Tubuca alcocki, Shih, Hsi-Te, Chan, Benny K. K. & Ng, Peter K. L., 2018

Shih, Hsi-Te, Chan, Benny K. K. & Ng, Peter K. L., 2018, Tubucaalcocki, 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, pp. 41-62 : 45-50

Tubuca alcocki sp. n. Figures 3, 4A, C, 5 A–D, 6, 7A, C, E, G

Gelasimus Dussumieri H. Milne Edwards, 1852: 148, pl. 4(12) [part; Malabar, India]; Kingsley 1880: 145 [part; list]; Chandy 1973: 402 [Gulf of Kutch, W India] (not Gelasimus dussumieri H. Milne Edwards, 1852 sensu stricto).

Gelasimus acutus - Alcock 1900: 360-361 [Sunderbunds, Mergui; Andamans; Karachi] (not Gelasimus acutus Stimpson, 1858).

Gelasimus Urvillei - Alcock 1900: 362-363 [Nicobars; Madras; Karachi] (not Gelasimus urvillei H. Milne Edwards, 1852).

Uca angustifrons - Lundoer 1974: 8 [Phuket, SW Thailand]; Ng and Davie 2002: 378 [list; Phuket, SW Thailand] (not Gelasimus signatus var. angustifrons De Man, 1892 = Tubuca bellator (White, 1847)).

Uca (Deltuca) [coarctata] urvillei - Crane 1975: 35, 58-61, figs 8B, 9E, pl. 9C, D [part, Pakistan to southern India]; Frith and Frith 1977a: 100-101 [Phuket, SW Thailand] (not Gelasimus urvillei H. Milne Edwards, 1852).

Uca urvillei - Frith et al. 1976: 14, 19, 23-24, 28 [Phuket, SW Thailand]; Tirmizi and Ghani 1996: 103-105, fig. 39 [Pakistan]; Jaroensutasinee et al. 2003: 1-3 [W Thailand]; Jaroensutasinee and Jaroensutasinee 2004: 534, 538, 540-548 [W Thailand]; Naiyanetr 2007: 133 [list; Thailand]; Saher 2008: 21-22, fig. 2.2, pl. 2.1 [Pakistan]; Dev Roy and Nandi 2012: 218 [Nicobar, India]; Hossain 2015: 203, 1 unnumbered fig. [Bangladesh]; Odhano et al. 2015: 170-171, figs 1-2 [Pakistan] (not Gelasimus urvillei H. Milne Edwards, 1852).

Uca (Deltuca) urvillei - Hogarth 1986: 222-223 [Red Sea]; Price et al. 1987: 456, 464 [Red Sea]; Krishnan 1992: 471-472 [Bombay, India] (not Gelasimus urvillei H. Milne Edwards, 1852).

Uca (Deltuca) dussumieri - Krishnan 1992: 471-472 [Bombay, India] (not Gelasimus dussumieri H. Milne Edwards, 1852)

Uca (Tubuca) urvillei - Beinlich and von Hagen 2006: 10, 14, 25, fig. 7f, k [Thailand; India] (not Gelasimus urvillei H. Milne Edwards, 1852).

Uca (Tubuca) acuta - Trivedi et al. 2015: 27 [Gujarat, India] (not Gelasimus acutus Stimpson, 1858).

Tubuca urvillei - Shih et al. 2016: 159, 174 [part], fig. 12A.

Material examined.

Holotype: ♂ (CW 30.1 mm, CL 17.9 mm; PL 58.2 mm) (ZRC 2017.1278), Ranong mangroves, Thailand, coll. H.-T. Shih et al., 27 May 2012. Paratypes: 2 ♂♂ (CW 22.4-29.9 mm), 1 ♀ (CW 25.1 mm) (NCHUZOOL 13661), 1 ♂ (CW 29.5 mm) (NCHUZOOL 14896), 13 ♂♂ (CW 14.7-31.2 mm), 4 ♀♀ (CW 19.9-24.1 mm), 1 ovig. ♀ (CW 25.7 mm) (NCHUZOOL 14905), same data as holotype; 1 ♂ (CW 24.6 mm), 1 ovig. ♀ (CW 14.8 mm) (ZRC 2017.1279), Kamphuan mangroves, Ranong, Thailand, 9 Sep. 2000; 1 ♂ (CW 24.0 mm) (ZRC 2001.2347), Ranong, Thailand, coll. P. Clark, 7 Nov. 2001.

Other material.

Thailand: 2 ♂♂ (CW 17.8-26.1 mm) (ZRC 1988.616-617), Phuket, coll. D. H. Murphy, 12 Nov. 1987; 2 ♂♂ (CW 20.3-22.4 mm) (ZRC 1999.1131), mangrove area south east of Phuket Town ca. 8 km, W. B. Jeffries and H. K. Voris, 14 June 1990; 4 ♂♂ (CW 13.0-16.9 mm), 1 ♀ (CW 18.8 mm), 1 ovig. ♀ (CW 19.8 mm) (NCHUZOOL 14897), 6 ♂♂ (CW 9.0-12.4 mm), 3 ♀♀ (CW 11.4-14.0 mm), 2 ovig. ♀♀ (CW 13.9-14.8 mm) (NCHUZOOL 14906), Chalong Bay, Phuket, coll. H.-T. Shih et al., 28 May 2012; 4 ♂♂ (CW 4.4-16.9 mm), 1 ♀ (CW 12.8 mm), 1 ovig. ♀ (CW 14.7 mm) (NCHUZOOL 14898), Laem Tukkae, Phuket, coll. H.-T. Shih et al., 29 May 2012; 1 ♂ (CW 17.2 mm), 2 ♀♀ (CW 14.0-15.6 mm) (NCHUZOOL 14907), Tha Thiap Ruea Bang Rong, Phuket, coll. H.-T. Shih et al., 30 May 2012. India: 1 ♂ (CW 17.7 mm) (NCHUZOOL 14925), 1 ♂ (CW 19.0 mm) (NCHUZOOL 14899), 1 ♂ (CW 12.6 mm) (NCHUZOOL 14901), 1 ♀ (CW 17.5 mm) (NCHUZOOL 14902), 13 ♂♂ (CW 9.9-18.2 mm), 3 ♀♀ (CW 11.4-17.9 mm), 1 ovig. ♀ (CW 19.9 mm) (NCHUZOOL 14903), Mumbai, coll. H.-N. Chen et al., 17 Mar. 2010; 1 ♀ (CW 22.6 mm) (NCHUZOOL 14900), Diu mangroves, coll. K. Wong, 20 Mar. 2010.

Diagnosis.

Male. Carapace (Figs 3A, 4A, 6A, C, G, 7A, C, E) trapezoidal, smooth; front narrow, with distinct, narrow median groove; anterolateral angle acutely triangular, directed obliquely anteriorly; anterolateral margin short to moderately long; dorsolateral margin long, definite, strongly converging; one posterolateral stria. Floor of orbit with row of 5-11 tubercles, sometimes with blunt ridge. Major cheliped (Figs 4C, 6B, D) with dactylus usually longer than palm, outer surface of dactylus and pollex each with 1 long groove proximally extending beyond midlength. Fingers of minor cheliped (Figs 3B, D, 6B, D) without conspicuous tooth on either finger. G1 (Fig. 5 A–D) with distal tube slender, slightly curved to almost straight, distal and proximal parts subequal in width; thumb of moderate length, extending beyond base of distal tube.

Female. Anterolateral angle more broadly triangular; anterolateral margin moderately long, joining dorsolateral margin as convex structure (Fig. 7G). Floor of orbit with row of 17-19 tubercles (Figs 3F, 6F). Fingers of cheliped (Fig. 3E, F) each with conspicuous tooth on occlusal margin.

Colouration in life.

Adults with carapace and legs brown or dark brown, posterior part gray, especially in females (Fig. 6A, C, E). Some females with anterolateral angles orange (Fig. 6E, F) or with dark blotches on blue carapace (Fig. 6G). Major cheliped with fingers white; lower palm deep yellow in large individuals, orange in young individuals; upper palm brown (Fig. 6 B–D). Females sometimes with minor chelipeds orange, sometimes with tint of blue (Figs 3F, 6F, G).

Ecological notes.

In western Thailand, this species inhabits muddy banks of mangroves (Fig. 6H) and is sympatric with several species of fiddler crabs, including Austruca annulipes (H. Milne Edwards, 1837), A. bengali , Tubuca forcipata (Adams & White, 1849) and T. paradussumieri (cf. Frith and Frith 1977a, 1978; this study). In Pakistan, this species is sympatric with Austruca iranica (cf. Saher et al. 2014).

Etymology.

This species is named after Alfred William Alcock, who first recorded this species from India and Pakistan as " Uca urvillei " (cf. Alcock 1900).

Distribution.

Western Thailand, India, Pakistan, and the Red Sea (see Remarks).

Remarks.

Although the number of tubercles on the floor of orbit and thumb morphology of G1 are sometimes useful for distinguishing species of fiddler crabs, they are too variable in Tubuca alcocki sp. n. and T. urvillei ( Crane 1975: 58-59; this study) to be used. The two species are similar, but can be morphologically distinguished by the characters of the anterolateral angle of the carapace and G1. The anterolateral angle in male T. alcocki is acutely triangular and directed obliquely anteriorly (Fig. 7A, C, E) (vs. relatively broadly triangular in shape and directed more laterally in position in T. urvillei ; Fig. 7B, D, F). In female T. alcocki , the anterolateral angle is broadly triangular in shape and the anterolateral margin is relatively longer and curves gently to join the dorsolateral margin (Fig. 7G) (vs. anterolateral angle acutely triangular in shape with the anterolateral margin short and merging with the dorsolateral margin in an almost straight line in T. urvillei ; Fig. 7H). The G1 structure is also different. The distal tube of the G1 of T. alcocki is proportionately more slender, being slightly curved to almost straight, with the widths of the distal and proximal parts subequal (Fig. 5 A–D) (vs. distal tube relatively stouter, more distinctly curved and gently tapering towards the tip, with the distal part distinctly narrower than the proximal part in T. urvillei ; Fig. 5 E–H).

Crane (1975) figured specimens of what she referred to as T. urvillei from southeastern Africa and western India, and they agree with the characters of T. urvillei and T. alcocki , respectively. The anterolateral angles of the male lectotype of T. urvillei (Fig. 1A; Crane 1975: pl. 9E) and the male specimen from Tanzania ( Crane 1975: fig. 7A) are both broadly triangular. In addition, the G1 distal tubes of the lectotype of T. urvillei as well as those from Somalia and Madagascar figured by Vannini and Valmori (1981: fig. 6F) and Crosnier (1965: figs 195-196) are all relatively stout, curved and tapering towards the tip. As such the material from Tanzania, Somalia and Madagascar should all be referred to T. urvillei sensu stricto.

The specimen from Malabar, western India, and one of the paralectotypes of Gelasimus dussumieri (see discussion earlier), have the G1 distal tube relatively more slender, almost straight, with the distal and proximal parts subequal in width ( Crane 1975: fig. 9E) and are thus is clearly referable to T. alcocki . The G1 structures of specimens from Pakistan ( Saher 2008: fig. 2.2; Tirmizi and Ghani 1996: fig. 39) also match that of T. alcocki . Interestingly, Hogarth (1986) reported " Uca (Deltuca) urvillei " from the Red Sea, which was a new record of this species for this region, but without any figure or description. The first author has examined specimens from the Red Sea and they are clearly T. alcocki as well (H-T Shih and BA Kumar, in preparation). The distribution of T. alcocki thus stretches from the northern part of the Indian Ocean (Red Sea) to the Arabian Sea and Andaman Sea.

There are also colour differences between T. urvillei and T. alcocki . While the colouration of females, young males, and juveniles are variable in Tubuca species, the colouration of the adult male carapace is generally more useful ( Crane 1975; von Hagen and Jones 1989; Beinlich and von Hagen 2006). Adult male T. urvillei sensu stricto have various degrees of blue on the carapace and ambulatory legs (Fig. 2D, E), with the palm of the major cheliped ochraceous to apricot brown (Fig. 2D); while young and females sometimes have pale and dark blotches on a blue background (Fig. 2F). In adult male T. alcocki , the dorsal surface of the carapace is always dark brown (Fig. 6A, C) whereas in T. urvillei , it is always blue (Fig. 2D, E).