Neopalicus simulus, Castro, 2010

Castro, Peter, 2010, A new species and new records of palicoid crabs (Crustacea, Decapoda, Brachyura, Palicoidea, Palicidae, Crossotonotidae) from the Indo-West Pacific region, Zoosystema 32 (1), pp. 73-86 : 75-78

Neopalicus simulus n. sp.

( Fig. 1 )

HOLOTYPE. — French Polynesia. Austral Is , BENTHAUS, stn CP 1907, ♂ holotype, cl 4.7 mm, cw 5.3 mm ( MNHN-B29134 ).

PARATYPES. — French Polynesia. Austral Is, BENTHAUS, stn CP 1880, Marotiri Is, 27°55’S, 143°29.4’W, 90-94 m, 6.XI.2002, 1 ♀, cl 4.6 mm, cw 4.9 mm (MNHN- B29132). — Stn CP 1881, Marotiri Is, 27°54.6’S, 143°28.5’W, 112-121 m, 6.XI.2002, 1 ovig. ♀, cl 4.5 mm, cw 4.9 mm ( MNHN-B 29133). — Stn CP 1913, Récif Neilson, 27°01.5’S, 146°00.3’W, 120 m, 11.XI.2002, 1 ovig. ♀, cl 5.5 mm, cw 5.9 mm ( MNHN-B 29135). — Stn CP 1920, Récif Neilson, 27°03.6’S, 146°03.8’W, 120-200 m, 11.XI.2002, 1 pre-adult ♂, cl 3.6 mm, cw 3.7 mm, 2 ♂♂, cl 4.3 mm, cw 4.8 mm, cl 5.1 mm, cw 6.0 mm ( MNHN-B 29136). — Stn CP 1923, Récif Neilson, 27°01.3’S, 146°05.3’W, 360-840 m, 11.XI.2002, 1 ♂, cl 3.2 mm, cw 3.8 mm ( MNHN-B 29137).

TYPE LOCALITY. — French Polynesia, Austral Is, Rapa I., Banc Nord-Est, BENTHAUS, stn CP 1907, 27°25.4’S, 144°02.6’W, 120- 125 m.

ETYMOLOGY. — From simulus , diminutive of simus, Latin for “flat” or “pug nosed,” in reference to the short, rounded, non-bilobed rostrum that is diagnostic of the species.

DISTRIBUTION. — Known only from the Austral Is, French Polynesia. Depth: 90-200 m and from a station (CP 1923) 360-840 m deep.

DESCRIPTION

Carapace ( Fig. 1A, B ) subquadrate, nearly as wide as long (cw/cl = 1.0-1.3); dorsal surface covered with fine granules, horizontal rows of large, low granular bosses.Confluence of branchial, mesogastric regions depressed; depression along median portion of frontal region. Short, simple (non-bilobed) rostrum. Anterolateral borders of carapace each with 2 large, truncated teeth, first (anteriormost) largest, most conspicuous. Posterior border with short, rounded tubercles (one at each end, 3 median), setae absent. Frontal border of carapace with single, rounded lobe. Borders between frontal lobe, supraorbital borders sinuous, ending in sharp angle, forming deep V-shaped fissure before supraorbital border ( Fig. 1A, B ). Supraorbital borders each with 2 rounded lobes. Postorbital angles short, not extending beyond dorsal border of retracted eye, nearly straight. Cornea of eyes dorso-ventrally depressed, wider than base of eye peduncle. Each peduncle with 3 dorsal tubercles: anterior, distal, crest-like (depressed); median tubercle smaller than other 2 tubercles; large, rounded tubercle on distal extension nearly encircled by cornea.

Suborbital borders ( Fig. 1C ) slightly convex; smooth. Pterygostomial lobes project ventrally, forming flat, rounded structure posterior to each inner suborbital lobe.

Basal antennal article ( Fig. 1C ) slender, rectangular, with short, wing-like extension; flagellum long, with few, simple setae. Epistome expanded dorso-ventrally, forming broad, semicircular, nearly flat surface; thin, carina-like process across median portion with two median teeth.

Inner margins of ischium of third maxillipeds straight; surface coarsely granular, upper margins rounded. Merus much narrower than ischium; straight-edged.

Chelipeds (P1) unequal in both sexes; propodus of larger cheliped of males much higher, thicker than smaller cheliped ( Fig. 1A ). Dorsal, outer margins of cheliped propodus with 2 high, rounded tubercles (except larger cheliped of males, which is smooth), inner surface with dense clusters of plumose setae in males, bare in females; fingers with cutting edges or rounded teeth. Carpus short, smooth; meri slender, smooth.

Ambulatory legs (P2-P4) dorso-ventrally flattened; P2 shorter than P3, P4; P3 nearly as long as P4 ( Fig. 1A ). Upper, lower margins of merus with short rounded tubercles; distalmost tubercle on each anterior margin wider at base, higher, directed distally. Anterior margins of carpus with tubercles. Dorsal surface of P3, P4 propodi, dactyli with many plumose setae; margins of P3, P4 propodi entire, anterior margins each with wide, convex carina-like extension; dactyli long, slender, entire margins. P5 short (0.7-0.9 cl), dorsal to P4 ( Fig. 1A ); merus slender, with microscopic tubercles along posterior margins, scattered simple setae; propodus with 4 or 5 short spines along posterior margin; dactylus with 3 or 4 short spines along posterior margin, terminal pointed tooth.

Abdomen of mature males elongated, with all somites freely articulating, smooth, without transverse ridges. Penis showing coxo-sternal condition. G1 ( Fig. 1D ) long, slender, with sinuous basal part; distal part with small teeth, simple, uniramous apex. G2 much shorter than G1.

Abdomen of mature females with all somites freely articulating.Transversal ridge along each somite 1-4, less pronounced in somite 5. Vulvae small, round, with simple margins, on thoracic sternite 6 but displaced to median plate of sternum.

REMARKS

The new species clearly belongs to Neopalicus as redescribed by Castro (2000: 548). The genus until now consisted of two species, N. contractus (Rathbun, 1902) and N. jukesii (White, 1847) . Neopalicus simulus n. sp. shares with these two species a subquadrate carapace with horizontal rows of large and low bosses on its dorsal surface; two large truncated teeth along each anterolateral border; large eyes with eye peduncles each having three dorsal tubercles; supraorbital borders with two rounded lobes; basal antennal article with a short, wing-like expansion; P2-P4 with dorso-ventrally flattened (not filiform) carpi, propodi, and dactyli; anterior margins of the P3 and P4 propodi each with a wide and convex extension; posterior margins of the dactyli entire; posterior margins of the P5 propodus spinous; abdomen of males elongated, all somites freely articulating; G1 long and slender, basal portion sinuous; abdomen of adult females with all somites freely articulating.

Diagnostic characters of N. simulus n. sp. are the presence of a short, non-bilobed rostrum (bilobed in N. contractus and N. jukesii ; see Castro 2000: figs 39, 40), a smooth suborbital border (two triangular, dentiform lobes in N. contractus and N. jukesii ; see Castro 2000: fig. 40a, b), abdomen of mature males with smooth somites (transverse ridges in N. contractus and N. jukesii ), and the simple, uniramous distal end of the G1 (biramous in N. contractus and N. jukesii ; see Castro 2000: fig. 41). The inner surface of the cheliped propodus of the male has dense clusters of plumose setae (barely visible in Figure 1A ) as in N. jukesii (see Holthuis 1977: fig. 2c, as Palicus carinipes (Paul’son, 1875)) but unlike N. contractus , which lacks setae.

Neopalicus contractus is known from locations across the Indian Ocean (type locality: Maldive Islands), western Pacific Ocean from the Philippines to New Caledonia, and the Marshall Islands in the central Pacific ( Castro 2000: table 6, fig. 49). Neopalicus jukesii (type locality: Queensland, Australia) shows a geographical distribution similar to that of N. contractus except that it is also known from the Red Sea and Japan but not from the central Pacific ( Castro 2000: table 6, fig. 49). Both species inhabit, sometimes sympatrically, coarse sand in relatively shallow water (44-80 m in N. contractus , 10-146 m in N. jukesii ; Castro 2000: table 5) adjacent to coral reefs. In contrast, N. simulus n. sp. is known from rocky bottoms containing coral rubble at depths of 90-200 m (one male [MNHN-B29137], however, was obtained from material dredged at 360-840 m) from the Austral Is, French Polynesia, southeastern Pacific. It is the only known species of Neopalicus in the southeastern Pacific.

Neopalicus simulus n. sp. is only known from small individuals, the maximum size recorded among the eight known specimens was only 5.5 mm (cw), an ovigerous female. All three large females showed the large, wide abdomen characteristic of adult female palicoids, two of the three were ovigerous. This is in sharp contrast to N. contractus and N. jukesii , where the largest females ever recorded were 18.6 mm and 15.1 mm (cw) respectively ( Castro 2000) and where females of comparable size are pre-adults, and hence with a narrow, thin abdomen.

Figures

FIG. 1. — Neopalicus simulus n. sp., ♂ holotype, cl 4.7 mm, cw 5.3 mm, Banc Nord-Est, Rapa I., French Polynesia, BENTHAUS, stn CP 1907 (MNHN-B29134): A, B, dorsal surface of carapace; C, suborbital border; D, left G1, dorsal view. Scale bars: B, 2 mm; C, 1 mm; D, 0.5 mm.