of research into the natural history of the countries visited during the Voyage of H. M. S. Samarang, under the command of captain Sir E. Belcher, C. B., F. R. A. S. Reeve, Benham, and Reeve, London, pp. 223–532, frontispiece. Adams A, White A. 1848–1849. Crustacea. In: Adams A (ed) The Zoology of the Voyage of H.M.S. Samarang; Under the Command of Captain Sir Edward Belcher, C.B., F.R.A.S., F.G.S., During the Years 1843-1846. Reeve, Bentham, and Reeve, London, i–viii + i–xv + 66 pp., pls. I–VI. Aoki M, Wada K. 2013. Genetic structure of the wide-ranging fiddler crab Uca crassipes in the West Pacific region. J Mar Biol Assoc UK 93:789–795. doi:10.1017/S0025315412001178. Balss H. 1922. Ostasiatische Decapoden. IV. Die Brachyrhynchen (Cancridea). Arch Naturg 88A(11):94–166. Bott R. 1973. Die verwandtschaftlichen Beziehungen der Uca-Arten. Senck Biol 54:315–325. Chen C, Lai Z, Beardsley RC, Xu Q, Lin H, Viet NT. 2012. Current separatin and upwelling over the southeast shelf of Vietnam in the South China Sea. J Geophys Res 117:C03033. doi:10.1029/2011JC007150. Chertoprud ES, Spiridonov VA, Marin IN, Mokievsky VO. 2012. Brachyuran crabs (Crustacea Decapoda Brachyura) of the mangrove intertidal zone of southern Vietnam. In: Britayev TA, Pavlov DS (eds) Benthic Fauna of the Bay of Nhatrang, Southern Vietnam. Volume 2. KMK Scientific Press Ltd., Moscow, pp. 258–295. Chu KH, Schubart CD, Shih H-T, Tsang LM. 2015. Genetic diversity and evolution of Brachyura. In: Castro P, Davie PJF, Guinot D, Schram FR, von Vaupel Klein JC (eds) Treatise on Zoology— Anatomy, Taxonomy, Biology—the Crustacea, complementary to the volumes translated from the French of the Traité de Zoologie. Brill, Leiden 9(C)(II), Decapoda: Brachyura (Part 2), pp. 775–820. doi:10.1163/9789004190832_016. Crane J. 1975. Fiddler Crabs of the World (Ocypodidae: Genus Uca). Princeton University Press, Princeton, New Jersey, 23+736 pp. Dai A-Y, Yang S-L. 1991. Crabs of the China Seas. China Ocean Press, Beijing, China, 21+608 pp., 74 pls. page 21 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Dai A-Y, Yang S-L, Song Y-Z, Chen G-X. 1986. Crabs of the China Seas. China Ocean Press, Beijing, 17+568 pp, 74 pls. (in Chinese) Davie PJF. 2002. Crustacea: Malacostraca: Eucarida (Part 2): Decapoda — Anomura, Brachyura. Zoological Catalogue of Australia. Wells A, Houston WWK (eds), vol. 19.3B. CSIRO Publishing, Melbourne, 641 pp. Dawydoff MC. 1952. Contribution a l’étude des invertébrés de la faune marine benthique de l’Indochine. Bull Biol Fr Belg Suppl 37:1–158. Do VN. 1996. Preliminary data of the composition of mangrove macrofaune in Cangio, Hochiminh City. Sci Inform Coll Educ Vietnam Nat Univ Hanoi Biol 5:32–41. (in Vietnamese) Do VN. 2003. Preliminary data on Brachyura in the Cangio mangrove area, Ho Chi Minh City. Tap Chi Sinh Hoc (Academia Journal of Biology) 25(4):6–10. (in Vietnamese) Do VN, Hoang NK. 2002. Some data on crustacean fauna in Giao Lac mangrove. Truong Dai Hoc Su Pham Ha Hoi (Journal of Science, Hanoi University of Education) 4:120–132. (in Vietnamese) Do VN, Hoang NK. 2004. Preliminary data of Brachyura in the mangrove of the estuarine zone of the Red River. Tap Chi Sinh Hoc (Academia Journal of Biology) 26(4):13–19. (in Vietnamese) Do VN, Hoang NK. 2006. Preliminary data on Brachyura (Crustacea) in coastal mangrove forests from Tinhgia (Thanhhoa Province) to Hoian (Quangnam Province). Tap Chi Sinh Hoc (Academia Journal of Biology) 28(1):35–39. (in Vietnamese) Do VN, Tran DH, Nguyen DH, Tran NH. 2021. Commmunity structure and ecological distribution of benthic animals in Tien Hai mangrove forest, northern Vietnam. Academia J Biol 43(3):95–112. doi:10.15625/2615-9023/14941. Doan NH, Nguyen NL, Dippner JW. 2010. Development of Phaeocystis globosa blooms in the upwelling waters of the south central coast of Viet Nam. J Mar Syst 83:253–261. doi:10.1016/ j.jmarsys.2010.04.015. Folmer O, Black M, Hoeh W, Lutz R, Vrijenhoek R. 1994. DNA primers for amplification of mitochondrial cytochrome c oxidase subunit I from diverse metazoan invertebrates. Mol Mar Biol Biotechnol 3:294–299. Fratini S, Ragionieri L, Cannicci S. 2016. Demographic history and reproductive output correlates with intraspecific genetic variation in seven species of Indo-Pacific mangrove crabs. PLoS ONE 11(7):e0158582. doi:10.1371/journal.pone.0158582. Frith DW, Frith CB. 1977. Range extensions of fiddler crabs (Decapoda, Brachyura, Ocypodidae) in the north-western Malay Peninsula area. Crustaceana 32:100–102. Frith DW, Frith CB. 1978. Notes on the ecology of fiddler crab populations (Ocypodidae: genus Uca) on Phuket, Surin Nua and Yao Yai Islands, western peninsular Thailand. Phuket Mar Biol Center Res Bull 25:1–13. García-Merchán VH, Robainas-Barcia A, Abelló P, Macpherson E, Palero F, García-Rodríguez M, de Sola LG, Pascual M. 2012. Phylogeographic patterns of decapod crustaceans at the AtlanticMediterranean transition. Mol Phylogenet Evol 62:664–672. doi:10.1016/j.ympev.2011.11.009. Haan W de. 1833–1849. Crustacea. In: Siebold PF von (ed) Fauna Japonica sive Descriptio Animalium, Quae in Itinere per Japoniam, Jussu et Auspiciis Superiorum, qui Summum in India Batava Imperium Tenent, Suscepto, Annis 1823–1830 Collegit, Noitis, Observationibus et Adumbrationibus Illustravit. Amstelodami apud J. Müller et Co., Lugduni-Batavorum = Leiden, i–xvii, i–xxxi, ix–xvi, 1–243, pls. 1–55, A–Q. Herbst JFW. 1782–1790. Versuch einer Naturgeschichte der Krabben und Krebse nebst einer systematischen Beschreibung ihrer verschiedenen Arten, [Erster Band =] 1. Mit XXI Kupfer-Tafeln und Register. Joh. Casper Fuessly, Zürich / Gottlieb August Lange, Berlin and Stralsund, pp. i–iv, 1–274, pls. 1–21. Hoang NK, Do VN, Nguyen TT, Nguyen TTH. 2012. Preliminary data of three zoobenthos groups (Brachyura, Gastropoda and Bivalviva) found in the mangrove forest ecosystems of the Tran De Estuary, Soc Trang Province. J Sci HNUE Chem Biol Sci 57(8):72–80. Hoang NK, Nguyen DH, Bui TTH, Nguyen TT. 2010. Preliminary investigation on some groups of Malacostraca and Mollusca in the Len River and estuarine coastal areas of Hau Loc District, Thanh Hoa Province. VNU J Sci Nat Sci Technol 26(2S):152– 158. (in Vietnamese) Hoang NK, Vu MG, Vu TL, Nguyen TB. 2021. Species composition of crab in mangrove ecosystem of Hau Loc District, Thanh Hoa Province. Sci J Tan Trao Univ 7(21):112–118. (in Vietnamese) doi:10.51453/2354-1431/2021/564. Huang C, Mao SY, Shih HT. 2021. Two new freshwater crab species of the genus Nanhaipotamon Bott, 1968 (Crustacea, Decapoda, Potamidae) from Huizhou, Guangdong Province, southern China. Zootaxa 5026:221–238. doi:10.11646/zootaxa.5026.2.4. ICZN, International Commission on Zoological Nomenclature. 1999. International Code of Zoological Nomenclature (4th ed.), The International Trust for Zoological Nomenclature, London, i– xxix, 306 pp. Jian Z-M, Yu Y-Q, Li B-H, Wang J-L, Zhang X-H, Zhou Z-Y. 2006. Phased evolution of the south-north hydrographic gradient in the South China Sea since the middle Miocene. Palaeogeogr Palaeoclimatol Palaeoecol 230:251–263. doi:10.1016/j.palaeo. 2005.07.018. Jones DS, Morton B. 1994. The fiddler crabs (Ocypodidae: Uca) of Hong Kong. Asian Mar Biol 11:9–40. Kimura M. 1980. A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences. J Mol Evol 16:111–120. Kingsley JS. 1880. Carcinological notes, no. II. - Revision of the Gelasimi. Proc Acad Nat Sci Philad 32:135–155, pls. 9–10. Kostina EE, Tsurpalo AP, Gulbin VV. 2016. The species composition and distribution of macrobenthic communities in the intertidal zone of Vietnam. In: Adrianov AV, Lutaenko KA (eds) Biodiversity of the Western Part of the South China Sea. Dalnauka, Vladivostok, Russia, pp. 139–278. Kosuge T, Wada K, Trong PD. 1997. Crab distribution in the Cam River estuary, Haiphong, northern Vietnam. In: Anh PN, Brands JT, Hong PN (eds) National Workshop on the Relationship between Mangrove Rehabilitation and Coastal Aquaculture in Vietnam. Cres & Actmang, Hanoi, pp. 178–184. Kwok WPW, Tang WS. 2006. Fiddler crabs in Hong Kong — an overview. Hong Kong Biodivers 12:1–7. Lau K-M, Wu H-T, Yang S. 1998. Hydrologic processes associated with the first transition of the Asian summer monsoon: A pilot satellite study. Bull Am Meteorol Soc 79:1871–1882. Le VT, Dang VS, Nguyen TMH, Phan DD, Tran NDM. 2020. Species diversity and distribution of brachyuran crabs (Crustacea: Decapoda: Brachyura) in the mangrove forest area in Cu Lao Dung District, Soc Trang Province. Vietnam J Sci Technol 62(6):13–18. (in Vietnamese) Le VT, Nguyen VT, Tran NDM, Lee D, Kim W, Dang VS, Phan DD, Luong DT. 2018. Species composition and distribution of brachyuran crabs in Duyen Hai Town, Tra Vinh Province. Vietnam J Sci Technol Eng 60(4):39–44 doi:10.31276/ VJSTE.60(4).39-44. Linnaeus C. 1758. Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis, 1: i–iv+1–824. Liu Z, Zhao Y, Colin C, Stattegger K, Wiesner MG, Huh C-A, Zhang page 22 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan Y, Li X, Sompongchaiyakul P, You C-F, Huang C-Y, Liu JT, Siringan FP, Le KP, Sathiamurthy E, Hantoro WS, Liu J, Tuo S, Zhao S, Zhou S, He Z, Wang Y, Bunsomboonsakul S, Li Y. 2016. Source-to-sink transport processes of fluvial sediments in the South China Sea. Earth-Sci Rev 153:238–273. doi:10.1016/ j.earscirev.2015.08.005. Milne Edwards H. 1837. Histoire naturelle des Crustacés comprenant l’anatomie, la physiologie et la classification de ces animaux. Librairie Encyclopedique de Roret, Paris, Vol. II: 531 pp. + separate atlas to Vol. II: 32 pp. Milne Edwards H. 1852. Observations sur les affinités zoologiques et la classification naturelle des Crustacés. Ann Sci Nat Zool 3(18):109–166. Miyake S. 1936. Reports on the Brachyura of Riukiu Islands collected by the Yaeyama Expeditions during the years 1932–1934. II. A list of the known species of the Brachyura from Ishigaki-shima. Annot Zool Japon 15(4):506–513. Miyake S. 1938. Notes on decapod crustaceans collected by Prof. Teiso Esaki from Micronesia. Annot Zool Japon 17(2):107–112. Miyake S. 1939. Notes on Crustacea Brachyura collected by Professor Teiso Esaki’s Micronesia Expedition 1937–1938 together with a check list of Micronesian Brachyura. Rec Oceanogr Works Jap 10(2):168–247. Naderloo R, Türkay M, Chen HL. 2010. Taxonomic revision of the wide-front fiddler crabs of the Uca lactea group (Crustacea: Decapoda: Brachyura: Ocypodidae) in the Indo-West Pacific. Zootaxa 2500:1–38. doi:10.5281/zenodo.195791. Ng PKL, Guinot D, Davie PJF. 2008. Systema Brachyurorum: Part I. An annotated checklist of extant brachyuran crabs of the world. Raffles Bull Zool Suppl 17:1–296. Ng PKL, Shih H-T, Ho P-H, Wang C-H. 2017. An updated annotated checklist of brachyuran crabs from Taiwan (Crustacea: Decapoda). J Nat Taiwan Mus 70(3/4):1–208. doi:10.6532/ JNTM.201712_70(3;4).01. Nguyen TS, Do DS, Nguyen TAN. 2022. A checklist of mangrove crabs (Crustacea: Decapoda: Brachyura) from Dong Rui Commune, Tien Yen District, Quang Ninh Province. J Sci Hanoi Pedagog Univ 73:36–46. (in Vietnamese) Phan NH, Hoang TS. 1993. Mangroves of Vietnam. IUCN, Bangkok, 173 pp. Quan Q, Xue H-J, Qin H-L, Zeng X-Z, Peng S-Q. 2016. Features and variability of the South China Sea western boundary current from 1992 to 2011. Ocean Dyn 66:795–810. doi:10.1007/s10236-0160951-1. Roman J, Palumbi SR. 2004. A global invader at home: population structure of the green crab, Carcinus maenas, in Europe. Mol Ecol 13:2891–2898. doi:10.1111/j.1365-294X.2004.02255.x. Rosenberg MS. 2019. A fresh look at the biodiversity lexicon for fiddler crabs (Decapoda: Brachyura: Ocypodidae). Part 1: taxonomy. J Crustacean Biol 39:729–738. doi:10.1093/jcbiol/ ruz057. Saher NU, Sahir O, Shih H-T, Kamal M, Qureshi NA. 2014. On a new record of the genus Uca (Decapoda, Brachyura, Ocypodidae) found along the coast of Pakistan. Crustaceana 87:666–673. doi:10.1163/15685403-00003317. Sasaki J. 2019. The species list of Decapoda, Euphausiacea, and Stomatopoda, all of the world, version 03-3.1. Local Independent Administrative Agency Hokkaido Research Organization, Resources Management and Enhancement Division, Abashiri Fisheries Research Institute, Fisheries Research Department, Hokkaido, Japan, 14644 pp. doi:10.13140/RG.2.2.22353.89446. Sakai K. 1999. J. F. W. Herbst - Collection of decapod Crustacea of the Berlin Zoological Museum, with remarks on certain species. Naturalists Publ Tokushima Biol Lab Shikoku Univ 6:1–45, pls. 1–21. Sakai T. 1936. Report on the Brachyura collected by Mr. F. Hiro at Palao Islands. Sci Rep Tokyo Bunrika Daigaku B 2(37):155– 177. Schubart CD. 2009. Mitochondrial DNA and decapod phylogenies: the importance of pseudogenes and primer optimization. Crust Issues 18:47–65. Serène R. 1937. Inventaire des Invertébrés marins de l’Indochine (1er liste). Inst Océanogr l’Indochine Saigon 30:1–83. Shih H-T. 2012a. Distribution of fiddler crabs in East Asia, with a note on the effect of the Kuroshio Current. Kuroshio Sci 6:83–89. Shih H-T. 2012b. Warrior – The Seashore Crabs of Dongsha Island. Marine National Park Headquarters, Kaohsiung, Taiwan, 159 pp. (in Chinese) Shih H-T. 2020. Crescent Swordsmen – The Seashore Crabs of Dongsha Island. Marine National Park Headquarters, Kaohsiung, Taiwan, 207 pp. (in Chinese) Shih H-T, Chan BKK, Ng PKL. 2018. Tubuca alcocki, a new pseudocryptic species of fiddler crab from the Indian Ocean, sister to the southeastern African T. urvillei (H. Milne Edwards, 1852) (Crustacea, Decapoda, Brachyura, Ocypodidae). ZooKeys 747:41–62. doi:10.3897/zookeys.747.23468. Shih H-T, Chan BKK, Teng S-J, Wong KJH. 2015. Crustacean Fauna of Taiwan: Brachyuran Crabs, Volume II – Ocypodoidea. National Chung Hsing University, Taichung, Taiwan, 14+320 pp. Shih HT, Kamrani E, Davie PJF, Liu MY. 2009. Genetic evidence for the recognition of two fiddler crabs, Uca iranica and U. albimana (Crustacea: Brachyura: Ocypodidae), from the northwestern Indian Ocean, with notes on the U. lactea species complex. Hydrobiologia 635:373–382. doi:10.1007/s10750-0099930-6. Shih H-T, Lee J-H, Ho P-H, Liu H-C, Wang C-H, Suzuki H, Teng S-J. 2016a. Species diversity of fiddler crabs, genus Uca Leach, 1814 (Crustacea: Ocypodidae), from Taiwan and adjacent islands, with notes on the Japanese species. Zootaxa 4083:57–82. doi:10.11646/zootaxa.4083.1.3. Shih H-T, Low MEY, Ng PKL. 2021. The nomenclature, identity and synonyms of Cancer vocans minor Herbst, 1782 and Gelasimus caerulens Adams, 1847 (Decapoda, Brachyura, Ocypodidae). Crustaceana 94:207–225. doi:10.1163/15685403-bja10077. Shih H-T, Naruse T, Ng PKL. 2010a. Uca jocelynae sp. nov., a new species of fiddler crab (Crustacea: Brachyura: Ocypodidae) from the Western Pacific. Zootaxa 2337:47–62. doi:10.5281/zenodo. 193214. Shih H-T, Ng PKL, Davie PJF, Schubart CD, Türkay M, Naderloo R, Jones DS, Liu M-Y. 2016b. Systematics of the family Ocypodidae Rafinesque, 1815 (Crustacea: Brachyura), based on phylogenetic relationships, with a reorganization of subfamily rankings and a review of the taxonomic status of Uca Leach, 1814, sensu lato and its subgenera. Raffles Bull Zool 64:139– 175. Shih H-T, Ng PKL, Fang S-H, Chan BKK, Wong KJH. 2010b. Diversity and distribution of fiddler crabs (Brachyura: Ocypodidae: Uca) from China, with new records from Hainan Island in the South China Sea. Zootaxa 2640:1–19. doi:10.11646/ zootaxa.2640.1.1. Shih H-T, Ng PKL, Liu M-Y. 2013. Systematics of the Indo-West Pacific broad-fronted fiddler crabs (Crustacea: Ocypodidae: genus Uca). Raffles Bull Zool 61:641–649. Shih H-T, Ng PKL, Ravichandran S, Prema M. 2019. Resurrection of Gelasimus variegatus Heller, 1862, a fiddler crab closely related to Austruca bengali (Crane, 1975) and A. triangularis (A. MilneEdwards, 1873) (Decapoda, Brachyura, Ocypodidae), from the Bay of Bengal, Indian Ocean. Zool Stud 58:12. doi:10.6620/ ZS.2019.58-12. Shih H-T, Ng PKL, Wong KJH, Chan BKK. 2012. Gelasimus page 23 of 24Zoological Studies 61:66 (2022) © 2022 Academia Sinica, Taiwan splendidus Stimpson, 1858 (Crustacea: Brachyura: Ocypodidae), a valid species of fiddler crab from the northern South China Sea and Taiwan Strait. Zootaxa 3490:30–47. doi:10.11646/zootaxa. 3490.1.2. Shih H-T, Poupin J. 2020. A new fiddler crab of Austruca Bott, 1973, closely related to A. perplexa (H. Milne Edwards, 1852) (Crustacea: Brachyura: Ocypodidae), from the South Pacific islands. Zool Stud 59:26. doi:10.6620/ZS.2020.59-26. Shih H-T, Prema M, Kumar AJ, Saher NU, Ravichandran S, Odhano S, Paulay G 2022. Diversity and distribution of fiddler crabs (Crustacea: Brachyura: Ocypodidae) around the Arabian Sea. Zool Stud 61:65. doi:10.6620/ZS.2022.61-65. Spalding MD, Fox HE, Allen GR, Davidson N, Fernaña ZA, Finlayson M, Halpern BS, Jorge MA, Lombana A, Lourie SA, Martin KD, McManus E, Molnar J, Recchia CA, Robertson J. 2007. Marine ecoregions of the world: A bioregionalization of coastal and shelf areas. BioScience 57:573–583. doi:10.1641/ B570707. Stimpson W. 1858. Prodromus descriptionis animalium evertebratorum, quae in Expeditione ad Oceanum Pacificum Septentrionalem, a Republica Federata missa, Cadwaladaro Ringgold et Johanne Rodgers Ducibus, observavit et descripsit. Pars VII. Crustacea Anomoura. Proc Acad Nat Sci Philad 10:225–252. Stimpson W. 1907. Report on the Crustacea (Brachyura and Anomura) collected by the North Pacific Exploring Expedition, 1853–1856. Smithson Misc Coll 49(1717):1–240, pls. 1–26. Tamura K, Stecher G, Kumar S. 2021. MEGA11: Molecular Evolutionary Genetics Analysis version 11. Mol Biol Evol 38:3022–3027. doi:10.1093/molbev/msab120. Tan CGS, Ng PKL. 1994. An annotated checklist of mangrove brachyuran crabs from Malaysia and Singapore. Hydrobiologia 285:75–84. doi:10.1007/BF00005655. Thurman CL, Hopkins MJ, Brase AL, Shih HT. 2018. The unusual case of the widely distributed fiddler crab Minuca rapax (Smith, 1870) from the western Atlantic: an exemplary polytypic species. Invertebr Syst 32:1465–1490. doi:10.1071/IS18029. Trivedi JN, Trivedi DJ, Vachhrajani KD, Ng PKL. 2018. An annotated checklist of the marine brachyuran crabs (Crustacea: Decapoda: Brachyura) of India. Zootaxa 4502:1–83. doi:10.11646/zootaxa. 4502.1.1. Tsang LM, Wu TH, Shih H-T, Williams GA, Chu KH, Chan BKK. 2012. Genetic and morphological differentiation of the IndoWest Pacific intertidal barnacle Chthamalus malayensis. Integr Comp Biol 52:388–409. doi:10.1093/icb/ics044. Tweedie MWF. 1950. Grapsoid crabs from Labuan and Sarawak. Sarawak Mus J 5(2):338–369. Veettil BK, Ward RD, Quang NX, Trangg NTT, Giang TH. 2019. Mangroves of Vietnam: Historical development, current state of research and future threats. Estu Coast Mar Sci 218:212–236. doi:10.1016/j.ecss.2018.12.021. Wada K. 2019. Brachyuran species recorded from the coastal region of Vietnam in 1995–2007. Cancer 28:e138–e143. (in Japanese) Xie S-P, Xie Q, Wang D, Liu WT. 2003. Summer upwelling in the South China Sea and its role in regional climate variations. J Geophys Res 108(C8):2361. doi:10.1029/2003JC001867. Xue H, Chai F, Pettigrew N, Xu D. 2004. Kuroshio intrusion and the circulation in the South China Sea. J Geophys Res 109:C02017. doi:10.1029/2002JC001724. Yamaguchi T. 1994. Fiddler crabs of the genus Uca in the collections of three natural history museums in Europe. 1. The specimens held by the Nationaal Natuurhistorisch Museum, Leiden and the Natural History Museum, London. Calanus 11:151–189. Yang J, Wu D, Lin X. 2008. On the dynamics of the South China Sea Warm Current. J Geophys Res 113:C08003. doi:10.1029/2007JC004427. Yang S-L, Chen H-L, Jiang W. 2008. Brachyura. In: Liu R-Y (ed) Checklist of Marine Biota of China Seas. Science Press, Beijing, pp. 761–810. (in Chinese) page 24 of 24Zoological Studies 61:66 (2022)