Uroptychus politus ( Henderson, 1885 )

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 : 407-411

Uroptychus politus ( Henderson, 1885)

Figures 201 , 202

Diptychus politus Henderson, 1885: 420 .

Uroptychus politus — Henderson 1888: 178, pl. 6: figs 2, 2a, 2b. — Thomson 1899: 196 (list). — Baba 1974: 387, fig. 5; 2005: 219 (key), 230 (list). — Schnabel 2009: 564 (examination of female syntype).

TYPE MATERIAL — Syntype: New Zealand, north of the Kermadec Islands , 600 fms (1098 m), female ( BMNH 1888 : 33). [examined].

MATERIAL EXAMINED — New Zealand, Kermadec Islands. CHALLENGER Stn 171, 28°33’S, 177°50’W, 600 fms (1098 m), 1 ov. ♀ 5.4 mm, syntype ( BMNH 1888: 33) . Solomon Islands. SALOMON 2 Stn CP2197, 8°24.2’S, 159°22.5’E, 897-1057 m, 24.X.2004, 2 ♂ 5.3, 7.5 mm, 1 ov. ♀ 7.2 mm (MNHN-IU-2014-16862) . New Caledonia, Loyalty Islands. BIOGEOCAL Stn CP297, 20°37’S, 167°11’E, 1230-1240 m, 28.IV.1987, 1 ♂ 6.3 mm ( MNHN- IU-2014-16863).

DISTRIBUTION„ Kermadec Islands, and now Solomon Islands and Loyalty Islands; in 897-1240 m.

SIZE„ Males, 5.3-7.5 mm; ovigerous females, 5.4-7.2 mm.

DESCRIPTION„ Medium-sized species. Carapace: Smooth, without setae and spines, 1.1 × longer than broad; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface somewhat convex, with or without depression between gastric and cardiac regions. Lateral margins convexly divergent posteriorly (divergent to point one-fifth from posterior end, then convergent), ridged along posterior half; short, elevated, granulated ridge bearing small spine (obsolete in holotype) at one-fifth length from anterior end (anterior end of branchial region); anterolateral spine small, distinctly posterior to level of lateral orbital spine, barely or fully reaching tip of that spine. Rostrum narrow triangular, with interior angle of 18-21°, horizontal; dorsal surface somewhat concave; length about half that of remaining carapace, breadth slightly less than half carapace breadth at posterior carapace margin. Lateral orbital spine somewhat smaller than anterolateral spine. Pterygostomian flap anteriorly roundish with or without very small spine.

Sternum: Excavated sternum strongly produced anteriorly between bases of Mxp1, bearing small spine in center of surface. Sternal plastron slightly broader than long, lateral margins somewhat divergent posteriorly. Sternite 3 moderately depressed; anterior margin moderately concave, with submedian spines nearly contiguous at base or separated by small notch. Sternite 4 long relative to width, surface with transverse ridge preceded by depression; anterolateral margin nearly straight, anteriorly ending in short process, length 1.6-1.8 × that of posterolateral margin. Sternite 5 two-thirds as long as sternite 4, anterolateral margins feebly convex and moderately divergent posteriorly, about as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous, lacking setae. Somite 1 somewhat convex from anterior to posterior. Somite 2 tergite 2.3-2.5 × broader than long; pleuron posterolaterally blunt, lateral margin feebly concave and strongly divergent posteriorly. Pleuron of somite 3 posterolaterally bluntly angular. Telson slightly more than half (0.56-0.66) as long as broad; posterior plate 1.7-1.8 × longer than anterior plate, posterior margin moderately emarginate or slightly concave.

Eye: Short relative to breadth, reaching at most distal quarter of rostrum, mesial margin somewhat concave. Cornea more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.7-3.2 × longer than high. Antennal peduncle relatively slender, overreaching cornea. Article 2 distolaterally angular, without distinct spine. Antennal scale 1.4 × as broad as article 5, overreaching distal end of article 4, falling short of midlength of article 5. Distal 2 articles unarmed; article 5 1.7-1.9 × length of article 4, breadth 0.4 × height of antennular ultimate article. Flagellum consisting of 14-18 segments, slightly falling short of distal end of P1 merus.

Mxp: Mxp1 with bases close to each other. Endopod of Mxp3 barely setose laterally, slender. Basis with a few denticles on mesial ridge, distalmost distinct, others obsolescent. Ischium having crista dentata with 5-10 (7 in holotype) small denticles rather distant from one another; flexor margin distally not rounded. Merus 1.9 × longer than ischium, unarmed; flexor margin roundly ridged. Carpus also unarmed.

P1: Smooth, nearly glabrous except for fingers, length 4.3-5.6 × that of carapace. Ischium with short dorsal spine, ventromesially unarmed. Merus 1.2 × longer than carapace. Carpus 2.6-4.0 × longer than broad, 1.2-1.3 × longer than merus. Palm 2.7-3.0 × longer than broad, about as long as carpus. Fingers relatively broad, slightly incurved distally, gaping in both sexes (not gaping in female syntype), opposable margins straight in distal quarter when gaping, in distal half when not gaping; movable finger about half as long as palm, opposable margin with 2 distinct proximal processes opposed to low process on fixed finger.

P2-4: Relatively thick mesio-laterally, sparsely setose but barely so on meri. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2-4; unarmed; length-breadth ratio, 6.1-6.9 (5.4 in syntype) breadth on P2, 5.7-6.6 (4.3 in syntype) on P3, 5.6-6.0 × on P4; P2 merus 0.87-0.98 × as long as carapace, 1.4 × longer than P2 propodus; P3 merus 1.1 × length of P3 propodus; P4 merus 1.0-1.1 × length of P4 propodus. Carpi successively shorter posteriorly (P3 carpus 0.9 × length of P2 carpus, P4 carpus subequal to or slightly shorter than P3 carpus); much longer than dactyli (carpus-dactylus length ratio, 2.1-2.3 on P2, 1.9-2.0 on P3, 1.6-1.7 on P4); carpus-propodus length ratio, 0.8-0.9 on P2, 0.7-0.8 on P3, 0.6-0.7 on P4. Propodi subequal on P2-4; flexor margin with pair of terminal spines slightly distant from juncture with dactylus, preceded by 6-7 spines on P2, 5-6 spines on P3, 3-5 spines on P4 at most on distal half. Dactyli strongly curving at proximal third, ending in strong spine preceded by 8-10 successively diminishing, somewhat inclined spines on flexor margin on P2, 9 or 10 spines on P3, 10 or 11 spines on P4, ultimate slightly longer than penultimate, antepenultimate closer to distal quarter than to penultimate; length 0.4 × that of propodus on P2-4, and 0.5 × that of carpi on P2 and P3, 0.6 × on P4.

Eggs. Number of eggs carried, 16 (2 in syntype); size, 2.18 mm × 2.22 mm - 2.22 mm × 2.43 mm (1.50 × 1.92 mm in syntype).

REMARKS — Henderson (1885) reported one male from north of the Kermadec Islands, and in his extensive description of the Challenger material, he provided an additional female. In an earlier paper ( Baba, 1974), the illustration of the female syntype drawn by R. W. Ingle was provided under “ holotype.” At that time Ingle did not find the male syntype so that it was called the holotype. In the lot now available of the syntypes (BM 1888:33), a pair of P1 (possibly of the male, due to its massiveness) and a left P1 (possibly of the female) are present. Left two and right two walking legs, and left Mxp3 removed from the ovigerous female syntype are available ( Figure 201 ).

The syntype has relatively broad P2 and P3, the length-breadth ratios of meri and propodi being somewhat greater than those of the other specimens examined. In addition, the anterolateral spine is as small as the lateral orbital spine and does not reach the tip of that spine, whereas in the present material the spine is larger than and fully reaches the tip of the lateral orbital spine. These difference are here considered as intraspecific variations. The species is very characteristic in the shape of the sternite 5, the anterolateral margin of which is very weakly convex instead of well convex as in most of the other known species.

The species is close to U. salomon n. sp. described below. Their relationships are discussed under that species.

Figures

FIGURE 201 Uroptychus politus (Henderson, 1885), A-F, syntype, ovigerous female 5.4 mm (BMNH 1888: 33);G, H, possibly male syntype; I-K, pereopods detached from body. A, carapace, dorsal. B, same, anterior part of abdomen included, lateral. C, anterior part of carapace, showing left eye, dorsolateral. D, anterior part of sternal plastron. E, left antenna, ventral. F, left P1, dorsal. G, right P1, dorsal.H, same,distal part,mesial.I, right P2, lateral.J, left P3, lateral.K, right P3, distal 3 articles, lateral. Scale bars: 1 mm.

FIGURE 202 Uroptychus politus (Henderson, 1885),male 7.5 mm (MNHN-IU-2014-16862). A, carapace and anterior part of abdomen, proximal part of left P1 included, dorsal. B, sternal plastron, with excavated sternum and basal parts of Mxp1.C, telson.D, right Mxp3,ventral. E, left P1, dorsal.F, left P2, lateral.G, same, distal part, setae omitted,lateral.Scales bars: A, E,5 mm; B, C,D, F,G, 1 mm.