Pycnoplax latifolia, Castro, 2007

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 667-669

Pycnoplax latifolia n. sp.

( Figs 16 ; 17 )

TYPE MATERIAL. — Shinnyo-maru, cruise SY96, ♂ holotype, cl 6.2 mm, cw 7.8 mm; 4 ♂♂ paratypes (cl 7.0 mm, cw 8.9 mm; cl 6.7 mm, cw 8.7 mm [parasitised by bopyrid]; cl 4.7 mm, cw 5.9 mm [parasitised by bopyrid]; cl 4.7 mm, cw 6.0 mm); 1 pre-adult ♀ paratype, cl 4.1 mm, cw 5.0 mm; 1 pre-adult female ♀ paratype cl 4.0 mm, cw 4.9 mm ( CBM-ZC 4624 ) .

TYPE LOCALITY. — Japan, Izu Is, Hyotan-se Bank, 34°20.75’N, 139°20.00’E, 275- 350 m.

MATERIAL EXAMINED. — Japan. Izu Is, Hyotan-se Bank, 34°20.75’N, 139°20.00’E, 275-350 m, Shinnyo-maru, cruise SY96, stn 6, 22.X.1996, ♂ holotype, 4 ♂♂ paratypes, 1 ♂, 2 pre-adult ♀♀ paratypes ( CBM-ZC 4624).

ETYMOLOGY. — From latus, Latin for “side”, and folium, Latin for “leaf”, for the rounded, leaf-like outer orbital teeth that are characteristic of the species.

DISTRIBUTION. — Known only from Japan. Depth: 275- 350 m.

DESCRIPTION

Carapace ( Figs 16A ; 17 ) quadrate, slightly wider than long (1.3 as wide as long in holotype).Carapace slightly convex, without clear indication of regions. Front lamellar, straight, not marked by median notch, bordered by tomentum. Slight notch between front, inner edge of supraorbital border.Supraorbital borders sinuous, margins granular.Suborbital borders granular, each with short, blunt inner tooth not visible dorsally. Outer orbital angle with blunt, granular tooth; 2 granular anterolateral teeth on each side of carapace; first triangular, dorso-ventrally flat, second acute, oriented dorsally; margin between anterolateral teeth nearly straight. Posterolateral borders arched.

Subhepatic, pterygostomial regions, pterygostomial crest, merus of third maxilliped endopod with short, conspicuous granules.

Eye peduncles ( Figs 16A ; 17 ) short (0.2 front width), dorsal surface granular, cornea slightly expanded distally.

Chelipeds (P1) ( Fig. 17 ) nearly equal in males, females; fingers slender, longer than propodus, with blunt teeth, fingers dark brown in males except short proximal portion of dactylus, about two-thirds dark brown in females.Dactylus, propodus, carpus, merus with short granules in small specimens (granules only on merus of holotype, largest specimens); dactylus, propodus, merus with some setae in small specimens; broad, curved, acute-tipped tooth on inner (ventral), proximal margin of carpus. Ambulatory legs (P2-P5) relatively short, broad articles, smooth; long, short, simple setae along inner, outer margins of articles. P5 dactylus relatively slender, smooth; length of P5 merus 0.6 cl.

Male abdomen ( Fig. 16B ) narrowly triangular, with 6 freely-movable somites plus telson; telson slightly wider than long. Somite 3 covers space between P5 coxae; somites 1, 2 as wide as somite 3, small portion of thoracic sternite 8 visible. G1 ( Fig. 16C ) stout, bent in outer direction; slender, spinous, pointed tip. G2 ( Fig. 16D ) slender, slightly longer than G1, slightly curved flagellum shorter than proximal part (peduncle), tip with 2 lateral spinules.

Revision of Goneplacinae ( Crustacea, Brachyura)

Female abdomen wide.Telson slightly wider than long. Somites 2, 3 cover space between P5 coxae, thoracic sternite 8 not visible. Vulva of mature female extending from edge of slightly deflected suture 5/6 to suture 6/7; oblong vulvar cover along the outer half of the vulva.

REMARKS

Pycnoplax latifolia n. sp. is a small-size species (cl 4.1 mm, cw 4.9 mm to cl 7.0 mm, cw 8.9 mm, n = 8). The G1 and G2 were fully developed and the P1 smooth and seemingly fully developed in the largest males, precluding the possibility that only pre-adult specimens were available. None of the two females examined was ovigerous but one (cl 4.1 mm, cw 5.0 mm) had fully developed pleopods and a vulvar cover, suggesting that it was a mature individual. The small number of specimens collected, all from one locality, does not exclude the possibility, however, that the species attains a larger size.

It differs from its congeners by the relative size of the anterolateral teeth, particularly the second one, which is smaller and less salient than in any of the species of Pycnoplax n. gen. The overall body size of the know specimens is also much smaller than in the other species.

The specimens were first identified as a possible new species of Carcinoplax by T. Komai (CBM), who generously allowed me to describe them as part of this work.

Figures

FIG. 16. — Pycnoplax latifolia n. sp.,♂ holotype,cl 6.2 mm,cw 7.8 mm,Izu Is, Japan,Shinnyo-maru, cruise SY96,275-350 m (CBM-ZC 4624): A, dorsal surface of the carapace; B, abdomen; C, left G1, dorsal view; D, left G2, ventral view. Scale bars: A, 5 mm; B, 3 mm; C, D, 1 mm.

FIG. 17. — Pycnoplax latifolia n. sp.,♂ holotype,cl 6.2 mm,cw 7.8 mm,Izu Is, Japan,Shinnyo-maru, cruise SY96,275-350 m (CBM-ZC 4624).