Gothus teemo sp. nov., by present designation.

Small species, CW under 10 mm. Carapace broader than long, dorsal surface bearing round granules, regions clearly defined; front wide, not protruding, divided into two slightly triangular lobes by a V-shaped notch; frontal lobes and dorsal inner orbital angle separated by shallow depression; eyestalks densely granulated; area beneath outer orbital angle slightly concave, not forming a subhepatic cavity; anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth; posterolateral margin almost straight; subhepatic region densely granulated.

Epistome central region with low median projection on posterior margin. Maxilliped 3 granulated, anterior edge of merus indented, external terminal angle expanded. Antennule folding transversely; basal segment of antenna subrectangular; contacting ventral external frontal margin and ventral internal orbital angle; antennal flagellum filling orbital hiatus.

Chelipeds symmetrical, merus short; carpi robust, surface granulated, aggregated into nodules; outer and dorsal surfaces of palm densely granulated; fingers elongated, with triangular teeth; tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granulated ridges. Fingers brownish-black, coloration of immovable finger extending onto inner and outer surfaces of palm in male.

Ambulatory legs with meri flattened, granulated along anterior and posterior edges; dactyli elongated, margins with granules and setae, terminal end chitinous, sharp, slightly curved backward, dactylo-propodal lock present but underdeveloped.

Male thoracic sternum with sternites 1 and 2 completely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, suture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tubercle of sterno-pleonal lock located on posterior of sternite 5. Male pleon narrow, pleonites 3 to 5 completely fused, lateral margins of pleonite 6 slightly concave. Telson long, broad, truncated oval, base margin wider than terminal margin of pleonite 6.

G1 slender, curving slightly outward, distal lobe spoon-shaped, long setae on inner subdistal part, small spines on outer part. G2 not exceeding 1/6 length of G1, distal lobe elongated.

The genus is named after the game of Go, alluding to the intermingled black and white patterns on the carapace, beneath which lie circular granules resembling the pieces of the game. “-thus” is a common suffix for species names within the Xanthidae family. Gender masculine.

Rizalthus anconis Mendoza & PKL Ng, 2008 (Fig. 6A). China • 1 female; CW 4.2 mm, CL 2.7 mm; Meiji Reef, Nansha Islands; 9°52'38.19"N, 115°31'17.08"E; 8 m; 7 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-MJ-2022-1457.

Hypocolpus haanii Rathbun, 1909 (Fig. 6B). China • 1 male; CW 45.3 mm, CL 34.2 mm; Lingao Cape, Hainan Island; 15–30 m; 20 Aug. 2018; Yunhao Pan coll.; MBM286755.

Euxanthus exsculptus (Herbst, 1790) (Fig. 6C). China • 1 male; Wenchang, Hainan Island; 20 Dec. 2018; Yunhao Pan coll.; Xan016 • 1 male; Yongxing Island, Xisha Islands; 15–17 May 1957; MBM163793 • 2 males; Wood Island, Xisha Islands; 1957; MBM163791 • 1 male, 2 females; Wood Island, Xisha Islands; 15–17 May 1957; MBM163788 • 3 males, 3 females; East Island, Xisha Islands; 28–31 May 1980; MBM163785 • 1 female; Yongxing Island, Xisha Islands; 11–13 Jun. 1980; MBM163784 • 1 female; East Island, Xisha Islands; 12 Jun. 1975; Xianqiu Ren coll.; MBM163792. CW 15–52.8 mm, CL 9.7–33.2 mm.

Euxanthus huonii (Hombron & Jacquinot, 1846) (Fig. 6D). China • 1 male; Dengqing Island, Xisha Islands; 11–17 Apr. 1958; MBM163762 • 1 female; Tree Island, Xisha Islands; 1 May 1958; MBM163761 • 1 female; Yongxing Island, Xisha Islands; 7 May 1980; MBM163780 • 2 females; Drummond Island, Xisha Islands; 1980; MBM163781 • 1 male; Meiji Reef, Nansha Islands; 9°53'30.84"N, 115°34'22.05"E; 10 m; 10 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-MJ-2022-1734. CW 19.3–37.3 mm, CL 13.1–26.4 mm.

Psaumis cavipes (Dana, 1852) (Fig. 6E). China • 1 female ovigerous; Xisha Islands, Jinqing Island; 10 Jul. 2019; azp01 • 1 male, 3 females; Sanya Station Front, Hainan; 30 Apr. 2021; Zhang Xu coll.; aop01 • 2 males; Xisha Islands, Yongle blue hole; 10 Jul. 2019; aop02 • 1 female ovigerous; Xisha Islands, Yongle blue hole; 10 Jul. 2019; aop03 • 1 male; Phoenix Island, Sanya, Hainan; Zhang Xu coll.; 2022010 • 1 juvenile; Xisha Islands, Yuzhuo Reef; 9 Jul. 2019; aop04 • 2 males; Hainan, subtidal 9–10 m; 21 Nov. 2016; Xan020-2. CW 5.1–17.4 mm, CL 3.3–10.6 mm

Gothus gen. nov. exhibits the closest resemblance to the subfamily Euxanthinae, particularly to Eux 1, as defined and morphologically summarized in the molecular systematic study by Lai et al. (2011)., mainly considering its anterolateral margin of the carapace, which does not clearly meet the orbit but instead continues down to the subhepatic region, presenting an ambiguous starting point (Fig. 1B). Other characteristics justifying its inclusion are chelipeds almost completely symmetrical, which can be coapted against the carapace (Fig. 1A); male pleon long, with the telson reaching to the level above the coxo-sternal condyles of pereiopod 1, and base of somite 3 only slightly wider than tip of somite 5 (Figs 2F, 3F) (see also Serène, 1984; Lai et al. 2011). However, its ambulatory legs do not form a similar perfect coapted structure, especially since the corresponding posterolateral margin is nearly non-concave (Fig. 1A, C). Other features notably distinguishing it from any member of the subfamily Euxanthinae are its extremely narrow male pleon with a long and broad, overall truncated oval telson (Figs 2F, 3F), the base of which is wider than the width of the end of the sixth pleonite, the terminal end wide and rounded, with the lateral edges barely converging inward but rather forming two opposing arcs, unlike the typically triangular telson common in the Euxanthinae.

Figure 1. 

Gothus teemo sp. nov. A–C. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; D–F. Paratype, CW 3.2 mm, CL 2.2 mm, MBM287026; A, D. Dorsal view; B, E. Frontal view; C, F. Carapace. Scale bar: 1 mm.

Figure 2. 

Gothus teemo sp. nov. A, C, E. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; B, D, F, G. Paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026; A. Male chelipeds; B. Female chelipeds; C. Male thoracic sternites; D. Female thoracic sternites; E. Male pleon; F. Female pleon; G. Female vulva. Scale bar: 1 mm (A–F); 0.2 mm (G).

Figure 3. 

Gothus teemo sp. nov. A–C, F, G–L. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; D, E. Paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026; A. Carapace; B. Maxilliped 3; C. Cheliped; D. Pereopod 5; E. Female pleon; F. Male pleon; G. right G1, ventral view; H. Same, dorsal view; I. Right G1, distal part, ventral view; J. Same, dorsal view; K. Right G2, ventral view; L. Same, dorsal view. Scale bar: 1 mm (A, C, D); 0.5 mm (B, E, F, G, H); 0.1 mm (I–L).

Gothus gen. nov. shares the closest similarities with the genus Rizalthus Mendoza & PKL Ng, 2008, due to both possessing a granule-covered carapace surface, similar carapace outlines and front, developed cheliped carpus, and analogous G1 structures. However, Gothus can be easily distinguished from Rizalthus by several key characteristics: its anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (vs. no clearly defined teeth in Rizalthus; Fig. 6A; cf. Mendoza and Ng 2008: fig. 1A); absence of etched depressions on body (Fig. 1A) (vs. distinct etched depressions on thoracic sternum in Rizalthus; cf. Mendoza and Ng 2008: fig. 1C); central part of epistome raised (Fig. 1B) (vs. central part of epistome not protruding in Rizalthus; cf. Mendoza and Ng 2008: fig. 1B); robust cheliped carpus, sometimes slightly expanded (Fig. 1A) (vs. strongly expanded and protruding in Rizalthus; Fig. 5A; cf. Mendoza and Ng 2008: fig. 1A); male pleon with a long, broad, truncated oval telson (Figs 2F, 3F) (vs. a smaller, triangular telson in Rizalthus; cf. Mendoza and Ng 2008: fig. 2C); G1 distal lobe curved inwards (Fig. 3G–J) (vs. nearly straight, not curved inwards in Rizalthus; cf. Mendoza and Ng 2008: fig. 2F–H) and G2 with a longer, straighter distal lobe (Fig. 3K, L) (vs. shorter and curved in Rizalthus; cf. Mendoza and Ng 2008: fig. 2I).

Due to its similar carapace outline, particularly the less concave posterolateral margins, Gothus also resembles Visayax Mendoza & Ng, 2008. However, it can be easily differentiated by the following characteristics: Gothus lacks erosive depressions across body (Fig. 1A) (vs. chelipeds, ambulatory legs, carapace, and thoracic sternum with erosive depressions in Visayax; cf. Mendoza and Ng 2008: figs 3–6); carapace regions more flattened (Fig. 1A, C) (vs. carapace regions more pronounced in Visayax; cf. Mendoza and Ng 2008: figs 3A, C, 5A, C); posterior three teeth on anterolateral margin of carapace well-developed (Fig. 1A, C, 3A) (vs. absence of developed teeth on anterolateral margin in Visayax; cf. Mendoza and Ng 2008: figs 3A, 5A); male abdominal telson larger, truncated oval (Figs 2F, 3F) (vs. smaller, semi-circular in Visayax; cf. Mendoza and Ng 2008: figs 4E, 6D); G1 more slender (Fig. 3G–J) (vs. G1 more robust in Visayax; cf. Mendoza and Ng 2008: figs 4F, G, 6F, G).

Figure 4. 

Gothus teemo sp. nov. A, B. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; C–E. Paratypes, 2 juvenile, CW 1.8–2.2 mm, CL 1.3–1.5 mm, MBM287023; A–D. Live coloration; E. Habitat and substrate conditions. Scale bar: 1 mm.

Figure 5. 

Gothus teemo sp. nov., paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026, artistic illustration, displaying live coloration. Drawn by Fei Gao.

Figure 6. 

Euxanthinae and Actaeodes species in comparative material. A. Rizalthus anconis Mendoza & PKL Ng, 2008, female; CW 4.2 mm, CL 2.7 mm, NS-MJ-2022-1457; B. Hypocolpus haanii Rathbun, 1909, 1 male, CW 45.3 mm, CL 34.2 mm, MBM286755; C. Euxanthus exsculptus (Herbst, 1790), 1 male, CW 52.6, CL 33.2 mm, MBM163793; D. Euxanthus huonii (Hombron & Jacquinot, 1846), CW 34.0 mm, CL 24.0 mm, NS-MJ-2022-1734; E. Psaumis cavipes (Dana, 1852), 1 male, CW 13.8 mm, CL 8.6 mm, aop01; F. Actaeodes mutatus Guinot, 1976, 1 female, CW 20.8 mm, CL 12.5 mm, BF02; G. Actaeodes hirsutissimus (Rüppell, 1830), 1 male, CW 31.9 mm, CL 21.0 mm, MBM164298; H. Actaeodes tomentosus (H. Milne Edwards, 1834), 1 male, CW 35.8 mm, CL 22.5 mm, Xan041. Scale bar: 1 mm (A); 5 mm (E, F); 10 mm (B–D, G, F).

The new genus exhibits a general morphological similarity to typical Euxanthinae members such as Euxanthus Dana, 1851, and Hypocolpus Rathbun, 1897. In addition to the existing comparative specimens, Guinot-Dumortier (1960) provided excellent descriptions and photographs of species from the above two genera. Subsequently published species also have relatively clear morphological descriptions and images available for comparison (cf. Guinot 1971b; Galil and Vannini 1990; Crosnier 1996). The new genus can be easily distinguished from Euxanthus by the following features: entire body covered with granules and short pubescence (Fig. 1A) (vs. relatively smooth in Euxanthus; Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. IX, figs 48–52); carapace anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (vs. 4–6 teeth on anterolateral margin in Euxanthus; Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. IX, figs 48–52); front not prominent, divided by a V-shaped notch (Figs 1C, 3A) (vs. more protruding, divided by a narrow fissure in Euxanthus; Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. IX, figs 48–52); male abdominal telson large and truncated oval (Figs 2F, 3F) (vs. small and triangular in Euxanthus; cf. Guinot-Dumortier 1960: pl. VIII, fig. 47); G1 with a prominent, spoon-shaped distal lobe, and long setae on inner subdistal part (Fig. 3G–J) (vs. G1 with a short, non-protruding distal lobe, inwardly curved and encircling, with short setae on inner subdistal part in Euxanthus; cf. Guinot-Dumortier 1960: pl. VI, figs 36–39). Similarly, the new genus is easily distinguishable from Hypocolpus by the absence of a developed subhepatic cavity (Fig. 1B) (vs. a developed subhepatic cavity in Hypocolpus; cf. Guinot-Dumortier 1960: pl. II, figs 40–41); posterior three teeth on anterolateral margin well-developed (Figs 1C, 3A) (vs. underdeveloped teeth in Hypocolpus; Fig. 6B; cf. Guinot-Dumortier 1960: pl. VII, figs 40–41); front not prominent, divided by a V-shaped notch (Figs 1C, 3A) (vs. more protruding, divided by a narrow fissure in Hypocolpus; Fig. 6B; cf. Guinot-Dumortier 1960: pl. VII, figs 40–41); male abdominal telson large and truncated oval (Figs 2F, 3F) (vs. small and triangular in Hypocolpus; cf. Guinot-Dumortier 1960: pl. IX, fig. 53, pl. X, fig. 55); G1 with a prominent, spoon-shaped distal lobe (Fig. 3G–J) (vs. G1 with a short, non-protruding distal lobe, inwardly curved and encircling in Hypocolpus; cf. Guinot-Dumortier 1960: pl. VI, figs 32–35).

The new genus slightly resembles Psaumis Kossmann, 1877, and Paractaeopsis Serène, 1984, but can be readily distinguished. Gothus can be easily distinguished from Psaumis by lack of erosive depressions across body (Fig. 1A) (vs. chelipeds, ambulatory legs, carapace with strong erosive depressions in Psaumis; Fig. 6E; cf. Serène 1984: pl. XVIII, fig. E); front divided by a V-shaped notch (Figs 1C, 3A) (front divided by a narrow fissure in Psaumis; Fig. 6E; cf. Serène 1984: pl. XVIII, fig. E); anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (anterolateral margin with very flat teeth, except for fourth tooth at junction of anterior and posterior lateral margins, which is more prominent in Psaumis; Fig. 6E; cf. Serène 1984: pl. XVIII, fig. E). It can be distinguished from Paractaeopsis by anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (anterolateral margin with four well development teeth in Paractaeopsis; cf. Takeda and Miyake 1968: fig. 1a); carapace broad, approximately 1.5 times as wide as long, with a relatively flat dorsal surface (Figs 1A, C, 3A) (carapace narrower, with a width not exceeding 1.4 times the length, and dorsal surface convex both anteroposteriorly and laterally in Paractaeopsis; cf. Serène 1984: pl. XVII, fig. E); carapace 2M region divided into two lobes (Figs 1A, C, 3A) (carapace 2M region divided into four lobes in Paractaeopsis; cf. Takeda and Miyake 1968: fig. 1a); ambulatory legs comparatively slender (Figs 1A, 3D) (ambulatory legs very short and stout in Paractaeopsis; cf. Takeda and Miyake 1968: fig. 1c).

Given the above comparisons, the current species cannot be placed within any known genera, necessitating the establishment of a new genus. The main morphological characteristics comparing Gothus gen. nov. with closely related genera are listed in Table 2.

Holotype. China • 1 male; CW 3.7 mm, CL 2.6 mm; Triton Island, Xisha Islands; 15°46'52.61"N, 111°12'28.62"E; 5 m; 10 May. 2024; Ziming Yuan coll.; 2404189149; MBM287027.

Paratypes. China • 1 female; CW 3.2 mm, CL 2.2 mm; Meiji Reef, Nansha Islands; 9°52'57.47"N, 115°33'48.59"E; 27 Apr. 2023; Aiyang Wang, Bingqin Liu coll.; 2304278379; MBM287026 • 1 male (decalcified); CW 3.2 mm, CL 2.4 mm; Meiji Reef, Nansha Islands; 9°53'1.15"N, 115°33'37.42"E; 27 Apr. 2023; Aiyang Wang, Bingqin Liu coll.; 2304278461; MBM287024 • 1 male (partially crushed); CW 4 mm, CL 2.7 mm; Meiji Reef, Nansha Islands; 9°53'1.15"N, 115°33'37.42"E; 27 Apr. 2023; Aiyang Wang, Bingqin Liu coll.; 2304278486; MBM287025 • 2 juveniles; CW 1.8–2.2 mm, CL 1.3–1.5 mm; Meiji Reef, Nansha Islands; 9°54'25.75"N, 115°29'49.44"E; 3 m; 6 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-MJ-2022-1287; MBM287023 • 1 juvenile; CW 2 mm, CL 1.3 mm; Meiji Reef, Nansha Islands; 9°53'30.84"N, 115°34'22.05"E; 5 m; 11 Apr. 2024; Ziming Yuan coll.; 2404188048; MBM287022.

Carapace (Figs 1, 3A) broader than long, CW about 1.5 times the CL, dorsal surface bearing round granules, regions well defined, 1M separated from 2M by shallow transverse groove; 2M indistinct divided, lateral lobe with elevated pointed tuberosity; 3M distinct, undivided; 4M indistinct; 1L, 3L, 4L indistinct; 2L, 5l, 6L distinct, with elevated sharp tuberosity each on 2L, 5L; 1P distinct, 2P indistinct, flat; 2M, 5L, and 6L regions each with a tuft of setae; front wide, about 0.4 times CW, not protruding, divided into two slightly triangular lobes by a V-shaped notch, a small pore visible from front introduced from median notch (Fig. 1B), frontal lobes and dorsal inner orbital angle separated by shallow depression; eyestalks densely granulated; area behind outer orbital angle slightly concave, not forming a subhepatic cavity; anterolateral margin starting from subhepatic region; first tooth nearly completely reduced; subsequent three teeth developed; second and third teeth nearly equal; fourth tooth smaller; carapace widest at second tooth; posterolateral margin almost straight; subhepatic region densely granulated; posterior margin nearly straight.

Epistome (Fig. 1B, E) central region with short median projection on posterior margin pronounced; lateral regions with undulating posterior margins; maxilliped 3 (Figs 1B, E, 3B) granulated; ischium subrectangular; presenting submedian groove; merus subquadrate; anterior margin indented; external anteroexternal angle expanded. Antennule (Fig. 1B, E) folding transversely; basal segment of antenna subrectangular; contacting ventral external frontal margin and ventral internal orbital angle; antennal flagellum filling orbital hiatus.

Chelipeds (Figs 2A, B, 3C) symmetrical; meri short; carpi robust, with square-shaped outward expansion, surface granulated, aggregated into nodules; palms dorsally with three protuberances, outer and dorsal surfaces densely granulated; fingers elongated, with triangular teeth, tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granular ridges; outer surface of immovable finger with two granular ridges.

Ambulatory legs (Figs 1A, D, 3D) meri flattened, P5 merus length about 3.6 times width of distal end, granulated dorsally and along anterior and posterior edges; carpi granulated dorsally and along anterior edge, dorsal surface with a grooved indentation near anterior edge; propodi granulated dorsally and along edges; dactyli elongated, margins armed with granules and setae, terminal end chitinous, sharp, slightly curved backward, dactylo-propodal lock very weak and inconspicuous.

Male thoracic sternum (Fig. 2C) with sternites 1 and 2 completely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, suture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tubercle of sterno-pleonal lock (press-button mechanism) located on posterior of sternite 5. Male pleon (Figs 2C, E, 3F) narrow; pleonites 3 to 5 completely fused, lateral margins of pleonite 6 slightly concave, telson long and broad, width slightly greater than length, truncated oval, basal margin wider than terminal margin of pleonite 6; paired tufts of setae present on margins of middle part and terminal margin of pleonites 3–5 and terminal margin of pleonite 6. Female pleon (Figs 2D, F, 3E) oval-shaped, margins of pleonite 6 slightly concave; telson triangular; vulva longitudinally ovate, located at upper of sternite 6, occupying anteromedial half, near sternites 5/6 (Fig. 2G).

G1 (Fig. 3G, H, I, J) slender, distal lobe prominent but not excessively elongated, long setae on inner subdistal side, small spines on outer side. G2 (Fig. 3K, L) short, distal lobe elongated, slightly curved upwards.

Overall white to coral pink in coloration, carapace adorned with symmetrical black to brown stripes, ambulatory legs and chelipeds bearing stripes of similar coloration, anterior part of chelipeds carpus red (Figs 4, 5). Fingers brownish-black, the coloration of immovable finger extending onto the palm along both the inner and outer surfaces in male (Fig. 2A, B).

The new species is named after Teemo, a character from the MOBA (Multiplayer Online Battle Arena) video game League of Legends. This character, modeled after a raccoon, has a fluffy, diminutive stature with a brown and white intermingled fur coat. This alludes to the new species’ small size, densely covered short setae, and brown-striped coloration.

Currently known from the type locality at Triton Island, Xisha Islands (Paracel Islands), and Meiji Reef (Mischief Reef), Nansha Islands (Spratly Islands), it inhabits crevices in shallow coral reefs.

Apart from the members of the subfamily Euxanthinae already compared in the remarks of Gothus gen. nov., the species is most similar to Actaeodes consobrinus (A. Milne-Edwards, 1873). They share similarities in the carapace outline, the shape of the male pleon, and even in the pattern of the live coloration. However, G. teemo sp. nov. can be differentiated from A. consobrinus by the following features: the first tooth on the anterolateral margin of the carapace is completely reduced, almost invisible (Figs 1A, C, 3A) (vs. the first tooth low but still visible in A. consobrinus; Figs 7A, B, 8A, 9A, B); carapace regions more pronounced, with tufts of setae (Figs 1C, 3A) (vs. carapace regions flatter, without tufts of setae in A. consobrinus; Figs 7A, B, 8A, 9A, B); cheliped carpus with square-shaped outward expansion (Fig. 1A) (vs. cheliped carpus nearly spherical in A. consobrinus; Figs 7A, 8A, B); male pleon relatively broader, telson width slightly greater than length (Figs 2F, 3F) (vs. pleon very narrow, telson longer than wide in A. consobrinus; Figs 7D, 8E); G1 distal lobe shorter (Fig. 3G–J) (vs. G1 distal lobe significantly elongated in A. consobrinus; Fig. 8F–G).

China • 1 male; CW 3.0 mm, CL 1.9 mm; Yongshu Reef, Nansha Islands; 9°39'51.97"N, 113°0'52.98"E; 10 m; 6 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-YS-2022-1226 • 1 male; CW 7.6 mm, CL 5.2 mm; same collection data as for preceding; 14 May 2022; NS-YS-2022-1227 • 2 juveniles; CW 2.1–2.2 mm, CL 1.5–1.6 mm; same collection data as for preceding; NS-YS-2022-1263 • 1 male; CW 6.7 mm, CL 4.4 mm; same collection data as for preceding; NS-YS-2022-1336 • 1 juvenile; CW 2.5 mm, CL 1.7 mm; Meiji Reef, Nansha Islands; 9°52'38.19"N, 115°31'17.08"E; 8 m; 7 May 2022; NS-MJ-2022-1438 • 1 juvenile; CW 2.2 mm, CL 1.5 mm; same collection data as for preceding but at 9°53'30.84"N, 115°34'22.05"E; 10 m; 10 May 2022; NS-MJ-2022-1789 • 1 female; CW 4.5 mm, CL 2.9 mm; Qilianyu, Xisha Islands; 16°58'04.2"N, 112°16'11.0"E; 10 m; 19 May 2022; XS-QL-2022-1014 • 1 juvenile; CW 2.9 mm, CL 2.0 mm; Bei Reef, Xisha Islands; 17°07'00.5"N 111°32'03.2"E; 8 May 2023; Aiyang Wang, Bingqin Liu coll.; 2305089358 • 1 male; not measured; Zhongsha Islands; 18–23 m; dead coral; 5 Jun. 2021; Geng Qin coll.; C13-5 • 1 male; not measured; same collection data as for preceding, 9 Jun. 2021; C57-3 • 1 male; CW 5.4 mm, CL 3.6 mm; Zhongsha Islands; 15°53'10.5"N, 114°47'29.76"E, 20 m; 26 Jun. 2020; Wei Jiang, Geng Qin coll.; ZS233C07.

Actaeodes mutatus Guinot, 1976 (Fig. 6F). China • 1 male; Lingao, Hainan Island; 25 Nov. 2007; Xan074 • 1 female; Hainan Island; 2022; Xu Zhang coll.; BF01 • 1 female; Phoenix Island, Sanya, Hainan Island; 2021; Xu Zhang coll.; BF02. CW 14.8–20.8 mm, CL 8.6–12.5 mm.

Actaeodes hirsutissimus (Rüppell, 1830) (Fig. 6G). China • 3 males; Zhao Shu Island, Xisha Islands; 15 Apr. 1976; MBM164262 • 1 female; north of Dong Island, Xisha Islands; 9 Jun. 1975; MBM164166 • 2 males, 3 ovigerous females; Dong Island, Xisha Islands; 9 Jun. 1975; MBM164155 • 1 male, 1 female, 3 juveniles; Northeast of Dong Island, Xisha Islands; 10 Jun. 1975; MBM164148 • 4 males, 2 females; Rocky Island, Xisha Islands; 2–4 Jun. 1981; MBM164151 • 1 female; Dong Island, Xisha Islands; 28–30 May 1980; MBM164140 • 2 juveniles; Jinqing Island, Xisha Islands; 10 Jul. 2019; MF01 • 2 males; E Xuan Port, Danzhou, Hainan Island; 7 Nov. 2021; Xan179 • 1 male; Yuzhuo Reef, Xisha Islands; 9 Jul. 2019; MF02 • 9 males, 9 females; Rocky Island, Xisha Islands; 9 May 1975; Xianqiu Ren coll.; MBM164298 • 8 males, 5 females, 2 juveniles; Coral Island, Xisha Islands; 19–23 May 1980; MBM164189 • 2 males, 4 females, 1 juvenile; Jinqing Island, Xisha Islands; 9 May 1980; MBM164190 • 1 female; Xian’e Reef, Nansha Islands; 12 May 1989; MBM164196 • 2 males, 2 females; Jinyin Island, Xisha Islands; 14 May 1980; MBM164185 • 2 ovigerous females; Northeast of Dong Island, Xisha Islands; 10 Jun. 1975; MBM164261 • 5 males, 4 females; Jinqing Island, Xisha Islands; 19 May 1981; MBM164225. CW 7.7–34.2 mm, CL 5.2–22 mm.

Actaeodes tomentosus (H. Milne Edwards, 1834) (Fig. 6H). China • 1 male; Wenchang, Hainan Island; 24 Jul. 2021; RF01 • 1 male; Xincun, Hainan Island; 29 Mar. 2008; Ping Lan, Yongqiang Wang coll.; MBM282509 • 3 males; Xiaodonghai, Hainan Island; 23 Mar. 2008; MBM282414 • 4 males, 4 females; same collection data as for preceding; 25 Dec. 2007; MBM283216 • 9 males, 6 females; same collection data as for preceding; 24 Dec. 2007; Xan045, MBM283218 • 2 males, 1 female; same collection data as for preceding; 23 Mar. 2008; Wei Jiang coll.; Xan041 • 1 female; Langhua Reef, Xisha Islands; 11 May 2015; Xan126 • 1 male; Houhai, Sanya, Hainan Island; 22 Mar. 2018; Xan048 • 1 female; Dadonghai, Hainan Island; 2021; Xu Zhang coll.; RF03 • 1 male; Sanya, Hainan Island; 2022; Xu Zhang coll.; RF04 • 1 female; Sanya, Hainan Island; 20 Aug. 2019; Yunhao Pan coll.; RF05 • 1 male; Yuzhuo Reef, Xisha Islands; 9 Jul. 2019; RF06 • 1 male; Lingyang Reef, Xisha Islands; 11 Jul. 2019; RF07 • 1 male; Yongxing Island, Xisha Islands; 27 Mar. 1980; MBM164194 • 1 female; Sanya Bay, Hainan Island; 22 Nov. 1990; MBM164492. CW 11.2–37.4 mm, CL 7.4–24.9 mm.

Carapace (Figs 7A, B, 8B, 9A, D, G) broader than long, CW about 1.5 times the CL, dorsal surface bearing round granules, granules interspersed with short pubescence; regions well defined, grooves wide and deep, 1M separated from 2M; 2M completely divided; 3M distinct, divided into three lobes; 4M distinct; 1L, 4L indistinct; 2L, 3L, 5l, 6L distinct, 5L, 6L partially divided; 1P, 2P distinct; front broad, about 0.3 times CW, not protruding, divided into two slightly triangular lobes by a wide and deep V-shaped notch, frontal lobes and dorsal inner orbital angle separated by shallow depression; eyestalks densely granulated; Anterolateral margin divided into four teeth by narrow but sometimes opened fissures; first tooth extremely flattened, second tooth broader, sometimes obtuse, third tooth prominent, fourth tooth slightly smaller than third; carapace widest at third tooth; posterolateral margin almost straight; subhepatic region densely granulated; Posterior margin nearly straight.

Figure 7. 

Gothus consobrinus (A. Milne-Edwards, 1873), male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336. A. Dorsal habitus; B. Carapace; C. Frontal view; D. Thoracic sternites and pleon; E. Chelipeds. Scale bar: 2 mm.

Figure 8. 

Gothus consobrinus (A. Milne-Edwards, 1873), male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336. A. Carapace; B. Maxilliped 3; C. Cheliped; D. Pereopod 5; E. Pleon; F. Left G1, ventral view; G. Left G1; H. Left G2, ventral view. Scale bar: 2 mm (A); 0.5 mm (B, F, H); 1 mm (C, D, E); 0.1 mm (G).

Figure 9. 

Gothus consobrinus (A. Milne-Edwards, 1873). A–C. Female, CW 10.5 mm, CL 6.8 mm, MNHN-IU-2000-3885 (=MP-B3885S); D–F. Female, CW 8.8 mm, CL 5.7 mm, MNHN-IU-2024-3483; photographed by Sébastien Soubzmaigne; G–I. Female, CW 4.5 mm, CL 2.9 mm, XS-QL-2022-1014. Scale bar: 2 mm (A–F); 1 mm (G–I).

Epistome (Figs 7C, 9B, E, H) Central region with median projection on posterior margin; lateral regions with undulating posterior margins. Maxilliped 3 (Figs 7C, 8B) granulated, ischium subrectangular, presenting submedian groove; merus subquadrate; anterior margin indented; anteroexternal angle square-shaped expanded. Antennule (Fig. 7C, 9B, E, H) folding transversely; basal segment of antenna subrectangular; contacting ventral external frontal margin and ventral internal orbital angle; antennal flagellum filling orbital hiatus.

Chelipeds (Figs 7E, 8C) symmetrical, meri short; carpi robust, nearly spherical, surface granulated, aggregated into nodules; outer and dorsal surfaces of palms densely granulated; fingers elongated, with triangular teeth, tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granular ridges; outer surface of immovable finger with two ridges. Fingers brownish-black, coloration of immovable finger extending onto palm along both inner and outer surfaces in male.

Ambulatory legs (Figs 7A, 8D) with meri flattened, P5 merus length about 3 times as wide as distal end, granulated dorsally and along anterior and posterior edges; carpi granulated dorsally and along anterior edge; dorsal surface with a grooved indentation near anterior edge; propodi granulated dorsally and along edges; dactyli elongated, margins armed with granules and setae, terminal end chitinous, sharp, slightly recurved, dactylo-propodal lock present.

Male thoracic sternum (Fig. 7D) with sternites 1 and 2 completely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, suture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tubercle of sterno-pleonal lock (press-button mechanism) located on posterior of sternite 5. Male pleon (Figs 7D, 8E) very narrow; pleonites 3 to 5 completely fused; lateral margins of pleonite 6 slightly concave; telson long, broad, longer than wide; truncated oval; basal margin wider than terminal margin of pleonite 6.

G1 (Fig. 8F–G) slender, distal lobe prominent, elongated, curved upwards, long setae on inner subdistal side, small spines on outer side. G2 (Fig. 8H) short, distal lobe elongated, slightly curved upwards.

Overall white to ivory-colored, carapace adorned with symmetrical black to brown stripes and orange spots, ambulatory legs and chelipeds bearing black to brown stripes, cheliped palm dorsal surface and anterior part of carpus sometimes coral pink (Fig. 10). Fingers brownish-black, coloration of immovable finger extending onto inner and outer surfaces of palm in male (Fig. 7E).

Figure 10. 

Gothus consobrinus (A. Milne-Edwards, 1873). A. Male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336; B. Female, CW 4.5 mm, CL 2.9 mm, XS-QL-2022-1014, displaying live coloration. Scale bar: 2 mm.

Distributed in the Zhongsha (=Macclesfield Bank), Xisha (=Paracel Islands), and Nansha Islands (=Spratly Islands) of the China Sea; widely found in the Indo-West Pacific, with the type locality at Upolu Island, inhabiting crevices in shallow coral reefs.

This report constitutes the first record of this species in the Chinese sea. Alphonse Milne-Edwards (1873: 255 [79]) briefly described “Actaea consobrina” from Upolu in present-day Samoa and provided the carapace measurements of one specimen (CW 10 mm, CL 7 mm), though they did not indicate the sex of the specimen nor how many other specimens they examined. This species remained in the genus Actaea until Guinot (1967b) transferred it to Actaeodes. As part of her revision of some Actaeinae genera, including Actaeodes, Guinot (1976: 246) examined two female specimens collected by A. Milne-Edwards and deposited in the MNHN (MP-B3885S from Upolu and a specimen without a collection number from “Samoa?”). She pointed out that based on the measurements (CW 10 mm, CL 7 mm), this specimen MP-B3885S could be the holotype of Actaeodes consobrinus. For the purposes of this study, we consider this specimen to be typical of A. consobrinus and use it for our comparisons (Fig. 9A–C). It exhibits a nearly truncated second anterolateral tooth with open fissures between the anterolateral teeth, which is also observed in some of the current specimens (Fig. 9G–I). Compared to the specimens from the China Sea, it has deeper grooves on the carapace, which may be attributed to growth-related differences considering its larger size. The other female individual (MNHN-IU-2024-3483) found together with this specimen is likely the one collected by A. Milne-Edwards that lacks a collection number (Guinot, 1976: 246; CW 8.5 mm, CL 6 mm), based on its measurements (CW 8.8 mm, CL 5.7 mm; Fig. 9D–F). This specimen possesses triangular anterior lateral teeth and shallower grooves on the carapace (Fig. 9D–F).

There are some issues regarding the classification of this species within its genus: Alphonse Milne-Edwards (1873) put the species in Actaea De Haan, 1833, and initially compared it with Actaea hirsutissimus (Rüppell, 1830) (presently known as Actaeodes) and Actaea kraussi (Heller, 1860) (presently known as Banareia) and primarily considered it similar to the former. Sakai (1939) considered the species to be close to Paractaea tumulosa (Odhner, 1925). Guinot (1967b, 1976) opposed the similarity to P. tumulosa but acknowledged its relationship with Actaeodes, and upon reviewing Actaeodes, Actaea consobrina was classified into the genus Actaeodes Dana, 1851, and supplemented its morphological characteristics.

In Guinot’s review (1976), the definition of Actaeodes includes the following characteristics: 1) carapace wide to very wide; 2) long anterolateral margins curving back over branchial regions, divided into lobes by fissures that extend as grooves into the subhepatic region; 3) very short posterolateral margins with a strong concavity that coapted against the last three pairs of ambulatory legs; 4) developed areolation of the dorsal surface with granular and pilosity lobules; 5). The frontal edge slopes downward with a central notch leading to the anterior tip of the epistome; the frontal lobes barely form a canopy above the antennules; 6) orbits round and relatively small, with specific fissures on supraorbital and exorbital edges; no infraorbital fissure 7) Equal and short chelipeds, with fingers either ending in a spoon-shaped tip or crossing at tips; 8) antenna fitting between front and orbit or with a closed orbit in Actaeodes semoni (Ortmann, 1894); 9) small and slightly depressed epistome, with the anterior tip projecting forward to join the anterior median groove of the dorsal face; 10) short ambulatory legs; 11) sub-hepatic region grooved; 12) thoracic sternite 4 traversed by two transverse grooves and two oblique grooves, and with a very clear longitudinal groove, hidden by telson; a median line present at levels of sternites 6, 7, and 8; 13) male pleon with fused pleonites 3–5, elongated and projecting forward, featuring a median longitudinal swelling from 3 to 6 pleonites; 14) G1 with a tapered distal lobe adorned with relatively short bristles.

Actaeodes currently comprises six species, among which the type species A. tomentosus, A. semoni (Ortmann, 1894), A. hirsutissimus (Rüppell, 1830), and A. mutatus Guinot, 1976 share a relatively similar appearance and match the description above. The most direct similarity is likely due to the very short posterolateral margins with a strong concavity that coapted against the last three pairs of ambulatory legs. However, A. consobrinus and A. quinquelobatus Garth & Kim, 1983 exhibit morphologies that differ significantly and may not fit well within the genus Actaeodes.

For the current species A. consobrinus, it indeed exhibits several features similar to typical Actaeodes species, which mainly include a carapace with developed dorsal areolation with granular and setae, longer anterolateral margins and shorter posterolateral margins, symmetrical chelipeds with sharply crossing tips, an elongated male pleon, and a G1 that is overall similar in morphology. However, this similarity is superficial, and there are some undeniable differences between A. consobrinus and typical Actaeodes species. A. Milne-Edwards, in the original description, compared A. consobrinus with A. hirsutissimus, noting the absence of a pronounced concavity in its posterior margin. In current observations, the posterior margin of this species is almost straight (Figs 7A, B, 8A, 9A, D, F), which significantly deviates from Actaeodes (Fig. 6F–H; cf. Guinot 1976: pl. XV, figs 1–4). Furthermore, the morphology of the thoracic sternum in the current species markedly differs from Actaeodes, with its third sternite being very short (Fig. 7D) (vs. elongated third sternite in Actaeodes; cf. Guinot 1976: fig. 41C) and the fourth sternite lacking oblique grooves (Fig. 7D) (fourth thoracic sternite of Actaeodes traversed by two transverse grooves and two oblique grooves; cf. Guinot 1976: fig. 41C). Other differences include A. consobrinus having an elongated pleon that barely extends beyond the coxo-sternal condyles of pereiopod 1 (Fig. 7D) (vs. pleon being significantly elongated, clearly surpassing the coxo-sternal condyles of pereiopod 1 in Actaeodes; cf. Guinot 1976: fig. 41C); like other species in Actaeodes, A. consobrinus has an elongated telson, but its overall shape is truncate-oval, with relatively arcuate lateral edges (Fig. 7D) (vs. triangular telson with converging lateral edges in Actaeodes; cf. Guinot 1976: fig. 41C); A. consobrinus has the first tooth flattened and the subsequent three teeth prominent (Figs 7A, B, 8A, 9A, D, F) (vs. anterolateral margin divided into four distinct but not very prominent lobes in Actaeodes; Fig. 6F–H; cf. Guinot 1976: pl. XV, figs 1–4); the cheliped carpus is more robust in A. consobrinus (Figs 7A, 9A, D, F) (vs. proportionally more slender carpus in Actaeodes; Fig. 6F–H; cf. Guinot 1976: pl. XV, figs 1–4). It is worth mentioning that although body color is generally not used as a basis for defining genera within the family Xanthidae, the vibrant and high-contrast living coloration of A. consobrinus is also quite unique in Actaeodes (Fig. 10). Based on the aforementioned reasons, A. consobrinus is not suitable for placement within the genus Actaeodes.

Another genus worth considering is Meractaea Serène, 1984, characterized by almost straight posterolateral margins, developed areolation on the dorsal surface of the carapace, and four underdeveloped small teeth on the anterolateral margins, all of which are similar to the current species. However, there are also differences between this genus and A. consobrinus, including an almost straight, quadrilobate frontal margin with a rounded central notch (cf. Serène 1984: pl. XIX, fig. C) (vs. front not very prominent but not straight, divided by a V-shaped notch into two inclined rounded lobes in A. consobrinus; Figs 7A, B, 8A, 9A, D, F); markedly slender ambulatory legs (cf. Serène 1984: pl. XIX, fig. C) (vs. flat and robust ambulatory legs in A. consobrinus; Figs 7A, 8D); a completely smooth dorsal surface of the carapace with irregularly sized granules, sometimes connected (cf. Serène 1984: pl. XIX, fig. C) (vs. carapace dorsal surface with setae, regularly sized granules, never connected in A. consobrinus; Figs 7A, B, 8A, 9A, D, F); G1 distal lobe slightly curved outward (cf. Serène 1984: fig. 63) (vs. G1 distal lobe curved inward in A. consobrinus; Fig. 8F–G). Considering these significant differences, A. consobrinus also cannot be placed within this genus.

Compared with the species of Actaeodes and Meractaea, A. consobrinus is actually more closely related to G. teemo. Beyond the most noticeable similarity in vibrant living coloration, both share similar carapace contours, flattened first anterolateral teeth, robust cheliped carpus, similar states of thoracic sternum, and special male abdominal morphology, particularly the truncate-oval telson (see the comparison in the remarks of G. teemo). We believe that placing this species into the current new genus and new combination is more appropriate.

Regarding the status of A. quinquelobatus, in the absence of specimens, we hereby present some limited queries. Similar to the new combination G. consobrinus, the morphology of A. quinquelobatus also appears to deviate from the definition of Actaeodes sensu stricto, featuring 5 instead of 4 anterolateral teeth and possessing non-concave posterior margins (cf. Garth and Kim 1983: fig. 5A). As Garth and Kim (1983) noted, A. quinquelobatus has carapace partitioning similar to G. consobrinus. However, current evidence does not affirm its placement within the genus Gothus, given it has 5 anterolateral teeth (cf. Garth and Kim 1983: fig. 5A) (vs. 3 or 4 in Gothus; Figs 1C, 7A), and the carapace and chelae exhibit a multitude of developed nodules (cf. Garth and Kim 1983: fig. 5A, B) (vs. surfaces have granules but lack nodules in Gothus; Figs 1A, 7A). Further examination is necessary to confirm its taxonomic status.