Paragalene longicrura ( Nardo, 1868 )

Castro, Peter & Ng, Peter K. L., 2008, Rhadinoplax, a new genus of Progeryonidae Števčić, 2005, for Carcinoplax microphthalmus Guinot & Richer de Forges, 1981, and a redescription of Paragalene longicrura (Nardo, 1868) (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 1777, pp. 53-68 : 63-66

Paragalene longicrura ( Nardo, 1868)

( Figs. 6–8)

Eriphia longicrura Nardo, 1868: 302 , pl. 13 fig. 1.

Paragalene neapolitana Kossmann, 1878: 253 .

For complete synonymy, see d’Udekem d’Acoz 1999: 241; Ng & Manuel-Santos 2007: 68.

Material examined. 2 ♂♂, 32.4 x 41.7 mm, 33.0 x 43.7 mm ( NHM 1959.5.26.187–188), Bay of Naples , collected by Zoological Station at Naples, Italy .

Description. Carapace hexagonal ( Fig. 6A; also see Türkay 1976b: fig. 1; González Pérez 1995: figs. 139, 140); front lamellar, marked by median notch bordered on each side by narrow prominence plus wide concave margin ending in a prominence; notch between front, supraorbital border. Orbits ( Fig. 6B) short, spherical, not expanded on outer portion; triangular, granular outer orbital tooth; supraorbital borders short, curved, with large granules, notches absent. Anterolateral borders ( Fig. 6A) curved; posterolateral borders long, nearly straight. Dorsal surface of carapace convex anteriorly, granular with granules larger, conspicuous along anterior border. Granular ridge across hepatic region. Elevated protogastric region with 2 granular ridges along anterior margin, deep bifurcated sulcus medially. Branchial region with short, transverse ridge, Cardiac region with 2 shallow, curved grooves. Outer orbital angle with granular margin; anterolateral margin with 4 teeth; anteriormost 2 granular, obtuse; third tooth (largest) curved upward, granular, with smooth, acute apex; fourth straight, granular with smooth, acute apex ( Fig. 6A). Basal antennal article short, mobile, almost closed by extension of carapace margin, thus distalmost (third) article almost reaches front ( Fig. 6 C, E). Eye peduncle short, cornea spherical, large, expanded distally ( Fig. 6B). Suborbital border with large, granular, acute inner tooth, similar median tooth ( Fig. 6C, E). Anterior border of endostome well demarcated from buccal cavern, ridges faint but clearly defined. Third maxillipeds completely close buccal cavern; anterior outer margin conspicuously expanded, rounded. Endostomial ridge distinct, granular. No visible stridulating mechanism.

Cheliped (P1) fingers slender, equal to or less than half propodus length, dark coloured ( Fig. 7A, B). Propodus dorsally granular; carpus with 2 acute teeth on inner margin ( Fig. 6A). P2–P5 meri, carpi, propodi long, slender; dorsal margins unarmed; dactyli long, slender, setose ( Fig. 6A).

Thoracic sternum relatively narrow ( Figs. 6D, 7E). Sternites 1, 2 completely fused, no trace of suture; S2/ 3 complete, deep; S3/4 complete but medially shallow; S4/5, S5/6 medially interrupted; S6/7, 7/8 complete; median longitudinal groove on sternites 7, 8 ( Fig. 7G). Somite 3 of male abdomen covers thoracic sternal space between P5 coxae, thoracic sternite 8 not visible ( Fig. 7D, F). Episternites 4–6 laterally expanded ( Fig. 7E, F); episternite 7 expanded laterally and posteriorly, reaching and partially covering anterior part of P5 coxa but not penis ( Fig. 7G). Penis coxal, small, short distal extension, emerging just anterior to condyle; very broad, soft proximal expansion ( Fig. 7G). Sterno-abdominal cavity relatively deep, reaching to before margin of S3/4 ( Fig. 7E). Press button of male abdomen locking mechanism on posterior half of sternite 5, closer to margin of sternite 6 ( Fig. 7E).

Male abdomen with 5 freely-movable somites (somites 3, 4 fused) plus telson, relatively narrow; somite 1 exposed, not covered by posterior carapace margin, transversely narrow, sublunate in shape; somites 4–6 sharply decreasing in length from somite 3 (widest somite) ( Fig. 7D, F). Telson subequal, slightly wider than long ( Fig. 6D). G1 very slender, spinous, slightly dilated apex ( Fig. 8A, B). G2 slightly longer than G1, flagellum as long as proximal part; thin, lateral projections; pointed, serrated apex ( Fig. 8C, D).

Female specimens unavailable for description.

Remarks. Paragalene longicrura is rarely collected and very little is known about its biology. It appears to live in relatively shallow water (usually 20–30 m but also as deep as 160 m) and mostly on hard bottoms, including sea caves (see d’Udekem d’Acoz 1999: 241; Türkay 1976a: 70, pl. 3; González Pérez 1995: 199, colour figs. 139, 140 for reviews of its ecology and geographical distribution).

Distribution. Mediterranean Sea and eastern Atlantic Ocean (Madeira and Canary Islands).

Comparative material. Progeryon mus Ng & Guinot, 1999 : holotype male (38.6 x 46.5 mm), 1 paratype female ( ZRC 1997.442 – 443 ), Nihoa Island , Hawaii, 441 m depth, coll. 1979.