Uroptychus abdominalis, 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 : 37-41

Uroptychus abdominalis n. sp.

Figures 3 , 4 , 305A

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. SMIB 3 Stn DW02, 24°54’S, 168°22’E, 537- 530 m, 20.V.1987, ♂ 4.9 mm ( MNHN-IU-2014-17135 ) . Paratypes: New Caledonia, Norfolk Ridge. SMIB 3 Stn DW01, 24°55’S, 168°22’E, 520 m, 20.V.1987, 1 ♂ 4.0 mm, 3 ov. ♀ 3.4-3.8 mm (MNHN-IU-2014-17136) . – Stn DW02, station data as for the holotype, 1 ♂ 4.5 mm, 1 ov. ♀ 4.7 mm (MNHN-IU-2014-17137) . – Stn DW03, 24°54’S, 168°22’E, 513 m, 20.V.1987, 1 ♂ 4.0 mm (MNHN-IU-2014-17138) . – Stn DW05, 24°55’S, 168°22’E, 502-512 m, 21.V.1987, 1 ov. ♀ 3.5 mm (MNHN-IU-2014-17139) . CHALCAL 2 Stn CC02, 24°55’S, 168°21’E, 500-610 m, 28.X.1986, 1 ov. ♀ 3.0 mm (MNHN-IU-2014-17140) . – Stn DW72, 24°54.5’S, 168°22.3’E, 527 m, 28.X.1986, 2 ♂ 2.6, 4.0 mm, 1 ov. ♀ 4.0 mm (MNHN-IU-2014-17141) . – Stn DW73, 24°40’S, 168°38’E, 573 m, 29.X.1986, 2 ov. ♀ 3.6, 4.0 mm (MNHN-IU-2014-17142) . NORFOLK 2 Stn DW2056, 24°40.32’S, 168°39.17’E, 573-600 m, 25.X.2003, 1 ♂ 4.7 mm, 1 ♀ 3.2 mm (MNHN-IU-2014-17143) . – Stn DW2058, 24°39.76’S, 168°40.43’E, 591-1032 m, 25.X.2003, 1 ov. ♀ 3.9 mm (MNHN-IU-2014-17144) . – Stn DW2060, 24°39.84’S, 168°38.50’E, 582-600 m, 25.X.2003, 1 ♂ 4.3 mm (MNHN-IU-2014-17145) . – Stn DW2087, 24°56.22’S, 168°21.66’E, 518-586 m, 28.X.2003, 1 ov. ♀ 3.4 mm (MNHN- IU-2014-17146) . – Stn CP2088, 24°57.48’S, 168°21.70’E, 627-1089 m, 28.X.2003, 3 ♂ 3.3-4.5 mm, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-17147) . – Stn CP2089, 24°44.30’S, 168°08.83’E, 227-230 m, 29.X.2003, 9 ♂ 3.0-5.0 mm, 5 ov. ♀ 3.1-4.3 mm (MNHN-IU-2014-17148) .

OTHER MATERIAL EXAMINED — New Caledonia, Norfolk Ridge. LITHIST Stn CP15, 23°40.4’S, 168°15.0’E, 389-404 m, 12.VIII.1999, 2 ov. ♀ 3.7, 3.8 mm (MNHN-IU-2014-17149) . BERYX 11 Stn CP08, 24°54’S, 168°21’E, 540-570 m, 15.X.1992, 7 ♂ 3.3-4.5 mm, 4 ov. ♀ 3.1-3.9 mm (MNHN- IU-2014-17150) . – Stn DW09, 24°52.10’S, 168°21.95’E, 630-680 m, 15.X.1992, 1 ov. ♀ 3.8 mm (MNHN-IU-2014-17151) . – Stn DW10, 24°52.85’S, 168°21.40’E, 560-600 m, 15.X.1992, 1 ♂ 5.1 mm, 1 ov. ♀ 3.8 mm, 1 ♀ 4.1 mm (MNHN-IU-2014-17152) . SMIB 4 Stn DW55, 23°21.4’S, 168°04.5’E, 215-260 m, 9.III.1989, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-17153) . SMIB 8 Stn DW153, 24°53.55’S, 168°21.33’E, 547-560 m, 27.I.1993, 1 ov. ♀ 3.9 mm (MNHN-IU-2014-17154) . NORFOLK 1 Stn DW1691, 24°55’S, 168°21’E, 509-513 m, 23.VI.2001, 2 ♂ 2.8, 4.3 mm, 1 ov. ♀ 3.8 mm (carapace broken) (MNHN-IU-2014-17155) . – Stn DW1697, 24°40’S, 168°39’E, 569-616 m, 24.VI.2001, 1 ♀ 3.5 mm (MNHN-IU-2014-17156) .

ETYMOLOGY„ The Latin abdominalis (abdominal) refers to the abdomen of the species that has tergites 1 and 2 each armed with two strong spines placed side by side, a character to separate the species from the close relative, U. anoploetron n. sp.

DISTRIBUTION„ Norfolk Ridge; 227-1089 m.

SIZE„ Males, 2.6-5.1 mm; females, 3.0- 4.7 mm; ovigerous females from 3.0 mm.

DESCRIPTION — Small species. Carapace: Broader than long (length 0.84-0.95 breadth); greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface somewhat convex, separated into anterior and posterior portions by well depressed concavity along ordinary site of cervical groove, with spines and very sparse setae as figured; gastric region indistinctly separated from hepatic region; epigastric region with 7 spines arranged roughly in transverse row, often with 1-2 additional small spines laterally; median and posterior gastric regions also with small spines; cardiac region delimited in inverse triangle, moderately elevated anteriorly, with 2 strong anterior (placed side by side) and 2 posterior (placed in midline) spines followed by pair of spines located on intestinal region; branchial region also with scattered spines often reduced to several in number and arranged in longitudinal row. Lateral margins convexly divergent posteriorly, armed with 6 spines, often somewhat constricted behind third spine; anterior 3 more or less close to one another; first anterolateral, somewhat overreaching small lateral orbital spine, and moderately distant from that spine; second distinctly more slender than first, closer to first than to third, ventral to level of remainder; third larger than first; fourth to sixth prominent, subequal, equidistant from one another; last (sixth) arising from ridged margin near posterior end. Rostrum long triangular, with interior angle of about 20°, directed slightly dorsally; length 0.6-0.7 × that of remaining carapace, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface concave; lateral margin with 4-7 denticle-like spines often very small or obsolete. Pterygostomian flap with scattered small spines, anteriorly produced, ending in distinct spine.

Sternum: Excavated sternum with anterior margin strongly convex between Mxps1, surface with relatively sharp ridge in midline. Sternal plastron about as long as broad, lateral extremities gently divergent posteriorly. Sternite 3 moderately depressed; anterolateral angle produced, rarely ending in bifid spine; anterior margin gently concave, with V-shaped, rarely U-shaped median notch flanked by spine distinct, obsolescent or obsolete; lateral margin with proximal small spine. Sternite 4 slightly narrower than sternite 5; with short, nearly straight anterolateral margin anteriorly ending in small spine often accompanying 1 or 2 smaller spines mesial to it, followed by posteriorly diminishing denticles; posterolateral margin about as long as anterolateral margin. Anterolateral margin of sternite 5 strongly convex, 0.6 × as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somites 1 and 2 each with pair of well-developed submedian spines on tergite; somite 2 tergite 2.6-2.7 × broader than long; pleuron having lateral margins well concave, knife-edge-like, sharply produced on anterior and posterior ends. Pleura of somites 3 and 4 laterally tapering. Telson about half as long as broad; posterior plate 1.5 × longer than anterior plate, posterior margin feebly concave or distinctly emarginate.

Eye: 1.7 × longer than broad, overreaching midlength of and barely reaching tip of rostrum. Cornea slightly broader than and much more than half as long as proximally narrowed remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.5-3.2 × longer than high. Antennal peduncle barely or slightly overreaching apex of rostrum. Article 2 with distinct distolateral spine. Antennal scale much broader than article 5, overreaching midlength of, and, falling short of distal end of article 4, rarely with lateral spine at proximal third. Article 4 with strong distomesial spine ventrally. Article 5 unarmed, about twice as long as article 4, breadth at most two-thirds height of ultimate article of antennular peduncle. Flagellum of 9-12 segments far falling short of distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 denticle (often bidentate) on distal portion of well-convex mesial ridge, bearing 1 or 2 additional small denticles proximal to it in large specimens. Ischium with flexor margin not rounded distally, crista dentata with more than 20 small denticles. Merus 1.7 × longer than ischium, flexor margin well crested, with 2 or 3 spines on distal half of length, often accompanying smaller spine proximal to each; distolateral spine well developed. Carpus with well-developed distolateral spine and often 1 or 2 additional small spines distantly proximal to it.

P1: Slender, spinose, sparsely or moderately setose, 5.6-6.6 × longer than carapace. Ischium with prominent dorsal spine and 4-6 proximally diminishing ventromesial spines, distal one subterminal and well developed. Merus 1.4 × longer than carapace, with 5 rows of spines (1 mesial, 2 dorsal, 1 lateral, 1 ventral) continued onto carpus; mesial spines stronger. Carpus 1.2-1.3 × longer than merus, with lateral row of small spines somewhat dorsal in position, often reduced in number. Palm 4.1-5.4 × longer than broad (with no distinct sexual difference), 0.9 × as long as carpus; mesial margin with spines except on distal two-fifths or more of length; dorsal proximal spines in midline often obsolescent; lateral margin unarmed. Fingers distally slender, slightly crossing, ending in small incurved blunt spine; opposable margins with row of denticles, not spooned, somewhat gaping in large males, proximal process on movable finger usually low and reduced in females and small males, moderate in size in large males; movable finger slightly less than half as long as palm.

P2-4: Relatively broad. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8-1.0 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 3.5-3.8 on P2, 2.9-3.5 on P3, 2.7-3.2 on P4; P2 merus 0.8 × length of carapace, about as long as P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.7 × length of P4 propodus; dorsal margins with 8-10 spines (occasionally distalmost spine with smaller accompanying spine), and 1 distoventral spine somewhat longer than distalmost dorsal spine; lateral surface with another row of several spines present usually on P3, occasionally on P4. Carpi subequal, about 0.3 × as long as propodi on P2-4; extensor margin with 5-7 spines paralleling row of smaller spines on lateral surface. Propodi shorter on P2 than on P3-4; extensor margin with 2-4 spines on proximal portion; flexor margin somewhat concave in lateral view, ending in pair of spines preceded by 3-5 slender spines on P2, 1 on P3, none on P4. Dactyli relatively stout, more than 1.5 × longer than carpi on P2-4, about 0.6 × length of propodi on P2-4; flexor margin slightly curving, with 11-13 obliquely directed movable spines including small ultimate (terminal); penultimate (distal second) prominent, short and broad at base; remaining proximal spines slender, distally blunt, diminishing toward base of article.

Eggs. Ova, 0.9-1.0 mm in diameter; up to 21 eggs carried.

Color. Ovigerous female from Chalcal 2, Stn CC02 (MNHN-IU-2014-17140): Basic color of translucent light purple; carapace and abdomen yellowish; P1 with yellow bands, 2 on each of merus, carpus and propodus, 1 on basi-ischium and dactylus; P2-4 also with yellow bands, 2 on merus and propodus, 1 on carpus, dactylus yellow-tinged.

REMARKS„ The species strongly resembles U. anoploetron n. sp. in the carapace ornamentation and spination of the pereopods. Their relationships are discussed under the remarks of that species (see below).

Figures

FIGURE 3 Uroptychus abdominalis n. sp.,holotype, male 4.9 mm (MNHN-IU-2014-17135).A, carapace and anterior part of abdomen, proximal articles of left P1 included,dorsal.B, same,P1 omitted,lateral.C,anterior part of sternal plastron,excavated sternum included.D, telson. E, left antenna, ventral.F, merus and carpus of left Mxp3,lateral.G, same, ventral. Scale bars:1 mm.

FIGURE 4 Uroptychus abdominalis n. sp.,holotype,male 4.9 mm (MNHN-IU-2014-17135). A, right P1, proximal articles omitted,dorsal. B, left P1, proximal part, ventral. C, same, fingers, ventral. D, right P2, lateral. E, same, distal part, setae omitted, lateral. F, right P3, setae omitted, lateral.G, right P4, 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.