Psopheticoides sanguineus Sakai, 1969

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 89-93

Psopheticoides sanguineus Sakai, 1969

( Figs. 36A–G ; 38D–F ; 39C )

Psopheticoides sanguineus Sakai, 1969: 274 , figs. 16b, 17a, a', b, 18b, c; 1976: 528, fig. 282, pl. 192, fig. 3 [ Japan]. — Serène & Vadon 1981: 120, 123, 127 [ Philippines] — Takeda 1982: 19 [list]; 2001: 248 (as Propheticoides [sic]), 251, 258 [list] [ Japan]. — Miyake 1991: 220 [in list] [ Japan]. — Castro 2007: 620 [discussion] [ Philippines, Tonga] — Ng et al. 2008: 78, fig. 63 [colour photograph] [in list].

Type material. Male holotype ( USNM 125888 ) ; 1 female paratype (unknown status)

Type locality. Japan, Kyushu , Tosa Bay, off Mimase, 100–150 m.

Material examined. Philippines. Bohol. Balicasag I., off Panglao I., 200–300 m, tangle nets of local fishermen, 12.2000 : 2 females ( ZRC 2001.0366 ) ; 50–500 m, 28.11.2001: 4 males, 1 female, 2 ovigerous females ( ZRC 2001.0539 ) ; 200–300 m, 06.2002: 1 male, 1 female ( ZRC 2002.0651 ) ; 25– 30.07.2003: 8 males, 1 female, 17.7 mm × 22.3 mm ( ZRC 2004.0752 ) ; 02.03.2004: 2 ovigerous females ( ZRC 2004.0713 ) ; 11.2003: 1 male, 2 females, 3 ovigerous females ( ZRC) ; 12.2003: 1 male ( ZRC 2008.1359 ) ; 02.2004: 1 ovigerous female ( ZRC 2008.1360 ) ; 05.2004: 2 males ( ZRC) .

Panglao I., Maribojoc Bay , 100–300 m, T. J. Arbasto coll., 11.2003 –04.2004: 1 ovigerous female ( ZRC 2008.1361 ) ; 28.05.2004: 1 male, 21.9 mm × 27.8 mm ( ZRC 2008.1357 ) ; 07.2004 –05.2005: 1 ovigerous female, 1 female ( ZRC 2008.1362 ) .

PANGLAO 2004: stn. P1, Nato coll., 30.05.2004: 1 male, 22.0 mm × 26.7 mm, 1 female, 20.1 mm × 25.3 mm ( MNHN-B29728 ). Vanuatu. SANTO 2006: no data: 1 male, 7.8 mm × 9.8 mm ( ZRC 2009.0974 ) .

Tonga. BORDAU 2: stn. DW 1634, 21°45’S, 175°20’W, 321–322 m, 20.06.2000: incomplete specimen ( MNHN-B29808 ) .

Diagnosis. Reniform eyes ( Fig. 36B ). Orange-red circle on dorsal surface of carapace ( Fig. 39C ).

Remarks. A large but damaged and incomplete specimen from Tonga (MNHN-B29808) clearly shows the characteristic carapace, including the colour spot.

Colour pattern. A distinctive orange-red circle fringed by a yellow-white border located on the cardiac region of the carapace ( Fig. 39C ; Ng et al. 2008: fig. 63). The rest of the carapace and the ambulatory legs are orange-red.

Distribution. Western Pacific from Japan to the Philippines, Vanuatu, and Tonga. Depth: 50– 322 m.

Genus Systroplax n. gen.

Carcinoplax — Tesch 1918: 154 (part). — Rathbun, 1914b: 142. — Serène 1968: 89 [in list] (part). — Sakai 1969: 269 (part). — Serène & Lohavanijaya 1973: 62, 63 [key to species] (part). — Guinot 1989: 273 (part). — Chen 1998: 266 [key to species] (part). [not Carcinoplax H. Milne Edwards, 1852 ]

Diagnosis. Carapace ( Fig. 37A ) suboctagonal, nearly round; front long, nearly straight (outer edges slightly arched in large individuals), marked by small median notch; transverse sulcus along margin; notch between front, supraorbital border. Orbits short, spherical ( Fig. 37B ); supraorbital borders short, arched, with 2 notches; suborbital borders arched, 2 very small notches in larger individuals; large, granular, ventrally oriented inner suborbital tooth ( Fig. 37B, C ); eye peduncles short, granular; large, spherical corneas. Anterolateral borders arched, 2 short, obtuse anterolateral teeth; posterolateral borders long, arched. Dorsal, ventral surface of carapace with short, spherical granules ( Fig. 37B, C ), strongly convex, without clear indication of regions. Outer orbital angle with very short, triangular tooth; 2 obtuse, small anterolateral teeth on each side of carapace, first larger (much reduced or absent in large individuals, particularly second tooth; Fig. 38I, J ). Basal antennal article immobile, with distolateral process so that orbital hiatus is closed excluding antennal flagellum from orbit ( Fig. 37B, C ). Outer (ventral) surface of third maxilliped carpus, merus granular, anteroexternal margin of merus auriculiform ( Fig. 37C ). Subhepatic, pterygostomian regions, pterygostomian crest granular. Thoracic sternum ( Fig. 37E, G ) wide, granular outer margins; thoracic suture 2/3 complete, straight ( Fig. 37E, G ); 3/4 deep, short, interrupted; 4/5, 5/6, 6/7, 7/8 interrupted ( Fig. 37G ); median groove on thoracic sternites 7, 8 ( Fig. 37G ). Sterno-abdominal cavity of male deep, reaching median portion of sternite 4 ( Fig. 37E ). Press-button of male abdominal-locking mechanism as tubercle near thoracic suture 4/5 (presence in pre-adult females unknown). Anteroexternal margin of third maxilliped merus auriculiform. Cheliped (P1) propodus, carpus, merus granular (inner surface of propodus relatively smooth); fingers moderately stout, slightly shorter than swollen propodus, tips darker in colour ( Fig. 37D ). Carpus with long, blunt tooth on distal, inner margin; merus with large, blunt tooth on inner surface near anterior margin. Dorsal margins of ambulatory legs (P2–P5) meri, carpi, propodi unarmed, dactyli slender, smooth, setose; P5 dactyli, propodi proportionally short, flattened, fringed with scattered, long setae, spines. Male abdomen narrow, slender (Tshaped), lateral margins of somites 4–6 abruptly narrowing from somite 3 to transversely narrow, pointed telson ( Fig. 37E ); somite 3 reaching inner margins of P5 coxae, outer end fitting under episternite 7; somite 2 transversely shorter than somite 3 but no portions of thoracic sternite 8 exposed by closed abdomen ( Fig. 37F ). G1 long, slender, slightly sinuous, acuminate apex, with small denticles ( Fig. 38G ). G2 less than onethird of G1, straight, with 2 processes: one long, tip acute; second much shorter, small, lobe-like ( Fig. 38H ). Male genital opening (gonopore) coxal; coxo-sternal disposition of long penis with very broad, soft proximal expansion, protected by concave posterior portion of thoracic sternite 7. Female abdomen relatively narrow, not covering outer portions of thoracic sternum, with six freely-mobile somites. Telson broadly triangular, wider than long. Somites 1, 2 cover space between P5 coxae, only small portion of each P5 condyle of sternite 8 left exposed by closed abdomen ( Fig. 37F ). Vulva of mature females ovoid, extending across median portion of thoracic sternite 6 close to median axis of thorax ( Fig. 37G ); covered by soft membrane, sternal vulvar cover absent.

Type species. Carcinoplax angusta Rathbun, 1914 (by present designation, gender feminine).

Etymology. From systremma, Greek for anything aggregated, generally a ball or round object, in reference to the diagnostic round shape of the carapace of the type species, and plax, Greek for “plate” or “tablet”, which is derived from the generic name Carcinoplax (from karkinos, Greek for crab), to denote that the species included in the new genus was formerly included in the latter.

Remarks. Although the carapace shape is superficially similar to two species assigned to the family Goneplacidae sensu stricto (i.e. Carcinoplax tenuidentata Castro, 2007 , and Pycnoplax bispinosa (Rathbun, 1914) ; Castro 2007: figs. 5, 13B), Systroplax n. gen. clearly belongs to the Euryplacidae ( Castro 2007: 623) . The male abdomen is slender, with a narrow and pointed telson ( Fig. 37E ), and the G1, also slender, is much longer than the G2. Although the shape of the abdomen of goneplacids varies, it is typically broad and triangular and a similarly shaped telson (i.e. Castro 2007: figs. 4B, 16B), never narrow as in the Euryplacidae . The G 1 in Carcinoplax H. Milne Edwards, 1852 , is never as slender as in euryplacids and the apex is much wider, never acuminate (e.g. Castro 2007: fig. 2), or thick and stout as in Pycnoplax Castro, 2007 (e.g. Castro 2007: fig. 16C). A G2 much shorter than the G1, however, is present in three goneplacid genera ( Castro 2007). The vulva of Systroplax n. gen. is typical of euryplacids, relatively small with thick margins and no sternal vulvar cover, in contrast to the much expanded vulva of Carcinoplax (e.g. Castro 2007: fig. 1), or the vulva covered by a sternal vulvar cover of Pycnoplax (e.g. Castro 2007: fig. 15).

In contrast to most euryplacids, thoracic suture 5/6 is interrupted, a character nevertheless shared with Nancyplax and Xenocrate ( Table 1).

Species included. Systroplax angusta (Rathbun, 1914) The genus is restricted to the Indo-West Pacific region.

Figures

FIGURE 36. Psopheticoides sanguineus Sakai, 1969; male (21.3 mm × 26.5 mm) (ZRC 2004.0752), Philippines, Bohol, Panglao. A, overall view; B, frontal view showing orbits and antennae; C, third maxillipeds; D, outer surface of right chela; E, anterior portion of male thoracic sternum and abdomen; F, posterior portion of male thoracic sternum and abdomen; G. female sternum and vulvae. Abbreviations: a1–a3 = male abdominal somites 1, 2, 3, respectively; cx5 = coxa of fifth pereopod (P5); s4–s7 = thoracic sternites 4 to 8, respectively; vc = sternal vulvar cover.

FIGURE 37. Systroplax angusta (Rathbun, 1914); A–C, G, female (27.8 mm × 31.4 mm) (MNHN-B29377), Fiji; D–F, male (32.3 mm × 37.2 mm) (MNHN-B29377), Fiji. A, overall view; B, frontal view showing orbits and antennae; C, third maxillipeds; D, outer surface of left chela; E, anterior portion of male thoracic sternum and abdomen; F, posterior portion of male thoracic sternum and abdomen; female sternum and vulvae; G, female sternum and vulvae. Abbreviations: a1–a3 = male abdominal somites 1, 2, 3, respectively; cx5 = coxa of fifth pereopod (P5); es7 = episternite 7; mg = median groove; s4–s7 = thoracic sternites 4 to 8, respectively; v = vulva.

FIGURE 38. Gonopods of Platyozius, Psopheticoides, and Systroplax; carapace of Systroplax. A–C, Platyozius laevis (Borradaile, 1902), male (6.1 mm × 7.8 mm) (ZRC 2007.0707), Maldives, Laamu Atoll; D–F, Psopheticoides sanguineus Sakai, 1969, male (21.9 mm × 27.8 mm) (ZRC 2008.1357), Philippines, Bohol, Balicasag I.; G–J, Systroplax angusta (Rathbun, 1914); G, G1 (after Guinot 1989: fig. 39D); H, male (32.3 mm × 37.2 mm) (MNHN-B29377), Fiji; I, J, variation in anterolateral borders of carapace (after Guinot 1989: fig. 39A, C). A, B, D, E, right G1, dorsal view; C, F, H, right G2, dorsal view. Scale bars: A, D, 1.0 mm; B, E, 0.5 mm; C, F, H, 0.2 mm; G, 0.1 mm.

FIGURE 39. Colours in life. A, Euryplax nitida Stimpson, 1871; male neotype (7.1 mm × 11.3 mm) (UF 15166), Gulf of Mexico; B, Euryplax nitida Stimpson, 1871; male (4.4 mm × 7.0 mm) (UF 15168), Gulf of Mexico; C, Psopheticoides sanguineus Sakai, 1969, male (22.2 mm × 26.7 mm) (MNHN-B29728), Philippines, Bohol, Panglao; D, Trissoplax dentata (Stimpson, 1858), male (6.2 mm × 8.3 mm) (NHM), Thailand, Andaman Sea; E, Trissoplax dentata (Stimpson, 1858), young male, not preserved, Singapore, Changi; F, Trissoplax dentata (Stimpson, 1858), female (8.7 mm × 11.5 mm) (ZRC 2000.2240), Singapore. Photo credits: A, B by Florida Museum of Natural History (UF); D by P. F. Clark (NHM).