Hexapus timika Rahayu & Ng, 2014

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 : 232-233

Hexapus timika Rahayu & Ng, 2014

( Figs. 1 , 2 )

Hexapus timika Rahayu & Ng, 2014: 405 , figs. 8, 9.

Material examined. 2 males (4.5 × 3.3 mm, 4.2 × 2.9 mm) (RCO), 2 females (4.0 × 2.9 mm, 3.3 × 2.4 mm) (RCO), 3 males (4.6 × 3.2 mm, 4.7 × 3.5 mm, 4 × 2.8 mm) (ZRC), 1 females (5.8 × 3.6 mm) (ZRC), station EM770, Muara Mawati, 4°58.045'S, 137°07.418'E, 17 November 2015; 1 female (4.2 × 2.9 mm) (RCO), same station, 27 October 2000, 1 female (4.5 × 3.5 mm) (RCO), same station, 12 July 2013.

Comparative material. Hexapus timika : male holotype (4.6 × 3.0 mm) ( MZB Cru 3789), station OT 14A, Otakwa, Timika , Papua; male paratype (6.2 × 4.5 mm) ( ZRC 2013.0946 ). station EM 771, Muara Mawati, Timika, Papua, coll. Abdul Haris, 11 August 2001 .

Hexapus sexpes : male (8.5 × 5.4 mm), female (7.1 × 4.5 mm) ( ZRC 2012.1014 ), sand flat, KoSirae , Phuket, Thailand, coll . T. Komai, 22 December 2009; 1 female (5.8 × 3.9 mm) ( ZRC 1965.11.24.5), Penang strait, Malaysia .

Amended description. Carapace rounded or subquadrate, about 1.5 times as broad as long; regions indistinct; scattered granules on anterolateral surfaces, dorsal surface with flattened tubercles, or pitted ( Figs. 1A, B , 2C ). Front deflexed, divided into 2 lobes. Eye small, slightly movable, cornea globular, narrower than peduncle. Pterygostomial region with 4 long oblique striae and scattered tubercles.

Third maxillipeds narrow, not covering buccal cavity; ischium longer and narrower than merus, mesial margin rounded subproximally, straight distally; merus slightly wider than ischium; combined length of dactylus, propodus and carpus slightly shorter than that of merus and ischium; exopod relatively narrow, about 0.4 width of ischium, flagellum well developed ( Fig. 2B, D ).

Male chelipeds stout, unequal; major chela with gap when fingers closed, with large tooth at cutting edge of dactylus, surface pitted, row of large teeth on mesiodorsal margin ( Figs. 1B , 2E ); minor chela with relatively wider gap when fingers closed; cutting edges of dactylus and fixed finger with row of small teeth, surface with scattered large tubercles ( Fig. 2F ). P2–P4 relatively long, slender, P3 longest ( Fig. 1A, B ).

Male thoracic sternum broad; short thoracic sternal groove slightly extend obliquely from sternopleonal cavity; sternopleonal cavity reaches base of sternite 3. Male pleon relatively narrow; somites 1 and 2 free, somites 3–5 fused, broad; somite 6 shorter than length of somites 3–5, expanded laterally near base; telson subtriangular with rounded tip ( Fig. 2D ).

G1 bent 60° medially, directed anterolaterally, with subdistal protuberance, distal part gradually tapered, not concealed under pleon, exposed on thoracic sternal groove, obscured by setae of telson.

Female chelipeds equal. Female pleon broad, telson and all somites free; with broad suture between somites, telson rounded ( Fig. 2B ), vulva positioned on anterior half of sixth sternite, no opercular cover, opening elongate ( Fig. 2A ).

Remarks. Hexapus timika was described from two males in which the carapace of the holotype was damaged and therefore appearing rounded (Rahayu & Ng 2014: fig. 8). The male specimens in this study have the carapace more quadrangular, similar to the paratype. Some minor morphological differences with the holotype and paratype are noted in the specimens examined here: the anterolateral surface of the carapace has scattered granules, with the remainder of the carapace surface pitted ( Fig. 1A, B ); the male pleon is slightly narrower with the sixth somite slightly longer than the telson ( Fig. 2D ). In the holotype, however, the carapace is covered with flattened tubercles on its surface, the male pleon is broad, and the telson is clearly shorter than the sixth somite of pleon (Rahayu & Ng 2014: figs. 8, 9). The shape of G1 (simple, bent 60°on distal third, tapering to pointed tip), and the third maxillipeds (merus narrower than carpus) in the specimens studied here, however, are typical for H. timika .

Distribution. West Papua, Indonesia, subtidal to 20 m.

Figures

FIGURE 1. Hexapus timika Rahayu & Ng, 2014, overall habitus. A, female (5.8 × 3.6 mm) (ZRC), right cheliped missing; B, male (4.6 × 3.2 mm) (ZRC).

FIGURE 2. Hexapus timika Rahayu & Ng, 2014. A, B, female (5.8 × 3.6 mm) (ZRC); C̅F, male (4.6 × 3.2 mm) (ZRC); A, vulvae; B, D, buccal field, third maxilliped, anterior thoracic sternum, telson and pleonal somites; C, carapace; E, major chela; F, minor chela.