Hexapinus ceres, 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 : 414-416

Hexapinus ceres , new species

( Figs. 14 , 15 )

Material examined. Holotype: female (5.2 × 3.2 mm) ( NMCR 39070 ), dive site at Basura , Anilao, Batangas, Philippines, 5 m, coll. H. Takakura, 22 August 2011.

Diagnosis. Carapace subquadrate, about 1.6 times as broad as long, dorsal surface granulated; regions indistinct, median depression shallow ( Fig. 14A ). Lateral margin with protuberance medially ( Figs. 14A , 15A ). Eye small, slightly movable, cornea globular, wider than tuberculate peduncle ( Fig. 14C ). Pterygostomial region with row of oblique striae. Third maxillipeds with outer surface tuberculate ( Figs. 14D , 15B ); ischium almost as long as merus, with rounded mesial margin; dactylus missing; exopod short, broad, more than 0.5 times width of ischium, flagellum well developed. Chelipeds slender ( Fig. 14C, D ) with slight gap when fingers closed. P2–P4 ( Fig. 14A, B ) short, stout, covered by tubercles; merus of P4 2 times as long as broad; dactylus of P2–P4 slightly longer than propodus, upper margin tuberculate. Female thoracic sternum relatively broad ( Fig. 14B, D ), sternites 1 and 2 fused, separated from sternite 3 by distinct ridge; sternite 3 separated laterally from sternite 4, appears medially fused, sternites 4–7 well developed, separated by distinct sutures. Female abdomen relatively broad ( Figs. 14B, D , 15C ) with 6 free somites and telson. Male unknown.

Colour. Not known.

Etymology. From the Latin “ ceres ” for grain; alluding to the granular dorsal carapace surface. The name is used as a noun in apposition.

Remarks. Although this species is known from only one female specimen, it can be placed in Hexapinus mainly on the basis of the form of the ischium and merus of the third

Rahayu & Ng: New genera and species of Hexapodidae

maxilliped ( Fig. 15B ), although the mesial margin of the ischium is relatively less convex compared to its congeners. Its exopod is also broad like its congeners although it is relatively shorter ( Fig. 15B ). It shares the pereopod condition with other Hexapinus species : the P2–P4 are short and stout with the dactylus slightly longer than propodus, and the merus of P4 is about twice as long as broad, without a longitudinal groove ( Fig. 14A ). A male specimen will nevertheless need to be collected to confirm the generic position of this species.

Hexapinus ceres , new species, differs markedly from H. latipes , H. latus , new species, and H. simplex , new species, in having numerous closely spaced tubercles on the carapace, chelipeds and P2–P4.

Type locality. Batangas, Philippines .

Distribution. Batangas, Philippines. Subtidal, 5 m.

Figures

Fig. 14. Hexapinus ceres, new species, holotype female (5.5 × 3.3 mm) (NMCR 39070). A, overall view of carapace, left cheliped and P2–P4; B, ventral view of cephalothorax; C, frontal view of cephalothorax; D, abdomen and telson.

Fig. 15. Hexapinus ceres, new species, holotype female (5.5 × 3.3 mm) (NMCR 39070). A, anterior view of carapace; B, left third maxilliped (dactylus missing); C, abdomen and telson. Scale bars = 1.0 mm.