Resurrection of Gelasimus variegatus Heller, 1862, A Fiddler Crab Closely Related to Austruca bengali (Crane, 1975) and A. triangularis (A. Milne-Edwards, 1873) (Decapoda, Brachyura, Ocypodidae), from the Bay of Bengal, Indian Ocean

© 2019 Academia Sinica, Taiwan Open Access Resurrection of Gelasimus variegatus Heller, 1862, A Fiddler Crab Closely Related to Austruca bengali (Crane, 1975) and A. triangularis (A. Milne-Edwards, 1873) (Decapoda, Brachyura, Ocypodidae), from the Bay of Bengal, Indian Ocean Hsi-Te Shih1,*, Peter K. L. Ng2, Samuthirapandian Ravichandran3, and Mani Prema3 1Department of Life Science and Research Center for Global Change Biology, National Chung Hsing University, Taichung, 402, Taiwan. *Correspondence: Tel/Fax: 886-4-22856496. E-mail: [email protected] 2Lee Kong Chian Natural History Museum, National University of Singapore, Singapore 117546, Republic of Singapore 3Center of Advanced Study in Marine Biology, Annamalai University, Parangipettai - 608 502, Tamil Nadu, India Received 20 February 2019 / Accepted 19 May 2019 / Published 2 July 2019 Communicated by Benny K.K. Chan The identity of the fiddler crab, Gelasimus variegatus Heller, 1862 (type locality: Madras, India), has long been uncertain. Examination of specimens from the Bay of Bengal shows that it is a valid species belonging to the genus Austruca Bott, 1973. Austruca variegata (Heller, 1862) can be separated from the closely related A. bengali (Crane, 1975) and A. triangularis (A. Milne-Edwards, 1873) by characters of the carapace, orbital floor, major and minor chelae, male first gonopod, vulva (female gonopore), gastric mill, and coloration in life. The three species are also supported by genetic data (nuclear 28S rDNA, mitochondrial 16S rDNA and cytochrome oxidase subunit I (COI)). Biogeographically, A. variegata is distributed in the Bay of Bengal and reaches to the Laccadive Sea; A. bengali is present in the Andaman Sea; and A. triangularis is widely distributed in the West Pacific. Key words: Fiddler crab, Austruca variegata, A. bengali, A. triangularis, Morphology, Cytochrome oxidase subunit I, 16S rDNA, 28S rDNA. Citation: Shih HT, 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. Milne-Edwards, 1873) (Decapoda, Brachyura, Ocypodidae), from the Bay of Bengal, Indian Ocean. Zool Stud 58:12. doi:10.6620/ZS.2019.58-12. BACKGROUND The most recent revision of the systematics of the family Ocypodidae recognized a total of 11 genera and 105 species of fiddler crabs in two subfamilies (Shih et al. 2016 2018). With regard to Austruca Bott, 1973, 11 Indo-West Pacific species are now recognised, composed of three main clades: the A. lactea, A. triangularis and A. sindensis groups (Shih et al. 2016). In Crane’s (1975) system, Gelasimus triangularis (A. MilneEdwards, 1873) contains two subspecies that have since been treated as two species, Austruca triangularis (A. Milne-Edwards, 1873) and A. bengali (Crane, 1975), which also have genetic support (see Shih et al. 2016). Biogeographically, A. triangularis is widely distributed in the West Pacific while A. bengali occurs in the eastern Indian Ocean (Bay of Bengal and Andaman Sea) (Crane 1975). However, the distribution of A. bengali seems to be disjunct, with a westermost population isolated in the southeastern Indian subcontinent (Crane 1975: Zoological Studies 58: 12 (2019) doi:10.6620/ZS.2019.58-12 1 © 2019 Academia Sinica, Taiwan 611, fig. 7), and populations apparently having a wider distribution in eastern and northeastern India, as well as Bangladesh (see Bairagi 1995; Rath and Dev Roy 2011; Hossain 2015; Akash and Chowdhury 2017). One broad-fronted species, Gelasimus variegatus Heller, 1862, with the type locality of Madras (= Chennai, Tamil Nadu, southeastern India), has long been treated as a species with “systematic uncertainties” (Crane 1975: 326). Crane (1975: 326) suspected G. variegatus was the same as Cranuca inversa (Hoffmann, 1874) because Heller (1862: 521) described the species with a denticulate crest on the merus of major cheliped (see below). As a result, Ng et al. (2008: 240) listed G. variegatus as a doubtful synonym of Uca inversa. However, C. inversa occurs in eastern Africa and is not known to extend to eastern India, and as such, Crane (1975: 326) considered the possibility that Heller’s label and locality data may be erroneous. Gelasimus variegatus was not included or even mentioned in the later publication of Heller (1865), probably because by then, he had decided it was synonymous with Gelasimus perplexus H. Milne Edwards, 1852. Heller (1865: 38) recorded “Gelasimus perplexus H. Milne Edwards, 1852” (Fig. 1a, b) and included Madras and Ceylon in the distribution. Based on the figure of the major chela of “G. perplexus” (cf. Fig. 1C; Heller 1865: pl. 5(4)) (not Gelasimus perplexus H. Milne Edwards, 1852 s. str.), Crane (1975: 291) identified it as A. bengali instead. In the short type diagnosis, however, Heller (1862) described Gelasimus variegatus as “G. annularis affinis, sed brachium chelipedum ad marginem superiorem carinatum et dentatum, index dactylo paulo brevior, acuminatus” [close to G. annulipes, merus of cheliped with higher carinate and dentate margin; dactylus of cheliped a little shorter, pointed], which agrees well with the structure of Austruca bengali or A. triangularis (cf. Huang et al. 1989: pl. 1A–D; Toyota and Seki 2014: 227; Shih et al. 2015: fig. 157), but apparently differ from the dorsal margin of major cheliped merus of Cranuca inversa, which has a crest without serration or only minutely serrate (Fig. 1d; cf. Crane 1975: pl. 16A; Bouchard et al. 2013: fig. 36B; Shih et al. 2016: fig. 9A). In addition, the description and figure of “G. perplexus” in Heller (1865: 38-39, pl. 5(4); Fig. 1C) also agree with the characters of major cheliped of G. variegatus, which support the idea that both are conspecific. It would appear that Heller (1862) had originally believed his material was a new species but decided in later work that it was just a synonym of G. perplexus H. Milne Edwards, 1852. We believe, however, that Gelasimus variegatus Heller, 1862, is a valid species in Austruca, with a similar morphology to A. triangularis and A. bengali. On the basis of a series of specimens recently examined from West Bengal and Tamil Nadu, we found a species that agrees very well with the original description of G. variegatus by Heller (1862: 3), notably in the morphology of the merus and dactylus of the major cheliped. In addition, their morphology also agrees well with the description and figure of “Gelasimus perplexus” from Madras and Ceylon in Heller (1865: 38–39, fig. 5(4); Fig. 1C). The molecular evidence from the nuclear 28S rDNA and mitochondrial 16S rDNA and cytochrome oxidase subunit I (COI) supports the hypothesis that this species is in fact distinct but closely related to A. triangularis and A. bengali. We herein formally recognize Gelasimus variegatus Heller, 1862, as a valid species of Austruca Bott, 1973. MATERIALS AND METHODS Specimens of the Austruca triangularis complex obtained from various sources in the Bay of Bengal, Andaman Sea and West Pacific and deposited in the Zoological Collections of the Department of Life Science, National Chung Hsing University, Taichung, Taiwan (NCHUZOOL); the Naturhistorisches Museum, Wien, Austria (NHMW); the Queensland Museum, Brisbane, Australia (QM); and the Zoological Reference Collection of the Lee Kong Chian Natural History Museum (formerly Raffles Museum of Biodiversity Research), National University of Singapore, Singapore (ZRC), were examined and illustrated with the help of a drawing tube attached to a stereomicroscope. Multiple photographic images of some structures were stacked using Helicon Focus 5.0. The abbreviation G1 is used for male first gonopod. Measurements, in millimeters (mm), are of the maximum carapace width (CW), carapace length (CL) and pollex length (PL). The terminology used essentially follows Crane (1975) and Davie et al. (2015). The gastric mill of the stomach from the three species was studied following the methods and terminology in Shih (2015). Multiple photographic images of the mill under the stereo-microscope were stacked using Helicon Focus and the scanning electron microscopy (SEM), mainly following Shih et al. (1999). Sequences of the nuclear 28S rDNA and the mitochondrial 16S rDNA and cytochrome oxidase subunit I (COI) were obtained following the method described by Shih et al. (2016), after verification with the complimentary strand. Sequences of the different haplotypes have been deposited in the DNA Data Bank of Japan (DDBJ) (accession numbers in Table 1). The sequences of other related species of the A. triangularis complex (see Shih et al. 2016), viz. A. albimana (Kossmann, 1877), A. annulipes (H. Milne Edwards, page 2 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan 1837), A. iranica (Pretzmann, 1971), A. lactea (De Haan, 1835), A. occidentalis (Naderloo, Schubart & Shih, 2016), A. mjoebergi (Rathbun, 1924), A. perplexa (H. Milne Edwards, 1852), and A. sindensis (Alcock, 1900), were used as outgroups in this paper. For the combined 28S, 16S and COI dataset, the best-fitting models for sequence evolution of individual datasets were determined by jModelTest (vers. 2.1.4, Guindon and Gascuel 2003; Darriba et al. 2012), selected by the Bayesian information criterion (BIC). The best models obtained were HKY + I, HKY + I + G and TIM3 + I, and were subsequently applied to the partitioned Bayesian inference (BI) analysis. The BI analysis was performed with MrBayes (vers. 3.2.6, Ronquist et al. 2012). The search was run with 4 chains for 10 million generations and 4 independent runs, with trees sampled every 1000 generations. The convergence of chains was determined by the average standard deviation of split frequency values below the recommended 0.01 (Ronquist et al. 2005) and the first 100 trees were discarded as burnin. The relationships of the COI haplotypes among A. variegata, A. bengali and A. triangularis were examined using the program PopART (vers. 1.7, Leigh and Bryant 2015). Basepair (bp) differences and the pairwise estimates of Kimura 2-parameter (K2P) distance (Kimura 1980) for genetic diversities between haplotypes were also calculated by MEGA (vers. 10.0.5, Kumar et al. 2018). RESULTS TAXONOMY Family Ocypodidae Rafinesque, 1815 Subfamily Gelasiminae Miers, 1886 (sensu Shih et al. 2016) Genus Austruca Bott, 1973 Table 1. The haplotypes of 28S rRNA, 16S rRNA and COI genes of specimens of Austruca species used in this study. *: species of the A. variegata complex, with additional COI haplotypes used in table 3 and figure 13 Species Locality Catalogue no. DDBJ Access. no. of 28S DDBJ Access. no. of 16S DDBJ Access. no. COI haplotype of COI A. albimana Egypt: Nabq, Sinai NCHUZOOL 13242 AB813689 AB471893 AB471906 A. annulipes Thailand: Phuket NCHUZOOL 13258 AB813686 AB471894 AB491161 A. bengali* Malaysia: Selangor NCHUZOOL 13575 AB813695 AB813651 AB813672 Ab2 Thailand: Phuket QM W27320 - - LC465132 Ab1 Thailand: Ranong NCHUZOOL 13646 - - LC015064 Ab3 A. iranica Iran: Gavbandi NCHUZOOL 13245 AB813688 AB471896 AB471908 A. lactea Hong Kong NCHUZOOL 13250 AB813693 AB471898 AB471912 A. mjoebergi Australia: Bedford I., West Australia QM-W20253 AB813690 AB471900 AB471914 A. occidentalis southern Madagascar ZRC THH04-30 AB813687 AB813648 AB813669 A. perplexa Taiwan: Dulanwan, Taitung NTOU AB813691 AB471901 AB471915 New Caledonia: Ouano Bay NCHUZOOL 13573 AB813692 AB813649 AB813670 Wallis and Futuna:Pointe Utu NCHUZOOL 14912 LC150460 LC150339 LC150400 A. sindensis Iran: Qeshm NCHUZOOL 13576 AB813696 AB813652 AB813673 A. triangularis* Taiwan: Baoli R. estuary NCHUZOOL 13254 - - AB471916 At1 Philippines: Cebu NCHUZOOL 13574 AB813694 AB813650 AB813671 At2 Philippines: Cebu NCHUZOOL 13574 - - LC465133 At3 Philippines: Mindanao NCHUZOOL 14354 - - LC465134 At4 Indonesia: Bali NCHUZOOL 14347 - - LC465135 At5 Australia: Queenslands QM W19251 - - LC465136, LC465137 At6, At7 New Caledonia: Pam QM W29056 - - LC465138 At8 New Caledonia: Dumbea Point QM W29057 - - LC465139 At9 A. variegata* India: Tamil Nadu ZRC 2001.0853 LC465129 LC465130 LC465131 Av5 India: Tamil Nadu ZRC 2001.0853 - - LC465140, LC465141, LC465142 Av8, Av1, Av3 India: Tamil Nadu NCHUZOOL 14366, 14364, ZRC 2018.1375 (neotype) - - LC465143, LC465144, LC465145 Av6, Av7, Av9 India: West Bengal ZRC 2017.0917 - - LC465146, LC465146 Av2, Av4 page 3 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Austruca variegata (Heller, 1862) (Figs. 1a–c, 2, 3a–b, 4a–d, 5a–d, 6a–c, f, 7a, b, e, 8a–d, 9) urn:lsid:zoobank.org:act:3E16AD8E-C907-4E0A-B14C3026181664DC Gelasimus variegatus Heller, 1862: 521 (type locality: Madras, India); Crane 1975: 326. Gelasimus perplexus – Heller 1865: 38, pl. 5(4) (Madras, India; Ceylon); A. Milne-Edwards 1873: 274 (India). (not Gelasimus perplexa H. Milne Edwards, 1837) Gelasimus triangularis – Henderson 1893: 388 (Madras and Ennore, India); Alcock 1900: 356 (Bay of Bengal). (not Gelasimus triangularis A. Milne-Edwards, 1873) Uca triangularis – Nobili 1903: 20 (Pondicherry, India); Altevogt 1957: 3, 5, figs. 11, 23, 27 (southeastern India); Feest 1969: 159, figs. 6, 7, 9, 11, 13, 14, 16, 18, 19, 20, 22, 24, 26, 28, 29 (Pondicherry, India); Dev Roy and Bhadra 2005: 509, pl. 3(8) (Andhra Pradesh, India); Dev Roy and Nandi 2007: 181, 188 (Tamil Nadu, India); Dev Roy and Bhadra 2008: 155 (list); Rath and Dev Roy 2008: 77, pl. 5(5) (Krishna, India); Dev Roy and Bhadra 2011: 207 (Tamil Nadu, India); Rath and Dev Roy 2011: 60, pl. 4(2) (Orissa, India); Kappalli et al. 2012: 967 (Muzhapilangad estuary, North Kerala, India); Satheeshkumar 2012: 315 (Pondicherry, India); Fredrick and Ravichandran 2013: 442 (Tamil Nadu, India); Hossain 2015: 202 (part; 1 unnumbered fig. = Metaplax sp.) (Bangladesh); Sen and Homechaudhuri 2015: 82 (Sundarban, India); Supriya et al. 2017: 647 (Muzhapilangad estuary, North Kerala, India). (not Gelasimus triangularis A. Milne-Edwards, 1873) Uca (Celuca) triangularis bengali Crane 1975: 286, figs. 24I, J, 32N, O, 59A, 68C, 101 (part); Krishnan 1992: 471, pl. 1; Bairagi 1995: 274 (West Bengal, India). (not Uca (Celuca) triangularis bengali Crane 1975) Uca bengali – Rosenberg 2001: 860, 866 (part). (not Uca (Celuca) triangularis bengali Crane 1975) Uca (Paraleptuca) bengali – Beinlich and von Hagen 2006: 26 (list), fig. 5i (part); Ng et al., 2008: 241 (list, part). (not Uca (Celuca) triangularis bengali Crane 1975) Uca triangularius bengali [sic] – Ravichandran and Kannupandi 2007: 334 (Pichavaram, India). (not Uca (Celuca) triangularis bengali Crane 1975) Uca triangularis bengali – Soundarapandian et al. 2008: 115 (Pichavaram, India); Chatterjee and Das 2014: 113, fig. 5 (West Bengal, India). (not Uca (Celuca) triangularis bengali Crane 1975) Uca inversa – Satheeshkumar and Khan 2011: 315; Satheeshkumar 2012: 315 (Pondicherry, India). (not Gelasimus inversa Hoffmann, 1874) ?Uca inversa – Dev Roy and Nandi 2012: 218 (list) (Andaman and Nicobar, India). Uca lactea – Talapatra et al. 2014: 908, fig. 4 (Odhissa, India). (not Ocypode (Gelasimus) lactea De Haan, 1835) Austruca bengali – Shih et al. 2016: 153 (list, part); Trivedi et al. 2018: 54. (not Uca (Celuca) triangularis bengali Crane 1975) ?Uca (Austruca) bengali – Akash and Chowdhury 2017: 201, fig. 2 (?) (Bangladesh). Austruca triangularis – Trivedi et al. 2018: 54 (part). (not Gelasimus triangularis A. Milne-Edwards, 1873) Cranuca inversa – Trivedi et al. 2018: 54. (not Gelasimus inversa Hoffmann, 1874) Material examined: Lectotype, ♂ (CW 16.7 mm, PL 24.7 mm) (NHMW 25656; original Novara label, #74 = AN. 1866.II.74.; labelled as “Gelasimus perplexus M. Edw.”), Madras, India, coll. Johann Zelebor. Others: 1 ♂ (17.2 mm) (NHMW 12974; no original label), Madras, India, coll. J. Zelebor. 5 ♂♂ (11.6–16.6 mm) (ZRC 2001.0853), Vellar River estuary, Parangipettai (= Porto Novo), Tamil Nadu, India, coll. N. N. Ng, 23 Mar. 2001; 1 ♂ (18.6 mm) (ZRC 2018.1375), 9 ♂♂ (9.8–17.3 mm) (NCHUZOOL 14362), 12 ♂♂ (8.8–17.8 mm) (NCHUZOOL 14363), Vellar River estuary, Parangipettai (= Porto Novo), Tamil Nadu, India, coll. M. Prema and S. Ravichandran, 6 Aug. 2017; 5 ♂♂ (12.0–17.1 mm), 1 ♀ (13.7 mm) (NCHUZOOL 14366), 1 ♀ (16.6 mm) (NCHUZOOL 14365), 6 ♂♂ (10.2–16.9 mm), 7 ♀♀ (9.7–15.4 mm) (NCHUZOOL 14367), Vellar River estuary, Parangipettai (= Porto Novo), Tamil Nadu, India, coll. M. Prema and S. Ravichandran, July–Aug. 2017; 2 ♂♂ (16.1–17.2 mm), 1 ♀ (14.5 mm) (ZRC 2003.0463), mangroves, Pitchavaram, Tamil Nodu, India, coll. N. Sivasothi and Chongsing, 12 Mar. 2000; 10 ♂♂ (14.5– 18.4 mm) (ZRC 2017.0917), Danthadhpatrobar, Cantai, Midnapure, West Bengal, India, coll. Z. Jaafar, 25 Nov. 2004; 2 ♂♂ (18.5–18.9 mm) (ZRC 2017.0915), Kolkata aquarium trade, Mar. 2010. Comparative material: Austruca bengali: Thailand: 1 ♂ (9.7 mm) (NCHUZOOL 13646), 1 ♀ (9.9 mm), 5 juv. (NCHUZOOL 14359), Bang Rin mangroves, Ranong, coll. H.-T. Shih, 27 May 2012; 2 ♂♂ (9.1–10.1 mm), 7 juv. (NCHUZOOL 14360), 3 ♂♂ (10.4–11.4 mm), 3 juv. (NCHUZOOL 14361), Tha Thiap Ruea Bang Rong, Phuket, coll. H.-T. Shih, 30 May 2012. Malaysia: 1 ♂ (8.0 mm) (NCHUZOOL 13575), 18 ♂♂ (10.4–14.5 mm), 8 ♀♀ (9.8–12.0 mm), 12 juv. (NCHUZOOL 14345), estuary of Sungai Sementa Besar, Kampung Perepat Kapar, Selangor, coll. H.-T. Shih, 10 Feb. 2009. Austruca triangularis: New Caledonia: 1 ♂ (10.4 mm), 2 ♀♀ (8.2–8.6 mm) (QM W29057), Dumbea Point, coll. P. Davie, 8 Feb. 1992; 2 ♂♂ (9.0–11.4 mm) (QM W29056), 1 ♀ (12.4 mm) (QM W29058), Pam, New Caledonia, coll. P. Davie, 10 Oct. 1992. Australia: 3 ♂♂ (9.8–12.1 mm), 1 ♀ (10.2 mm) (QM W19251), Thomatis Creek, Queensland, coll. P. Davie et al., 30 Oct. 1993. Indonesia: 2 ♂♂ (13.1–15.3 mm) (NCHUZOOL 14347), Badung, Kuta, Bali, coll. H.- T. Shih, 16 July 2014; 2 ♂♂ (11.3–11.4 mm) (QM W24251), Pantuan, Kalimantan, coll. E. Dutrieux, unknown date. Malaysia: 1♀ (8.3 mm) (NCHUZOOL 14346), Labuan, coll. H.-T. Shih, 24 July 2010. Philippines: 1 ♂ (10.6 mm) (NCHUZOOL 14354), 4 ♂♂ (10.9–12.5 mm), 1 ♀ (12.2 mm) (NCHUZOOL 14355), Zamboanga, Mindanao, coll. C. K. R. Ong, 10 June 2006; 6 ♂♂ (12.4–17.1 mm) (NCHUZOOL 14357), Pago R., Mindanao, coll. H.-C. Liu, 13 page 4 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan July 2007; 5 ♂♂ (12.4–14.2 mm), 1 ♀ (11.9 mm) (NCHUZOOL 13574), 1 ♂ (14.8 mm) (NCHUZOOL 14358), Cebu, coll. L. Liao, 2 Sep. 2003; 1 ♂ (11.5 mm), 2 ♀♀ (10.3–10.4 mm) (NCHUZOOL 14349), 1 ♀ (14.6 mm) (NCHUZOOL 14350), 1 ♂ (11.2 mm) (NCHUZOOL 14351), 1 ♂ (10.6 mm), 2 ♀♀ (10.4–12.4 mm) (NCHUZOOL 14352), Matutinao R. Badian, Cebu, coll. H.-T. Shih, 6 Sep. 2003; 3 ♂♂ (8.1–10.1 mm), 2 juv. (NCHUZOOL 14356), Puerto Galera, coll. P.-C. Tsai and K. Wong, Fig. 1. Male Austruca variegata (Heller, 1862) (a–d) and Cranuca inversa (Hoffmann, 1874) (e). (a) habitus; (b, c) major cheliped; (d, e) merus of right major cheliped. (a, b) lectotype, CW 17.2 mm (PL 24.7 mm, NHMW 25656; Madras, India), originally identified as A. perplexa. (c) “Gelasimus perplexus” in Heller (1865: pl. 5(4)). (d) male (CW 18.6 mm, ZRC 2018.1375; Tamil Nadu, India). (e) CW 19.9 mm (NCHUZOOL 14904; Al Darb, Arabia). Scale bars = 5.0 mm. (a) (b) (d) (e) (c) page 5 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan 5 June 2009. Taiwan: 2 ♂♂ (9.1–12.5 mm), 2 ♀♀ (8.8–12.3 mm) (NCHUZOOL 14710), Baoli River estuary, Pingtung, coll. H.-T. Shih, 14 Sep. 1997; 1 ♂ (13.2 mm), 1 ♀ (5.2 mm) (NCHUZOOL 14712), Baoli River estuary, Pingtung, 20 July 2011; 3 ♂♂ (11.4–13.0 mm) (NCHUZOOL 14745), Yanshuei River estuary, Tainan, coll. students, 4 Aug. 2009; 1 ♀ (8.7 mm) (NCHUZOOL 14711), Yanshuei River estuary, Tainan, coll. students, 18 Oct. 2011; 2 ♂♂ (10.2–11.5 mm), 1 ♀ (11.9 mm) (NCHUZOOL 14709), Lanyang River estuary, Yilan, 25 July 2004. Cranuca inversa: 1 ♂ (19.9 mm) (NCHUZOOL 14904), Al Darb, Red Sea, Arabia, coll. Anand. Jeya Kumar, 25 Apr. 2017. Diagnosis: Male. Front moderately broad. Carapace (Figs. 1a, 2a, 3a, b) with orbits slightly oblique; anterolateral angles (= external orbital angles) broadly triangular, directed anteriorly; anterolateral margins short; dorsolateral margin long, definite, converging. Floor of orbits with some weak tubercles medially (Fig. 4a–d). Major cheliped (Fig. 1a–c, with posterodorsal margin of merus with a single row of Fig. 2. Austruca variegata (Heller, 1862). a–d, male (CW 18.6 mm, CL 10.7 mm, PL 26.6 mm, ZRC 2018.1375). (a) habitus; (b) major cheliped; (c) pleon; (d) minor cheliped. Scale bar = 5.0 mm. (a) (b) (c) (d) page 6 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan small, sharp tubercles or serrations at convex crest, anterodorsal margin not arched, with serrated row (Fig. 1c); palm broad, with minute tubercles on outer surface, inner surface with proximal predactylar ridge strong and oblique row of granules proximoventrally; dactylus broad, with 1 short shallow groove proximal and subdorsally; pollex broad. Merus of minor cheliped with weak longitudinal row of tubercles above posteroventral margin, curves abruptly upward at distal end, short distance before end of segment. Gape of minor cheliped with serrations on distal part. Meri of second, third ambulatory legs moderately wide, dorsal margin of first, fourth meri almost straight. G1 with flange short, slightly curved, distal edge slightly expanded, almost truncate; thumb tumid, broad as adjacent shaft, extending well beyond flange base (Fig. 6a–c, f). Urocardiac ossicles of gastric mill moderately complex, with 4 or 5 pairs of transverse ridges of median tooth, separated by gaps reached deeply near central ridge, on posterior tooth plate; 4 pairs of cusps on stem region (Fig. 7a, b, e). Female. Anterolateral (Fig. 8a) margins long, almost straight, turning at angle into dorsolateral margins. Meri of ambulatory legs moderately wide (Fig. 8a). Vulva (female gonopore) (Fig. 8d) in shallow sternal depression, but not tuberculate. Coloration in life (Fig. 9): Carapace interlaced with black and pale blue (or yellowish white) transverse bands, some individuals with wider black bands on posterior portion. Eyestalks and major cheliped yellow. Legs pale blue (or yellowish white) with black speckles. Ecological notes: According to Krishnan (1992), this species in Madras “exhibits a patchy distribution, restricted to the high saline areas where the substratum is clay-mud”. Austruca annulipes (H. Milne Edwards, 1837) is the only sympatric species in southeastern India (Altevogt 1957; Feest 1969; Krishnan 1992; Dev Roy and Bhadra 2005; Fredrick and Ravichandran 2013). In the northern Bay of Bengal, it was reported to be sympatric with Austruca annulipes, Tubuca rosea (Tweedie, 1937), T. paradussumieri (Bott, 1973), Gelasimus hesperiae (Crane, 1975) (see Talapatra et al. 2014; Sen and Homechaudhuri 2015). Distribution: From the Bay of Bengal (including Sri Lanka) to the Laccadive Sea (see the synonym list). According to Krishnan (1992), the distribution may be extended to the whole eastern side of the Indian subcontinent (from Ganges Delta to Karaikal). Kappalli et al. (2012) and Supriya et al. (2017) studied the population (as Uca triangularis) from southwestern India in the Laccadive Sea. Remarks: As discussed earlier, Heller (1862: 521) briefly diagnosed Gelasimus variegatus from Madras (present day Chennai) in India but did not indicate how many specimens he had. Later, even after he synonymized it with “Gelasimus perplexus” (not Gelasimus perplexa H. Milne Edwards, 1837, s. str.), he did not indicate how many specimens he had from Madras. Crane (1975: 326) searched for the types in vain, commenting that “I have been unable to locate any material referred to this species. In particular the type-specimen was not found in the museum in Fig. 3. Carapaces of male Austruca variegata (Heller, 1862) (a, b), A. bengali (Crane, 1975) (c) and A. triangularis (A. Milne-Edwards, 1873) (d). (a) CW 16.6 mm (ZRC 2001.0853; left-handed; Tamil Nadu, India); (b) CW 14.5 mm (ZRC 2017.0917; left-handed; West Bengal, India); (c) CW 14.5 mm (NCHUZOOL 14345; right-handed; Selangor, Malaysia); (d) CW 14.8 mm (NCHUZOOL 13574; lefthanded; Cebu, Philippines). (a) (b) (c) (d) page 7 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Vienna when I asked for it in 1963. According to the short type description in Latin, this species is close to annulipes but includes a denticulate crest on the major merus. Almost certainly variegatus and inversa are synonymous. However, inversa has not been recorded from eastern India, while variegatus was described from Madras. The specimens were collected on the roundthe-world expedition of the “Novara”. According to oral reports, mistakes on the labels have been encountered in other material resulting from that trip, and it is not unlikely that the type-material of variegatus was collected farther west.” A fresh search for “Gelasimus variegatus” in the Naturhistorisches Museum Wien failed to find specimens under this name, but there Fig. 4. Floors of orbit of male Austruca variegata (Heller, 1862) (a–d), A. bengali (Crane, 1975) (e, f) and A. triangularis (A. Milne-Edwards, 1873) (g, h). (a, b) CW 18.6 mm (ZRC 2018.1375; right-handed; Tamil Nadu, India); (c, d) CW 14.5 mm (ZRC 2017.0917; left-handed; West Bengal, India); (e, f) CW 14.5 mm (NCHUZOOL 14345; right-handed; Selangor, Malaysia); (g, h) CW 14.8 mm (NCHUZOOL 13574; left-handed; Cebu, Philippines). Scale bars = 5.0 mm. (a) (c) (e) (g) (b) (d) (f) (h) page 8 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan are two extant lots labelled as “Gelasimus perplexus” among Heller’s material from Madras (P. C. Dworschak, personal communication). They were all collected by Johann Zelebor who was a staff member during the Novara Expedition. One of these lots (NHMW 25656 and 12980) still carries the original Novara label which states “#74 = AN. 1866.II.74” and contains 100 males and 2 females. The other lot (NHMW 12974), with seven males, does not have the original label but is also part of the expedition material. Although these specimens do not carry the name “Gelasimus variegatus”, it is quite clear that they are part of the type Fig. 5. Outer and inner sides of major palm of Austruca variegata (Heller, 1862) (a–d), A. bengali (Crane, 1975) (e, f) and A. triangularis (A. MilneEdwards, 1873) (g, h). (a, b) CW 16.6 mm (ZRC 2001.0853; left-handed; Tamil Nadu, India); (c, d) CW 14.5 mm (ZRC 2017.0917; left-handed; West Bengal, India); (e, f) CW 14.5 mm (NCHUZOOL 14345; right-handed; Selangor, Malaysia); (g, h) CW 14.8 mm (NCHUZOOL 13574; lefthanded; Cebu, Philippines). (a) (c) (e) (g) (b) (d) (f) (h) page 9 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Major chela slender .................................................................... 2 2. Anterolateral margins absent. Orbital floor without tubercles. Major cheliped with proximal predactylar ridge long and strong. Major cheliped yellowish orange, no speckles; ambulatory legs without mottles or banding ........................................... A. bengali – Anterolateral margins very short. Orbital floor with tubercles in females and males (at least on minor side). Major cheliped with proximal predactylar ridge short and the tubercles fewer or, rarely, absent. Major cheliped pale brown, covered with brown speckles; ambulatory legs with banding (dark ground with paler bands) .................................................................... A. triangularis Fig. 11. The live coloration of Austruca triangularis (A. Milne-Edwards, 1873). (a–d) dorsal view of adult male; (e, f) dorsal view of juvenile male; (g, h) frontal view of adult male. (a, g) NCHUZOOL 14347 (140716, Bali, Indonesia); (b, h) male (CW 11.5 mm, NCHUZOOL 14349; Cebu, Philippines); (c, d) specimens lost (Baoli River estuary, Pingtung, Taiwan); (f) NCHUZOOL 14346 (Labuan, Malaysia). (a) (c) (e) (g) (b) (d) (f) (h) page 16 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Molecular analyses A 624 bp segment of the 28S, 571 bp segment of 16S, and 658 bp segment of COI from 11 species of the genus Austruca were amplified and aligned (Table 1). The bp differences and nucleotide divergences with the K2P distance of haplotypes, based on 616 bp of COI, of the three species of the A. variegata complex is shown in table 3. With regard to A. variegata, the bp difference and nucleotide divergence within species are ≤ 5 (0.81%) and ≤ 0.82%, respectively; and are ≥ 76 (12.34%) and ≥ 13.7%, respectively, between species (Table 3). Thus, the interspecific divergence is at least 15 times more than intraspecific values, supporting A. variegata as a distinct species. A phylogenetic tree of the combined markers was reconstructed using BI analysis (Fig. 12), with A. variegata as sister to A. triangularis + A. bengali. The haplotype network based on the COI haplotypes (Fig. 13) shows that the three species were separated by 34–42 steps, which is consistent with the large genetic distances among them. DISCUSSION In this study, we formally recognize Gelasimus variegatus Heller, 1862, as a valid species, belonging to the genus Austruca Bott, 1973. This species can be separated from the closely related A. bengali (Crane, 1975) and A. triangularis (A. Milne-Edwards, 1873) by characters of the carapace, orbital floor, major and minor chelae, male first gonopod, vulva (female gonopore), gastric mill, and coloration in life, as well as the genetic data of nuclear 28S rDNA, mitochondrial 16S rDNA and COI. With regard to the molecular evidence, the phylogenetic tree of the three combined markers (Fig. 12) supports A. variegata, A. triangularis and A. bengali as three closely related species. In addition, the interspecific distances of COI among the three species are high (Table 3), which are consistent with most studies of other fiddler crab species from the Indo-West Pacific (Chu et al. 2015; Shih et al. 2018). In southeastern India, A. variegata and A. annulipes are always sympatric (Fig. 9g), but their distributional ranges are different. While A. annulipes is widely distributed from the eastern Indian Ocean to the South China Sea (Shih et al. 2009; Naderloo et al. 2016), A. variegata appears to be limited in the Bay of Bengal. Their different ranges are believed to be related to several factors, including the ocean currents, pelagic larval duration, larval behavior etc. (Young 1995; Levin 2006; López-Duarte et al. 2011; Anger et al. 2015; Chai et al. 2017). Apparently, the two sympatric species are exposed to the same ocean currents in the Table 3. Matrix of percentage pairwise nucleotide divergences with K2P distance (lower-left) and number of bp differences (upper-right) based on 616 bp of COI among specimens (see Table 1) of Austruca variegata, A. bengali and A. triangularis A. variegata A. bengali A. triangularis Av1 Av2 Av3 Av4 Av5 Av6 Av7 Av8 Av9 Ab1 Ab2 Ab3 At1 At2 At3 At4 At5 At6 At7 At8 At9 A. variegata Av1 - 0 1 2 1 2 1 3 1 80 79 78 82 84 84 86 85 84 85 85 84 Av2 0.00 - 1 2 1 2 1 3 1 80 79 78 82 84 84 86 85 84 85 85 84 Av3 0.16 0.16 - 3 2 3 2 4 2 81 80 79 83 85 85 87 86 85 86 86 85 Av4 0.33 0.33 0.49 - 3 4 3 5 3 82 81 80 83 85 85 87 86 85 86 86 85 Av5 0.16 0.16 0.33 0.49 - 3 2 4 2 81 80 79 83 85 85 87 86 85 86 86 85 Av6 0.33 0.33 0.49 0.65 0.49 - 1 5 3 78 77 76 80 82 82 84 83 82 83 83 82 Av7 0.16 0.16 0.33 0.49 0.33 0.16 - 4 2 79 78 77 81 83 83 85 84 83 84 84 83 Av8 0.49 0.49 0.65 0.82 0.65 0.82 0.65 - 4 79 78 77 80 82 82 84 83 82 83 83 82 Av9 0.16 0.16 0.33 0.49 0.33 0.49 0.33 0.65 - 81 80 79 81 85 83 85 84 83 84 84 83 A. bengaliAb1 14.53 14.53 14.74 14.95 14.74 14.12 14.33 14.33 14.74 - 2 6 83 82 83 85 84 85 84 83 83 Ab2 14.33 14.33 14.53 14.74 14.53 13.91 14.12 14.12 14.53 0.33 - 4 81 80 81 83 82 83 82 82 81 Ab3 14.12 14.12 14.33 14.53 14.33 13.70 13.91 13.91 14.33 0.98 0.65 - 80 79 80 82 81 82 81 81 80 A. triangularis At1 14.94 14.94 15.15 15.15 15.15 14.52 14.73 14.52 14.73 14.99 14.58 14.38 - 6 4 4 3 6 5 9 4 At2 15.36 15.36 15.57 15.57 15.57 14.94 15.15 14.94 15.57 14.79 14.38 14.17 0.98 - 4 4 3 6 5 9 4 At3 15.36 15.36 15.57 15.57 15.57 14.94 15.15 14.94 15.15 14.99 14.58 14.38 0.65 0.65 - 2 1 4 3 7 2 At4 15.79 15.79 16.00 16.00 16.00 15.36 15.57 15.36 15.57 15.41 14.99 14.79 0.65 0.65 0.33 - 1 4 3 7 2 At5 15.57 15.57 15.79 15.79 15.79 15.15 15.36 15.15 15.36 15.20 14.79 14.58 0.49 0.49 0.16 0.16 - 3 2 6 1 At6 15.36 15.36 15.57 15.57 15.57 14.94 15.15 14.94 15.15 15.41 14.99 14.79 0.98 0.98 0.65 0.65 0.49 - 5 9 4 At7 15.57 15.57 15.79 15.79 15.79 15.15 15.36 15.15 15.36 15.20 14.79 14.58 0.82 0.82 0.49 0.49 0.33 0.82 - 8 1 At8 15.55 15.55 15.77 15.77 15.77 15.13 15.34 15.13 15.34 14.98 14.78 14.57 1.48 1.48 1.15 1.15 0.98 1.48 1.31 - 7 At9 15.36 15.36 15.57 15.57 15.57 14.94 15.15 14.94 15.15 14.99 14.58 14.38 0.65 0.65 0.33 0.33 0.16 0.65 0.16 1.15 - page 17 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Fig. 12. A Bayesian inference tree of the Austruca variegata complex, with the outgroups of other congeneric species, based on the combined 28S, 16S and COI markers. Values at the nodes are Bayesian posterior probabilities. Fig. 13. Genealogical network for the COI haplotypes observed within the clades of Austruca variegata (Heller, 1862), A. bengali (Crane, 1975) and A. triangularis (A. Milne-Edwards, 1873). Unlabelled hatches indicate inferred haplotypes not found in the sampled population. For haplotype names, see table 1. page 18 of 21Zoological Studies 58: 12 (2019) © 2019 Academia Sinica, Taiwan Bay of Bengal, and their total larval duration (from zoea I to megalopa) is similar (42–43 days; Feest 1969). According to López-Duarte et al. (2011), the estuarine species of fiddler crabs express a stronger circatidal rhythm in vertical swimming by larvae than that of the coastal species, which may explain the different distributional ranges between the coastal A. annulipes and the estuarine A. variegata. More studies on the larval behaviors of the two species will clarify the possible mechanisms of distribution. Acknowledgment: This work and the reinstated species name have been registered with ZooBank under urn:lsid:zoobank.org:pub:054A6462-210D-4D59AD38-F10060BD3645. This study was supported by a grant from the Ministry of Science and Technology (MOST 105-2621-B-005-002-MY3), Executive Yuan, Taiwan, to HTS. We wish to express thanks to Ng Ngan Kee, Zeehan Jaafar, N. Sivasothi, Lee Bee Yan and Tan Siong Kiat, for helping with specimen collection in the field; Peter Davie for loaning specimens of A. triangularis; Min-Yun Liu for helping with the molecular work of 28S; Min-Wan Chen, Kwen-Shen Lee and Chiou-Rong Sheue for SEM work; and PeiYi Hsu for measuring specimens and doing part of the molecular work. Special thanks to Peter C. Dworschak and Sara M. Schnedl of the Naturhistorisches Museum Wien who kindly helped check the collection of Heller and the photos of specimens. We acknowledge the helpful comments on the manuscript from Shane Ahyong. Authors’ contributions: HTS conceived this study, performed the morphological description and the molecular analysis, and drafted the manuscript. PKLN performed the discussion and drafted the manuscript. SR and MP collected and processed the samples, performed the ecological observation, 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 have been deposited in the DNA Data Bank of Japan (DDBJ) database (accession numbers in table 1 in the manuscript). Consent for publication: Not applicable. Ethics approval consent to participate: Not applicable. REFERENCES Akash M, Chowdhury GW. 2017. First record of the Bengal fiddler crab Uca (Austruca) bengali Crane, 1975 (Braychura: Ocypodidae) from Kuakata National Park, Bangladesh. Dhaka Univ J Biol Sci 26:199–203. Alcock A. 1900. Materials for a carcinological fauna of India. No. 6. The Brachyura Catometopa or Grapsoidea. J Asia Soc Bengal 69:279–456. Altevogt R. 1957. Untersuchungen zur Biologie, ökologie und Physiologie Indischer Winkerkrabben. Z Morph Okol Tiere 46:1–110. Anger K, Queiroga H, Calado R. 2015. Larval development and behaviour strategies in Brachyura. 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