Mariaplax narusei, 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 : 443-446

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/43D82DCB-2F68-4EA0-8381-848ED738253C
taxon LSID	lsid:zoobank.org:act:43D82DCB-2F68-4EA0-8381-848ED738253C
treatment provided by	Tatiana
scientific name	Mariaplax narusei
status	sp. nov.

Treatment

Mariaplax narusei View in CoL , new species

( Figs. 2C View Fig , 39 View Fig , 40 View Fig )

Material examined. Holotype: male (9.6 × 5.8 mm) (RUMF- ZC-2112), Funaura Bay , Iriomote Island, Ryukyu Islands, Japan, coll. T. Naruse, 1 July 2011 . Paratypes: Japan: 1 female (12.0 × 7.1 mm) ( ZRC 2012.1031 View Materials ), 1 ovigerous female (11.5 × 6.7 mm) (RUMF-ZC-2113), same locality as holotype .

Diagnosis. Carapace much broader than long, about 1.7 times as broad as long, dorsal surface smooth, granulated near margin; regions indistinct, H-shaped depression shallow medially ( Fig. 39A View Fig ). Anterolateral margin arcuate; posterolateral margin with angled prominence over base of posterior pereopods ( Figs. 39A View Fig , 40A View Fig ,). Eye small, slightly movable, cornea globular, peduncle granular ( Fig. 39C View Fig ). Pterygostomial region with row of 3 relatively long, widely separated oblique striae and some tubercles. Third maxillipeds broad, completely covering buccal cavity ( Figs. 39D View Fig , 40D View Fig ); ischium of third maxillipeds slightly longer and wider than merus, with straight mesial margin; combined length of dactylus, propodus and carpus slightly shorter than that of merus and ischium; exopod narrow, 0.4 width of ischium, flagellum well developed. Chelipeds stout, unequal ( Fig. 39E View Fig ); major chela with gap when fingers closed; palm slightly wider than long, outer surface covered by tubercles; minor chela with relatively wider gap when fingers closed. P2–P4 relatively long ( Fig. 39A View Fig ); dactylus of P2 slightly upcurved; P3 with shallow longitudinal groove on outer surface; P4 entirely covered by tubercles, merus 2.8 times as long as broad. Male thoracic sternum relatively broad ( Figs. 39B View Fig , 40B, C View Fig ); sternites 1 and 2 fused, slightly curved posteriorly, separated from sternite 3 by distinct ridge; sternite 3 separated from sternite 4 by distinct tuberculate ridge laterally, thoracic sternal groove narrow, short, oblique, extends from sternoabdominal cavity to middle of sternite 4 ( Figs. 39B View Fig , 40B View Fig ); sternite 8 exposed, rectangular, slightly longer than abdominal somite 1; abdominal cavity not reaching base of sternite 3 ( Figs. 39B View Fig , 40C View Fig ). Male abdomen relatively narrow ( Figs. 39B View Fig , 40E View Fig ); somites 1 and 2 free, somites 3–5 fused, slightly wider than somite 6; lateral margin sinuous, somite 6 sligthly shorter than length of somites 3–5, lateral margin slightly expanded medially; telson subpentagonal with distal margin rounded, margin sparsely setose. G1 ( Fig. 40F, G View Fig ) stout, bent 60° along two-thirds of length, slightly twisted, distal part tapered, apices not concealed under abdomen, exposed on thoracic sternal groove, obscured by setae of telson, with sparse short setae laterally and mesially. Female abdomen broad, with 6 somites free and subtriangular telson ( Fig. 40H View Fig ).

Colour. In life, generally uniformly yellowish brown with the carapace slightly darker ( Fig. 2C View Fig ).

Etymology. This species is named after Tohru Naruse who kindly passed the specimens to us for this study; and helped us carefully read this long manuscript.

Remarks. Mariaplax narusei , new species, can be distinguished from congeners by the following characters: the carapace is much broader than long, the ischium of the third maxilliped is wider than the merus, and P4 is entirely covered by tubercles.

The much broader carapace and the shape of the G1 superficially resemble the condition in Latohexapus granosus . However, the carapace of L. granosus is covered by numerous tubercles and the regions are distinct, thoracic sternites 1 and 2 are bent inwards towards the buccal cavity, and the G1 is not twisted ( Huang et al., 2002: Figs. 1B View Fig , 3A, B, D, E View Fig ; 54A, C View Fig ). In M. narusei , the carapace surface is smooth with the regions indistinct, thoracic sternites 1 and 2 are only very slightly curved (not bent inwards) and the G1 is twisted medially ( Figs. 39A View Fig , 40F, G View Fig ).

Two characters of M. narusei resemble species of Hexapinus : the ischium of the third maxilliped is relatively broader than the merus, and the P2 to P4 are relatively shorter. However, the ischium of the third maxillipeds is still more angular in M. narusei , with the mesial margin not distinctly convex ( Fig. 40D View Fig ) (versus the mesial margin is strongly convex and subauriculiform in Hexapinus species ). Unlike Hexapinus species , the outer surface of the ambulatory merus in M. narusei has a longitudinal groove albeit shallow ( Fig. 39A View Fig ) (versus smooth and entire). The G1 structures are also different, with that of M. narusei S-shaped ( Fig. 40F, G View Fig ) (typical for Mariaplax species ) while Hexapinus species have gently curved G1s.