Kume tigra, Naruse & Ng, 2012

Naruse, Tohru & Ng, Peter K. L., 2012, Kume tigra, a new genus and new species of carupine swimming crab (Crustacea: Brachyura: Portunidae) from Kume Island, Ryukyu Islands, Japan *, Zootaxa 3367 (1), pp. 204-210 : 206-208

Kume tigra n. sp.

( Figs. 1–3 )

Material examined. Holotype: male, 2.4 × 4.7 mm, RUMF-ZC-1400, KUMEJIMA 2009 Stn. Diving 1, Umagai , Kume Island, Ryukyu Islands, Japan, 26°20.769' N, 126°51.506' E, - 55 m, coll. KUMEJIMA 2009, 9 Nov. 2009.

Paratypes, 1 female, 2.9 × 6.1 mm, ZRC 2010.0182 , 1 ovig. female, 3.3 × 6.4 mm, RUMF-ZC-1401, same data as holotype .

Diagnosis. See for genus.

Description. Carapace broadly transverse, carapace width 1.94–2.12 times length, dorsal surface almost smooth except for granulated epi- and mesobranchial regions and prominent oblique granulated crest on metabranchial region. Frontal margin almost straight, slightly produced, deflexed medially, medially notched in dorsal view. Supra- to infraorbital magins continuous, rimmed, supraorbital margin without fissure; infraorbital margin concave on mesial half. Orbit rounded; eyes mobile, relatively short, with thick eyestalk, upper surface rather flattened, almost completely filling orbit; cornea well developed. External orbital angle low, indistinct, anterolateral margin with 5 small teeth, weakly cristate between first to fifth teeth, teeth slightly larger than granules on branchial regions, first to fourth teeth placed equidistantly, maximum width of carapace between fifth teeth. Subhepatic and pterygostomial regions granulated. Epistome relatively narrow longitudinally; posterior margin with distinct median notch. Endostomial ridges distinct. Third maxilliped rectangular, ischium slightly longer than merus without trace of median sulcus; merus with distolateral angle produced; distal end of exopod not reaching distolateral angle of merus, with long flagellum.

Male thoracic sternum relatively broad; sternites 1–3 completely fused; sternites 3 and 4 delimited by groove, deep medially, shallow laterally; sternoabdominal cavity relatively wide; sutures between thoracic sternites 4–8 medially interrupted, ending just at inner part of lateral slope of cavity; distinct press button present near inner end of suture 4/5 on sternite 5; no longitudinal line discernible; slight depression visible on each side below level of inner ends of suture 7/8. Female thoracic sternum wide, condition of sternites same as male; vulva on middle part of sternite 6; transversely elliptical.

Chelipeds subequal in male and female, relatively long, robust; chela as long as carapace width; merus slightly longer than palm, triangular in cross-section, anterior margin lined with granules, without distinct tooth or spine; carpus short, smooth, inner angle rounded. Chela relatively long, palm shorter than fingers; fingers straight in outer view, weakly curved inwards in upper view, distal ends strongly hooked; occlusal margins lined with numerous sharp teeth.

P2–P4 similar in shape, P2 longest. Male P2 granulated on anterior and posterior margins of merus, outer, inner margins of propodus, outer margin of dactylus; granulation relatively weaker in P3; P4 similar but no granulation on posterior margin of merus and inner margin of propodus. Female legs similar to that of male, but P2 propodus granulated only on inner margin, P3 and P4 meri and dactyli granulated only on anterior margins and outer margins, respectively. P 5 in both sexes shortest, propodus slightly longer and wider than carpus, laterally flattened; dactylus slightly longer than propodus, lanceolate, laterally flattened, outer margin nearly straight, outer margin and distal quarter of inner margin lined with fine spines.

Male abdomen relatively wide; somite 1 longitudinally narrow; somite 2 laterally separated but functionally fused to somite 3 medially, without indication of a suture; somites 3–5 completely fused; telson triangular, tip rounded, slightly broader than long; somite 3 to telson forming almost right-angled triangle.

G1 simple, gently curving outwards, distal half almost straight, cylindrical in shape, tapering gently to subtruncate tip. G2 slender, about half G1 length, tip distinctly bifurcated.

Colour. In life, the carapace is pinkish to yellowish white, while the ambulatory legs are white with pink patterns. The cheliped is also pinkish white, but the fingers are striped with white and maroon ( Fig. 1 ). The striped pattern is somewhat variable, being prominent in the two female specimens ( Fig. 1b ) but less obvious in the holotype male ( Fig. 1a ).

Etymology. The new species is named after the Latin “ tigra ” for tiger, alluding to its striped cheliped fingers. The name is used as noun in apposition.

a, carapace, dorsal view; b, cephalothorax, anterior view; c, right third maxilliped; d, left cheliped, upper view; e, left chela; f, right fifth pereopod. Scales = 1.0 mm. a, anterior thoracic sternum; b, posterior thoracic sternum; c, abdomen and telson; d, left G1; e, left G2. cx5 = coxa of fifth pereopod; G1 = male first gonopod; pb = press-button; pe = penis; st3–8 = thoracic sternites 3–8. Scales: a–c = 1 mm; d, e = 0.5 mm.

Figures

FIGURE 1. Colours in life. Kume tigra n. gen. et sp. a, holotype male, 2.4 × 4.7 mm, RUMF-ZC-1400; b, paratype female (2.9 × 6.1 mm), ZRC 2010.0182.

FIGURE 2. Kume tigra n. gen. et sp. Paratype female (2.9 × 6.1 mm), ZRC 2010.0182.

FIGURE 3. Kume tigra n. gen. et sp. Holotype male (2.4 × 4.7 mm), RUMF-ZC-1400.