Uroptychus belos Ahyong & Poore, 2004

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 : 94-96

Uroptychus belos Ahyong & Poore, 2004

Figure 31

Uroptychus belos Ahyong & Poore, 2004: 25 , fig. 5.

TYPE MATERIAL — Holotype: Australia, Britannia Seamount , SE of Brisbane, Tasman Sea, 419 m holotype, female ( AM P 65830). [not examined].

MATERIAL EXAMINED — New Caledonia, Chesterfield Islands. MUSORSTOM 5 Stn DW337, 19°53.80’S, 158°38.00’E,412-430 m, gorgonian corals, 15.X.1986, 1 ov. ♀ 4.0 mm (MNHN-IU-2014-16320) . New Caledonia. MUSORSTOM 4 Stn DW222, 22°57.6’S, 167°33.0’E, 410-440 m, 30.IX.1985, 1 ♀ 4.2 mm (MNHN-IU-2014-16321) . BATHUS 2 Stn DW719, 22°48’S,167°15’E, 444-445 m, 11.V.1993, 1 ov.♀ 3.7 mm (MNHN-IU-2014-16322) . New Caledonia, Norfolk Ridge. LITHIST Stn DW13, 23°45.0’S, 168°16.7’E, 400 m, 12.VIII.1999, 1 ov. ♀ 3.3 mm (MNHN-IU-2014-16323) . NORFOLK 1 Stn DW1654, 23°28’S, 167°52’E, 366-560 m, 19.VI.2001, 1 ♂ 3.4 mm (MNHN-IU-2014-16324) . – Stn DW1733, 22°56’S, 167°15’E, 427-433 m, 28.VI.2001, 1 ♀ 4.3 mm (MNHN-IU-2014-16325) . NORFOLK 2 Stn DW2156, 22°54’S, 167°15’E, 468-500 m, 05.XI.2003, 1 ♂ 3.6 mm (MNHN-IU-2014-16326) .

DISTRIBUTION„ Tasman Sea, and now Chesterfield Islands, New Caledonia and Norfolk Ridge; 366- 560 m.

SIZE„ Males, 3.4-3.6 mm; females, 3.3-4.2 mm; ovigerous females from 3.3 mm.

DESCRIPTION„ Small species. Carapace: Distinctly broader than long (0.8 × as long as broad); greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface with sparse short setae, weakly convex from anterior to posterior, without groove and depression. Lateral margins convexly divergent posteriorly, bearing 5 spines: first anterolateral, overreaching small lateral orbital spine, situated directly lateral to and somewhat distant from that spine, subequal in size to second but smaller than third, second somewhat posterior to midpoint between first and third, second to fifth equidistant, fourth smaller than second, fifth (last) very small or rudimentary; no ridge along posterior lateral margin. Rostrum elongate triangular, with interior angle of 28-30°, ending in sharp point, dorsally concave moderately, length varying from slightly less than half to more than half that of carapace, breadth half carapace breadth measured at posterior carapace margin. Lateral orbital angle ending in small spine. Pterygostomian flap smooth on surface, anteriorly angular, ending in distinct spine.

Sternum: Excavated sternum with distinct longitudinal ridge in midline, anterior margin nearly transverse or slightly convex. Sternal plastron as long as or slightly longer than broad, lateral extremities subparallel between sternites 4-6, sternite 7 broadest. Sternite 3 weakly depressed, anterior margin shallowly excavated with deep or shallow U- or V-shaped median notch but no submedian spines, lateral margin smooth, spineless. Sternite 4 with nearly straight or slightly concave anterolateral margin about 1.5 × longer than posterolateral margin. Anterolateral margin of sternite 5 anteriorly convex, about as long as posterolateral margin of sternite 4

Abdomen: With sparse short setae. Somite 1 smooth on surface. Somite 2 tergite 2.5 × broader than long; pleuron posterolaterally blunt, lateral margin gently concave and moderately divergent posteriorly. Pleuron of somite 3 somewhat angular laterally. Telson about half as long as broad; posterior plate nearly as long as anterior plate, posterior margin somewhat or distinctly emarginate.

Eye: Slender, subcylindrical, about twice as long as broad, slightly overreaching midlength of rostrum. Cornea not dilated, half as long as remaining eyestalk.

Antennule and antenna: Ultimate antennular article 2.7-2.9 × longer than high. Antennal peduncle overreaching cornea, not reaching rostral tip. Article 2 with small distolateral spine. Antennal scale much broader than article 5, varying from slightly falling short of to slightly overreaching distal end of article 5. Article 4 with distoventral spine small, blunt or often obsolete. Article 5 unarmed or with very small distal spine discernible under high magnification; length 1.4-1.6 × that of article 4, breadth slightly more than half height of ultimate antennular article. Flagellum consisting of 12 or 13 segments, reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with long setae on lateral faces of ischium and merus. Basis with proximally rounded mesial ridge bearing no denticle. Ischium with tuft of long setae lateral to rounded distal end of flexor margin; denticles on crista dentata very small. Merus 1.7 × longer than ischium, flattish on mesial face; distolateral spine very small, often obsolescent; flexor margin with long setae and 2 very small, often obsolete spines. Carpus unarmed.

P1: 4.3-4.4 × longer than carapace in females (missing in males); subcylindrical but palm more or less depressed; with fine setae particularly along mesial margins of merus and carpus, and on fingers, less setose on palm. Ischium with small distodorsal spine, without subterminal spine on ventromesial margin. Merus slightly longer than carapace. Merus and carpus each with pair of very small distoventral spines (distomesial and distolateral). Carpus slightly longer than merus. Palm about 4 × longer than broad, 1.1-1.2 × longer than carpus. Fingers with longer setae distally, distally somewhat deflected ventrally, not gaping, distally incurved, crossing when closed; movable finger 0.4 × as long as palm, opposable margin with dorsoventrally depressed process at proximal third fitting into narrow longitudinal groove on opposite fixed finger when closed.

P2-4: Moderately compressed, sparsely setose, more setose on dactyli. Meri unarmed, successively decreasing in size posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2-4 or slightly narrower on P4 than on P3; length-breadth ratio, 3.3-3.5 on P2, 2.9-3.5 on P3, 2.5-3.0 on P4; P2 merus 0.6-0.7 × length of carapace, 0.8-0.9 × (rarely 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. Carpi subequal on P2-4 or slightly shorter on P4, length about one-third that of propodi on P2-4. Propodi successively longer posteriorly or slightly shorter on P2 than on P3 and P4; flexor margin somewhat concave in lateral view, with pair of terminal spines only. Dactyli stout, about half as long as propodi and much longer than carpi (dactylus-carpus length ratio, 1.5 on P2, 1.6 on P3, 1.7 on P4); flexor margin nearly straight, with 9-10 more or less loosely arranged spines, ultimate somewhat more slender and longer than antepenultimate, penultimate pronouncedly broad, remaining spines much smaller than penultimate, moderately inclined, successively diminishing toward base of article.

Eggs. Number of eggs carried, 4; size, 1.00 mm × 1.08 mm.

REMARKS — The material generally agrees with the description of U. belos Ahyong and Poore, 2004 from the Tasman Sea. The distolateral spine and the flexor marginal spines of the Mxp3 merus, originally described as distinct, are usually barely discernible, and very tiny in one of the material examined (MNHN-IU-2014-16324); also usually very small or obsolete in the present material is the distolateral spine of the antennal article 5, and rarely absent is the distolateral spine of article 4. These spines are small but distinct in the type.

The carapace ornamentation, elongate eyes, elongate sternal plastron, and spination of P2-4 dactyli are very similar to those of U. grandior n. sp. Their relationships are discussed under that species (see below).

Figures

FIGURE 31 Uroptychus belos Ahyong & Poore, 2004, ovigerous female 4.0 mm (MNHN-IU-2014-16320). A, carapace and anterior part of abdomen, dorsal.B, same,lateral. C, anterior part of sternal plastron. D, right antenna,ventral. E, left Mxp3, lateral. F, right P1, dorsal.G, left P3, lateral. H, same,distal part,setae omitted, lateral. Scale bars: 1 mm.