Mariaplax hispida, Rahayu & Widyastuti, 2018

Rahayu, Dwi Listyo & Widyastuti, Ernawati, 2018, Additions to the Indonesian crab fauna of the genus Mariaplax Rahayu & Ng, 2014, and notes on Hexapus timika Rahayu & Ng, 2014 (Crustacea, Decapoda, Brachyura, Hexapodidae), Zootaxa 4379 (2), pp. 231-246 : 239-241

Mariaplax hispida n. sp.

( Figs. 6 ̄8)

Material examined. Holotype, ovigerous female (7.7 × 5.1 mm) ( MZB Cru 4682), St. A 1C, Tanjung Pasir , Jakarta Bay, 06°00.647' S, 106°69.658' E, sandy mud, coll. P. Widianwari, 10 March 2013.

Diagnosis. Carapace subquadrate, about 1.5 times as broad as long, dorsal surface covered with closelyspaced, prominent tubercles, cardiac and mesogastric regions almost smooth or with less prominent tubercles; regions indistinct, with shallow H-shaped depression medially ( Figs. 6A , 8A ); front deflexed, slight depression medially. Orbit distinct, eyes thick, slightly movable, cornea small, pigmented, slightly smaller than granular stalk ( Fig. 6B ). Pterygostomial region covered with granules, with row of 4 oblique striae ( Figs. 6B, C ).

Epistome longitudinally narrow; posterior margin concave with broadly triangular median projection.

Third maxillipeds broad ( Figs. 6C , 8C ); ischium slightly longer than merus, covered with tubercles, lateral and mesial margins straight, paralel, surface of merus with tubercles, short stiff setae; combined length of dactylus, propodus and carpus as long as merus and ischium; exopod covered with tubercles, lateral and mesial margins with dense setae, about 0.5 width of ischium, flagellum well developed.

Chelipeds asymmetrical, covered by closely spaced tubercles and short stiff setae ( Fig. 6B, C ). Major chela ( Figs. 7C , 8E ) with slightly gaping finger when closed; dactylus with longitudinal ridge at midline, tubercles on proximal third; cutting edge of dactyl with 2 large teeth proximally, smaller teeth distally; fixed finger with longitudinal ridge medially, cutting edge with row of teeth, smaller than teeth on dactyl; palm as long as broad; merus short, fringe of setae dorsomesially. Minor chela ( Figs. 7B , 8D ) with relatively narrower gap when fingers closed; same armament as major chela, cutting edges of dactylus and fixed finger with row of small teeth.

P2–P4 ( Fig. 6A ) short, thick, surfaces covered by short, stiff setae, upper and lower margins with longer, denser setae; dactylus gently upcurved; P3 longest. Dactylus of P2, P3 longer than propodi, slightly shorter than carpi, meri with indistinct median groove on lateral face, 2.8 and 3.0 as long as broad, respectively, row of large tubercles on dorsal and ventral margin of meri; dactylus of P4 longer than propodus, subequal to carpus, merus relatively short, stout, about 2.2 times longer than broad; lateral face covered by dense, large tubercles and sparse, short setae, separated by median longitudinal groove which furnished by short sparse setae ( Figs. 7A , 8F ).

Female thoracic sternum broad ( Fig. 6E ), surface prominently granular; sternites 1 and 2 fused, separated from sternite 3 by distinct furrow; sternite 3 separated from sternite 4; sternites 4–7 well developed, separated from each other by distinct suture; sternite 8 not exposed; sternopleonal cavity reaches distal part of sternite3. Female pleon broad, tuberculate, medially slightly less tuberculate; with 6 free somites and telson; somite 4 broadest; telson shorter than its basal width ( Figs. 6D , 8B ); female vulvae large, positioned on distal part of sternite 5, opening circular, without opercular cover ( Fig. 5E ). Male unknown.

Etymology. From the Latin hispidus, hairy, for the short, dense setae on the chelipeds and P2̄P4.

Remarks. The most remarkable character of this new species is the covering of large, prominent tubercles with short, stiff setae on the chelipeds and pereopods 2̄4, the long, plumose setae along the upper and lower margins of P2–P4, which each have short, thick meri.

The short, thick pereopods, place M. hispida n. sp. close to M. narusei Rahayu & Ng, 2014 from Japan and M. aspera from Lombok, Indonesia. These three species are easily separated by the presence of a longitudinal groove, bordered by large tubercles on the meri of pereopods 2–4 in the new species, while in M. narusei and M. aspera this longitudinal groove is barely visible. The carapace of M. narusei is much broader than long, 1.7 times as broad as long with smooth surface, while in M. hispida n. sp. the carapace is subquadrate (1.5 times as broad as long), the surface is partly covered by large, closely spaced tubercles. In M. aspera , the carapace surface is entirely covered by small, closely-spaced tubercles.

Distribution. Jakarta Bay, Indonesia.

Figures

FIGURE 5. Mariaplax pitrai n. sp., holotype, female (4.0 × 2.8 mm) (MZB Cru 4681); A, carapace; B, pleon; C, left third maxilliped; D, outer view of major chela; E, outer view of minor chela; F, outer view of right P2; G, outer view of right P3; H, outer view of right P4. Scales: A, B, F̅G = 1.0 mm; C̅E = 0.5 mm

FIGURE 6. Mariaplax hispida n. sp. holotype, female (7.7 × 5.1 mm) (MZB Cru 4682). A, overall habitus; B, buccal field, third maxilliped, pterygostomial regions, chelipeds; C, third maxilliped, thoracic sternites 1–3, chelipeds; D, thoracic sternites 6, 7, telson and pleonal somites; E, sternopleonal cavity and vulvae.

FIGURE 7. Mariaplax hispida n. sp. holotype, female (7.7 × 5.1 mm) (MZB Cru 4682). A, outer view of right P4; B, outer view of minor chela; C, outer view of major chela.

FIGURE 8. Mariaplax hispida n. sp. holotype, female (7.7 × 5.1 mm) (MZB Cru 4682). A, carapace; B, pleon; C, left third maxilliped;D, outer view of minor chela; E, outer view of major chela; F, outer view of left P4. Scales = 1.0 mm.