Uroptychus rutua, Schnabel, 2009

Schnabel, Kareen E., 2009, A review of the New Zealand Chirostylidae (Anomura: Galatheoidea) with description of six new species from the Kermadec Islands, Zoological Journal of the Linnean Society 155 (3), pp. 542-582 : 564-567

UROPTYCHUS RUTUA SP. NOV. ( FIG. 13 )

Type material: HOLOTYPE: ♀ (4.5 mm), Raoul Island , Kermadec Ridge , 30° 33.79′S, 178° 30.59′W, 30.vii.1974, 165– 180 m, stn NZOI K857 ( NMNZ Cr. 012083). 1 ♂ (3.9 mm), paratypes, same locality as holotype ( NIWA 43869 ). 1 ♀ ovig. (3.6 mm), Raoul Island, Kermadec Ridge, 28° 45.0′S, 178° 00.0′W, 179 m, 24.viii.1972, stn B.S. 297 ( NMNZ Cr. 012084).

Diagnosis: Carapace approximately as wide as long; lateral margin without distinct spines or processes; dorsal surface unarmed except for small spines and granules in hepatic region, epigastric region distinctly inflated. Sternal plastron slightly wider than long along midlength. Penultimate antennal article with well-developed distal spine, ultimate unarmed. Maxilliped 3 unarmed. Pterygostomian flap surface with spines (anterior spines bifurcated). Pereopod 1 (cheliped) with small distodorsal spine. Pereopods 2–4 dorsal margin of P2 merus irregular, otherwise smooth; carpi smooth on dorsal margin; propodi with pair of distal spines on flexor margin only; dactyli straight, longer than half length of propodi, with seven or eight sharp triangular spines, slender distal spine, loosely arranged and perpendicular to flexor margin, penultimate prominent.

Description of holotype: Carapace: 1.1 times as long as broad (0.8 without rostrum), strongly convex from side to side. Dorsal surface sparsely setose; cervical groove indistinct (faintly indicated), gastric region with two broad prominences and transverse row of small denticles; hepatic region with scattered small spines and granules; dorsum otherwise unarmed. Frontal margin deeply excavate. Outer orbital angle produced into small spine. Anterolateral margin rounded, with small spine dorsomesial of margin. Lateral margin slightly divergent posteriorly, irregular but unarmed. Posterior margin unarmed. Rostrum triangular, slightly deflected ventrally; 0.4 times length of remaining carapace; dorsal surface excavate; lateral margins smooth; unarmed. Pterygostomian flap lateral surface covered with small spines (bifurcate spines in anterior half), anterior margin produced into a spine (directed dorsally).

Sternum: sternal plastron 1.2 times as wide as long, lateral extremities subparallel between sternites 5–7, surface smooth. Anterior margin rounded, with median u-shaped notch with one small submedian spine (no spine on right). Lateral margins slightly produced. Sternite 4 two times as wide as sternite 3, anteriorly shallowly concave, anterior midline grooved, anterolateral margin rounded with blunt terminus (nearly reaching terminus of sternite 3).

Abdomen: tergites smooth and unarmed. Pleural margins of segments 2 to 4 rounded (tergite 2 wide, nearly square). Telson and tergite 6 2.7 times as broad as long, telson posterior portion emarginate; posterior portions two times length of anterior portion.

Eyes: nearly reaching end of rostrum. Cornea globular (distally narrowing), 0.3 times length of ocular peduncle, nearly reaching end of rostrum.

Antennal peduncle: Article 2 with strong and slender outer spine. Penultimate article with distal spine. Ultimate article unarmed, 1.2 times as long as penultimate. Antennal scale reaching to midlength of ultimate article; 2.8–3.0 times as long as wide.

Maxilliped 3: surface smooth, ischium without distal spines, three or four teeth on mesial ridge among otherwise obsolescent spines, basis smooth. Merus, carpus, propodus, and dactylus unarmed.

Pereopod 1: slender, 3.1–3.7 times as long as carapace (4.3–5.0 without rostrum), surface moderately setose (particularly distally). Ischium with dorsal distal spine. Merus and carpus unarmed, carpus 1.0– 1.2 times as long as palm. Propodus with palm 2.5– 3.7 times as long as high. Dactylus 0.5 times as long as propodus; occlusal margins not gaping, denticulate.

Pereopods 2–4: similar (meri slightly shortening from P2–4), surfaces setose, unarmed. Merus dorsal margin unarmed (P2 slightly irregular margin where setae attach, smooth on P3–4); 1.1–0.8 times as long as propodus (P2 merus longest, P3–4 meri subequal, propodi increasing in length). Propodus 1.6–1.9 times as long as dactylus (propodi slightly lengthening from P2–4), extensor margin smooth. Flexor margin with only distal pair of spines. Dactylus straight; flexor margin with eight loosely arranged spines, ultimate small, penultimate larger, subequal to antepenultimate, antepenultimate and remaining proximal spines subperpendicular to margin.

Ovum : 0.6 mm (female paratype with two large eggs under abdomen).

Variation: All legs are detached from the specimens of Uroptychus rutua . The two paratypes agree well with the holotype female in proportions and spination. The frontal margin of the sternal plastron bears small submedian spines in both paratype specimens (a spine is only visible on one side of the holotype) indicating that submedian spines adjacent to the median notch is the more common condition. The cervical groove is more distinct in the male paratype and the left antennal scale falls short of the midlength of the ultimate antennal article (the right scale is normal). The female paratype has only been preserved with a single walking leg, the dactylus bears six spines in addition to the ultimate spine (instead of seven for holotype and male paratype). The palm of the cheliped of the small female paratype is more slender but comparable to the left cheliped of the female holotype (4.4 and 4.0 for paratype, 3.74 and 2.52 for holotype). The male paratype is missing its chelipeds; however, the particularly robust right cheliped accompanying the holotype probably belongs to the male paratype (the suture lines appear to match).

Remarks: Uroptychus rutua sp. nov. is most closely related to Uroptychus toka sp. nov. with respect to carapace shape and size and armature of the abdomen, maxilliped 3, pereopods, and sternal plastron. Their relationships are discussed under that species (see below).

Uroptychus rutua is closely allied to species with unarmed dorsal and lateral carapace surfaces, maxilliped 3 unarmed, with distal pair of spines on P2–4 propodi, dactyli with six or seven spines along the flexor margin. This includes Uroptychus paenultimus Baba, 2005 , Uroptychus glaber Baba, 1981 , and Uroptychus tomentosus Baba, 1974 . Uroptychus rutua is readily distinguished from these by the strongly convex carapace with distinctly elevated epigastric inflations and a field of spinules on the hepatic carapace region (all three species have very shallowly convex and smooth carapace curvature without spines on the dorsal surface). Uroptychus paenultimus further differs from Uroptychus rutua in having an acute frontal margin of the sternal plastron (rounded in Uroptychus rutua ), maxilliped 3 merus with spines (unarmed in Uroptychus rutua ) and eight or nine slender and inclined spines on the P2–4 dactyli (seven sharp triangular spines arranged perpendicular to margin in Uroptychus rutua ). Uroptychus tomentosus can further be distinguished from Uroptychus rutua by carapace size (6.4–17.7 mm for Uroptychus tomentosus and 3.6–3.9 mm for Uroptychus rutua ) and length of P2–4 dactylus (less than half length of propodus for Uroptychus tomentosus and more than half length for Uroptychus rutua ). Finally, Uroptychus glaber additionally differs from Uroptychus rutua in having an unarmed antennal peduncle.

The record for Uroptychus rutua overlaps with the distribution range for Uroptychus tomentosus whereas Uroptychus paenultimus and Uroptychus glaber are known from Indonesia and Japan, respectively.

Distribution: Raoul Island, Kermadec Islands, 165– 180 m ( Fig. 7 ).

Etymology: Rutua is the plural Māori word for bump or bulge with reference to the paired inflations on the anterior portion of the dorsal carapace.

Figures

Figure 7. Records of Uroptychus kaitara sp. nov., Uroptychus paku sp. nov., Uroptychus rutua sp. nov., Uroptychus toka sp. nov., Uroptychus webberi sp. nov., and Uroptychus yaldwyni sp. nov. around the Kermadec Islands, New Zealand. 250, 1000, and 2500 m bathymetric contours are shown.

Figure 13. Uroptychus rutua sp. nov., holotype, ♀, NMNZ Cr. 012083: A, carapace and abdomen, dorsal, setae omitted; B, carapace and abdomen, lateral, setae omitted; C, sternal plastron; D, telson, setae omitted; E, antenna, left, ventral; F, endopod of third maxilliped, left, lateral, setae omitted; G, mesial ridge, left; H, right cheliped, dorsal; I–K, right pereopods 2–4. Scale bars = 2 mm.