Tetralia glaberrima (Herbst, 1790)

(Fig. 3A–F, 4A–B)

Cancer glaberrimus Herbst, 1790: 262, pl. 20 fig. 115.

Tetralia glaberrima . — Castro et al. 2004: 25, pl. 1D, E, 2A (list).—Machida 2005: 22, fig. 3 (Tosa shimizu).— Castro & Godwin 2006: 54. — Liu et al. 2008: 791 (list).—Castro & Titelius 2008: 320.— Ng et al. 2008: 184 (list).— Castro 2009: 277, fig. 2F (the Philippines).— Limviriyakul 2016: 4, fig. 4j (list) (Taiwan Island).— Maenosono 2017: 40, fig. 2A, C, 8A, B (the Ryukyus).— Poupin, 2018: 37, fig. 12D (Mayotte Island).

Tetralia fulva Serène, 1984: 282 .—Galil 1988: 62 (western New Guinea).— Castro 1997a: 65, pl. 1C (Vanuatu).— Castro 1997b: 112 (Polynesia); 1999a: 40 (Indonesia); 1999b: 101; 2003: 441.

Tetralia glaberrima laevissima Stimpson, 1858: 38 .

Tetralia laevissima Stimpson, 1858: 38; 1907: 74, pl. 9 figs. 4, 4a.

Tetralia glaberrima f. fulva Patton, 1966: 286 .

Tetralia glaberrima fulva Serène, 1984: 282 .

Tetralia sanguineomaculata Galil & Clark, 1990: 375, figs. 4, 5, 6b.

Material examined. Nansha Islands: Mischief Reef, 115°32.5’E 9°55.7’N, 11 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 5 May 2022, 1 pre-adult (3.73 × 3.22 mm), NS-MJJ-2022-1103; 115°29.8’E 9°54.4’N, 13 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 6 May 2022, 1 male (6.05 × 4.88 mm), NS-MJJ-2022-1209; 1 female (5.83 × 4.81 mm), NS-MJJ-2022-1210; 1 megalopa (1.38 × 1.78 mm), NS-MJJ-2022-1254; 1 pre-adult (3.09 × 2.46 mm), NS-MJJ-2022-1319; 1 male (7.54 × 6.95 mm), NS-MJJ-2022-1320; 1 female (8.01 × 7.22 mm), NS-MJJ-2022- 1321; 1 male (5.85 × 5.14 mm), NS-MJJ-2022-1322; 1 female (5.48 × 4.76 mm), NS-MJJ-2022-1323; 115°31.3’E 9°52.6’N, 8 m, 7 May 2022, 1 pre-adult (3.18 × 2.5e 7 mm), NS-MJJ-2022-1411; 1 male (7.32 × 6.71 mm), 1 female (7.89 × 7.05 mm); NS-MJJ-2022-1449; 115°33.6’E 9°53.0’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 8 May 2022, 2 males (6.80 × 6.18 mm; 9.10 × 8.12 mm), 2 females (8.28 × 7.51 mm; 9.10 × 7.56 mm), NS-MJJ-2022- 1520; 1 pre-adult (3.02 × 2.38 mm); NS-MJJ-2022-1561; 115°33.8’E 9°52.9’N, 8 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 9 May 2022, 1 male (8.92 × 8.34 mm); NS-MJ-2022-1637; 115°34.4’E 9°53.5’N, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 8 m, 11 May 2022, 1 male (8.56 × 7.97 mm), 1 female (8.84 × 8.20 mm); NS-MJ-2022-1862; 1 male (6.44 × 6.12 mm), 1 female (7.14 × 6.51 mm), NS-MJ-2022-1869. Fiery Cross Reef 112°58.6’E 9°38.7’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 12 May 2022, 9 juveniles (2.40 × 2.12 mm; 2.06 × 1.53 mm; 2.12 × 1.74 mm; 2.38 × 1.99 mm; 1.96 × 1.49 mm; 2.22 × 1.92 mm; 2.02 × 1.68 mm; 1.87 × 1.38 mm; 2.18 × 1.96 mm), NS-YS-2022-1058; 112°58.9’E 9°39.5’N, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 3 m, 13 May 2022, 1 male (7.03 × 6.42 mm), 1 female (7.99 × 7.15 mm), NS-YS-2022-1091; 113°0.8’E 9°39.9’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 14 May 2022, 1 male (7.30 × 6.74 mm), 1 female (6.87 × 6.48 mm), NS-YS-2022-1270. — Zhongsha Islands: Margesson Shoal, 114°38.7’E 15°55.3’N, 20 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 17 May 2022, 1 male, 1 pre-adult (4.83 × 4.32 mm), ZS-NF-2022-1019. — Xisha Islands: The Seven Connected Islets, 112°16.2’E 16°58.0’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 19 May 2022, 1 male (6.80 × 6.02 mm), 1 female (6.60 × 5.88 mm), XS-QL-2022-1006; 1 pre-adult (3.46 × 3.18 mm), XS-QL-2022-1016; 1 male (4.50 × 4.21 mm), 1 female (4.24 × 4.06 mm) ， XS-QL-2022-1022; 1 pre-adult (3.34 × 2.95 mm), XS-QL-2022-1055; 112°19.6’E 16°57.1’N, 10 m, coll. Shaobo Ma, Yuli Sun, Ziming Yuan, 21 May, 1 female (5.07 × 4.28 mm), XS-QL-2022-1088; 1 pre-adult (3.69 × 3.22 mm), XS-QL-2022-1153; 10 m, coll. Shaobo Ma, May 2019, 1 male (5.83 × 5.30 mm), 1 female (6.72 × 5.92 mm), 1 pre-adult (3.44 × 3.02 mm), M911. — Hainan Island: Lu Hui Tou, 3 m, coll. Yuli Sun, 29 November 2022, 1 male (5.32 × 5.00 mm), 1 female (5.82 × 4.74 mm), XY1101. Xin Cun, 21 December 2007, coll. Xianqiu Ren, 2 males (6.62 × 5.81 mm; 6.98 × 6.09 mm), 2 females (7.08 × 6.45 mm; 7.15 × 6.49 mm), 3271. Xiao Dong Hai, 2–3 m, coll. Lecheng Qu, 5 December 2021, 1 female (5.63 × 5.09 mm), 2 females (5.98 × 5.22 mm; 6.00 × 5.24 mm), SYDH. Hou Hai, 2–3 m, coll. Yuli Sun, 25 July 2022, 1 female (4.90 × 4.47 mm), SY72; 1 male (4.55 × 4.13 mm), SY74. All found in Acropora sp. ( Acroporidae).

Geographical distribution. Across Indo-West Pacific (Castro et al. 2004; Castro & Godwin 2006)

Remarks. Tetralia glaberrima is one of the most common coral symbionts in the South China Sea. This species has two distinct color patterns, one with a uniform orange body (Fig. 3A, NS-MJ-2022-1520) and the other with an almost white body (Fig. 3C, E, XY1101). The orange color pattern is the most common phenotype, which has several black spots at the dorsal propodal-dactylar articulation on all pereopods (Fig. 3A). The white color pattern has a conspicuous black band across frontal margin of the white carapace and only one black spot between the dactylus and the propodus on all pereiopods (Fig. 3C, E), which resembles juvenile or pre-adult specimens of Tetralia nigrolinea . The white color pattern of Te. glaberrima lacks a line of vivid brilliant blue color that delimit the black frontal band posteriorly, and with spines on the anterior margin of the merus of the cheliped are developed as long and sharp (Fig. 4A, XY1101; Fig. 4B, XS-QL-2022-1006) rather than granules in Te. nigrolineata (Fig. 4C, XY1102; Fig. 4D, SY24), which are the key features that distinguish Te. glaberrima from Te. nigrolinea . The width of carapace of the white-pattern individuals is around 5 mm, significantly smaller on average than those of the orange pattern, but they can be identified as adults by the size of ovigerous females. The white pattern is found more frequently in water less than 3 m in Hainan Island. The phylogenetic tree (Fig. 11) and genetic distance (Table 3) indicate minimal genetic divergence between the orange pattern (Fig. 11, NS-MJ-2022-1520) and white pattern (Fig. 11, M911).