Uroptychus anoploetron, 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 : 65-69

Uroptychus anoploetron n. sp.

Figures 16 , 17 , 305B

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. CHALCAL 2 Stn DW73, 24°39.9’S, 168°38.1’E, 573 m, 29.X.1986, 1 ♂ 4.2 mm ( MNHN-IU-2014-17301 ) . Paratypes: New Caledonia, Norfolk Ridge. CHALCAL 2 Stn DW73, station data as for the holotype, 2 ♂ 2.3, 3.6 mm, 1 ov. ♀ 2.7 mm (MNHN-IU-2014-17302) . – Stn DW74, 24°40.36’S, 168°38.38’E, 650 m, 29.X.1986, 1 ♂ 2.9 mm, 1 ov. ♀ 3.1 mm (MNHN-IU-2014-17303) . – Stn DW75, 24°39.31’S, 168°39.67’E, 600 m, 29.X.1986, 4 ♂ 2.5-3.8 mm, 2 ov. ♀ 3.3, 3.7 mm, 2 ♀ 3.7, 4.2 mm (MNHN-IU-2014-17304) . BATHUS 2 Stn CP735, 23°01’S, 166°56’E, 530-570 m, 13.V.1993, 1 ov. ♀ 3.0 mm (MNHN-IU-2014-17305) . NORFOLK 1 Stn DW1694, 24°40’S, 168°39’E, 575-589 m, 24.VI.2001, 1 ov. ♀ 3.6 mm (MNHN-IU-2014-17306) . – Stn DW1699, 24°40’S, 168°40’E, 581-600 m, 24.VI.2001, 5 ov. ♀ 2.9-3.5 mm (MNHN-IU-2014-17307) . – Stn DW1700, 24°40’S, 168°40’E, 605-752 m, 24.VI.2001, 1 ♂ 3.2 mm (MNHN-IU-2014-17308) . NORFOLK 2 Stn DW2056, 24°40.32’S, 168°39.17’E, 573-600 m, 25.X.2003, 1 ov. ♀ 2.8 mm (MNHN-IU-2014-17309) . – Stn DW2057, 24°40.10’S, 168°39.34’E, 555-565 m, 25.X.2003, 2 ♂ 3.9, 4.4 mm, 1 ov. ♀ 4.0 mm (MNHN-IU-2014-17310) . – Stn DW2059, 24°39.96’S, 168°39.84’E, 564 m, 25.X.2003, 1 ♂ 3.1 mm (MNHN-IU-2014-17311) . – Stn DW2060, 24°39.84’S, 168°38.50’E, 582-600 m, 25.X.2003, 1 ♂ 3.4 mm (MNHN-IU-2014-17312) . – Stn CP2062, 24°40.05’S, 168°39.70’E, 560-572 m, 25.X.2003, 1 ov. ♀ 3.4 mm (MNHN-IU-2014-17313) .

ETYMOLOGY„ The specific name is a noun in apposition from the Greek anoplos (unarmed) and etron (abdomen), for the unarmed abdominal somites by which the species is distinguished from the congener U. abdominalis n. sp. described above.

DISTRIBUTION„ Norfolk Ridge; 530- 650 m.

SIZE„ Males, 2.3-4.4 mm; females, 2.7-4.2 mm; ovigerous females from 2.7 mm.

DESCRIPTION„ Small species. Carapace: Slightly broader than long (0.9 × as long as broad); greatest breadth 1.4 × distance between anterolateral spines. Dorsal surface nearly horizontal in profile, with gastric and cardiac regions bordered by transverse depression, cardiac region moderately inflated; epigastric region with transverse row of 5-7 spines: median strong spine flanked by 3 spines, lateral-most occasionally very small or absent; mesogastric region unarmed, occasionally with a few to several smaller spines and very sparse setae; cardiac, intestinal and branchial regions also with spines: 3 transversely arranged anterior cardiac spines usually prominent, followed by smaller spines on intestinal region; branchial region with 3 spines arranged in longitudinal row paralleling lateral margin, posteriorly decreasing in size (anterior second and posteriormost often obsolescent) and often with additional few small spines mesial to row. Lateral margins usually divergent posterolaterally, occasionally somewhat convex on branchial region, armed with 6 acute spines: first (anterolateral) spine extending far beyond lateral orbital spine; first to third subequal, smaller than remainder, closer to each other than fourth to sixth; second distinctly ventral to level of remainder; fourth to sixth prominent, remotely equidistant, situated on branchial region, last (sixth) located near posterior end. Rostrum straight, directed slightly dorsally, sharply triangular, with interior angle of 20°; length distinctly more than half that of remaining carapace, breadth half carapace breadth measured at posterior carapace margin; dorsal surface moderately concave; lateral margin with 3-6 small spines (distinct in specimens having a few spines, obsolescent in those having more spines). Lateral orbital spine small, moderately remote from anterolateral spine and situated anterior to level of that spine. Pterygostomian flap anteriorly ending in sharp spine, surface with small spines arranged roughly in mid-longitudinal row.

Sternum: Excavated sternum anteriorly ending in broad triangular or convex margin between bases of Mxp1, with well-developed ridge in midline. Sternal plastron slightly broader than long, somewhat broadened posteriorly. Sternite 3 moderately depressed, anterior margin moderately concave, with deep U-shaped, rarely narrowly V-shaped median notch flanked by small incurved spine; anterolateral angle produced. Sternite 4 broad relative to length, about as broad as sternite 5; anterolateral margin about as long as posterolateral margin, anteriorly ending in spine of moderate size, occasionally reduced to small size and followed by a few small spines. Sternite 5 having anterolateral margin strongly convex and much shorter than posterolateral margin of sternite 4.

Abdomen: Smooth, barely setose. Somite 1 with cristiform transverse ridge. Somite 2 tergite 2.3-2.5 × broader than long; tergite with feeble anterior transverse ridge occasionally bearing a few very small spines and a few setae, pleuron anterolaterally strongly produced and sharply angular, posterolaterally bluntly angular, lateral margins knife-edge-like, strongly concave and strongly divergent posteriorly. Pleuron of somite 3 tapering to blunt tip. Telson about half as long as broad or slightly more than so; posterior plate twice as long as anterior plate, posterior margin distinctly emarginate.

Eye: Relatively large, 1.8 × longer than broad, overreaching midlength of, but falling short of apex of rostrum, distally broadened, lateral and mesial margins concave. Cornea dilated, about half as long as remaining eyestalk. Antennule and antenna: Ultimate article of antennular peduncle 3.5 × longer than high. Antennal peduncle slender, reaching rostral tip. Article 2 with strong distolateral spine. Antennal scale 1.5 × broader than article 5, overreaching midlength of, but not reaching distal end of peduncle, rarely with lateral spine near midlength. Distal 2 articles each with well-developed distomesial spine; article 5 slightly more than twice as long as article 4, breadth two-thirds height of ultimate article of antennule. Flagellum consisting of 9-12 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 denticle often obsolete on distal part of mesial ridge. Ischium with 15-20 small denticles on crista dentata, flexor margin not rounded distally. Merus 1.7 × longer than ischium, concavely smooth on mesial face; lateral surface with distal spine; flexor margin sharply ridged, bearing 2-6 spines of irregular sizes on distal two-thirds of length, distalmost usually strong. Carpus with distinct distolateral spine, and occasionally with additional scattered small spines on lateral surface.

P1: 6-9 × longer than carapace, slender, subcylindrical, with sparse setae. Ischium with prominent dorsal spine, ventromesially with well-developed subterminal spine and a few tubercles on proximal portion. Merus and carpus very spinose. Merus 1.5-1.9 × longer than carapace, with 5 rows of spines (2 dorsal, 1 mesial, 1 lateral, 1 ventromesial) continued on to carpus, mesial spines larger than remainder. Carpus 1.3-1.7 × longer than merus. Palm 7-8 × longer than broad, as long as or slightly shorter than carpus, with a few to several mesial marginal spines (usually on proximal half) paralleling very small tubercle-like dorsal spines occasionally absent; ventral surface with row of 3 or 4 tubercles on proximal ventromesial portion. Fingers somewhat gaping in large specimens, not gaping in females and small males, slightly crossing distally; opposable margins slightly sinuous; when gaping, opposable margin of movable finger convex on proximal half bearing small notch somewhat proximal to its midlength; movable finger one-third length of palm or less than so.

P2-4: Relatively broad. 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; length-breadth ratio, 4.0 on P2, 3.0-4.0 on P3 and P4; P2 merus as long as or slightly shorter than carapace as well as P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.7 × length of P4 propodus; dorsal margin with 8-11 spines on P2, 7-9 on P3, 5-8 on P4; ventrolaterally with terminal spine; lateral surface with another few small spines paralleling dorsal row on P4. Carpi subequal, with row of 4 marginal spines on extensor margin and another 2 or 3 smaller ones on lateral surface; length about half that of dactylus and 0.3 × that of propodus on P2-4. Propodi longer on P3 and P4 than on P2; extensor margin with 2-4 spines proximally; flexor margin somewhat concave in lateral view, ending in pair of spines preceded by 1 or 2 spines on P2 and P3, none on P4. Dactyli successively longer posteriorly, subequal on P2-4 or slightly longer on P3 than on P2 and P4, length 0.6 × that of propodus on P2-P3, 0.6-0.7 × on P4, distally relatively broad; flexor margin nearly straight, with 13-15 spines on P2, additional 1 or 2 spines on P3 and P4; all of these spines elongate, obliquely directed and nearly contiguous to one another, ultimate spine more slender than antepenultimate, penultimate broadest, 2 × broader than antepenultimate, remaining spines proximally diminishing.

Eggs. Up to 15 eggs carried; size, 1.0 mm × 1.2 mm.

Color. Ovigerous female paratype (MNHN-IU-2014-17302) from CHALCAL 2, Stn DW73: Carapace and abdomen pale grayish yellow, spines reddish at base; pereopods pale purple in basic color and yellow-tinged, with 2 reddish bands on merus, carpus, propodus.

REMARKS — The carapace ornamentation, spination of P1-P4, shape of the sternal plastron and the color pattern displayed by the species are very similar to those of U. abdominalis n. sp. Uroptychus anoploetron is differentiated from that species by the following: the P1-4 are more slender and the carapace spines are more pronounced; the abdominal somite 1 and 2 are unarmed, instead of bearing a pair of strong submedian spines; the tergite of abdominal somite 1 is sharply ridged transversely rather than convex from anterior to posterior; the antennal article 5 bears a distinct distomesial spine instead of being unarmed. These two species have the similar color pattern but the colorations are different: bands on the pereopods are reddish in U. anoploetron , yellowish in U. abdominalis .

Figures

FIGURE 16 Uroptychusanoploetron n.sp.,A-C,E-G,holotype,male4.2mm (MNHN-IU-2014-17301);D,maleparatype 3.1mm (MNHN-IU-2014-17311). A, carapace and anterior part of abdomen,dorsal.B, same,lateral. C, anterior part of sternal plastron,with excavated sternum, basal parts of Mxp1 included. D, telson. E, right antenna, ventral. F, right Mxp3, ventral. G, same, merus and carpus, lateral. Scale bars:1 mm.

FIGURE 17 Uroptychus anoploetron n. sp., holotype, male 4.2 mm (MNHN-IU-2014-17301). A, right P1, proximal part, dorsal. B, same,ventral. C, same,proximal part omitted,dorsal. D, left P2,lateral.E, same, distal part,setae omitted, lateral. F, left P3,lateral.G, left P4, setae omitted, lateral.Scale bars: 1 mm.

FIGURE 305 A, Uroptychus abdominalis n.sp.,paratype,ovigerous female 3.0 mm,MNHN-IU-2014-17140,Norfolk Ridge.B, U.anoploetron n.sp.,paratype,ovigerous female 2.7 mm, MNHN-IU-2014-17302,Norfolk Ridge.C, U.babai Ahyong & Poore, 2004,male 9.2 mm, MNHN-IU-2014-16300,Chesterfield Islands.D, U.elongatus n. sp., holotype,ovigerous female 4.3 mm, MNHN-IU-2014-16440,Vanuatu.E, U.joloensis Van Dam, 1933,ovigerous female, 3.0 mm,MNHN-IU-2014-16595, Vanuatu.F, U.joloensis Van Dam, 1933, ovigerous female, MNHN-IU-2014-16602,Wallis and Futuna Islands.G, U. joloensis Van Dam, 1933, male 2.3 mm and ovigerous female 2.1 mm, in situ habitat, associated with nidaliid corals, QM W25105, Papua New Guinea.H, U. nanophyes McArdle, 1901, male, 10.7 mm, MNHN-IU-2014-16757, Norfolk Ridge.I, U.nebulosus n. sp., paratype, male,8.1 mm, MNHN-IU-2014-16812,Vanuatu.