Uroptychus sarahae, Baba, 2018

Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), Tropical Deep-Sea Benthos (Mémoires du Muséum national d'Histoire naturelle 212), pp. 1-612 : 450-454

Uroptychus sarahae n. sp.

Figures 225 , 226

TYPE MATERIAL — Holotype: New Caledonia, Loyalty Ridge. CALSUB Stn PL 08, 20°48,3’S, 167°05’E, 880- 516 m, 26.II.1989, ov. ♀ 3.2 mm ( MNHN-IU-2013-8525 ) . Paratypes: New Caledonia, Norfolk Ridge. BATHUS 3 Stn CP 844, 23°06’S, 166°46’E, 908 m, 10.XII.1993, 1 ov. ♀ 4.1 mm (MNHN-IU-2013-8531). NORFOLK 2 Stn DW 2056, 24°40.32’S, 168°39.17’E, 573-600 m, 25.X.2003, 1 ♀ 4.2 mm (MNHN-IU-2013-8532) . – Stn DW2065, 25°15.65’S, 168°55.62’E, 750-800 m, 26.X.2003, 1 ♂ 4.5 mm (MNHN-IU-2013-8533). Vanuatu. MUSORSTOM 8 Stn DW 1128, 16°02.14’S, 166°38.39’E, 778-811 m, 10.X.1994, 1 ♂ 3.6 mm, 1 ov. ♀ 3.2 mm (MNHN-IU-2013-8526) .

ETYMOLOGY„ Named for Sarah Samadi of MNHN for her help with DNA analyses.

DISTRIBUTION„ Vanuatu, Loyalty Islands and Norfolk Ridge; 516- 908 m.

SIZE„ Males, 3.6-4.5 mm; females, 3.2-4.2 mm; ovigerous females from 3.2 mm. DESCRIPTION„ Small species. Carapace: 0.8-0.9 × as long as broad; greatest breadth 1.6-1.7 × distance between anterolateral spines. Dorsal surface well convex from side to side and from anterior to posterior, without distinct groove or depression, covered with short fine setae, sparingly bearing denticles on hepatic, anterior branchial and lateral epigastric regions. Lateral margins somewhat convexly divergent posteriorly with denticles arranged on short oblique ridges; anterolateral spine small, located slightly posterior to level of lateral orbital spine (in dorsal view, well separated from that spine at base). Rostrum broad triangular, with interior angle of 30-35°, nearly horizontal; length 0.9-1.0 × breadth, less than half that of remaining carapace, breadth less than half carapace breadth at posterior carapace margin; dorsal surface distinctly depressed along midline; lateral margin with obsolescent spine near tip. Lateral orbital spine subequal to or slightly larger than anterolateral spine. Pterygostomian flap high relative to length, covered with denticles or tubercle-like small spines on surface, anteriorly angular, ending in small spine.

Sternum: Excavated sternum with anterior margin convex between bases of Mxp1, surface with weak ridge in midline on anterior half. Sternal plastron nearly as long as broad, lateral extremities slightly divergent between sternites 4 and 7. Sternite 3 shallowly depressed, with anterior margin gently concave with U-shaped median sinus flanked by very tiny or obsolescent spine; anterolateral end rounded or somewhat angular. Sternite 4 with relatively short anterolateral margin anteriorly rounded; posterolateral margin relatively long, slightly shorter than anterolateral margin. Anterolateral margin of sternite 5 anteriorly somewhat convex, about as long as posterolateral margin of sternite 4.

Abdomen: Setose like carapace. Somite 1 convex from anterior to posterior. Somite 2 tergite 2.4-2.6 × broader than long; pleuron posterolaterally blunt, lateral margin weakly concave and slightly divergent posteriorly. Pleura of somites 3 and 4 laterally rounded. Telson about half as long as broad; posterior plate 1.1-1.3 × longer than anterior plate, feebly concave on posterior margin.

Eye: Broad relative to length (1.4-1.6 × longer than broad), reaching at most distal third of rostrum, medially somewhat inflated. Cornea not dilated, length more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.3-3.5 × longer than high. Antennal peduncle relatively slender, barely or nearly reaching rostral tip. Article 2 with distinct distolateral spine. Antennal scale 1.6-1.8 × broader than article 5, slightly overreaching article 4, barely reaching midlength of article 5, laterally bearing 1 or 2 very small spines. Article 4 with small distomesial spine. Article 5 unarmed, 1.2-1.3 × longer than article 4, breadth slightly less than half height of antennular ultimate article. Flagellum of 11 segments slightly falling short of distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with sparse setae on lateral surface. Basis without denticles on convex mesial ridge. Ischium having flexor margin not rounded distally; crista dentata with 10-15 distally diminishing denticles. Merus 2 × longer than ischium, unarmed, flexor margin not cristate but rounded, occasionally with obsolescent denticle distal to midlength.

P1: Slender, subcylindrical, with fine setae, lacking spines; length 5.1-5.9 × (males), 4.7-5.6 × (females) that of carapace. Ischium with short, flattish, laciniate dorsal process, unarmed elsewhere. Merus 1.1-1.3 × longer than carapace. Carpus 1.3-1.5 × longer than merus. Palm 0.9-1.0 × length of carpus, 4.6-4.7 × (males), 5.4-5.9 × (females) longer than broad. Fingers slightly gaping, ending in incurved spine, distally not spooned; movable finger 0.4 × length of palm, opposable margin with small subtriangular process proximal to opposing low prominence located at midlength of fixed finger.

P2-4: Moderately compressed, with soft fine setae. Meri successively shorter posteriorly (P3 merus 0.9 (rarely 1.0) × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2 and P3, very slightly narrower on P4 than on P3; length-breadth ratio, 4.2-4.4 on P2, 3.8-4.3 on P3, 3.7-4.0 on 4; P2 merus 0.8-0.9 × length of carapace, subequal to length of P2 propodus; P3 merus 0.8-0.9 × length of P3 propodus; P4 merus 0.7-0.8 × length of P4 propodus; extensor margin with a few eminences, denticles or very tiny spines on proximal half on P2, obsolescent on P3 and P4. Carpi subequal, unarmed, length less than half that of propodi (carpus-propodus length ratio, 0.34-0.36 on P2, 0.32-0.34 on P3, 0.29-0.32 on P4). Propodi successively slightly longer posteriorly, or shorter on P2 than on subequal P3 and P4; flexor margin with pair of movable slender terminal spines only. Dactyli proportionately broad in lateral view, length 1.1-1.3 × (P2 and P3), 1.2-1.3 × (P4) that of carpi, 0.4 × that of propodi; flexor margin nearly straight, with 6-9 loosely arranged spines often obscured by setae, ultimate small, slender, and very close to strongest penultimate spine preceded by 4-7 successively

diminishing spines nearly perpendicular to flexor margin but proximal 1 or 2 usually obliquely directed; ultimate smaller than antepenultimate, penultimate 1.5-2.0 × broader than antepenultimate.

Eggs. Number of eggs carried, 2-6; size, 0.88 × 1.04 mm - 0.98 × 1.08 mm.

REMARKS„ This new species resembles U. bertrandi n. sp., U. philippei n. sp., U. rutua Schnabel, 2009 , U. toka Schnabel, 2009 and U. volsmar n. sp. in the shapes of the carapace, sternal plastron, antenna, third maxilliped and pereopods. Uroptychus sarahae shares with U. toka and U. volsmar the penultimate spine of the P2-4 dactyli that is prominent, 2 times as broad as the antepenultimate, whereas in the other three species that spine is less pronounced (less than 1.3 times). Uroptychus sarahae differs from U. toka and U. volsmar in having the anterolateral spine of the carapace remote from instead of close to the lateral orbital spine, separated by a U-shape instead of V-shape when viewed dorsally. Uroptychus bertrandi is unique in having proximally strongly inflated eyes. Uroptychus philippei differs from all the others in having the relatively long rostrum and smoother dorsal surface of the carapace (see under U. philippei ). Uroptychus rutua has two broad prominences on the gastric region, which are absent in the other species.

Figures

FIGURE 225 Uroptychus sarahae n. sp., holotype, ovigerous female 3.2 mm (MNHN-IU-2013-8525). A, carapace and anterior part of abdomen, proximal part of right P1 included, dorsal. B, same, lateral. C, anterior part of carapace, lateral. D, lateral part of carapace, dorsal. E, sternal plastron, with excavated sternum and basal parts of Mxp1. F, telson.G, left antenna, ventral. H, left Mxp3, ventral. I, same, lateral. Scale bars:1 mm.

FIGURE 226 Uroptychus sarahae n. sp., holotype, ovigerous female 3.2 mm (MNHN-IU-2013-8525). A, right P1, proximal part (ischium), lateral. B, same,proximal part (ischium and merus),setae omitted,ventral.C, same,proximal part omitted,dorsal.D, left P2,lateral.E, same, setae omitted, lateral.F, same,distal part,setae omitted,lateral.G, left P3, lateral.H, left P4, lateral. Scale bars: 1 mm.