Uca (Tubuca) acuta ( Stimpson, 1858 )

Shih, Hsi-Te, Lee, Jung-Hsiang, Ho, Ping-Ho, Liu, Hung-Chang, Wang, Chia-Hsiang, Suzuki, Hiroshi & Teng, Shao-Jyun, 2016, Species diversity of fiddler crabs, genus Uca Leach, 1814 (Crustacea: Ocypodidae), from Taiwan and adjacent islands, with notes on the Japanese species, Zootaxa 4083 (1), pp. 57-82 : 69-70

Uca (Tubuca) acuta ( Stimpson, 1858)

( Figs. 4G, H , 5 , 6A, B )

Gelasimus acutus Stimpson, 1858: 99 [type locality: Macao]; 1907: 105, pl. 14(3). Uca (Deltuca) [ acuta ] acuta acuta — Crane 1975: 25, fig. 61B, pl. 1E–H. Uca acuta acuta — Yamaguchi 1994: 183.

Uca acuta — Jones & Morton 1994: fig. 1, pls. 1A, B, 2A, B. Uca (Tubuca) acuta —Ng et al. 2008: 241 [list].

Material examined. Taiwan: 4 ♂♂ (18.1–20.2 mm), BM 58.162, “ Formosa Is. ”, coll. R. Swinhoe, 1850s . Kinmen Islands: 1 ♂ (21.2 mm) (NCHUZOOL 13996), Wujiang R. estuary, coll. J.- H. Lee, 30 May 2004 ; 1 ♂ (18.8 mm) (NCHUZOOL 13650), Wujiang R. estuary, coll. J.-H. Lee, 21 May 2005; 1 ♂ (11.4 mm) (NCHUZOOL 14602), Wujiang R. estuary, H.-T. Shih & Y.-H. Wang, 7 Mar. 2008.

Distribution. China (including Hainan), Taiwan (including Kinmen), and Vietnam.

Remarks. Four male specimens of Uca acuta (BM 58.162) ( Fig. 4G–H ), collected by R. Swinhoe, with the locality as “ Formosa Is.”, were examined and confirmed by J. Crane in 1963 (see Yamaguchi 1994: 183). Crane (1975), however, did not include this Taiwanese record in her monograph and there have been no additional reports from Taiwan until now (see below). In his visit to Tainan, southwestern Taiwan, in 1858 Swinhoe (1859: 148) mentioned “A species of crab, with one large white claw, dotted the mud like flowers. They were very quick, and off in an instant into their holes”, which is very likely referred to U. acuta , based on the white chela character and muddy habitat. The four specimens of U. acuta collected by R. Swinhoe in the 1850s, should be the oldest specimens of crabs recorded from Taiwan.

The G1 of the specimen from Taiwan (CW 22.2 mm, BM 58.162; Fig. 5A, B ) with tip tapering; thumb subdistal, short, reaching base of anterior flange; inner process small, scarcely reaching flange base, agrees with that from Kinmen (CW 18.8 mm, NCHUZOOL 13650; Fig. 6C ) (also see Crane 1975: fig. 61B; Jones & Morton 1994: fig. 1). Uca acuta and U. arcuata are always sympatric in the field, e.g. Kinmen (this study), Hong Kong ( Jones & Morton 1994), and Vietnam ( Kosuge et al. 1997). It is easier to identify them based on the adult color pattern, but it is difficult to distinguish them after preservation. Crane (1975) and Jones & Morton (1994) have discussed the difference of morphology. Adults of U. arcuata is much larger than adults of U. acuta , with CW ~ 37 mm and ~ 20 mm, respectively. Compared to young individuals of U. arcuata , U. acuta do not has strongly arched carapace but always with posterolateral stria on carapace. The major cheliped of U. acuta with thinner and longer fingers, more slender manus, and smaller tubercles on outer manus of male cheliped, when compared to U. arcuata .

Figures

FIGURE 4. Species of the subgenera Uca (Gelasimus) (A, B), U. (Paraleptuca) (C – F), and U. (Tubuca) (G, H) from Taiwan. A, B, Uca tetragonon (Herbst, 1790), males from Siyu, Penghu; C, D, U. crassipes (White, 1847), male and female from Dongsha Island, respectively; E, F, U. splendida (Stimpson, 1858), male and female from Cingluo, Penghu; G, H, U. acuta (Stimpson, 1858), males from “ Formosa Is. ”, collected by R. Swinhoe (BM 58.162).

FIGURE 5. The G 1 s of specimens from Taiwan (A, B) and Kinmen (C). A, right G 1, mesial view; B, C, distal part of right G 1. A, B, male (CW 22.2 mm), BM 58.162, “ Formosa Is. ”; C, male (CW 18.8 mm), NCHUZOOL 13650, Kinmen, Taiwan.

FIGURE 6. Species of the subgenus Uca (Tubuca) from Taiwan. A, B, Uca acuta, male from Kinmen; C – E, U. arcuata (De Haan, 1835), adult male and juvenile from Guandu, Taipei City (C, E), mating pair from Shengang, Changhua (D); F – H, U. coarctata (H. Milne Edwards, 1852), male from the Yanshuei River estuary, Tainan (F, G) and female from the Baoli River estuary, Pingtung (H).