Uroptychus scandens Benedict, 1902

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 : 454-458

Uroptychus scandens Benedict, 1902

Figures 227 , 228

Uroptychus scandens Benedict, 1902: 298 , fig. 42. — Miyake & Baba 1967: 227 (not fig. 2). Not Uroptychus scandens – Baba 1981: 132 (= U. imparilis n. sp.). Identity questioned:

Uroptychus scandens – Balss 1913b:27,fig.20.— Van Dam l933:27,fig.38.— Yokoya 1933:68. — Van Dam 1937:102; 1940: 97.— Miyake in Miyake & Nakazawa 1947:734,fig.2123.— Miyake 1960:97,pl. 48,fig. 7; 1965:634, fig.1040.— Baba 1969:47.— Kim & Choe 1976: 43, fig.1 — Takeda 1982: 50, fig. 148. — Baba 2005:58.

TYPE MATERIAL — Holotype: Japan, off Honshu , Suruga Bay, Ose Zaki, S 56° W, 1.6 miles, 124- 119 m, ov. female ( USNM 26166 ). [examined].

OTHER MATERIAL EXAMINED — Japan. Off Honshu Island, ALBATROSS Stn 3715 [ Suruga Bay , Ose Zaki , S 56° W, 1.6 miles], 119-124 m, 11.V.1900, holotype, ov. ♀ 3.8 mm ( USNM 26166 ) . Off Daio-zaki, 26.IV.1936, I. Kubo coll., 26.IV.1936, 1 ♂ 3.4 mm, 3 ov. ♀ 3.2-3.8 mm, 3 ♀ 2.7, 3.3 mm (1 ♀, carapace missing) ( ZLKU 4868) . Off Nojima Zaki, Chiba Pref., SOYO-MARU Stn B1, 34°58.4’N, 140°04.3’E, 120-130 m, 26.V.1963, 1 ♂ 3.2 mm, 1 ♀ 3.1 mm ( NSMT) . Tosa Bay, 150 m, on pennatulacean, 31.I.1959,K.Kurohara coll., 1 ♂ 3.2 mm, 1 ov. ♀ 3.3 mm ( ZLKU 5871) . East China Sea. 31°29.8’N, 128°01.5’E, 145 m, on pennatulacean, 23.VI.1963, H. Yamashita coll., 1 ♂ 3.1 mm, 1 ov. ♀ 3.1 mm, 3 ♀ 2.7-3.8 mm ( ZLKU 9443) . Solomon Islands. SALOMON 2 Stn CP2210, 7°34.2’S, 157°41.8’E, 240-305 m, 26.X.2004, 1 ♂ 3.6 mm (MNHN-IU-2014-16941) .

DISTRIBUTION„ Japan, East China Sea and Solomon Islands; 119- 305 m.

SIZE„ Males, 3.1-3.6 mm; females 2.7-3.8 mm; ovigerous females from 3.1 mm.

DESCRIPTION„ Small species. Carapace: Broader than long (0.8 × as long as broad); greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, with very small spines on anterior part around epigastric, hepatic and anterior lateral branchial regions, those on hepatic region larger. Lateral margins convexly divergent posteriorly, with row of small spines; anterolateral spine larger than others, overreaching much smaller lateral orbital spine, directed somewhat anterolaterally. Rostrum narrow triangular, with interior angle of 21°, straight horizontal on ventral surface; lateral margin somewhat concave, with several obsolescent denticles; dorsal surface somewhat concave; length slightly smaller than breadth, 0.4 × that of remaining carapace, breadth less than half carapace breadth at posterior carapace margin; lateral orbital spine slightly anterior to level of anterolateral spine. Pterygostomian flap anteriorly somewhat rounded, produced to strong sharp spine; surface with small spines on anterior half, including row of spines along linea anomurica.

Sternum: Excavated sternum with slightly convex anterior margin; surface smooth, without ridge and central spine, with setae along anterior margin. Sternal plastron 0.8 × as long as broad, lateral extremities subparallel between sternites 5 and 7. Sternite 3 with anterior margin broadly and deeply excavated in subsemicircular shape with pair of small median spines basally contiguous. Sternite 4 with anterolateral margin feebly convex with small, posteriorly diminishing spines on anterior half, length 1.3 × as long as posterolateral margin. Sternite 5 with anterolateral margin somewhat convex, as long as posterolateral margin of sternite 4.

Abdomen. Somite 1 moderately convex from anterior to posterior. Somite 2 tergite 2.2 × broader than long, pleuron slightly concavely divergent posteriorly, ending in rounded margin. Pleura of somites 3-5 laterally rounded. Telson half as long as broad; posterior plate distinctly emarginate, 2.0-2.4 × longer than anterior plate.

Eyes: Elongate, 2.2-2.4 × longer than broad, slightly falling short of apex of rostrum, swollen around proximal third, lateral margin convex, mesial margin concave around distal third. Cornea short, less than half length (0.3-0.4) of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle relatively slender, 3.7 × longer than high. Antennal peduncle slightly falling short of apex of rostrum. Antennal scale fused with article 2, 1.5 × broader than article 5, terminating in midlength of article 5, laterally with 2 or 3 spines, proximalmost situated at ordinary site of article 2. Articles 4 with distinct distomesial spine. Article 5 with small or obsolescent distomesial spine, length 1.9-2.0 × that of article 4, breadth 0.6 × height of ultimate article of antennule. Flagellum of 7-10 segments falling short of distal end of P1 merus, apical seta half length of flagellum.

Mxp: Mxp1 with bases broadly separated. Mxp3 with long setae. Basis with 1-4 denticles on mesial ridge. Ischium with small spine (and much smaller accompanying spine in holotype) lateral to distal end of flexor margin, crista dentata with a few obsolescent denticles. Merus more than twice (2.7 ×) length of ischium, ridged along flexor margin, not well compressed; with 3 o 4 spines on distal third of flexor margin and 1 or 2 spines on distolateral margin. Carpus unarmed.

P1: Slender, subcylindrical, 6.9 × (male), 5.4 × (female) longer than carapace. Ischium dorsally with basally broad, depressed, short spine, ventromesially unarmed. Merus 1.2-1.4 × longer than carapace, dorsal surface with several small spines along proximal half of mesial margin and denticles along distal margin. Carpus 1.3-1.5 × longer than merus, unarmed. Palm 5.8 × (male), 4.9 × (female) longer than broad, 0.9-1.0 × as long as carpus, slightly broadened distally. Fingers relatively narrow distally, somewhat gaping in proximal half; opposable margins fitting to each other in distal half, with row of very small spines or denticles when closed; movable finger 0.4 × length of palm, with obtuse process at midpoint of gaping portion.

P2-4: Thickly setose like P1. Meri successively shorter posteriorly (P3 merus 0.8-0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), slightly broader on P3 and P4 than on P2; length-breadth ratio (holotype), 4.3 on P2, 3.3 on P3, 2.8 on P4; dorsal margins with small spines, 3 in number on P2, obsolescent on P3, absent on P4; P2 merus 0.9 × length of carapace; 1.2 × longer than P2 propodus; P3 merus 1.2 × length of P3 propodus; P4 merus subequal to P4 propodus. Carpi successively shorter posteriorly; carpus-propodus length ratio, 0.5 on P2-P4. Propodi successively shorter posteriorly; flexor margin straight in lateral view, with pair of slender terminal spines only. Dactyli subequal in length on P2-4, shorter than carpus; dactylus-carpus length ratio, 0.6 on P2, 0.7 on P3 and P4; dactylus-propodus length ratio, 0.3 on P2, 0.3-0.4 on P3 and P4; truncate, bearing 7 or 8 slender spines obscured by setae, 3-4 of these located on terminal margin, remainder on flexor margin, distalmost smaller than distal second.

Eggs. Number of eggs (yolky) carried, 28; size, 0.60 × 0.57 mm - 0.65 × 0.59 mm.

REMARKS„ In an earlier stage of the present study, Uroptychus articulatus n. sp., U. imparilis n. sp., and U. parisus n. sp., had been placed together under U. scandens Benedict, 1902 on the basis of the uniquely truncate dactyli of P2-4. In addition, they share nearly all of essential characters such as the anterior carapace with denticles or small spines, all pereopods slender and very setose with the same spination, and also have Mxp3 and sternal plastron almost similar to one another. Careful examination of the material at hand and the type material of U. scandens made available on loan showed that there are two different shapes of eyes. One is proximally swollen and distally narrowed, and the other is nearly uniform in breadth, with the cornea broader than the greatest breadth of the remaining eyestalk. Also the antennal scale is either articulated or fused with article 5. Whether these represented intraspecific or interspecific differences was determined by DNA analyses (COI gene sequences) conducted at my request by S. Samadi, M.-C. Boisselier and L. Corbari. They showed genetic divergences between the four different forms are sufficiently high to secure their specific value.

The antennal scale is articulated in U. articulatus and U. imparilis , whereas it is fused with article 2 in U. parisus and U. scandens . These couples each are different in the shape of the eyestalk. Uroptychus articulatus and U. scandens have an elongate, proximally broadened and distally narrowed eyestalk, with the cornea distinctly narrower than the maximum breadth of the eyestalk, whereas in U. imparilis and U. parisus the eyestalk is equally broad proximally and distally, with the cornea slightly broader than the eyestalk at its maximum. Other features are extremely similar in the four species.

Examination of the material reported by Miyake & Baba (1967) from the East China Sea showed that it is referable to U. scandens sensu stricto but the antenna shown in their illustration that is articulated with antennal article 2 is apparently from another specimen of a different species, probably U. imparilis n. sp.

The previously reported specimens need to be reexamined for correct identification (see under synonymy, for identification questioned). The specimens reported by Balss (1913b: fig. 19) from Japan and by Kim & Choe (1976: fig. 1) from Korea may be referable to U. scandens because of the elongate eyestalks although there is no mention or illustration of the antennal scale. The other possible species is U. articulatus that shares with U. scandens the elongate eyestalks but it is common in New Caledonia and vicinity.

The distributional range of the species appears to be restricted to Japan and the East China Sea, but exceptional is the male from the Solomon Islands (MNHN-IU-2014-16941) that could not be discriminated from the type material. This specimen is provisionally placed in this species until more material and molecular data become available.

Figures

FIGURE 227 Uroptychus scandens Benedict,1902, holotype, ovigerous female 3.8 mm (USNM 26166). A, carapace and anterior part of abdomen, dorsal. B, same, anterior part, dorsal.C, same, lateral. D, sternal plastron, with excavated sternum and basal parts of Mxp1. E, pleura of abdominal somites 2-5,dorsolateral.F, telson.G, right antenna,ventral.H, right Mxp3, lateral.I, same,setae omitted,ventral.Scale bars:1 mm.

FIGURE 228 Uroptychus scandens Benedict, 1902, holotype, ovigerous female 3.8 mm (USNM 26166). A, right P1, dorsal. B, same, proximal part, lateral.C, same proximal part,ventral.D,left P2,lateral.E, same,distal part,setae omitted,lateral.F, left P3,setae omitted,lateral.G, same, distal part,lateral.H, left P4,lateral.I, same, distal part, lateral. Scale bars: 1 mm.