Gothus consobrinus (A. Milne-Edwards, 1873 ) Yuan & Jiang & Sha, 2024

Yuan, Zi-Ming, Jiang, Wei & Sha, Zhong-Li, 2024, Morphological and molecular evidence for Gothus teemo gen. et sp. nov., a new xanthid crab (Crustacea, Brachyura, Xanthoidea) from coral reefs in the South China Sea, with a review of the taxonomy of Actaeodes consobrinus (A. Milne-Edwards, 1867), Zoosystematics and Evolution 100 (3), pp. 965-987 : 965-987

Gothus consobrinus (A. Milne-Edwards, 1873) comb. nov.

Figs 7 , 8 , 9 , 10

Actaea consobrina A. Milne-Edwards, 1873: 255; de Man, 1896: 503; Odhner, 1925: 67, pl. 4, fig. 14; Ward, 1933: 246; Sakai, 1939: 491, pl. 94, fig. 2; Tweedie, 1950: 118; Serène & Lang, 1959: 291, fig. 2, A 1 - A 3; Guinot, 1967 a: 260

Actaea suffuscula Rathbun, 1911: 220, pl. 17, figs 10–11; Ward, 1934: 18; Estampador, 1959: 81.

Actaeodes consobrinus Guinot, 1967 b: 561; Guinot, 1976: 246, pl. 15, fig. 5; Sakai, 1976: 448, pl. 158, fig. 3; Takeda & Miyake, 1976: 108; Serène, 1984: 133 (key), 134 (key), 135, pl. 18 C; Galil & Vannini, 1990: 37.

Actaeodes consobrina Guinot, 1971 a: 1072 .

Non Actaea consobrina Nobili, 1907: 390 .

= Pseudoliomera ruppellioides ( Odhner, 1925) .

Material examined.

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.; C 13-5 • 1 male; not measured; same collection data as for preceding, 9 Jun. 2021; C 57-3 • 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.; ZS 233 C 07 .

Comparative material.

Actaeodes mutatus Guinot, 1976 (Fig. 6 F ). China • 1 male; Lingao, Hainan Island; 25 Nov. 2007; Xan 074 • 1 female; Hainan Island; 2022; Xu Zhang coll.; BF 01 • 1 female; Phoenix Island , Sanya, Hainan Island; 2021; Xu Zhang coll.; BF 02. CW 14.8–20.8 mm, CL 8.6–12.5 mm .

Actaeodes hirsutissimus ( Rüppell, 1830) (Fig. 6 G ). China • 3 males; Zhao Shu Island, Xisha Islands ; 15 Apr. 1976; MBM 164262 • 1 female; north of Dong Island, Xisha Islands ; 9 Jun. 1975; MBM 164166 • 2 males, 3 ovigerous females; Dong Island, Xisha Islands ; 9 Jun. 1975; MBM 164155 • 1 male, 1 female, 3 juveniles; Northeast of Dong Island, Xisha Islands ; 10 Jun. 1975; MBM 164148 • 4 males, 2 females; Rocky Island, Xisha Islands ; 2–4 Jun. 1981; MBM 164151 • 1 female; Dong Island, Xisha Islands ; 28–30 May 1980; MBM 164140 • 2 juveniles; Jinqing Island, Xisha Islands ; 10 Jul. 2019; MF 01 • 2 males; E Xuan Port, Danzhou, Hainan Island ; 7 Nov. 2021; Xan 179 • 1 male; Yuzhuo Reef, Xisha Islands ; 9 Jul. 2019; MF 02 • 9 males, 9 females; Rocky Island, Xisha Islands ; 9 May 1975; Xianqiu Ren coll.; MBM 164298 • 8 males, 5 females, 2 juveniles; Coral Island, Xisha Islands ; 19–23 May 1980; MBM 164189 • 2 males, 4 females, 1 juvenile; Jinqing Island, Xisha Islands ; 9 May 1980; MBM 164190 • 1 female; Xian’e Reef, Nansha Islands ; 12 May 1989; MBM 164196 • 2 males, 2 females; Jinyin Island, Xisha Islands ; 14 May 1980; MBM 164185 • 2 ovigerous females; Northeast of Dong Island, Xisha Islands ; 10 Jun. 1975; MBM 164261 • 5 males, 4 females; Jinqing Island, Xisha Islands ; 19 May 1981; MBM 164225 . CW 7.7–34.2 mm, CL 5.2–22 mm .

Actaeodes tomentosus (H. Milne Edwards, 1834) (Fig. 6 H ). China • 1 male; Wenchang , Hainan Island; 24 Jul. 2021; RF 01 • 1 male; Xincun , Hainan Island; 29 Mar. 2008; Ping Lan, Yongqiang Wang coll.; MBM 282509 • 3 males; Xiaodonghai , Hainan Island; 23 Mar. 2008; MBM 282414 • 4 males, 4 females; same collection data as for preceding; 25 Dec. 2007; MBM 283216 • 9 males, 6 females; same collection data as for preceding; 24 Dec. 2007; Xan 045, MBM 283218 • 2 males, 1 female; same collection data as for preceding; 23 Mar. 2008; Wei Jiang coll.; Xan 041 • 1 female; Langhua Reef , Xisha Islands; 11 May 2015; Xan 126 • 1 male; Houhai , Sanya, Hainan Island; 22 Mar. 2018; Xan 048 • 1 female; Dadonghai , Hainan Island; 2021; Xu Zhang coll.; RF 03 • 1 male; Sanya , Hainan Island; 2022; Xu Zhang coll.; RF 04 • 1 female; Sanya , Hainan Island; 20 Aug. 2019; Yunhao Pan coll.; RF 05 • 1 male; Yuzhuo Reef , Xisha Islands; 9 Jul. 2019; RF 06 • 1 male; Lingyang Reef , Xisha Islands; 11 Jul. 2019; RF 07 • 1 male; Yongxing Island , Xisha Islands; 27 Mar. 1980; MBM 164194 • 1 female; Sanya Bay , Hainan Island; 22 Nov. 1990; MBM 164492 . CW 11.2–37.4 mm, CL 7.4–24.9 mm .

Description.

Carapace (Figs 7 A, B , 8 B , 9 A, 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, 1 M separated from 2 M; 2 M completely divided; 3 M distinct, divided into three lobes; 4 M distinct; 1 L, 4 L indistinct; 2 L, 3 L, 5 l, 6 L distinct, 5 L, 6 L partially divided; 1 P, 2 P 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.

Epistome (Figs 7 C , 9 B, E, H ) Central region with median projection on posterior margin; lateral regions with undulating posterior margins. Maxilliped 3 (Figs 7 C , 8 B ) granulated, ischium subrectangular, presenting submedian groove; merus subquadrate; anterior margin indented; anteroexternal angle square-shaped expanded. Antennule (Fig. 7 C , 9 B, 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 7 E , 8 C ) 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 7 A , 8 D ) with meri flattened, P 5 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. 7 D ) 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 7 D , 8 E ) 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.

G 1 (Fig. 8 F – G ) slender, distal lobe prominent, elongated, curved upwards, long setae on inner subdistal side, small spines on outer side. G 2 (Fig. 8 H ) short, distal lobe elongated, slightly curved upwards.

Live coloration.

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. 7 E ).

Distribution.

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.

Remarks.

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 (1967 b) 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-B 3885 S 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-B 3885 S 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. 9 A – 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. 9 G – 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. 9 D – F ). This specimen possesses triangular anterior lateral teeth and shallower grooves on the carapace (Fig. 9 D – 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 (1967 b, 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) G 1 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 G 1 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 7 A, B , 8 A , 9 A, D, F ), which significantly deviates from Actaeodes (Fig. 6 F – 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. 7 D ) (vs. elongated third sternite in Actaeodes ; cf. Guinot 1976: fig. 41 C) and the fourth sternite lacking oblique grooves (Fig. 7 D ) (fourth thoracic sternite of Actaeodes traversed by two transverse grooves and two oblique grooves; cf. Guinot 1976: fig. 41 C). Other differences include A. consobrinus having an elongated pleon that barely extends beyond the coxo-sternal condyles of pereiopod 1 (Fig. 7 D ) (vs. pleon being significantly elongated, clearly surpassing the coxo-sternal condyles of pereiopod 1 in Actaeodes ; cf. Guinot 1976: fig. 41 C); like other species in Actaeodes , A. consobrinus has an elongated telson, but its overall shape is truncate-oval, with relatively arcuate lateral edges (Fig. 7 D ) (vs. triangular telson with converging lateral edges in Actaeodes ; cf. Guinot 1976: fig. 41 C); A. consobrinus has the first tooth flattened and the subsequent three teeth prominent (Figs 7 A, B , 8 A , 9 A, D, F ) (vs. anterolateral margin divided into four distinct but not very prominent lobes in Actaeodes ; Fig. 6 F – H ; cf. Guinot 1976: pl. XV, figs 1–4); the cheliped carpus is more robust in A. consobrinus (Figs 7 A , 9 A, D, F ) (vs. proportionally more slender carpus in Actaeodes ; Fig. 6 F – 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 7 A, B , 8 A , 9 A, D, F ); markedly slender ambulatory legs (cf. Serène 1984: pl. XIX, fig. C) (vs. flat and robust ambulatory legs in A. consobrinus ; Figs 7 A , 8 D ); 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 7 A, B , 8 A , 9 A, D, F ); G 1 distal lobe slightly curved outward (cf. Serène 1984: fig. 63) (vs. G 1 distal lobe curved inward in A. consobrinus ; Fig. 8 F – 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. 5 A). 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. 5 A) (vs. 3 or 4 in Gothus ; Figs 1 C , 7 A ), and the carapace and chelae exhibit a multitude of developed nodules (cf. Garth and Kim 1983: fig. 5 A, B) (vs. surfaces have granules but lack nodules in Gothus ; Figs 1 A , 7 A ). Further examination is necessary to confirm its taxonomic status.

Figures

Figure 1. Gothus teemo sp. nov. A – C. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM 287027; D – F. Paratype, CW 3.2 mm, CL 2.2 mm, MBM 287026; A, D. Dorsal view; B, E. Frontal view; C, F. Carapace. Scale bar: 1 mm.

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, MBM 286755; C. Euxanthus exsculptus (Herbst, 1790), 1 male, CW 52.6, CL 33.2 mm, MBM 163793; 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, aop 01; F. Actaeodes mutatus Guinot, 1976, 1 female, CW 20.8 mm, CL 12.5 mm, BF 02; G. Actaeodes hirsutissimus (Rüppell, 1830), 1 male, CW 31.9 mm, CL 21.0 mm, MBM 164298; H. Actaeodes tomentosus (H. Milne Edwards, 1834), 1 male, CW 35.8 mm, CL 22.5 mm, Xan 041. Scale bar: 1 mm (A); 5 mm (E, F); 10 mm (B – D, G, F).

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 G 1, ventral view; G. Left G 1; H. Left G 2, 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-B 3885 S); 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).

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.