Mariaplax daviei, 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 : 434-435

Mariaplax daviei , new species

( Figs. 30 , 31 )

Hexapus sexpes – Haswell, 1882: 71. (not Cancer sexpes Fabricius, 1798 )

Hexapus granuliferus – Campbell & Stephenson, 1970: 286 (in part), fig. 49G, H. (not Hexapus granuliferus Campbell & Stephenson, 1970 )

Material examined. Holotype: male (6.0 × 4.5 mm) ( WAM C23270), Tasmania, Spring Bay , 42°33.00'S 147°55.50'E, 15 m, black mud and some fine shell, coll. R. S. Wilson, 23 April 1985 . Paratypes: Australia: 3 females (5.1 × 3.9 mm, 6.2 × 4.9 mm, 6.8 × 5.0 mm) ( WAM C23270), same locality as holotype ; 2 females (4.6 × 3.3 mm, 3.8 × 2.6 mm), 1 ovigerous female (4.8 × 3.3 mm) ( WAM), Jervis Bay , New South Wales, coll. P. Hutching, 5 June 1989 .

Diagnosis. Carapace subquadrate, about 1.3–1.4 times as

broad as long, dorsal surface pubescent, finely granulated ( Fig. 30A ). Anterolateral margin arcuate; posterolateral corner with angled prominence over base of posterior pereopods ( Figs. 30A , 31A ). Eye small, slightly movable, cornea wider than peduncle. Pterygostomial region with oblique row of broken striae. Third maxillipeds broad, completely covering buccal cavity ( Figs. 30C , 31D ); mesial margin of ischium of third maxillipeds slightly rounded; combined length of dactylus, propodus and carpus subequal to that of merus and ischium; exopod narrow, 0.4 width of ischium, flagellum well developed. Chelipeds stout, unequal ( Figs. 30D, E , 31F, G ); major chela ( Figs. 30D , 31F ) with narrow gap when fingers closed, dactylus and fixed finger with shallow longitudinal groove on outer surface; palm pubescent, finely tuberculate, slightly wider than long; minor chela ( Figs. 30E , 31G ) with relatively wider gap when fingers closed; dorsal surface of palm covered by large tubercles and short pubescent. P2–P4 relatively long ( Fig. 30A, B ); merus of P4 3.7 times as long as broad; outer face with longitudinal groove and sparse short setae. Male thoracic sternum broad ( Figs. 30B, C , 31B, C ), sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 not clearly delimited from sternite 4, thoracic sternal groove very short, slightly extend outward from sternoabdominal cavity; sternite 8 exposed, quadrangular, as long as male abdominal somite 1; sternoabdominal cavity not reaching base of sternite 3. Male abdomen relatively narrow ( Figs. 30B , 31E ); somites 1 and 2 free; somites 3–5 fused, lateral margin slightly arched; somite 6 slightly shorter than half length of somites 3–5, lateral margin expanded medially into blunt triangular projection; distal margin of telson rounded, setose. G1 ( Fig. 31H, I ) slightly curved medially, directed anterolaterally, distal part tapered, ended in blunt tip, not concealed under abdomen, exposed on thoracic sternal groove, obscured by setae of telson. Abdomen of female with 6 free somites and telson ( Fig. 31J ).

Colour. Not known.

Etymology. Named after our friend, Peter Davie, who provided important advice on the type material of Hexapus granuliferus .

Remarks. The holotype and male paratype of H. granuliferus described by Campbell & Stephenson (1970) are not conspecific, and should be referred to two separate species. The shape of the third maxilliped, structure of the G1, and the relative length of P2–P4 of both species, however, agree with Mariaplax as presently defined (see remarks for M. granulifera ). The G1 of M. daviei , new species, resembles those of H. simplex , both are simple, arched, and without spinules. Nevertheless these two species cannot be placed in the same genus as the generic characters such as the strongly convex mesial margin of the ischium of the third maxilliped and the longitudinally broad sternite 4 in Hexapinus , are only slightly rounded mesial margin of ischium of the third maxilliped and transversally broad sternite 4 in Mariaplax .

Type locality. Spring Bay , Tasmania, Australia .

Distribution. Port Jackson, New Southwell and Tasmania, Australia; 15 m.

Figures

Fig. 30. Mariaplax daviei, new species, holotype male (6.0 × 4.5 mm) (WAM C23270). A, overall view of carapace, chelipeds and P2–P4; B, ventral view of cephalothorax; C, ventral view of cephalothorax showing third maxillipeds and telson, D, major chela; E, minor chela.

Fig. 31. Mariaplax daviei, new species. A–I, holotype male (6.0 × 4.5 mm) (WAM C23270); J, paratype female (6.2 × 4.9 mm) (WAM C23270). A, dorso-lateral 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, right third maxilliped; E, male abdomen and telson, F, major chela; G, minor chela; H, I, G1; J, female abdomen and telson. Scale bars = 1.0 mm.