Mariaplax chenae, 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 : 427-431

publication ID	https://doi.org/ 10.5281/zenodo.5353945
publication LSID	lsid:zoobank.org:pub:4CF42744-861A-4635-9703-E6639CEBFAA9
persistent identifier	https://treatment.plazi.org/id/2D7CA7DF-83BA-49AC-9A47-08AECACFDD69
taxon LSID	lsid:zoobank.org:act:2D7CA7DF-83BA-49AC-9A47-08AECACFDD69
treatment provided by	Tatiana
scientific name	Mariaplax chenae
status	sp. nov.

Treatment

Mariaplax chenae View in CoL , new species

( Figs. 1H View Fig , 24–27 View Fig View Fig View Fig View Fig )

Hexapus (Hexapus) granuliferus View in CoL – Dai et al., 1986: 388, pl. 56(5), text fig. 205(1-2); Dai & Yang, 1991: 418, pl. 56(5), text fig. 205(1–2). (not Hexapus granuliferus Campbell & Stephenson, 1970 View in CoL )

Hexapus granuliferus View in CoL – Liu & He, 2007: 149, unnumbered figure. (not Hexapus granuliferus Campbell & Stephenson, 1970 View in CoL )

Hexapinus granuliferus View in CoL – Yang et al., 2008: 771.

Hexapus (Lambdophallus) anfractus View in CoL – Sakai, 1976: 554, pl. 196, fig. 3. (not Lambdophallus anfractus Rathbun, 1909 View in CoL )

Material examined. Holotype: male (9.2 × 6.1 mm) ( IOCAS), station 1066 ( R578 B-23), coastal waters of Zhejiang Province, East China Sea, China , 39 m, soft mud, coll. AT & J. Xu, 27 August 1960 . Paratypes: China: 1 male (4.0 × 2.7 mm) ( ZRC 2012.1020 View Materials ), station 9 (K 56A-7), Jiaozhou Bay, southern coast of Shandong Peninsula, Yellow Sea , very likely 36°06'N 120°17'E, 11 m, soft mud, 5 September 1979 GoogleMaps ; 1 female (5.3 × 3.5 mm) ( ZRC 2012.1021 View Materials ), station 23 (WC38B-10), coastal water outside Dongtou Island, Zhejiang Province, East China Sea , 4 m, soft mud, coll. AT, Y. Cui & Y. Wu, 8 October 1979 ; 1 male (5.3 × 3.6 mm) ( ZRC 2012.1022 View Materials ), station 29 (WC26B-56), coastal waters outside Dongtou Island, Zhejiang Province, East China Sea , 12 m, soft mud, coll. AT, Y. Cui & Y. Wu, 3 October 1979 ; 2 males (9.9 × 6.7 mm, 7.1 × 4.8 mm), 1 female (8.2 × 5.4 mm) ( ZRC 2012.1023 View Materials ), off Xiamen, Fujian Province, soft mud, 13 Aug. 1981 . Others : China: 1 female (4.4 × 2.3 mm) ( ZRC 2012.1024 View Materials ), station 817, Wutong, Xiamen , Fujian Province, mud, 5 m, coll. 18 May 1981 ; 1 female juvenile (3.3 × 2.1 mm) ( ZRC 2012.1025 View Materials ), station 4071, East China Sea , soft mud, 8 mm, coll. Y. Cui, 10 December 1979 ; 1 female (6.0 × 4.0 mm) ( ZRC 2012.1026 View Materials ), East China Sea , soft mud, 20 m, coll. Y. Cui, 14 December 1979 ; 1 female (6.4 × 4.3 mm) ( ZRC 2012.1027 View Materials ), station 40, Jiaozhou Bay, Qingdao , Shandong, soft mud, 12 m, coll. Y. Cui, 7 September 1979 ; 1 female (5.0 × 3.4 mm) ( ZRC 2012.1028 View Materials ), station 819, Wutong, Xiamen , Fujian Province, mud, 6 m, 15 July 1981 ; 2 females (7.7 × 5.2 mm, 8.6 × 5.8 mm) ( ZRC 2012.1029 View Materials ), Xiamen Harbour, Fujian Province, February 1988 ; 2 females (4.4 × 2.5 mm, 4.5 × 2.9 mm) ( ZRC 2012.1030 View Materials ), Xiamen Harbour, Fujian Province, coll. April 1988 . Japan: 1 female (10.8 × 7.5 mm) (NSMT-Cr. 8229), Suo-nada Sea, Seto Inland Sea , coll. T. Habe ; 1 male (9.5 × 6.5 mm) ( ZRC 1970.1.20.26), Anake Bay , Nagasaki, coll. T. Sakai, 1967 ; 1 female (NSMT-Cr 6894), Amakusa, Ike-jima Island, Matsu-shima , coll. Y. Fukuda, 10 June 1979 .

Diagnosis. Carapace subquadrate, about 1.5 times as broad as long, dorsal surface granulated; regions indistinct, median H-shaped depression shallow ( Figs. 24A View Fig , 25A View Fig ). Eye small, slightly movable, cornea not pigmented ( Fig. 24B View Fig ). Pterygostomial region with long and short, oblique striae and scattered tubercles ( Fig. 25B View Fig ). Third maxillipeds relatively broad, almost completely covering buccal cavity ( Figs. 25E View Fig , 26D View Fig , 27F View Fig ); ischium longer than merus, distalmost mesial margin slightly rounded, median part of mesial margin straight; combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod relatively narrow, about 0.4 width of ischium, flagellum well developed. Chelipeds stout, unequal ( Fig. 24D View Fig ); major chela ( Fig. 25G View Fig ) with gap when fingers closed; dactylus and fixed finger with shallow longitudinal groove on outer surface; palm almost as long as broad covered by tubercles; minor chela ( Fig. 25H View Fig ) with relatively smaller gap when fingers closed. P2–P4 ( Fig. 24A View Fig ) short, relatively slender; merus of P4 3 times as long as broad, tubercles on upper and lower halves of outer surface, separated by longitudinal groove; dactylus of P4 slightly upcurved. Male thoracic sternum relatively broad ( Figs. 24C View Fig , 25C, D View Fig ); sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 by distinct ridge laterally, medially appearing fused, thoracic sternal groove extends obliquely from sternoabdominal cavity, not reaching base of third maxillipeds ( Figs. 24C View Fig , 25D View Fig ); sternite 8 exposed, subrectangular, as long as abdominal somite 1; sternoabdominal cavity reaches middle to sternite 4. Male abdomen relatively narrow ( Figs. 24C View Fig , 25F View Fig ); somites 1 and 2 free, somites 3–5 fused, lateral margin slightly sinuous; somite 6 shorter than length of somites 3–5, lateral margin expanded subproximally, forming triangular projection; telson subtriangular, distal margin rounded, sparsely setose. G1 ( Fig. 25I, J View Fig ) S-shaped distally, directed anterolaterally, distal part tapering, slightly twisted, apice not concealed under abdomen, row of spinules on midlength laterally, long setae on mesial and lateral margins. Female abdomen relatively narrow, 6 free somites and telson ( Fig. 25K View Fig ).

Variation. In larger individuals of M. chenae , new species (e.g., 9.2 × 6.1 mm, holotype, IOCAS), the male thoracic sternal groove is relatively wider and longer, oblique, and reaching the middle of sternite 4 ( Fig. 25C, D View Fig ), and the G1 is curved medially with the tip twisted ( Fig. 25I, J View Fig ). In a small individual (5.3 × 3.6 mm, ZRC 2012.1022), the thoracic sternal groove is slightly wider, shorter and oblique, but not reaching the middle of sternite 4 ( Fig. 26A, B View Fig ), the G1 curved at midlength, without row of spinules and the tip is only slightly twisted ( Fig. 26E, F View Fig ). In an even smaller individual (4.0 × 2.7 mm, ZRC 2012.1020), the thoracic sternal groove is very short, oblique, and barely extends from the sternoabdominal cavity into sternite 4 ( Fig. 27A, B View Fig ), with the G1 only slightly curved, tip not twisted ( Fig. 27C, D View Fig ). The shape of male abdomen, however, does not vary substantially with size ( Figs. 25F View Fig , 26C View Fig , 27E View Fig ).

Colour. Carapace, cheliped and pereopods uniformly yellowish-brown ( Fig. 1H View Fig ).

Etymology. The species is named after the late Chen Hui- Lian, a doyen of Chinese crab taxonomy and a good friend. She had in fact passed the present material to the second author many years ago as part of an anticipated broader study of Asian hexapodids. However, this was never realised with her untimely death.

Remarks. Mariaplax chenae , new species, resembles M. anfracta in having closely spaced tubercles on the carapace and cheliped, and the rounded distal margin of the telson. However, there are differences in the shapes of the third maxillipeds and G1s. In M. chenae , the ischium of the third maxilipped is obviously longer than the merus, the lateral and mesial margins along the distal half of the ischium are parallel, with distalmost mesial margin slightly rounded, the proximal half being narrow ( Figs. 25E View Fig , 26D View Fig , 27F View Fig ). In M. anfracta , the ischium is only slightly longer than merus, and although the lateral and mesial margins of the ischium are parallel, the narrow proximal part is very short, only about one-tenth the length of the ischium ( Fig. 23D View Fig ). Although the G1 of M. chenae varied with individual size, the difference is noticeable in the same size male individual of both species. The G1 of M. chenae (male, 5.3 × 3.6 mm, ZRC 2012.1022) is stout, tapering to twisted tip ( Fig. 26E, F View Fig ) while in M. anfracta (male, 5.0 × 3.2 mm, USNM 39752), the G1 is more slender, sinuous, the bent tip is longer, but not clearly twisted ( Fig. 23F, G View Fig ).

Significantly, M. anfracta s. str. is also a much smaller species, with males measuring 5.0 × 3.2 mm (USNM 39752) already mature, and females measuring 4.1 × 2.8 mm (ZRC 1965.11.24.6) already ovigerous. Female specimens of M. chenae of similar sizes are still immature.

The Chinese records of “ Hexapus granuliferus ” by Dai et al. (1986), Dai & Yang (1991) and Liu & He (2007), as well as the Japanese records of “ Hexapus (Lambdophallus) anfractus ” by Sakai (1976) are almost certainly M. chenae . The figures provided in these references agree very well with what is here diagnosed for this species.

Type locality. Coastal waters of Zhejiang Province, East China Sea, China.

Distribution. East China Sea and Japan. Subtidal, 4– 39 m.