Pilumnus bohol, 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 : 20-27

Pilumnus bohol n. sp.

( Figs 14–17 , 18 C, D)

Pilumnus dofleini . — Ng et al. 2008: fig. 112. Not Pilumnus dofleini Balss, 1933 .

Material examined. Holotype: male (16.2 x 19.2 mm), AURORA Expedition, Bohol Sea, CA 2345, 09°28.7’N, 123°55.3’E to 9°28.3’N 123°54.1’E, 106–276 m, sandy/muddy bottom, 23 May 2005, NMCR 39036.

Paratypes: 1 ovigerous female (10.2 x 12.6 mm), Balicasag, Panglao, Philippines, 50–500 m, 28 November 2001, tangle net, ZRC 2001.0688; 1 female (9.0 x 10.5 mm), same locality, November 2005, ZRC 2012.0132; 1 male (10.7 x 12.7 mm), 1 ovigerous female (10.4 x 11.9 mm), PANGLAO 2004, stn T2, Bolod, Panglao I., 09°32.4'N 123°47.8'E, 152 m, coarse sand, 31 May 2004, ZRC 2012.0133; 1 female (10.5 x 12.2 mm), same data, ZRC 2012.0134.

Non-types: 1 female (5.5 x 6.6 mm), 1 juvenile (4.3 x 5.1 mm), PANGLAO 2004, stn T2, Bolod, Panglao I., 09°32.4'N 123°47.8'E, 152 m, coarse sand, 31 May 2004, ZRC 2012.0135; 4 juveniles (4.0 x 4.6 to 5.4 x 6.5 mm), PANGLAO 2004, stn T36, Cervera shoal, west of Pamilacan I., 09°29.3'N 123°51.5'E, 95–128 m, sand on echinoderms bed, 4 July 2004, ZRC 2012.0136.

Description. Carapace ( Figs 14 A, B, 16A–C, 18C) fairly vaulted, subovoid in dorsal view, surface covered with numerous short setae; greatest width across fourth anterolateral spines, 1.2 times of length; dorsal surface somewhat convex longitudinally and transversely, regions slightly defined, surface of regions with some tiny tubercles; cardiac region not elevated, only with few tubercles partially obscured by setae; grooves between regions also with short setae. Frontal margin slightly produced, separated medially by shallow V-shaped notch; each frontal lobe divided in two parts by small hiatus, mesial lobe 9–12 granules, lateral lobes each consisting of tiny conical tubercle; inner supraorbital angle with minute tubercle; supraorbital margin bordered with row of small tubercles, with or without trace of 2 clefts. Anterolateral margin with 4 principal spines (including spinose external orbital angle) interspersed by spinules or tubercles; these anterolateral spines relatively small, subequal in size, obliquely erect, first and fourth spines simple, second and third spines bearing 1–4 accessory spinules. Posterolateral margin almost straight, converging towards posterior margin. Posterior part with or without submarginal row of tubercles, if present, tubercles tiny, low, partially obscured by setae; posterior margin nearly straight. Suborbital margin sinuous with mesial angle prominent, spinose, with row of tiny spines or tubercles. Suborbital region with covering of coarse granules; pterygostomial groove lined with microscopic granular row along dorsal side. Dorsolateral portion of buccal frame with some granules.

Orbits ( Fig. 16 A, C) moderately large, slightly obliquely transversal in dorsal view, transverse in anterior view; eyes filling entire orbits. Basal segment of antennular peduncle with granular, obliquely transversal ridge on outer surface, bordering fossa. Antennal peduncle just entering orbital hiatus; second segment with few minute granules on outer surface.

Epistome divided into 4 crested lobes. Endostomal ridges indistinct.

Third maxilliped ( Fig. 16 D) similar to that of P. dofleini . Ischium with mesial margin irregularly denticulate; outer surface microscopically granular. Merus coarsely granular on outer surface. Carpus without distinct granules. Propodus, dactylus surfaces smooth. Exopod with inner subdistal tooth distinct; outer surface nearly smooth.

Chelipeds ( Figs 14 A, 15A, 17A–E) slightly unequal, slightly dissimilar with right stouter than left. Anterodorsal margin of basis-ischium fused segment with row of granules. Merus nearly as long as high; upper surface concave to fit lateral surface of carapace; posterodorsal margin crested, with 2 prominent spines distally plus row of much smaller spines; outer distal margin unarmed, lower distal angle with few minute spinules; outer (posterior) surface with covering of short setae; anterior (inner) surface nearly flat, unarmed; lower margin bluntly carinate, with minute sharp granules. Carpus with scattered, numerous, tiny spines on dorsal to outer surface, inner distal angle with small spine. Palm with scattered numerous tiny spines and covering of short setae on outer surface, inner dorsal margin not carinate with row of tiny spines; ventral surface rounded, nearly smooth (major chela) or bluntly carinate, tuberculate (minor chela); inner surface nearly smooth. Fingers meeting at tip (major chela) or crossing at tips (minor chela). Fixed finger of major cheliped faintly deflexed or straight at base, with row of prominent, rounded teeth on cutting edge; outer surface slightly convex, with very low granules. Fixed finger of minor chela slightly deflexed, with sharply edged, faintly dentate cutting edge. Dactylus of major chela weakly curved, with several granules proximally on dorsal surface; outer surfaces with trace of median sulcus, otherwise smooth; cutting edge with row of low, rounded teeth. Dactylus of minor cheliped distinctly slenderer than that of major cheliped, with patch of granules on proximal 0.3 of dorsal to outer surfaces; outer surface with shallow median sulcus; cutting edge nearly smooth.

Ambulatory legs ( Figs 14 A, 15A, 17F, G) moderately long, moderately stout (merus of fourth leg about 2.4 times longer than wide); surfaces with covering of very short setae, dorsal (extensor) and ventral (flexor) margins with sparse, moderately short to long, stiff setae; first leg (second pereopod) longest, about 1.5 times of carapace width. Coxa unarmed on ventral surface. Basis-ischium fused segment with coarse granules on ventral surface.

Merus with single row of spines increasing in size distally on dorsal (extensor) margin; ventral (flexor) surface flanked by clearly delimited margins each bearing row of tiny spiniform granules or tubercles; outer (posterior) surface unarmed or armed with few minute granules. Carpus with single row of spines on extensor margin; outer (posterior) surface each with 2 rows of spines in dorsal half. Propodus with 2 or 3 rows of small spines on extensor surface; flexor margin unarmed (first to third legs). Dactylus moderately slender, slightly curved distally, terminating in small corneous claw, distinctly longer than propodus; surfaces densely setose; extensor margin unarmed.

Thoracic sternites 1–4 ( Fig. 15 B) smooth, with very sparse short setae. Sternites 5–8 covered with microscopic granules plus numerous short setae. Female vulvae ( Fig. 18 D) narrower than those of P. curvipenis n. sp., crescentshaped.

Male abdomen ( Fig. 16 E) moderately narrow, surface covered with numerous short setae. Somites 1 and 3 widest. Somite 1 transversely trapezoidal, margins and surface unarmed. Somite 2 subtrapezoidal, narrower than flanking somites, without paired minute tubercles laterally. Somites 3–6 unarmed; somite 3 broadly trapezoidal, narrowed distally, lateral margin gently convex, unarmed; somite 4 trapezoidal, lateral margins slightly concave; somites 5 and 6 subrectangular, with straight lateral margins. Telson ( Fig. 16 E) triangular with rounded tip, 1.2 times longer than wide, lateral margins nearly straight.

Female abdomen also lacking tubercles on first and second somites.

First gonopod ( Fig. 16 F–I) slightly sinuous; distal 0.2 slightly arcuate in lateral or mesial view, slightly curved laterally in ventral view, gradually tapering, bearing rows of minute spiniform setae not extending to apex. Second gonopod similar to that of P. dofleini .

Coloration in life. Carapace generally reddish brown, mottled with white (pattern of markings fairly variable), sometimes having red spots. Chelipeds generally reddish brown on dorsal and outer surfaces, with some dark red spots. Ambulatory legs obscurely banded with reddish brown, distal part of meri to propodi with tinge of reddish brown. Eggs dark red. See Ng et al. (2008: fig. 112).

Distribution. So far known only from Panglao, the Philippines; 95– 276 m.

Remarks. Pilumnus bohol n. sp. is similar to P. curvipenis n. sp. Shared diagnostic characters include: the armature on the carapace is relatively weaker compared with P. acanthosoma , P. dofleini and P. a r m a t u s n. sp., in particular, the posterior part of the carapace is provided with a row of low, indistinct tubercles or unarmed; there are no clefts on the upper orbital margin; the palms of chelipeds are armed with scattered small spines or tubercles on the outer surfaces; the thoracic sternum is smooth or microscopically granular; the first abdominal somite is devoid of tubercles; and the distal part of the first gonopod bears a row of stout spinules. However, P. bohol n. sp. is distinguished from P. curvipenis n. sp. by the shape of the first gonopod. In P. bohol n. sp., the distal part of the first gonopod is only slightly curved, rather than strongly curved and hooked in P. curvipenis n. sp. ( Fig. 16 F–I versus Fig. 13 F–I). In addition, the anterolateral spines of the carapace are relatively weaker in P. bohol n. sp. than in P. curvipenis n. sp. ( Fig. 18 C versus Fig. 18A ); the fourth ambulatory leg is proportionally stouter in P. bohol n. sp. than in P. curvipenis n. sp. (the merus is about 2.4 times as long as wide in P. bohol n. sp. in contrast to about 2.9 times as long in P. curvipenis n. sp.) ( Fig. 17 G versus Fig. 13 E); and the female vulvae are relatively narrower in P. bohol n. sp. than in P. curvipenis n. sp. (cf. Fig. 18 D versus Fig. 18B ).

Ng et al. (2008: fig. 112) showed a photograph of a female specimen that they identified as P. d o f l e i n i, but this specimen most probably represents P. bohol , as mentioned before.

Etymology. Named after the Bohol Sea, the Philippines, where the specimens of the new species were collected. Used as a noun in apposition.

Figures

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 14. Pilumnus bohol n. sp., holotype, male (16.2 x 19.2 mm), NMRC 39036. A, entire animal, dorsal view; B, carapace, dorsal view.

FIGURE 15. Pilumnus bohol n. sp., holotype, male (16.2 x 19.2 mm), NMRC 39036. A, entire animal, ventral view; B, thoracic sternum and abdomen, ventral view.

FIGURE 16. Pilumnus bohol n. sp., holotype, male (16.2 x 19.2 mm), NMRC 39036. A, left upper orbital and anterolateral margins, dorsal view (setae omitted); B, frontal margin, anterodorsal view (setae omitted); C, left anterior part of carapace and cephalic appendages, anterior view (setae omitted); D, left third maxilliped, ventral (outer) view (setae partially omitted); E, abdomen and telson, ventral view (setae omitted); F, left first gonopod, mesial view; H, same, lateral view; I, same, distal part, mesial view; J, same, lateral view. Scale bars: 2 mm for A – E; 1 mm for F, G; 0.5 mm for H, I.

FIGURE 17. Pilumnus bohol n. sp., holotype, male (16.2 x 19.2 mm), NMRC 39036. A, right major chela, outer view; B, carpus of right major cheliped, dorsal view; C, merus of right major cheliped, outer view; D, left minor chela, outer view; E, merus of left minor cheliped, outer view; F, left third ambulatory leg (fourth pereopod), posterior view; G, left fourth ambulatory leg (fifth pereopod), posterior view. Setae omitted. Scale bars: 5 mm for A – E; 2 mm for F, G.

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.