Schizophroida gracilis, Ng & Ahyong, 2018

Ng, Peter K. L. & Ahyong, Shane T., 2018, New Species of Reef Spider Crabs of the Genus Schizophroida Sakai, 1933 (Crustacea: Brachyura: Majidae) from the Western Pacific, Records of the Australian Museum (Rec. Aust. Mus.) 70 (4), pp. 377-390 : 384-386

Schizophroida gracilis sp. nov.

Figs 5C, D , 6–9 , 10 G–L

Schizophroida hilensis .— Paulay et al., 2003: 496 [ Guam].— Yang et al., 2008: 780 [ Taiwan]. [Not S chizophroida hilensis ( Rathbun, 1906) ].

Holotype: NTOU, male (cl 20.6 mm, pcl 11.5 mm, cw 10.5 mm), Lanyu Island , Taitung County, 22°N 121°W, coll. S.-H. Wu, August 2000 . Paratypes: ZRC 2017.1026 , 1 male (cl 21.3 mm, pcl 15.5 mm, cw 10.8 mm), 2 females (cl 20. 5 mm, pcl 15.8 mm, cw 11.0 mm; cl 22.8 mm, pcl 17.6 mm, cw 12.0 mm), Lanyu Island , 4–5 m, reefs, coll. S.-H. Wu, 7 October 1997 – August 2000 ; AM P101292 , 1 female (cl 22.7 mm, pcl 17.1 mm, cw 12.0 mm), same. All Taiwan .

Other material examined. GUAM: ZRC 2000.625 , 1 male (cl 15.1 mm, pcl 11.8 mm, cw 7.8 mm mm), Pago Bay , reef front, under overhang, 5 m, coll. G. Paulay, 2 December 1995 ; ZRC 2000.626 , 1 male (cl 21.1 mm, pcl 15.7 mm, cw 10.8 mm), 1 spent female (cl 19.5 mm, pcl 15.4 mm, cw 10.5 mm), 1 ovigerous female (cl 17.7 mm, pcl 13.6 mm, cw 9.4 mm), beach, in channels, on walls, night dive, ca. 3 m, coll. L. Kirkendale, 5 December 1998 .

Diagnosis. Rostral spines subparallel, margins slightly sinuous, longer than 0.25 pcl. Carapace protogastric region with transverse row of no more than 2 low tubercles in adults; posterolateral margin with subdorsal tubercle between posteromedian spines and posterior branchial marginal spine; marginal branchial spines and posteromedian spines straight. Basal antennal article with inner distal spine longer than outer. Supraorbital eave transversely narrow, anterior width distinctly narrower than half basal width of rostral spine; intercalated spine small, triangular, directed almost laterally, separated from posterior spine of supraorbital eave by wide sinus with divergent margins. G1 with distal half distinctly curving laterally about 80° to longitudinal axis.

Description. Carapace ( Figs 6 , 7 ) distinctly pyriform, lOngEr than widE, rEgiOns wEaklY dEfinEd, sUrfacE dEnsElY covered with coarse straight and hooked setae. Rostral spines 0.27–0.38 pcl, margins slightly sinuous, subparallel. Supraorbital eave transversely narrow, anterior width distinctly narrower than half basal width of rostral spine; intercalated spine small, triangular, directed almost laterally, separated from posterior spine of supraorbital eave by wide sinus with divergent margins. Carapace postfrontal region with longitudinal row of 2 tubercles behind each rostral spine; gastric region with low tubercles: protogastric with low to prominent granule on each side; mesogastric with 1 very low, indistinct tubercle; cardiac region with very low, indistinct granule; intestinal region with low tubercle. HEpatic rEgiOn inflatEd; prOminEnt, brOad, cOnical, latErallY directed spine, larger than branchial spines; small subhepatic granules. Lateral branchial margin with 4 spines; posterior branchial margin with blunt subdorsal tubercle positioned midway between last branchial spine and paired posterior carapace spines (subdorsal tubercle indistinct in 17.1 mm pcl female; AM P101292). Posterior carapace spines straight, directed posteriorly, inclined slightly dorsad.

Epistome ( Figs 8B , 9B ) with stout anteroventrally directed spine at base of each antennular sinus. Interantennular septum cristate; interantennular spine recurved anteriorly, clearly visible in dorsal view ( Fig. 7 ). Basal antennal article distally bispinous, inner spine longer than outer spine ( Fig. 8B ).

Maxilliped 3 merus with rounded proximomesial lobe, margins usually with small denticles, distomesial margin with small spine; ischium distomesially auriculiform ( Figs 8C , 9C ).

Cheliped 1.19–1.64 pcl (male), 1.10–1.26 pcl (female); articles subcylindrical to subovate in cross-section. Propodal palm smooth, fingers with gape in adult males, pollex occlusal margin with blunt tooth near midlength. Dactylus slightly shorter than half palm length, occlusal margin with blunt tooth proximally. Carpus two-thirds to three-fourths palm length in adult males, with 8–11 rounded granules ( Fig. 6A, C ); in females, smooth, unarmed, as long as palm.

Pereopods 2–5 strongly setose, unarmed; dactylus simple, with curved, corneous tip. Pereopod 2 longest, merus 0.54–0.61 pcl (males), 0.50–0.53 pcl (females). Pereopod 5 merus 0.36–0.41 pcl (males), 0.31–0.36 pcl (females) ( Figs 5C, D , 6 ).

Male pleon with somite 4 trapezoidal, lateral margins weakly concave, margins converging distally; somites 5 and 6 subrectangular, margins weakly convex, widest at midlength and distal end, respectively; telson wider than long, distal margin evenly rounded ( Figs 8D , 9D ).

G1 long, slender, with distal half distinctly curving laterally about 80° to longitudinal axis, becoming almost perpendicular ( Fig. 10G, J ). G2 simple, distally bilobed, abOUt OnE-fifth lEngth Of G1, ExOpOd absEnt ( Fig. 10I, L ).

Etymology. The species is named after its relatively long and slender pseudorostral spines and ambulatory legs.

Remarks. Schizophroida gracilis sp. nov. is distinctive in the genus in the possession of long, slightly sinuous, subparallel rostral spines (0.27–0.38 pcl), a narrow supraorbital eave (anterior width distinctly narrower than half rostral spine width), a wide V-shaped rather than narrrow U-shaped sinus between the intercalated spine and the posterior spine of the supraorbital eave and a much more strongly bent G 1 in which the distal portion becomes almost perpendicular to the proximal portion. Although most other species of Schizophroida have distinctly divergent rostral spines and a comparatively wide supraorbital eave, S. colemani also has subparallel rostral spines and a relatively narrow supraorbital eave. The rostral spines of S. colemani , however, are proportionately shorter than those of S. gracilis (0.13–0.22 versus 0.27–0.38 pcl in adults), and the supraorbital eave is comparatively wider, but still narrower than half rostral spine width ( Figs 3A, B , 4 ).

All examined specimens appear to be mature, with males having slightly more elongated walking legs and distinctly more robust chelipeds than females. Specimens from Taiwan and GUam arE almOst indistingUishablE, bUt diffEr slightlY in pereopod length as measured by the pereopod 5 merus. Taiwanese males have a proportionally longer pereopod 5 merus than those from Guam (0.38–0.41 pcl versus 0.36 pcl), although corresponding measurements in females overlap (0.31–0.37 pcl versus 0.34 pcl) ( Figs 5C, D , 6 ). Additionally, the cheliped of the largest male from Taiwan is more elongated (1.64 pcl versus 1.19 pcl) and more robust than a size-matched male from Guam ( Fig. 2 ), suggesting that sizE at matUritY might diffEr bEtwEEn thE twO pOpUlatiOns. In the Taiwanese specimens, the lateral margins of male pleonites 4–6 are distincly more sinuous, with somite 4 more trapezoidal in shape compared to those from Guam ( Figs 8D , 9D ). ThE diffErEncEs, hOwEvEr, arE nOt sUbstantial, and, likE the length of the chelipeds, may be associated with maturity. It is pOssiblE that thEsE diffErEncEs indicatE that thE Taiwan and GUam pOpUlatiOns bElOng tO diffErEnt spEciEs, bUt thE availablE matErial dOEs nOt prOvidE sUfficiEnt EvidEncE for this. The marked similarities in the structures of their carapaces, rostrums, and notably the G1s, suggest that it is bEst tO trEat thE TaiwanEsE and GUam matErial as cOnspEcific for the time being.

Distribution. Presently known only from Taiwan and Guam; rocky and coral reefs, 3– 5 m.

Figures

Figure 2. Schizophroida spp., carapace (all or most setae removed). (A) S. colemani sp. nov., male holotype, cl 33.5 mm, Lord Howe Island, AM P19606; (B) S. colemani sp. nov., ovigerous female, cl 26.8 mm, between Jervis Bay and Gabo Island, NSW, AM P53496; (C) S. hilensis (Rathbun, 1906), male lectotype, cl 16.1 mm, Hawaii, USNM 29794; (D) Schizophroida sp., juvenile female, cl 19.0 mm, New Caledonia, AM P29817.

Figure 3. Schizophroida colemani sp. nov., male holotype, cl 33.5 mm, Lord Howe Island, AM P19606. (A) ventral surface; (B) anterior cephalothorax, ventral view; (C) right maxilliped 3; (D) pleon and sternum; (E) right cheliped.

Figure 4. Schizophroida hilensis (Rathbun, 1906), male lectotype, cl 16.1 mm, Hawaii, USNM 29794. (A) ventral surface; (B) anterior cephalothorax, ventral view; (C) left maxilliped 3; (D) pleon and sternum.

Figure 5. Schizophroida spp., pereopod 5 (A, left; B–D, right; A–C, setae removed). (A) S. colemani sp. nov., male holotype, cl 33.5 mm, Lord Howe Island, AM P19606;(B) S. hilensis (Rathbun, 1906), male, cl 12.4 mm, Hawaii, ZRC 2000.459; (C) S. gracilis sp. nov., holotype male, cl 20.6 mm, Taiwan, NTOU; (D) S. gracilis sp. nov., male, cl 21.1 mm, Guam, ZRC 2000.626.

Figure 6. Schizophroida gracilis sp. nov., dorsal habitus (setae removed). (A) holotype male, 20.6 mm, Taiwan, NTOU; (B) paratype female, cl 22.8 mm,Taiwan,ZRC 2017.1026; (C) male,cl 21.1 mm, Guam, ZRC 2000.626;(D) female, cl 19.5 mm, Guam, ZRC 2000.626.

Figure 7. Schizophroida gracilis sp. nov., carapace (setae removed).(A) holotype male,cl 20.6 mm, Taiwan, NTOU;(B) paratype female, cl 22.8 mm, Taiwan, ZRC 2017.1026; (C) male, cl 21.1 mm, Guam, ZRC 2000.626.

Figure 8. Schizophroida gracilis sp. nov., holotype male, cl 20.6 mm, Taiwan, NTOU. (A) ventral surface; (B) anterior cephalothorax, ventral view; (C) right and left maxilliped 3; (D) pleon.

Figure 9. Schizophroida gracilis sp. nov., male, cl 21.1 mm, Guam, ZRC 2000.626. (A) ventral surface; (B) anterior cephalothorax, ventral view; (C) left maxilliped 3; (D) pleon.

Figure 10. Schizophroida spp., G1 and G2. (A–C) S. colemani sp. nov., male holotype, cl 33.5 mm, Lord Howe Island, AM P19606; (D–F) S. hilensis (Rathbun, 1906), male lectotype, cl 16.1 mm, Hawaii, USNM 29794; (G–I) S. gracilis sp. nov., holotype male, cl 20.6 mm, Taiwan, NTOU; (J–L) S. gracilis sp. nov., male, cl 21.1 mm, Guam, ZRC 2000.626. A, D, G, J: left G1, abdominal view. B, E, H, K: left G1 distal end, sternal view. C, F, I, L: left G2, abdominal view. Scale: A, C, D, F, G–L = 0.5 mm, B, E = 0.25 mm.