Pycnoplax aspera, Castro, 2009

Castro, Peter, 2009, Two new species of Carcinoplax H. Milne Edwards, 1852, and Pycnoplax Castro, 2007, from the western Pacific, and a description of the female of Thyraplax truncata Castro, 2007 (Crustacea, Decapoda, Brachyura, Goneplacidae), Zoosystema 31 (4), pp. 949-957 : 953-956

Pycnoplax aspera n. sp.

( Fig. 2 )

TYPE MATERIAL. — Loyalty Is. MUSORSTOM 6, stn DW 406, 20°40.65’S, 167°06.80’E, 373 m, 15.II.1989, ♂ holotype, cl 6.0 mm, cw 7.4 mm ( MNHN-B30805 ) ; 1 ♂ paratype, cl 6.7 mm, cw 8.2 mm, colour photograph ( MNHN-B30806 ). New Caledonia. 22°32.1’S, 166°26.1’E, 175-250 m, 6.VI.1979, 1 ovigerous ♀ paratype, cl 8.2 mm, cw 10.4 mm ( MNHN-B30795 ) .

SMIB 5, stn DW 98, Norfolk Ridge, 23°01.7’S, 168°16.1’E, 335 m, 14.IX.1989, 1 ♀ paratype, cl 4.9 mm, cw 6.5 mm ( MNHN-B 30803). MUSORSTOM 4, stn 234, 22°15.4’S, 167°08.3’E, 350-365 m, 2.X.1985, 1 ♂ paratype, cl 5.3 mm, cw 6.5 mm (MNHN-B30804). EBISCO, stn DW 2522, 22°46.0’S, 159°21.0’E, 310- 318 m, 9.X.2005, 1 ♀ paratype cl 4.9 mm, cw 6.5 mm ( MNHN-B30792 ) ; 1 ♂ paratype, cl 6.3 mm, cw 7.9 mm ( ZRC 2008.1338 ) . Solomon Is. SALOMON 1, stn CP 1857, north of Guadalcanal I., 09°39.8’S, 160°48.6’E, 720-849 m, 7.X.2001, 1 ♂ paratype, cl 5.3 mm, cw 6.4 mm (MNHN-B30794).

Fiji. BORDAU 1, stn DW 1497, 18°44’S, 178°25’W, 335-350 m, 12.III.1999, 1 ♂ paratype, cl. 5.5 mm, cw 6.7 mm ( MNHN-B 30802).

TYPE LOCALITY. — Loyalty Is, 20°40.65’S, 167°06.80’E, 373 m.

OTHER MATERIAL EXAMINED. — Philippines. MUSORSTOM 2, stn CP 51, 14°00’S, 120°17’E, 170-187 m, 27.XI.1980, 1 ♀, cl 8.1 mm, cw 9.9 mm (MNHN-B30793).

New Caledonia. BATHUS 4, stn DW 887, 21°06.67’S, 164°27.62’E, 320-344 m, 2.VIII.1994, 1 ♀, cl 5.4 mm, cw 6.6 mm ( MNHN-B 30807). — Stn CP 946, 20°33.81’S, 164°58.35’E, 386-430 m, 10.VIII.1994, 1 ♂, cl 6.8 mm, cw 8.8 mm ( MNHN-B 30808).

EBISCO, stn DW 2520, 24°6.0’S, 159°41.0’E, 350- 400 m, 8.X.2005, 1 ♂, cl 6.4 mm, cw 7.9 mm (MNHN-B30791).

Fiji. BORDAU 1, stn CP 1478, 20°50’S, 178°44’W, 386-396 m, 9.III.1999, 1 ♂, cl 4.3 mm, cw 5.3 mm, parasitised by Sacculina ( MNHN-B 30841).

ETYMOLOGY. — From asper, Latin for “rough”, in reference to the diagnostic coarse, granular surface of the chelipeds, eye peduncles, and, in the largest individuals, portions of the dorsal and ventral surface of the carapace.

DISTRIBUTION. — Western Pacific Ocean: Philippines, Solomon Is, New Caledonia, Loyalty Is, and Fiji. Depth: 170- 849 m.

DESCRIPTION

Carapace ( Fig.2A ) quadrate, slightly wider than long (1.2 as wide as long in male holotype). Carapace slightly convex, without clear indication of regions; dorsal surface granular (granules restricted to hepatic, anterior branchial regions in largest female paratypes); slight depression across cardiac region, giving appearance of two transversal carinae across carapace. Front lamellar, straight, not marked by median notch. Slight notch between front,inner edge of supraorbital border.Supraorbital borders sinuous,without notches, margins weakly granular.Suborbital borders granular, each with short, blunt inner tooth visible dorsally. Outer orbital angle with broad, rounded, anteriorly projecting, slightly asymmetrical, granular tooth; 2 weakly granular anterolateral teeth on each side of carapace; first (anteriormost) angular, straight outer margin, slightly dorsally projecting; second (posteriormost) anterolateral tooth acute, dorsally projecting; margin between anterolateral teeth nearly straight, coarsely granular. Plumose setae on lateral margins of carapace; simple setae on posterior margin. Posterolateral borders arched, granular. Posterior margin nearly straight, slightly shorter than front.

Subhepatic, pterygostomial regions, pterygostomial crest with conspicuous, short, spherical granules. Third maxillipeds completely close buccal cavern; merus auricular, palp, merus with short, conspicuous granules. Anterior border of endostome well demarcated from buccal cavern, ridges faint but clearly defined.

Eye peduncles ( Fig. 2A ) short (0.1 front width), dorsal surface granular, cornea slightly expanded distally. Orbits narrow, not expanded distally.

Chelipeds (P1) nearly equal in males and females (chelipeds missing in two largest female specimens); fingers slender,crossing over in some specimens,longer than propodus, with blunt teeth, approximately half distal portion of fingers dark brown. Surface of dactylus, propodus with small, short granules ( Fig. 2F ); ventral surface, anterior margin of merus with large granules; simple setae on dactylus, propodus, merus. Broad, curved, acute-tipped tooth on inner (ventral), proximal margin of carpus. Ambulatory legs (P2-P5) relatively short, distal end of P5 merus not reaching second anterolateral tooth when folded; articles unarmed, with slightly granular margins, more conspicuous granules on inner (ventral) margins of P2-P5 meri; long, short, simple setae along margins of articles; scattered plumose setae on meri; long, simple setae along inner margin of P5 propodus. P5 dactylus long, slender, varying number of particularly small, slender teeth on distal end (0 to 7 on outer margin, 0 to 4 on inner margin; at least present on one margin); length of P5 merus 0.5 cl.

Median sulcus present on thoracic sternites 7-8; sutures 4/5, 5/6, 7/8 interrupted medially, 6/7 complete ( Fig. 2E ).

Male abdomen ( Fig. 2B ) narrowly triangular, with 6 freely-movable somites plus telson; telson slightly wider than long. Abdominal-locking mechanism with medium-size button on edge of thoracic sternite 5 pairing with shallow socket on underside (ventral surface) of abdominal somite 6. Somite 3 covers space between P5 coxae, episternite 7, outer edge of somite fitting under episternite; somites 1, 2 as wide as somite 3, small portion of thoracic sternite 8 visible when abdomen closed. Penis emerging from coxal gonopore, protected by episternite 7. G1 ( Fig. 2C ) stout, sinuous, slightly bent in outer direction, spinous outer margin; slender, spinous, rounded apex. G2 ( Fig. 2D ) slender, slightly longer than G1, curved flagellum almost as long as proximal part (peduncle), row of spinules along proximal margin; expanded, leaf-like apex.

Female abdomen wide.Telson slightly wider than long. Somites 2, 3 cover space between P5 coxae, small portion of thoracic sternite 8 visible when abdomen closed. Vulva of mature female ( Fig. 2E ) oblong, extending from edge of suture 5/6 to markedly deflected suture 6/7; triangular, salient sternal vulvar cover on posterior margin of vulva.

Colour

A colour photograph (MNHN, Zoologie Arthropodes) of a male paratype (MNHN-B30806) shows an orange carapace with a few light-orange spots, mostly on the posterior half. Th e pereopods are orange with scattered light orange spots.

REMARKS

Pycnoplax aspera n. sp. shares with the five previously described species of Pycnoplax Castro,2007 ( P.bispinosa (Rathbun, 1914) , P.latifolia Castro, 2000 , P.meridionalis (Rathbun, 1923) , P.surugensis (Rathbun, 1932) , and P.victoriensis (Rathbun, 1923)) a stout G1 armed with spinules on its distal portion,a G2 with a flagellum that is slightly longer or almost as long as the proximal part (peduncle), and the presence of a sternal vulvar cover. Unique to Pycnoplax and the Goneplacidae s.s., however, is the expanded, foliaceous apex of its G2 ( Fig.2D ). Th ere are two terminal spinules on the apex of the G 2 in four of the five previously described species of Pycnoplax (i.e. P. latifolia: Castro 2007 : fig. 16D) or it is pointed as in P. surugensis (see Guinot 1989: fig. 31B, as Carcinoplax surugensis ).

The new species is closest to P. latifolia Castro, 2007 , which is known only from Japan, in the general morphology of the carapace.Th e dorsal surfaces of the carapace and chelipeds, however, are conspicuously granular in the new species (smooth in P. latifolia ; Castro 2007: fig. 17), the G1 is sinuous and with a rounded apex (more straight, with bent distal portion, slender apex in P. latifolia ; Castro 2007: fig. 16C), the G2 has an expanded, foliaceous tip (two spinules in P. latifolia ; Castro 2007: fig. 16D), the vulva has a conspicuously salient, triangular sternal vulvar cover on its posterior margin (oblong, median sternal vulvar cover in P. latifolia ), the P5 dactylus has small, distal teeth (smooth in P.latifolia ), and the cheliped fingers are light in colour with dark-brown tips (fingers completely dark brown in P. latifolia ; Castro 2007: fig. 17).

The carapace is superficially similar to that in some goneplacid genera, most particularly Carcinoplax H. Milne Edwards, 1852 . Th e 19 known species of Carcinoplax , in contrast to Pycnoplax , have a slender and dorsoventrally flattened G1, the vulva is greatly expanded and lacks a sternal vulvar cover ( Castro 2007: fig. 1), and the 6/7 thoracic suture is complete (see Castro 2007: 662). Th ere are also differences in the G2 (the presence of proximal denticles on the distal part in Pycnoplax , absent in most species of Carcinoplax ; distal part relatively longer than proximal portion in Pycnoplax than in Carcinoplax ).

There are also some similarities in the general morphology of the denticulated G1 of the new species and the five species included in Thyraplax Castro, 2007 . In Thyraplax , however, the G1 is slender with a pointed distal part, each arched anterolateral border of the carapace has one tooth plus a shallow lobe or carina ( Fig. 3A ), the posterolateral borders of the carapace are conspicuously longer than the anterolateral borders, and the P5 dactylus is carinated in most species.

Figures

FIG. 2. — Pycnoplax aspera n. sp.: A-D, ♂ holotype, cl 6.0 mm, cw 7.4 mm,Loyalty Is, MUSORSTOM 6, stn DW 406 (MNHN-B30805): A, dorsal view; B, abdomen; C, left G1, dorsal view;D, left G2, ventral view; E, F, ♀ paratype, cl 8.2 mm, cw 10.4 mm,New Caledonia, (MNHN-B30795); E, thoracic sternum and vulvae; F, right cheliped (P1), dorsal view. Scale bar: C, D, 2.0 mm.

FIG. 3. — Thyraplax truncata Castro, 2007, ♀, cl 7.2, cw 9.7 mm, New Caledonia, EBISCO, stn CP 2498 (MNHN-B30794): A, dorsal view; B, thoracic sternum and vulvae.