Mariaplax sinensis, Rahayu & Ng, 2014

Rahayu, Dwi Listyo & Ng, Peter K. L., 2014, New genera and new species of Hexapodidae (Crustacea, Brachyura) from the Indo-West Pacific and east Atlantic, Raffles Bulletin of Zoology 62, pp. 396-483 : 455-457

Mariaplax sinensis , new species

( Figs. 48 , 49 )

Material examined. Holotype: male (7.5 × 5.2 mm) ( IOCAS), station 21, Bohai Gulf, very close to 38°40'N 117°50'E, to 7 m depth, soft mud, coll. D. Sun & G. Lin, 27 August 1979.

Diagnosis. Carapace subquadrate, about 1.5 times as broad as long, dorsal surface granulated; regions indistinct, with shallow median H-shaped depression ( Fig. 48A ). Anterolateral margin arcuate; posterolateral margin with angled prominence over base of posterior pereopods ( Figs. 48A , 49A ). Eye slightly movable, small, cornea pigmented, wider than peduncle. Pterygostomial region with row of oblique striae. Third maxillipeds broad ( Figs. 48B , 49D ), without distinct gap between them; ischium longer than broad, much longer than merus, mesial margin straight, combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod narrow, 0.4 width of ischium, slightly granular, flagellum well developed. Chelipeds asymmetrical; both chelae ( Fig. 48C ) with gap when fingers closed; palm slightly longer than wide, surface finely tuberculate. P2–P4 tomentose, surfaces granulated ( Fig. 48A ); merus of P4 three times as long as broad, shallow longitudinal groove on outer surface medially; dactylus of P4 gently upcurved. Male thoracic sternum broad ( Figs. 48B , 49B, C ), surface finely granular; sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 by distinct ridge; wide transverse groove extends obliquely from edge of sternoabdominal cavity, not reaching base of chelipeds ( Figs. 48B , 49B ); sternite 8 exposed, subrectangular, slightly longer than abdominal somite 1; sternoabdominal cavity reaching midlength of thoracic sternite 4 ( Fig. 49C ). Male abdomen relatively narrow ( Fig. 49E ), surface granular, somites 1 and 2 free; somites 3–5 fused, lateral margin slightly arched; somite 6 slightly shorter than somites 3–5, lateral margin expanded into blunt triangular projection subproximally; telson subtriangular, distal margin rounded ( Figs. 48B , 49E ). G1 slender ( Fig. 49F, G ), S-shaped, distal part tapered, sparse short setae present laterally and mesially; row of minute spines on mesial margin medially; distal part exposed on thoracic sternal groove, not concealed under abdomen.

Colour. Not known.

Etymology. Named after the type locality, China.

Remarks. Mariaplax anfracta , M. propinqua , new species, and M. sinensis , new species, share the same general shape of G1: S-shaped with a long and bent distal part. The differences between these three species are as follow: the male anterior thoracic sternum in M. sinensis is proportionately much wider ( Fig. 49B, C ) (versus Figs. 23B, C , 44A , 45C, D ), and the presence of row of small spines on the G1 medial lateral margin in M. sinensis ( Fig. 49F, G ) (no spines present in M. anfracta , Fig. 23F, G ; and three large spines in M. propinqua , Fig. 45I, J ). Although M. chenae also possesses a row of minute spines at the middle of the lateral margin of the G1, the shape of the G1 is different, being relatively stouter and distally twisted ( Fig. 25I, J ) (versus more slender, tapering, and only slightly twisted distally in M. sinensis , Fig. 49F, G ).

Type locality. Bohai Gulf , East China Sea .

Distribution. East China Sea. Subtidal, 7 m.

Figures

Fig. 48. Mariaplax sinensis, new species, holotype male (7.5 × 5.2 mm) (IOCAS). A, overall view of carapace, chelipeds and P2–P4; B, ventral view of cephalothorax; C, major and minor chelae.

Fig. 49. Mariaplax sinensis, new species, holotype male (7.5 × 5.2 mm) (IOCAS). A, dorsolateral margin of carapace; B, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites 1–5, showing thoracic sternal groove and telson; D, left third maxilliped; E, male abdomen and telson; F, G, G1. Scale bars = 1.0 mm.

Fig. 23. Mariaplax anfracta (Rathbun, 1909). A–G, paratype male (5.0 × 3.2 mm) (USNM 39752); H, female (4.1 × 2.8 mm) (ZRC 1965.11.24.6). A, dorso-lateral margin of carapace; B, thoracic sternites 1–4, showing sternoabdominal cavity and thoracic sternal groove; C, thoracic sternites3 and 4, showing thoracic sternal groove and telson; D, right third maxilliped; E, major chela; F, G, G1; H, female abdomen and telson. Scale bars = 1.0 mm.

Fig. 44. Mariaplax propinqua, new species, holotype male (10.3 × 6.5 mm) (IOCAS).A, abdomen and telson; B, major chela; C, minor chela.

Fig. 45. Mariaplax propinqua, new species, holotype male (10.3 × 6.5 mm) (IOCAS). A, dorsolateral margin of carapace; B, anterior view of cephalothorax; C, thoracic sternites 3–5, showing thoracic sternal groove and telson; D, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; E, left third maxilliped; F, male abdomen and telson, G, major chela; H, minor chela; I, J, G1. Scale bars = 1.0 mm.

Fig. 25. Mariaplax chenae, new species, A–J, holotype male (9.2 × 6.1 mm) (IOCAS); K, paratype female (8.2 × 5.4 mm) (ZRC 2012.1023). A, dorso-lateral margin of carapace; B, anterior view of cephalothorax; C, thoracic sternites 3 and 4, showing thoracic sternal groove and telson; D, thoracic sternites 1–5, showing sternoabdominal cavity and thoracic sternal groove; E, left third maxilliped; F, male abdomen and telson, G, major chela; H, minor chela; I, J, G1; K, female abdomen and telson. Scale bars = 1.0 mm.