Hexapus timika, 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 : 405-407

Hexapus timika , new species

( Figs. 8 , 9 )

Material examined. Holotype: male (4.6 × 3.0 mm) ( MZB Cru 3789), station OT 14A, Otakwa, Timika, Papua, Indonesia, coll. A. Haris, 8 December 2003 . Paratype: Indonesia: 1 male (6.2 × 4.5 mm) ( ZRC 2013.0946 ), station EM 771, Muara Mawati, Timika, Papua, coll. A. Haris, 11 August 2001 .

Diagnosis. Carapace rounded, about 1.5 times as broad as long; regions indistinct, with median H-shaped shallow depression; dorsal surface with flattened granules ( Fig. 8A ). Anterolateral margin arcuate; posterolateral corner with feeble angle over base of posterior pereopods ( Fig. 9A ). Orbit distinct, eye slightly movable, cornea globular. Pterygostomial region ( Fig. 9B ) with long oblique striae and scattered tubercles. Third maxillipeds narrow, not covering buccal cavity, with gap when closed ( Figs. 8B , 9D ); ischium longer than merus, mesial margin rounded subproximally, straight distally; merus slightly wider than ischium; combined length of dactylus, propodus and carpus shorter than that of merus and ischium; exopod relatively broad, about 0.5 width of ischium, flagellum well developed. Chelipeds stout, unequal ( Fig. 8B ); major chela with gap when fingers closed, with large tooth at cutting edge of dactylus; palm slightly longer than wide; minor chela with narrow gap when fingers closed; shallow longitudinal groove on outer surface of dactylus and fixed finger; outer surface of palm covered by large tubercles on lower half. P2–P4 ( Fig. 8A ) relatively short, slender; dactylus of P2 slightly upcurved, dactylus of P3 and P4 straight; merus of P4 about 3 times as long as broad. Male thoracic sternum broad ( Figs. 8B , 9C ), sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 and 4 separated by distinct ridge, very short thoracic sternal groove extends slightly from sternoabdominal cavity ( Fig. 9C ); sternite 8 exposed, triangular, slightly shorter than abdominal somite 1; sternoabdominal cavity reaches base of sternite 3. Male abdomen relatively wide ( Figs. 8B , 9E ); somites 1 and 2 free, somites 3–5 fused, lateral margin weakly produced subproximally, slightly constricted distally; somite 6 half length of somites 3–5, expanded laterally near base; telson triangular with rounded tip, margin setose. G1 ( Fig. 9F, G ) bent 60° on distal third, directed anterolaterally, distal part tapered, unarmed, not concealed under abdomen, exposed on thoracic sternal groove, obscured by setae of telson. Female unknown.

RAFFLES BULLETIN OF ZOOLOGY 2014

Colour. In life, dirty white overall, covered with black mud and stains.

Etymology. Named after the type locality Timika. The name is used as a noun in apposition.

Remarks. The differences in the shape of the carapace, male abdomen and G1 between H. sexpes and H. timika , new species, are distinct. The carapace of H. sexpes is subquadrate with dorsal surface pitted, the granulation is only on the dorsolateral surface ( Figs. 3A , 5A ) while in H. timika , the carapace is more or less rounded, and the dorsal surface covered by flattened granules ( Figs. 8A , 9A ). The abdomen of H. sexpes is also relatively narrower and longer than the stouter and wider abdomen of H. timika ( Fig. 5F versus Fig. 9E ). The G1 of H. sexpes and H. timika are both bent at around 60° but in H. sexpes , a protuberance is present subdistally and the lower margin has a row of small spines ( Fig. 6D, E ), whereas in H. timika , it is unarmed ( Fig. 9F, G ).

Type locality. Otakwa , Papua, Indonesia .

Distribution. Timika, Papua, Indonesia. Subtidal, 7– 14 m.

Figures

Fig. 8. Hexapus timika, new species, holotype male (4.6 × 3.0 mm) (MZB Cru 3789). A, overall view of carapace, chelipeds and P2–P4; B, ventral surface of cephalothorax.

Fig. 9. Hexapus timika, new species, holotype male (4.6 × 3.0 mm) (MZB Cru 3789). A, dorso-lateral margin of carapace; B, ventral view of cephalothorax; C, thoracic sternites 1–4, showing thoracic sternal groove and sternoabdominal cavity; D, left third maxilliped; E, male abdomen and telson; F, G, G1. Scale bars: A–E = 1.0 mm; F, G = 0.5 mm.

Fig. 3. Hexapus sexpes (Fabricius, 1798), male (8.5 × 5.4 mm) (ZRC 2012.1014). A, overall view of carapace, chelipeds and P2–P4; B, carapace.

Fig. 5. Hexapus sexpes (Fabricius, 1798). A–F, male (8.5 × 5.4 mm) (ZRC 2012.1014); G, female (5.8 × 3.9 mm) (ZRC 1965.11.24.5). A, carapace; B, thoracic sternites 3 and 4, showing thoracic sternal groove and telson; C, thoracic sternites 1–4, showing thoracic sternal groove; D, anterior view of cephalothorax; E, left third maxilliped; F, male abdomen and telson; G, female abdomen and telson. Scale bars = 1.0 mm.

Fig. 6. Hexapus sexpes (Fabricius, 1798), male (8.5 × 5.4 mm) (ZRC 2012.1014). A. major chela; B, minor chela; C, right P4; D, E, right G1. Scale bars = 1.0 mm.