Thranita cerasma ( Wee & Ng, 1995 )

Huang, Yu-Hsuan & Shih, Hsi-Te, 2021, Chthonius rhodochelatus Hadzi 1933, Zoological Studies 60 (60), pp. 1-45 : 28-31

Thranita cerasma ( Wee & Ng, 1995) ( Figs. 4E , 17 )

Thalamita cerasma Wee & Ng, 1995: 62 , figs. 30–32 (type locality: Singapore); Ng et al. 2008: 154 (list).

Thalamita cerasma rectifrons – Crosnier and Moosa 2002: 395 , figs. 6, 7A, C–F, H–J ( French Polynesia: Austral Is. and Society Is.).

Thalamita cerasma cerasma – Naruse and Shokita 2003: 43, figs. 2, 3 ( Japan: Ryukyus).

Thranita cerasma – Evans 2018: 43 (list); Sasaki 2019: 9281 (list).

Thranita cf. cerasma – Shih et al. 2020b: 36 (Dongsha I.).

? Thalamita cerasma – Takeda and Marumura 1997: 16, fig. 1C, D ( Japan: Kii Peninsula: Shirahama: Tanabe Bay).

Material examined: Taiwan: 1 male (44.5 × 28.9 mm), 1 female (59.7 × 38.8 mm) (NCHUZOOL 16509), Dongsha I. (20°42'26.3"N 116°43'16.3"E), coll. YH Huang and CY Chi, 2 Nov. 2019; 1 female (35.1 × 24.8 mm) (NCHUZOOL 16526), Dongsha I. (20°42'26.3"N 116°43'16.3"E), coll. YH Huang and CY Chi, 23 Sep. 2019; 1 male (16.3 × 11.0 mm) (NCHUZOOL 16527), Dongsha I. (20°42'3.1"N 116°43'4.4"E), coll. YH Huang and CY Chi, 16 Aug. 2019; 1 male (20.1 × 13.5 mm) (NCHUZOOL 16528), Dongsha I. (20°42'23.1"N 116°43'37.7"E), coll. YH Huang and K Chang, 5 Nov. 2019; 1 male (38.5 × 23.7 mm), 1 female (26.8 × 17.5 mm) (NCHUZOOL 16529), Dongsha I. (20°42'26.3"N 116°43'16.3"E), coll. YH Huang and CY Chi, 3 Nov. 2019; 3 females (22.2– 66.4 × 14.4–42.6 mm) (NCHUZOOL 16537), Dongsha I. (20°42'26.3"N 116°43'16.3"E), coll. YH Huang and CY Chi, 25 Sep. 2019.

Diagnosis: Carapace subhexagonal, 1.5–1.6 times broader than long, with broadest between anterolateral tooth 3, surface smooth. Frontal, protogastric and epibranchial regions each with a pair of ridges; mesogastric and metagastric ridges unbroken; mesobranchial and cardiac ridges absent ( Fig. 17A ). Front with 6 lobes. Supraorbital margins with 2 notches, inner lobe arched ( Fig. 17A ). Inner infraorbital lobes ending at acute angle. Anterolateral margins with 5 teeth, first 3 teeth large, tooth 4 smaller than 5 ( Fig. 17A ). Basal antennal segment with 2–3 sharp spines. Chelipeds slightly unequal; merus with 3 sharp spines on inner margin, a spinule each on distal end of dorsal and ventral surfaces near articulation of carpus; carpus with granules on dorsal surface, 1 strong spine on inner margin, 3 smaller spines on outer margin; palm with 5 sharp spines on dorsal surface, outer surface with 1 ridge, inner surface smooth. P5 with merus having strong spine on inner margin, distal end with small spine; propodus with inner margin serrated. G1 stout, with distal part gradually curved ( Fig. 17B–E ).

Coloration in life: Carapace and chelipeds bright orange; P2–P4 green, joints orange, dactylus white with

5 mm 1 mm 5 mm

pink stripes; P5 with dactylus green, border orange ( Fig. 4E ).

Distribution: French Polynesia; Taiwan (Dongsha I.; Fig. 1 : no. 17); Japan (Ryukyus); Malaysia; Singapore ( Sasaki 2019; this study).

Ecological notes: The habitat is the shallow subtidal zone of coral reefs and seagrass beds. Adult specimens were collected from around the corals ( Porites ) in the shallow subtidal zone, and the juveniles were found on the seagrass beds.

Remarks: Thranita cerasma ( Wee & Ng, 1995) is similar to Thr. rubridens ( Apel & Spiridonov, 1998) , with Thr. cerasma distributed in the Pacific Ocean ( Sasaki 2019) and Thr. rubridens restricted in the Arabian Gulf ( Apel and Spiridonov 1998). The specimens from Taiwan agree with Thr. cerasma by the following characters: (1) P2–P4 green with joints orange in Thr. cerasma ( Fig. 4E ; Naruse and Shokita 2003: fig. 2a) (vs. P2–P4 uniformly orange with joints pink in Thr. rubridens ; Apel and Spiridonov 1998: pl. 9); (2) G1 with distal part stout, tip with setae on lateral and mesial sides in Thr. cerasma ( Fig. 17B–E ; Wee and Ng 1995: fig. 32C–E) (vs. distal part slender, tip with setae on lateral side in Thr. rubridens ; Apel and Spiridonov 1998: figs. 79a–c, 80, 81); (3) basal antennal segment with elongated spines ( Wee and Ng 1995: fig. 32F) (vs. with short spines in Thr. rubridens ; Apel and Spiridonov 1998: fig. 78a). With regard to the specimens identified as Thr. cerasma in Takeda and Marumura (1997: fig. 1C, D) with whole body orange and joints pink, which is similar to Thr. rubridens ( Apel and Spiridonov 1998: pl. 9) and may not belong to Thr. cerasma .

Figures

Fig. 4. Species of the family Portunidae. A, Thalamita gatavakensis Nobili, 1906, male (16.5 × 9.3 mm) (NTOU), Mao-ao, New Taipei City; B, Thalamita spinifera Borradaile, 1902, female (12.6 × 9.0 mm) (NCHUZOOL 16531), Erzihliao Fishing Port, Kaohsiung; C, Thalamitoides quadridens A. Milne-Edwards, 1869, male (25.4 × 13.3 mm) (NTOU), Sansiantai, Taitung; D, Thalamitoides tridens A. Milne-Edwards, 1869, female (16.1 × 8.2 mm) (NCHUZOOL 16520), Dongsha I.; E, Thranita cerasma (Wee & Ng, 1995), female (66.4 × 42.6 mm) (NCHUZOOL 16537), Dongsha I.; F, Thranita coeruleipes (Hombron & Jacquinot, 1846), male (59.7 × 40.5 mm) (NCHUZOOL 16507), Wanlitong, Kenting, Pingtung.

Fig. 17. Thranita cerasma (Wee & Ng, 1995), male (44.5 × 28.9 mm). A, carapace; B–E, right G1; B, C, dorsal view; D, E, ventral view.

Fig. 1. Taiwan main island and adjacent islets, with the collection localities shown in gray circles (see Table 1).