Uroptychus brevisquamatus Baba, 1988

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 : 124-128

Uroptychus brevisquamatus Baba, 1988

Figures 47 , 48

Uroptychus brevisquamatus Baba, 1988: 28 , fig. 10.

TYPE MATERIAL — Holotype: Indonesia, off southern Obi , ALBATROSS Stn 5635, 732 m, female ( USNM 150319). [examined].

MATERIAL EXAMINED — Solomon Islands. SALOMON 2 Stn CP2230, 6°27.8’S, 156°24.3’E, 837-945 m, 29.X.2004, 1 ♀ 7.3 mm (MNHN- IU-2014-16344) . Vanuatu. MUSORSTOM 8 Stn DW1128, 16°02.14’S, 166°38.39’E, 778-811 m, 10.X.1994, 1 ov. ♀ 7.2 mm (MNHN-IU-2014-16345) . Wallis and Futuna Islands. MUSORSTOM 7 Stn DW548, 12°23’S, 177°24’W 700-740 m, 17.V.1992, 1 ♀ 7.7 mm (MNHN-IU-2014-16347) . – Stn DW635, 13°49S, 179°56’E, 700-715 m, 30.V.1992, 1 ♀ 6.3 mm (carapace broken) (MNHN-IU-2014-16348) . New Caledonia, Loyalty Ridge. BATHUS 3 Stn DW776, 24°44’S, 170°08’E, 770-830 m, 24.XI.1993, 2 ♂ 4.3, 7.3 mm, 1 ov. ♀ 7.0 mm (MNHN-IU-2014-16349) . – Stn DW778, 24°43’S, 170°07’E, 750-760 m, 24.XI.1993, 7 ♂ 3.8-7.8 mm, 6 ov. ♀ 6.3-7.8 mm, 3 ♀ 3.6-8.3 mm (MNHN-IU-2014-16350) . New Caledonia, Norfolk Ridge. NORFOLK 2 Stn DW2047,23°43.04’S,168°01.92’ E, 759-807 m, 23.X.2003,1 ♂ 7.9 mm, 1 ov. ♀ 7.0 mm (MNHN-IU-2014-16351) . – Stn DW2107, 23°53’S, 167°41’E, 742-820 m, 30.X.2003, 1 ♀ 7.2 mm (MNHN-IU-2014-16346) . – Stn DW2113, 23°45.17’S, 168°17.99’ E, 888-966 m, 31.X.2003, 1 ♂ 6.7 mm (MNHN- IU-2014-16352) .

DISTRIBUTION„ Off southern Obi, and now Solomon Islands, Wallis and Futuna Islands, Vanuatu, Norfolk Ridge and Loyalty Ridge; 700- 966 m.

SIZE„ Males, 3.8-7.9 mm; females, 3.6-8.3 mm; ovigerous females from 6.3 mm.

DESCRIPTION„ Medium-sized species. Carapace: Nearly as long as broad; greatest breadth 1.9 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, with weak depression on ordinary site of cervical groove; gastric region more elevated than level of rostrum; anterior part of carapace including rostrum with sparse, very short, fine setae discernible under high magnification. Lateral margins convexly divergent, with finely granulate short ridges at anterior end of branchial region; ridged along posterior half; anterolateral spine relatively stout, reaching distal end of antennal article 2, situated at level of, but distinctly overreaching small lateral orbital spine Rostrum slightly overreaching cornea, bluntly triangular, with interior angle of 26-30° (rarely 35°), somewhat deflected ventrally; length less than one-third postorbital carapace length, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface flattish or slightly concave. Pterygostomian flap smooth on surface, anteriorly roundish with very small spine.

Sternum: Excavated sternum anteriorly sharp triangular, produced between bases of Mxp1, surface somewhat ridged in midline, with small spine in center. Sternal plastron slightly broader than long; lateral extremities gently divergent posteriorly. Sternite 3 depressed well, anterior margin deeply emarginate, bearing 2 submedian spines separated by narrow notch. Sternite 4 denticulate on anterolateral margin, posterolateral margin relatively long, more than half (0.6- 0.7) as long as anterolateral margin. Anterolateral margin of sternite 5 granulated, gently convexly divergent posteriorly, somewhat longer than posterolateral margin of sternite 4.

Abdomen: Nearly glabrous and smooth. Somite 1 strongly convex from anterior to posterior. Somite 2 tergite 2.3- 2.8 × broader than long; pleuron having lateral margin strongly concave, divergent posteriorly, posterolaterally bluntly angular. Pleuron of somite 3 posterolaterally blunt angular. Telson half as long as broad; posterior plate 1.4-1.6 × longer than anterior plate, somewhat emarginate on posterior margin.

Eye: Broad relative to length (length 1.6 × breadth), lateral margin convex, mesial margin concave. Cornea slightly dilated, more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.0-2.5 × longer than high. Antennal peduncle slightly overreaching cornea. Article 2 with short stout spine. Antennal scale twice (rarely 1.5 x) as broad as article 5, terminating in or somewhat overreaching midlength of article 5. Distal 2 articles unarmed; article 5 1.7-2.0 × longer than article 4, breadth half or less than half height of ultimate antennular article. Flagellum consisting of 14-18 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases very close to each other or nearly contiguous. Mxp3 basis with 3 or 4 denticles on mesial ridge. Ischium with 21-23 denticles on crista dentata, flexor margin not rounded distally. Merus 3 × longer than ischium, relatively thick mesio-laterally, flattish on mesial face, unarmed. Carpus unarmed.

P1: More or less massive, length about 4 × that of carapace; smooth (occasionally somewhat granulose on ventral surface of merus), fingers setose. Ischium dorsally with strong curved spine, ventromesially with short subterminal spine. Merus as long as or slightly shorter than carapace (0.8 × in holotype). Carpus 1.2-1.3 × longer than merus. Palm 2.4-3.0 × longer than broad, subequal to or slightly shorter than carpus. Fingers ending in slightly incurved tip, gaping in large males, not gaping in females and small males; movable finger half length of palm or slightly more; opposable margin with low bilobed process at proximal third.

P2-4: Moderately compressed mesio-laterally, with sparse long setae, particularly on carpi and propodi. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus; P4 merus 0.8 × length of P3 merus), equally broad on P2-4 (occasionally slightly narrower on P4 than on P3); dorsal margin unarmed; length-breadth ratio, 4.3-4.8 on P2, 3.9-4.4 on P3, 3.4-3.9 on P4; P2 merus 0.8 × length of carapace, 1.2-1.3 × length of P2 propodus; P3 merus subequal to length of P3 propodus; P4 merus 0.9-1.1 × length of P4 propodus. Carpi successively slightly shorter posteriorly (P3 carpus 0.9 × length of P2 carpus, P4 carpus 0.9 × length of P3 carpus); carpus-propodus length ratio, 0.5-0.6 on P2 and P3, 0.5 on P4, much longer than dactyli (carpus-dactylus length ratio, 1.6 on P2, 1.5 on P3, 1.4 on P4. Propodi subequal on P2-3 (longer on P4) or P3-4 (longer on P2), more than twice as long as dactyli; flexor margin with 6-8 slender spines on distal half, distalmost single, slightly proximal to juncture with dactylus and mesial to midline in flexor view. Dactyli proportionately broad distally, strongly curving at proximal quarter, length 0.3-0.4 × that of propodus; dactylus-carpus length ratio, 0.6 on P2, 0.7 on P3 and P4; flexor margin 10-12 loosely arranged, relatively short spines, but ultimate spine longer and broader than penultimate, remaining spines successively smaller proximally, obliquely directed, not directed parallel to margin, and obscured by dense setae.

Eggs. Up to 25 eggs carried; size, 1.50 mm × 1.60 mm - 1.30 mm × 1.60 mm.

PARASITES — The female from NORFOLK 2 Stn DW2107 (MNHN-IU-2014-16346) bears a rhizocephalan externa.

REMARKS — In the type, the P2 merus is shorter relative to the carapace than in the present material (0.7 versus 0.8), as is also the P4 merus relative to the P4 propodus (0.8 versus 0.9-1.1); and the lateral limit of the orbit is rounded instead of bearing a small spine. These differences are regarded as individual variation.

This material is assigned to U. brevisquamatus based on the following characters: the anterolateral spine of the carapace is relatively stout; the pterygostomian flap bears a roundish anterior margin with a tiny spine; the eyes are relatively short bearing a concave mesial margin; the antennal scale at most slightly overreaches the midlength of antennal article 5; the distalmost of the flexor marginal spines of the P2-4 propodi is single, not paired, all also confirmed by examination of the holotype.

The species resembles U. disangulatus n. sp. and U. webberi Schnabel, 2009 from the Kermadec Ridge in the shapes of the carapace and sternal plastron, and in having a short and broad antennal scale and small inclined spines on the flexor margin of the P2-4 dactyli. The relationships with U disangulatus are discussed under the remarks of that species (see below). Uroptychus brevisquamatus shares the roundish anterior margin of the pterygostomian flap with U. webberi , from which it clearly differs in having the P2-4 propodi with a single instead of paired terminal spines on the flexor margin; and the carapace lateral margins are convexly divergent rather than subparallel.

Figures

FIGURE 47 Uroptychus brevisquamatus Baba, 1988, female 7.7 mm (MNHN-IU-2014-16347). A, carapace and anterior part of abdomen, proximal part of right P1 included, dorsal. B, same, abdomen omitted, lateral. C, anterior part of cephalothorax, showing eye and orbit, dorsal. D, sternal plastron,with excavated sternum and basal parts of Mxp1.E, telson.F, right antenna,ventral.G, rightMxp3,ventral.H, left Mxp3,lateral.I, right P1, proximal part, ventral. J, same, proximal part omitted, dorsal.Scale bars: A-H,1 mm; I, J, 5 mm.

FIGURE 48 Uroptychus brevisquamatus Baba,1988,female 7.7 mm (MNHN-IU-2014-16347).A, right P2,lateral.B, same,distal part,setae omitted,lateral.C, right P3, lateral. D, same, distal part, lateral. E, right P4,lateral.F, same,distal part,lateral. Scale bars:1 mm.