Garthiella aberrans ( Rathbun, 1906 )

Mendoza, Jose Christopher E. & Manuel-Santos, Marivene R., 2012, Revision of Garthiella Titgen, 1986 (Crustacea: Decapoda: Brachyura: Xanthidae), with description of a new subfamily and a new species from the central Philippines, Zootaxa 3446, pp. 32-48 : 37-39

Garthiella aberrans ( Rathbun, 1906)

Figs. 1–3, 6A, B, 7 A-D, 8A

Chlorodopsis aberrans Rathbun, 1906: 859 , fig. 20.— Edmondson 1925: 43; 1946: 295; 1962: 274, fig. 20a.— Serène & Nguyen 1958: 90, 91; 1959: 302, 328, figs. 2L, 5L, pl. 2 fig. D, pl. 3 fig. K.— Forest & Guinot 1961: 89.

Pilodius aberrans — Amerson & Shelton 1976: 76.— Peyrot-Clausade 1977: 212; 1989: 111, 115.— Serène 1984: 235, 239.— Guinot, 1985: 451.

Garthiella aberrans — Titgen 1986: 57, figs. 1, 2.— Poupin 1996: 54.— Coles et al. 2001: 52.— Ng et al. 2008: 197 (list).— Castro 2011: 90 .

Material examined. Holotype, ♂, 7.9 × 4.9 mm ( USNM 29434 ), dredged, 23–26 fms (42–47 m), stn 4146, near Modu Manu (=Nihoa), Northwestern Hawaiian Islands , coll. Albatross, 1902.

Other material: 1 ♂, 8.7 × 5.7 mm ( UF 16154 ), outer reef slope, under rocks, 15–32 m, south of Vaiare Pass , Moorea, Society Is., French Polynesia, coll. C. Meyer, S. McKeon, G. Paulay & J. Moore, 27 October 2008 ; 1 ♂, 8.7 × 5.6 mm ( UF 15682 ), outer reef slope, within rubble, 29 m, northern end of Temae , Moorea, Society Is., French Polynesia, coll. J. Poupin, 17 October 2008 ; 1 ♀, 9.7 × 6.0 mm ( UF 15605 ) , 1 ♀, 7.4 × 4.8 mm ( UF 15624 ), outer reef slope, gentle & sandy, within rubble, 17–18 m, east of Opunohu Pass , Moorea, Society Is., French Polynesia, coll. S. McKeon, J. Moore & G. Paulay, 16 October 2008 ; 1 ♀, 7.9 × 5.1 mm ( UF 16380 ), outer reef slope, spur & groove zone, 4–7 m, between Cook’s Bay & Sheraton, Moorea, Society Is., French Polynesia, coll. S. McKeon, J. Moore & A. Anker, 12 November 2008 .

Diagnosis. Carapace transversely subhexagonal to subovate, width about 1.5–1.6 times length; dorsal surface profusely covered with large, conical granules especially on anterior, lateral regions. Front bilobed, with pronounced teeth on lateral angle, appearing quadridentate. Supero-external surfaces of cheliped palm and carpus covered with large, conical granules. Distal tip of G1 bilobed, lower lobe recurved, pointing inward toward sternoabdominal cavity and base of G1; with few subterminal setae.

Description. Carapace transversely subhexagonal to subovate, width about 1.5–1.6 times length; dorsal surface depressed, sparsely setose, covered with large, conical or truncate granules, especially in anterolateral regions; regions well defined, separated by wide, smooth grooves without setae; 1F, 2F indistinguishable from each other, 1M fused with inner branch of 2M, 2M partially divided longitudinally, 3M entire, well defined, 4M indistinct, 1L, 3L, 4L indistinct, 2L, 5L, 6L entire, well defined; 1P, 2P flattened, indistinct, 1R-3R indistinct. Front bilobed, deflexed, strongly granular; frontal width about 0.3 times carapace width; lobes separated by deep, U- shaped, median sinus; each lobe with projecting margin medially, well-separated tooth laterally, giving front quadridentate appearance. Anterolateral margin slightly convex, slightly shorter than posterolateral margin, with 4 teeth posterior to exorbital angle; first tooth small almost indistinguishable from surrounding granules, second to fourth teeth larger, curved at tips, margins denticulate. Posterolateral margin granular, nearly straight. Posterior margin finely granular, slightly concave at central area. Orbits rounded; superior, inferior margins cristate, spinulose; supraorbital region clearly demarcated by wide, smooth groove; eyes large, corneas well developed. Pterygostomial region similar to dorsal surface of carapace.

Antennular fossae large. Basal antennal article subrectangular, with strongly projecting granules, inner angle touching ventral prolongation of front; outer angle prolonged partially into wide orbital hiatus, not closing hiatus to antennal flagellum. Pterygostome with small, narrow, accessory plate abutting against lateral margin of antennal basal segment. Anterior portion of epistome bordering antennules strongly spinulose; posterior margin of epistome crenate, with median projection. Endostomial ridges developed only on posterior region. Third maxillipeds coarsely granular, densely bristled medially, with scattered setae over external surface; merus subquadrate, anterior margin concave, anterolateral angle produced; ischium subrectangular, with median longitudinal sulcus.

Thoracic sternum of male profusely covered with round granules. Sternites 1, 2 fused, separated from sternite 3 by clear suture; sternite 3 partially fused to sternite 4, sutures limited to extreme lateral regions only, replaced centrally by distinct, smooth, transverse groove; sternite 4 large, with short median line; sternites 5–8 well separated by sutures; sternite 8 partially visible externally between abdominal somite 2, coxa of P5; sternoabdominal cavity moderately deep; press-button relatively large, positioned anteriorly, close to suture 4/5; median line continuing uninterrupted on sternite 4, absent on sternites 5, 6, present on sternites 7, 8.

Chelipeds subequal, densely covered with large conical granules, sparsely setose. Merus short, distal end barely exceeding carapace; carpus with several prominent conical granules on inner angle; palm slightly inflated, superior half covered with large conical granules, inferior half with smaller, round granules, internal surface similar. Fingers deeply grooved; conical granules extending almost to distal tips; teeth well developed; tips curved, pointed, crossing each other; entire length pigmented except at tips, pigment on fixed finger extending into palm.

Ambulatory legs moderately long, P3, P4 longest, slightly longer than maximum carapace width; surfaces granular, moderately setose, anterior margins of meri, carpi, propodi spinose; meri length about 0.3–0.4 times total leg length, anterior margins with prominent, regularly spaced spines, terminating distally with large spine, posterior margin with smaller spines, granules; carpi with 2 rows of spines on, near anterior margin; propodi longer than carpi, spinose on anterior and disto-posterior margins; dactyli straight, slender, slightly longer than propodi, with small granules, margins lined with spiniform setae mixed with longer plumose setae, distal tip terminating in long, curved, chitinous claw, subdistal calcareous teeth absent on flexor surface; dactylo-propodal locking mechanism absent.

Male abdomen relatively large, lateral margins concave; somites 1, 2, proximal region of somite 3 all granular, rest smooth; somites 3–5 immovably fused with traces of sutures visible; somite 6 subquadrate, wider than long, disto-lateral angles slightly produced; telson subtriangular, basal width greater than median length, tip level with sterno-coxal condyles of chelipeds.

G1 moderately long, slender, curved; mesial side of distal half with row of small spines along length; distal portion with about 5 stiff, simple, subterminal setae; terminal end bilobate, mesial lobe extended, straight, lateral lobe folded, directed toward sternum, base of G1. G2 about one-third length of G1. Penis short, emerging from gonopore anterior to coxo-sternal condyle of P5 coxa.

Morphology of female identical to that of male, except in sexual characters. Abdomen wide, oval, lateral margins convex, all somites freely articulated; somite 4 widest; telson large, subtriangular. Segmentation of thoracic sternum, condition of median line as in male. Vulvae on thoracic sternite 6, close to median axis, suture 5/ 6; sternal vulvar cover originating from medial margin of vulvae, rounded, almost completely closing vulvae.

Remarks. Garthiella aberrans is easily distinguished from G. sikatuna sp. nov. by the morphological features of the carapace, mouthparts, pereiopods and G1 (see Remarks on the new species). The live colouration of this species ( Fig. 8A) consists of a white carapace, with the conical granules tipped in orange, and red pereiopods, except for the P5 coxae (and sometimes the distal tips of the ambulatory propodi), which are also white, and the fingers of the chelae, which are brown; the eyes are also white, including the corneas, but those have small, underlying, spots of red. Some variants have a carapace that is mostly red with scattered white spots or blotches, and red eyes with a white longitudinal stripe on the eyestalk.

Ecology and geographical distribution. The holotype of Garthiella aberrans was collected from Nihoa, Northwestern Hawaiian Islands, at a depth of 42–48 m, from a substrate described as coarse coral, sand and foraminiferans ( Rathbun 1906; Titgen 1986). Specimens were also collected from shallower waters around Johnston Atoll to the southwest of the main Hawaiian island group ( Edmondson 1925, 1962). This species was also recorded from French Polynesia, particularly from Moorea, Society Islands, and Tikehau, Archipelago (Peyrot- Clausade 1977, 1989; Poupin 1996), were they were also collected from shallow water (0–30 m) on hard bottom. The new material examined for this study all came from Moorea and were collected from fringing reefs, in sandyrocky-coral rubble substrates at depths of 4– 32 m. In addition, photographs of freshly collected crabs, from Saipan and Wake islands, were kindly provided by Gustav Paulay (UF) and Molly Timmers (NOAA), and have been positively identified as G. aberrans by the authors. These specimens were collected from two Autonomous Reef Monitoring Structures (ARMS) deployed in coral reefs, at depths of 18 and 14 m, respectively, by the National Oceanic & Atmospheric Administration (NOAA, USA).