Pilumnus curvipenis, Komai, Tomoyuki & Motoh, Hiroshi, 2012

Komai, Tomoyuki & Motoh, Hiroshi, 2012, The identity of Pilumnus dofleini Balss, 1933 (Crustacea: Decapoda: Brachyura Pilumnidae), with descriptions of three new species from the Western Pacific, Zootaxa 3305, pp. 1-27 : 17-20

Pilumnus curvipenis n. sp.

( Figs 12 , 13 , 18A, B )

Pilumnus dofleini . –– Ng 2000: 301, figs 1, 2. Not Pilumnus dofleini Balss, 1933 .

Material examined. Holotype: male (11.4 x 14.2 mm), NSMT-Cr 6665, Shin-Kurose Bank, Izu Islands, 230– 160 m, 26 November 1974, dredge, coll. T. Okutani.

Paratypes: 2 males (8.0 x 9.5, 8.8 x 10.2 mm), 1 ovigerous female (13.4 x 16.4 mm), NSMT-Cr 22177, same data as holotype; 1 female (12.3 x 14.8 mm), NSMT-Cr 6666, Hyotan-se Bank, Izu Islands, 26 June 1973, coll. T. Okutani.

Diagnosis. Carapace ( Fig. 12 A–D, 18A) transversely ovoid, surface covered with dense short setae; greatest width across fourth anterolateral spines, about 1.2 times of length; regions poorly defined, grooves defining regions very shallow, indistinct; anterior part of dorsal surface with scattered small, conical spines or spinulose tubercles; cardiac region without conspicuous spines or tubercles; frontal margin nearly horizontal in dorsal view, weakly deflexed, separated medially by shallow, U-shaped notch; each frontal lobe not markedly divided, granular or tuberculate on margins, with or without small tubercle at inner supraorbital angle; supraorbital margin with row of small spines, without clefts; anterolateral margin spinose, with 4 principal spines (including spiniform external orbital angle), these anterolateral spines slightly unequal in size (first slightly smaller than others), obliquely erect; second, third each bearing 1 or 2 accessory spinules; posterolateral margin almost straight, converging towards posterior margin; posterior part without submarginal row of spines or tubercles; suborbital margin bordered with row of small spines or tubercles, innermost spine largest, visible in dorsal view; suborbital region with covering of numerous granules or small spinulose tubercles; pterygostomial groove smooth; dorsolateral portion of buccal frame with several granules.

Third maxilliped with ischium nearly smooth on outer surface; outer surface of merus and distal part of exopod coarsely granular.

Chelipeds ( Fig. 13 A–C) slightly unequal, slightly dissimilar with right larger than left; anterior margin of basis-ischium fused segment with row of small tubercles; merus with distal spine on crested posterodorsal margin; carpus with scattered small spines on dorsal to outer surfaces (these spines conical or subconical, sometimes curving), inner distal angle produced in prominent spine; palm with scattered numerous spines or spinulose tubercles on outer surface (most spines subacute), inner dorsal margins not carinate, ventral surface with small, blunt to subacute tubercles in right, acute or subacute spines in left; fingers slightly longer than palm, with row of low, broadly rounded teeth on cutting edges (major chela) or with faintly denticulate cutting edges (minor chela); dactylus with small, occasionally spinulose granules on dorsal surface proximally, with 1 (minor) or 2 (major) longitudinal grooves on outer surface.

Ambulatory legs ( Fig. 13 D, E) moderately long, moderately stout for genus (merus of fourth leg about 2.9 times longer than wide), bearing moderately long, stiff setae on margins of merus to dactylus; basis-ischium fused segment unarmed on ventral surface in first to third legs, that of fourth leg (fifth pereopod) with few small tubercles on ventral surface; merus with single row of conspicuous spines on dorsal (extensor) margin and single row of small tubercles or sharp granules on ventral (flexor) margins; outer (posterior) surface smooth; carpus with 2 rows of long spines on extensor margin and 1 or 2 additional spines on outer (posterior) surface dorsally (in fifth, outer surface unarmed); propodus with 2 rows of spines on extensor margin, flexor margin unarmed; dactylus slender, distinctly longer than propodus, unarmed on extensor margin.

Thoracic sternum nearly smooth (cf. Ng 2000: fig. 1g).

Male abdomen ( Fig. 12 F) with somites 1 and 2 unarmed on outer surfaces and margins. Telson ( Fig. 12 F) triangular with rounded tip, 1.2 times longer than wide, lateral margins nearly straight.

First gonopod ( Fig. 13 F–I) sinuous; distal 0.1 strongly bent, bearing row of spinules subterminally on lateral side, these spinules increasing in size distally; apex sharply pointed.

Coloration. Not known.

Distribution. So far known only from Izu Islands at depths of 160– 230 m.

Remarks. A full description of this new species was given by Ng (2000: 301) under the name Pilumnus dofleini . Pilumnus curvipenis n. sp. appears closest to P. bohol n. sp. Differentiating characters between P. curvipenis n. sp. and P. bohol n. sp. are discussed under the account of the latter species.

Etymology. From the Latin curvis (= curved), and penis in reference to the strongly curved distal part of the first gonopod.

Figures

FIGURE 12. Pilumnus curvipenis n. sp., holotype, male (11.4 x 14.2 mm), NSMT-Cr 6665. A, carapace, dorsal view (setae omitted); B, left upper orbital and anterolateral margins, dorsal view (setae omitted); C, frontal margin, anterodorsal view (setae omitted); D, left anterior part of carapace and cephalic appendages, anterior view (setae omitted); E, left third maxilliped, ventral (outer) view (setae partially omitted); F, abdomen and telson, ventral view (setae omitted). Scale bars: 2 mm for A – D, F; 1 mm for E.

FIGURE 13. Pilumnus curvipenis n. sp., holotype, male (11.4 x 14.2 mm), NSMT-Cr 6665. A, right major chela, outer view; B, carpus of right major cheliped, dorsal view; C, left minor chela, outer view; D, left third ambulatory leg (fourth pereopod), posterior view; E, left fourth ambulatory leg (fifth pereopod), posterior view; F, left first gonopod, mesial view; G, same, lateral view; H, same, distal part, mesial view; I, same, lateral view. Setae omitted. Scale bars: 2 mm for A – E; 1 mm for F, G; 0.2 mm for H, I.

FIGURE 18. A, B, Pilumnus curvipenis n. sp., paratype, ovigerous female (13.4 x 16.4 mm), NSMT-Cr 6666; C, D, Pilumnus bohol n. sp., paratype, ovigerous female (10.2 x 12.6 mm), ZRC 2001.0688. A, C, upper orbital and anterolateral margin, dorsal view; B, D, vulvae, ventral view. Scale bars: 2 mm for A, C; 1 mm for B; 0.5 mm for D.