Notonyx castroi Rahayu & Ng, 2010, n. sp.
Creators: name: Rahayu, Dwi Listyo
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Goneplacidae
Notonyx
Notonyx castroi

description: Notonyx castroi n. sp.
(Figs. 1–3)
Material. Holotype: male, 7.2 × 5.6 mm (MZB Cru 2780), Kecinan, northern Lombok, Lesser Sunda Islands, Indonesia, 08°24.368’S, 116°03.561’E, coll. 15 May 2007. Paratypes: 1 male, 5.5 × 4.4 mm (ZRC 2010.0290), Teluk Kombal, northern Lombok, Lesser Sunda Islands, Indonesia, coll. 8 June 2009; 1 male, 4.7 × 3.7 mm (ZRC 2010.0291), Sira, northern Lombok, Lesser Sunda Islands, Indonesia, 08°21.641’S, 116°06.272’E, coll. 13 June 2007; 1 male, 4.9 × 3.6 mm (MZB Cru 2781), Seram, Maluku, Indonesia.
Diagnosis. Carapace subquadrilateral, wider than long (1.3 times as wide as long in holotype) (Figs. 1 A, 2A). Dorsal surface of carapace smooth, without indication of regions; gently convex anteriorly, posteriorly (Figs. 1 A, B, 2A). Front margin straight or slightly bilobed, about 0.4 times carapace width (Figs. 1 A, B, 2A). Anterolateral margin short, entire, curved, unarmed; posterolateral margin longer (Figs. 1 A, 2A). Antennules relatively long, terminal setae overreaching cornea (Fig. 1 B, 2A). Basal antennal joint small, short, positioned on orbital hiatus (Fig. 1 B). Eye peduncle moderately long, 0.6 times frontal width, cornea small (Figs. 1 A, B, 2A). Small gape between third maxillipeds when closed (Fig. 2 B); merus, ischium subequal; antero-external angle of merus forms right angle (Fig. 2 B). Chelipeds subequal, right larger (Figs. 1 C, D, 2D); fingers stout, dactylus smooth; fixed finger with low longitudinal keel on ventral margin, palm smooth; inner margin of carpus with feeble angle (Fig. 2 C), clump of setae on inner margin; merus with long, stiff setae on anterior, posterior margins. Ambulatory legs relatively stout (Figs. 1 A, 2E), smooth; dactylus with carina on lateral surface; scattered setae on meri, carpi. Thoracic sternum relatively broad; surface lightly pitted; sternites 1, 2 fused, separated from sternite 3 by distinct transverse suture; sternites 3, 4 fused with only lateral incision visible. Male abdomen triangular, relatively wide with 7 movable somites including telson; somite 1 underneath carapace, wider than somite 2; somite 2 longitudinally narrow; somite 3 widest; somites 4 to 6 tapering to triangular telson; telson longer than somite 6 (Fig. 2 F). G1 relatively stout (Fig. 3 A–E), distal part slightly produced, tip bilobed; ventral part slightly swollen with scattered spiniform setae. G2 long (Fig. 3 F, G), tip slightly twisted, spatuliform, directed dorsally.
Habitat. Sandy mud substrate with coral debris in seagrass bed.
Etymology. The authors take pleasure in naming this species after our friend and colleague, Peter Castro, whose revision of the Goneplacidae has substantially advanced our knowledge of the family.
Remarks. The species of Notonyx may be separated by the relative proportion of the carapace, proportions of the merus and ischium of the third maxilliped, structure of the carpus of the cheliped, shape of the male abdomen, but most easily in the shape of their G1s and G2s. The G1 of most of the species is curved or bent. In N. gigacarcinicus, the G1 is slightly curved with a swollen subdistal part (Clark & Ng 2006: fig. 5); in N. guinotae it is dorsomesially curved with an elongated distal part (Rahayu & Ng 2010: fig. 4); in N. kumi it is dorsomesially curved along the distal two-fifths (Naruse & Maenosono 2009: fig. 2 b, c); in N. latus the distal part of is elongated and hooked, with a subtruncate tip (Ng & Clark 2008: fig. 3); in N. nitidus it is gently curved distally with a small lateral distal opening (Clark & Ng 2006: fig. 3); in N. rayneri it is slightly outwardly curved (Ng & Clark 2010: fig. 6); and in N. sagitifer it is curved outwards with the distal part folded open (Ng & Clark 2010: fig. 3).
Notonyx castroi n. sp. is easily distinguished from all congeners by the straight distal part of its G1 and a round distal opening. The most closely related species is N. gigacarcinicus, with the subdistal part of its G1 swollen, but the shapes of the structures are very different. The G1 of N. castroi n. sp. is short and slightly curved medially with the tip wide and round (Fig. 3 A–E), while in N. gigacarcinicus, the distal part of the G1 is relatively longer, more strongly curved and the tip is produced (Clark & Ng 2006: fig. 5J, K). Their G2 structures are also different. The G2 of N. castroi n. sp. has a slightly twisted tip that is directed upwards (Fig. 3 F, G), while, it is twisted twice and pointed upwards in N. gigacarcinicus (Fig. 5 F, G; Clark & Ng 2006: fig. 5I). Notonyx nitidus has a slightly curved G1 but no part of it is swollen (Clark & Ng 2006: fig. 3H, I) while that of N. castroi n. sp. is swollen subdistally. The difference on the shape of the G2 is also apparent, in N. nitidus the subdistal part of G2 is curved (Clark & Ng 2006: fig. 3G), while in N. castroi n. sp., it is straight (Fig. 3 F, G).
Distribution. Only known from Lombok, Lesser Sunda Islands (Indonesia).
description: Published as part of Rahayu, Dwi Listyo & Ng, Peter K. L., 2010, The species of Notonyx A. Milne-Edwards, 1873, from Lesser Sunda and Maluku Islands, Indonesia, with description of a new species (Crustacea: Decapoda: Brachyura: Goneplacidae), pp. 51-60 in Zootaxa 2570 on page 52, DOI: 10.5281/zenodo.197360