Ptychognathus glaber Stimpson, 1858

Komai, Tomoyuki, Maenosono, Tadafumi, Saeki, Toshifumi & Naruse, Tohru, 2021, Redescription of the brackish water crab Ptychognathus glaber Stimpson, 1858 based on the topotypic material from the Ogasawara Islands and new record of P. lipkei N. K. Ng, 2010 from Japan (Decapoda: Brachyura: Varunidae), Zootaxa 5048 (1), pp. 58-76 : 60-66

publication ID	https://doi.org/ 10.11646/zootaxa.5048.1.3
publication LSID	lsid:zoobank.org:pub:1D03DDA8-5A1E-48AA-9254-E52C071BE3F3
persistent identifier	https://treatment.plazi.org/id/03F1AB03-0D02-487D-57CD-FF3E5D5CFC7B
treatment provided by	Plazi
scientific name	Ptychognathus glaber Stimpson, 1858
status

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Ptychognathus glaber Stimpson, 1858 View in CoL

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 5A–D View FIGURE 5 )

Ptychognathus glaber Stimpson, 1858: 104 View in CoL [type locality: Port Lloyd, Bonin Islands (= Futami Port, Chichi-jima Island, Ogasawara Islands)]; 1907: 129, pl. 17, fig. 5, 5a.— Sakai 1939: 660, pl. 108, fig. 3; 1976: 639 (English text; in part), 397 (Japanese text), pl. 219, fig. 4.— Ooishi 1970: 95, pl. 16, fig. 10.— Takeda & Miyake 1976: 113 (list).— Marumura & Kosaka 2003: 64.— Nakasone & Irei 2003: 274 (key).— Ng et al. 2008: 229 (list).— Kobayashi & Satake 2009: fig. 2, table 2.—N.K. Ng 2010: 548 (in part).— Komatsu 2011: 277 (list).— Wada 2012: 204, unnumbered fig.

Ptychognathus glaber glaber View in CoL .— Pretzmann 1984: 141.

Not Ptychognathus glaber View in CoL .—De Man 1892: 324, pl. 19, fig. 11 (= P. lipkei N.K. Ng, 2010 View in CoL ); 1905: 541 (list), 543 (key) (= P. lipkei View in CoL ).— Tesch 1918: 87 (key) (= P. lipkei View in CoL ).— Muraoka 1998: 52 (= P. ishii Sakai, 1939 View in CoL ).

Record needs to be verified.

Ptychognathus glaber View in CoL .— Sakai 1955: 112.— Takeda et al. 2006: 208 (list).

Material examined. Ogasawara Islands. Chichi-jima Island : CBM-ZC 10765, 3 males (11.5×14.0, 11.5×14.3, 12.2× 15.4 mm), Kiyose River down stream, Futami Port , 27°05.56’E, 142°11.52’E, intertidal, under rock, 13 July 2009, coll. T. Komai; CBM-ZC 11394, 1 male 10.4×13.0 mm), 1 female (10.2× 12.5 mm), same locality, 9 December 2005, coll. T. Komai; CBM-ZC 11659, 3 males (8.1×10.2, 8.6×10.8, 10.3×13.0 mm), 1 female (10.8× 13.1 mm), same locality, 10 December 2005, coll. T. Komai; CBM-ZC 16568, 2 males 11.8×14.3, 12.6× 16.2 mm), 1 female (10.8× 13.1 mm), same locality, 15 December 2020; CBM-ZC 16569, 1 male (11.0× 13.6 mm), 1 female (8.7× 10.6 mm), same data, DNA voucher; RUMF-ZC-3616, 1 male (12.4× 15.3 mm), same locality, 25 June 2010, coll. Y. Fujita; RUMF-ZC-5047, 1 male (9.4× 11.4 mm), Okumura River , Futami Bay , 27°05.93’N 142°12.28’E, 16 September 2016, coll. T. Sasaki; RUMF-ZC-3637, 1 male (7.9×10.0 mm), Kopepe Beach, 22 June 2010, coll. Y. Fujita; RUMF-ZC-3612, 1 male (12.4× 15.3 mm), same data. Haha-jima Island : RUMF-ZC-4169, 1 male (14.2× 18.1 mm), Otani River , Oki Port, 1 March 2015, coll. Y. Fujita; RUMF-ZC-4170, 1 female (10.7× 13.2 mm), same locality and date, coll. R. Yoshida; RUMF-ZC-4171, 1 male (14.9× 18.5 mm), Koromodate River , Kitako Bay , 1 March 2015, coll. R. Yoshida; RUMF-ZC-4172, 2 males (4.2×5.0, 9.2×11.0 mm), 1 female (7.0× 8.4 mm), same data; RUMF- ZC-4173, 8 males (ca 4.1×5.0 [damaged], 5.1×5.9, 6.4×7.7, 6.9×8.9, 7.7×9.2, 7.7×9.5, 7.8×9.7, 11.7× 14.7 mm), Kirihama, Higashiko Bay , 27 February 2015, coll. T. Sasaki; RUMF-ZC-4167, 1 female (7.8× 9.6 mm), same locality and date, coll. R. Yoshida; RUMF-ZC-4168, 1 male (10.0× 12.3 mm), same locality and date, coll. T. Sasaki. Muko-jima Island: RUMF-ZC-5049, 1 male (12.9× 16.1 mm), western coast of southern peninsula, 27°40.56’N 142°08.37’E, 7 October 2016, coll. T. Sasaki. Nakoudo-jima Island: RUMF-ZC-5048, 1 male (7.9× 9.6 mm), Fukuro Port, 27°37.59’N 142°10.66’E, 20 September 2016, coll. T. Sasaki; RUMF-ZC-5095, 1 female (6.1× 4.9 mm), same locality and date, coll. T. Sasaki et al GoogleMaps .

Redescription. Male. Carapace ( Figs. 1A View FIGURE 1 ; 2A View FIGURE 2 ) subrectangular, 1.2–1.3 times as wide as long, substantially flattened; dorsal surface flat, with sparse minute stiff setae (more numerous on lateral sides), regions poorly defined; cervical groove shallow, but clearly discernible, H-shaped, connected anteriorly with paired deep, small depressions; epigastric cristae rudimentary or absent; postorbital cristae absent. Anterolateral margin lined with microscopic granules, not clearly demarcated from posterolateral margin, bearing 1 small blunt tooth defined by shallow notch; external orbital angle triangular, with subacute, forwardly directed tip; posterolateral margins slightly converging posteriorly, almost straight, no distinct ridge present at region just adjacent to junction between posterolateral margin and posterior carapace margin. Supraorbital margin slightly oblique and sinuous; frontal margin with broad, shallow median notch in dorsal view. Front ( Fig. 2B View FIGURE 2 ) abruptly deflexed, very narrow longitudinally, demarcated dorsally with transverse line of minute granules, medially shallowly concave, bisected by low transverse ridge continuing to upper margins of antennular fossae, attaching ventrally with upper margin of pro-epistome. Infraorbital margins ( Fig. 2C View FIGURE 2 ) with about 10 well-spaced granules, not congruent with anterolateral margin, inner orbital tooth subconical, not extending to lateral angle of front, with few distinct granules on surface. Suborbital region with scattered granules; pterygostomial region with covering of soft plumose setae.

Inter-antennular septum ( Fig. 2B View FIGURE 2 ) broadly triangular, medially slightly depressed; upper margin bordered with minute granules laterally.

Thoracic sternum ( Figs. 1B View FIGURE 1 ; 2D View FIGURE 2 ) glabrous, with few punctae. Sternite 1 ( Fig. 2D View FIGURE 2 ) small, narrowly triangular, somewhat depressed; surface obscured by setae. Sternite 2 ( Fig. 2D View FIGURE 2 ) widely trapezoidal, clearly demarcated from sternite 3. Sternites 3 and 4 ( Fig. 2D View FIGURE 2 ) fused, subtrapezoidal; lateral margin with small triangular process at base of maxilliped 3. Sternite 5–7 lateral parts ( Fig. 1B View FIGURE 1 ) subrectangular respectively; lateral parts of sternite 8 exposed, subrectangular. Sterno-pleonal cavity deep, anterior end reaching anterior 0.2 of sternite 4 ( Fig. 2D View FIGURE 2 ); press buttons on sternite 5 reduced, obsolescent.

Eyes ( Figs. 1A View FIGURE 1 ; 2A View FIGURE 2 ) well developed, cornea distinct, darkly pigmented. Antennular peduncle basal articles ( Fig. 2B View FIGURE 2 ) broad, widely separated; distal 2 peduncular articles folded slightly obliquely into antennular fossa. Antennal peduncle ( Fig. 2B View FIGURE 2 ) entering into orbital hiatus.

Maxilliped 3 ( Figs. 1B View FIGURE 1 ; 2E View FIGURE 2 ) broad, outer surface with sparse short setae. Exopod distinctly broader than endopodal ischium, mesial margin noticeably convex, lateral margin less convex than mesial margin. Ischium-merus lateral margin strongly concave to accommodate mesial margin of exopod, mesial margin with small notch at articulation; articulation between ischium and merus slightly sinuous. Ischium mesial margin gently convex, outer surface with shallow median sulcus. Merus with broad longitudinal sulcus on outer surface along mesial margin, distolateral angle strongly produced into roundly triangular projection. Carpus articulated at concave distomesial margin of merus. Dactylus longer than propodus, tapering to blunt apex.

Chelipeds ( Figs. 1A, B View FIGURE 1 ; 3A, B View FIGURE 3 ) usually symmetrical. Ischium convex on lower surface, with row of small tubercles on lower anterior margin. Merus without spines; upper surface with deep subdistal transverse groove and long soft plumose setae; lower surface flat, glabrous, inner lower margin bordered with small tubercles, outer lower margin bluntly carinate, smooth. Carpus sub-globular, smooth on surfaces; inner surface sometimes with short setae sparsely; inner distal angle rounded. Palm outer surface gently convex, microscopically granulate, glabrous; inner surface also gently convex, glabrous. Fixed finger without ridges on outer and inner surfaces, tapering to rounded, hollowed apex bordered by chitinous plate; occlusal margin with row of distinct, triangular teeth and small, rounded membranous protuberance proximally, and occasionally with very small patch of short setae at base of proximalmost tooth. Dactylus distinctly longer than palm measured along upper margin, gently arched, terminating in blunt, hollowed apex bordered by chitinous plate; occlusal margin with row of small, blunt or subacute teeth over entire length, teeth becoming smaller distally.

Ambulatory legs (pereopods 2–5) ( Figs. 1A, B View FIGURE 1 ; 3C, D View FIGURE 3 ) moderately slender, pereopods 3 and 4 longest, all similarly compressed (except for propodus of pereopod 5, more flattened than those of other legs). Pereopod 2–4 meri each with shallow transverse groove on anterior margin subdistally, extending onto upper and lower surfaces, and with row of moderately long, soft feathered setae; upper and lower surfaces almost glabrous except for minute bristle-like setae on anterodistal margin; posterior surfaces each with mesh-like pattern of setal field consisting of minute black setae in proximal half, posterior-upper margins each with row of sparse, moderately long stiff setae. Carpi each with dense covering of minute black setae on extensor surface, extending onto lower surface; upper surface with mesh-like pattern of setal filed consisting of minute black setae and sparse moderately long stiff setae; flexor surfaces almost glabrous, with few stiff setae on distal margins. Propodi each with covering of minute black setae and scattered moderately long stiff setae at least on extensor and flexor surfaces; pereopod 4 propodus 1.8–1.9 times as long as wide. Dactyli almost straight, each terminating in sharp, conical corneous claw; surfaces with covering of minute black setae interspersed by 4 naked longitudinal lines; pereopod 4 dactylus 1.3 times as long as propodus, 5.2 times as long as basal width.

Pereopod 5 having setation similar to preceding pereopods. Merus with shallow transverse groove on subdistally, posterior surface slightly inflated proximally. Carpus with sparse, short, feathered setae on extensor surface. Propodus 1.1–1.2 times as long as wide, with covering of black minute setae and sparse long stiff setae on extensor and flexor surfaces. Dactylus slightly recurved, 0.9 times as long as propodus, 2.1 times as long as basal width.

Male pleon ( Figs. 1B View FIGURE 1 ; 2F View FIGURE 2 ) moderately narrow, surface smooth, margins with short setae. Pleomere 1 widest. Pleomeres 2 and 3 subequal in width. Pleomeres 3–5 becoming gradually narrower toward distal. Pleomere 6 subtrapezoidal, 1.8–2.0 times as wide as long; distolateral angle forming sloping shoulder. Telson tongue-shaped, about 1.2–1.3 times long as pleomere 6, 1.1–1.3 times as long as wide; lateral margins slightly concave basally; distal margin rounded, with sparse setae not forming prominent tuft.

Male gonopod 1 ( Fig. 3E, F View FIGURE 3 ) slender, slightly curving dorsally, reaching suture between thoracic sternite 4 and 5 in situ; tip roundly truncate, forming short chitinous structure; subdistal lobe obtuse, partially obscured by stiff setae. Gonopod 2 0.25 length of gonopod 1.

Female. Carapace ( Figs. 4A View FIGURE 4 ; 5A View FIGURE 5 ) with sparse setal punctae, particularly on lateral sides.

Chelipeds ( Figs. 4A, B View FIGURE 4 ; 5C View FIGURE 5 ) symmetrical, moderately small for genus, chela length about 0.5 of carapace width; outer surface of carpus and chela with sparse granules and minute stiff setae. Carpus with small tubercle on inner distal angle. Palm outer surface convex, glabrous, devoid of tuft of setae at base of fixed finger, with row of granules adjacent to ventral margin, extending onto fixed finger; inner surface convex at middle part, with scattered coarse granules, devoid of setae; ventral surface rounded, coarsely granular. Fixed finger nearly straight, gradually tapering; occlusal margin with row of small, blunt teeth, decreasing in size proximally on proximal 0.7, hollowed distal part bordered by chitinous ridge. Dactylus slightly curved, 1.6 times as long as palm; surface rough with sparse granules and minute stiff setae; occlusal margin with row of small blunt teeth on proximal 0.7–0.8, hollowed distal part bordered by chitinous ridge.

Ambulatory legs proportionally shorter than those of males; minute stiff setae on surfaces generally fewer than in males; tomentum on carpi, propodi and dactyli less developed than in males.

Vulva on sternite 6 ( Fig. 5B View FIGURE 5 ) located at midpoint between sutures demarcating sternites 4/5 and 5/6, low, rounded, papilla-like.

Pleon ( Figs. 4B View FIGURE 4 ; 5D View FIGURE 5 ) covering entire thoracic sternum, subsemicircular in general outline. Somite 1 very narrow, sharply carinate along distal margin. Somite 6 subtrapezoidal, 4.3 times as wide as long; lateral margins slightly convex; distal margin shallowly concave. Telson 2.5 times as wide as long; terminal margin broadly rounded, lateral margins slightly sinuous.

Colouration in life. Body and pereopods generally brown on dorsal or upper side, paler or whitish on ventral or lower side; darker in females than in males ( Figs. 1A, B View FIGURE 1 ; 4A, B View FIGURE 4 ).

Distribution. Presently known only from the Ogasawara Islands: Chichi-jima, Haha-jima, Muko-jima and Nakoudo-jima islands.

Habitat. At Kiyose River in the Futami Port, Chichi-jima Island, individuals of Ptychognathus glaber are seen in tidal area of the river mouth, which are hidden under rocks on sand at daytime. Other decapods, which are seen around the habitat of P. glaber , include: Caridina typus (H. Milne Edwards) (Caridea: Atyidae ); Clibanarius longitarsus (de Haan) (Anomura: Diogenidae ); Metopograpsus thukhar (Owen) (Brachyura: Grapsidae ); Orisesarma magnum (Komai & Ng) (Brachyura: Sesarmidae ) and Pseudohelice quadrata (Dana) (Brachyura: Varunidae ).