Uroptychus dualis, 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 : 185-189

Uroptychus dualis n. sp.

Figures 80 , 81

TYPE MATERIAL — Holotype: New Caledonia. MUSORSTOM 4 Stn DW 156, 18°54’S, 163°19’E, 530 m, 15.IX.1985, ♂ 3.4 mm ( MNHN-IU-2014-16396 ) . Paratypes: New Caledonia. MUSORSTOM 4 Stn DW156, 18°54.00’S, 163°18.80E, 530 m, 15.IX.1985, 2 ♂ 3.0- 3.4 mm, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-16397) . – Stn DW162, 18°35’S, 163°10’E, 535 m, 16.IX.1985, 1 ♂ 3.7 mm, 1 ov. ♀ 4.0 mm (MNHN-IU-2014-16398) . – Stn CP194, 18°52’S, 163°21’E, 550 m, 19.IX.1985, 1 ov. ♀ 4.7 mm (MNHN-IU-2014-16399), 24 ♂ 3.5-5.4 mm, 22 ov. ♀ 3.4-5.0 mm, 3 ♀ 3.5-3.7 mm (MNHN-IU-2014-16400) . – Stn DW197, 18°51’S, 163°21’E, 560 m, 20.IX.1985, 29 ♂ 2.6-5.1 mm, 19 ov. ♀ 2.7-5.1 mm, 5 ♀ 2.5-4.4 mm ( MNHN- IU-2014-16401) . – Stn CP199, 18°51’S, 163°14’E, 600 m, 20.IX.1985, 1 ♂ 3.2 mm (MNHN-IU-2014-16402) .

OTHER MATERIAL EXAMINED — New Caledonia, Chesterfield Islands. MUSORSTOM 5 Stn DW355, 19°36.43’S, 158°43.41’E, 580 m, 18. X.1986, 1 ♂ 2.7 mm (MNHN-IU-2014-16404) . New Caledonia. BIOCAL Stn DW38, 23°00’S, 167°15’E, 360 m, 30.VIII.1985, 1 ♂ 1.7 mm ( MNHN- IU-2010-5435) . – Stn DW77, 22°15’S, 167°15’E, 440 m, 5. IX.1985, 1 ov. ♀ 3.3 mm (MNHN-IU-2014-16407) . New Caledonia, Isle of Pines. MU- SORSTOM 4 Stn CP216, 22°59.5’S, 167°22.0’E, 490-515 m, 29.IX.1985, 1 ov. ♀ 3.4 mm (MNHN-IU-2014-16408) . – Stn DW221, 22°58.6’S, 167°36.8’E, 535-560 m, 29.IX.1985, 9 ♂ 2.5-4.2 mm, 6 ov. ♀ 2.5-3.8 mm (MNHN-IU-2014-16409) . – Stn DW222, 22°57.6’S, 167°33.0’E, 410-440 m, 30.IX.1985, 1 ♂ 2.8 mm (MNHN-IU-2014-16410) . BERYX 11 Stn DW27, 23°37.25’S, 167°41.20’E, 460-470 m, 18.X.1992, 9 ♂ 3.6-5.0 mm, 7 ov. ♀ 3.9-5.0 mm, 1 ♀ 3.9 mm (MNHN-IU-2014-16411) . BIOCAL Stn CP52, 23°06’S, 167°47’E, 540-600 m, 31.VIII.1985, 1 ♀ 3.2 mm (MNHN-IU-2014-16412) . SMIB 2 Stn DC26, 22°59’S, 167°23’E, 500-535 m, 21. IX.1986, 1 ♀ 3.2 mm (MNHN-IU-2014-16413) . SMIB 3 Stn DW12, 23°42’S, 167°41’E, 470- 470 m, 22.V.1987, 2 ♂ 4.5, 5.0 mm, 1 ov. ♀ 4.6 mm, 1 ♀ 4.3 mm (MNHN-IU-2014-16414) . – Stn DW24, 22°58.7’ S, 167°21.1’E, 535 m, 24.V.1987, 1 ♂ 4.1 mm, 1 ov. ♀ 3.6 mm (MNHN-IU-2014-16415) . New Caledonia, Norfolk Ridge. CHALCAL 2 Stn DW76, 23°40.5’S, 167°45.2’E, 470 m, 3.X.1986, 2 ♂ 4.2, 4.4 mm (MNHN-IU-2014-16416) . – Stn DW77, 23°38.35’S, 167°42.68’E, 435 m, 30.X.1986, 1 ♀ 2.0 mm (MNHN-IU-2014-16417) . BERYX 11 Stn DW38, 23°37.53’S, 167°39.42’E, 550-690 m, 19.X.1992, 2 ♂ 4.1, 4.8 mm, 2 ov. ♀ 4.9,5.0 mm (MNHN-IU-2014-16418) . LITHIST Stn CP02, 23°37.1’S, 167°41.1’E, 442 m, 10.VIII.1999, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-16419) . – Stn CP03, 23°37.0’S, 167°41.5’E, 447 m, 10.VIII.1999, 1 ov. ♀ 4.5 mm, 1 ♀ 4.5 mm (MNHN-IU-2014-16420) . NORFOLK 1 Stn CP1655, 23°26’S, 167°51’E, 680 m, 19.VI.2001, 1 ♂ 3.5 mm (MNHN-IU-2014-16421) . – Stn DW1659, 23°37’S, 167°41’E, 449-467 m, 20.VI.2001, 1 ♂ 5.0 mm, 4 ov. ♀ 3.9-4.9 mm (MNHN-IU-2014-16422) . – Stn DW1662, 23°38’S, 167°42’E, 462-491 m, 20.VI.2001, 2 ov. ♀ 4.1, 4.4 mm (MNHN-IU-2014-16423) . – Stn DW1666, 23°42’S, 167°44’E, 469-860 m, 20.VI.2001, 7 ♂ 3.8-5.2 mm, 6 ov. ♀ 4.0- 4.7 mm ( MNHN- IU-2014-16424) . – Stn DW1667, 23°40’S, 168°01’E, 237-250 m, 21.VI.2001, 1 ♂ 5.1 mm (MNHN-IU-2014-16425) . – Stn CP1671, 23°41’S, 168°00’E, 320-397 m, on Chironephthya sp. ( Nidaliidae : Alcyonacea ), 21.VI.2001, 1 ov. ♀ 3.7 mm (MNHN-IU-2014-16426) . – Stn DW1707, 23°43’S, 168°16’E, 381-493 m, 25.VI.2001, 1 ♂ 4.0 mm, 2 ov. ♀ 4.8, 4.9 mm (MNHN-IU-2014-16427) . – Stn DW1722, 23°18’S, 168°01’E, 540m, 26.VI.2001, 3 ov. ♀ 4.2- 4.7 mm, 3 ♀ 2.6-4.0 mm (MNHN-IU-2014-16428) . – Stn DW1732, 23°21’S, 168°16’E, 347-1063 m, 27.VI.2001, 1 ♂ 3.7 mm (MNHN-IU-2014-16429) . NORFOLK 2 Stn DW2024, 23°27.92’S, 167°50.90’ E, 370-371 m, 21.X.2003, 2 ♂ 3.0, 3.2 mm, 1 ov. ♀ 4.0 mm, 2 ♀ 4.5, 4.3 mm (MNHN-IU-2014-16430) . – Stn DW2031, 23°38.83’S, 167°44.01’E, 440- 440 m, 22.X.2003, 4 ov. ♀ 4.3-5.4 mm (MNHN-IU-2014-16431) . – Stn DW2034, 23°40.64’S, 167°41.36’E, 485-505 m, 22.X.2003, 3 ♂ 3.4-5.4 mm, 2 ov. ♀ 4.2, 4.5 mm (MNHN-IU-2014-16432) . – Stn DW2035, 23°39.82’S, 167°40.43’E, 515-540 m, 22.X.2003, 1 ov. ♀ 5.0 mm, 1 ♀ 5.3 mm (MNHN-IU-2014-16433) . – Stn DW2049, 23°42.88’ S, 168°15.43’ E, 470-621 m, 24.X.2003, 1 ♂ 4.1 mm, 1 ov. ♀ 3.8 mm, 2 ♀ 3.2, 3.6 mm (MNHN-IU-2014-16434) . – Stn DW2056, 24°40’S, 168°39’E, 573-600 m, 25.X.2003, 2 ov. ♀ 4.7, 4.8 mm (MNHN-IU-2014-16435) . – Stn DW2132, 23°17.30’ S, 168°13.56’E, 405-455 m, 2.XI.2003, 1 ♂ 4.1 mm, 1 ♀ 2.7 mm (MNHN-IU-2014-16436) . – Stn DW2136, 23°00.73’S, 168°22.68’E, 402-410 m, 3.XI.2003, 1 ♂ 3.0 mm, 1 ov. ♀ 3.6 mm (MNHN-IU-2014-16437) . Wallis and Futuna Islands. MUSORSTOM 7 DW525, 13°11’S, 176°15’W, 500-600 m, 13.V.1992, 1 ov. ♀ 4.0 mm (MNHN-IU-2014-16403) . Vanuatu. MUSORSTOM 8 Stn DW988, 19°16’S, 169°24’E, 372-466 m, 23.IX.1994, 1 ov. ♀ 3.3 mm, 1 ♀ 3.8 mm (MNHN-IU-2014-16405) . – Stn DW1003, 18°49’S, 168°59’E, 327- 200 m, 25.IX.1994, 1 ♂ 3.7 mm (MNHN-IU-2014-16406) .

ETYMOLOGY„ From the Latin dualis (of two) in reference to two strong ventromesial spines on the P1 merus by which the species can be separated from U. floccus , U. quinarius , and U. lumarius , the latter three species bearing three or four spines.

DISTRIBUTION — Wallis and Futuna Islands, Chesterfield Islands, Vanuatu, New Caledonia, Isle of Pines and Norfolk Ridge; 200- 860 m.

SIZE„ Males, 2.5-5.4 mm; females, 2.0- 5.4 mm; ovigerous females from 2.5 mm.

DESCRIPTION„ Small species. Carapace: Slightly broader than long (0.8 × as long as broad); greatest breadth 1.4 × distance between anterolateral spines. Dorsal surface slightly convex from anterior to posterior, with depression (occasionally obsolescent) suggesting cervical groove; epigastric region with transverse row of 7 or 8 small spines preceded by depressed rostrum, laterally leading to small spine dorsal to third lateral marginal spine. Lateral margins slightly convex, with 6 sharp spines: first anterolateral, well developed, extending far beyond small lateral orbital spine; second ventral to level of others, much smaller; third to sixth strong, last (sixth) followed by ridge. Rostrum sharp triangular, with interior angle of ca. 20° (18-23°), horizontal; length 0.4-0.6 × postorbital carapace length (relatively long in small specimens), breadth less than half carapace breadth measured at posterior carapace margin; lateral margin with a few very small spines distally but often obsolescent or absent; dorsal surface moderately concave. Lateral orbital spine situated directly mesial to but remote from anterolateral spine. Pterygostomian flap with anterior margin produced to strong spine; surface with a few spines small or obsolete, often well developed, situated on anterior median portion, without spine below linea anomurica between second and third lateral spines.

Sternum: Excavated sternum blunt triangular between bases of Mxp1, surface with longitudinal ridge in midline. Sternal plastron somewhat broader than long, with gently divergent lateral extremities. Sternite 3 depressed well, anterior margin strongly concave, with median notch of narrow V-shape flanked by obsolescent spine, anterolateral end sharply angular, lateral margin with small spine. Sternite 4 with anterolateral margin relatively short, slightly convex, entire, with anterior end angular or produced to small spine; posterolateral margin distinctly longer than anterolateral margin. Anterolateral margin of sternite 5 anteriorly angular or rounded, about half as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somite 1 with distinct transverse ridge. Segment 2 tergite 2.6-2.8 × broader than long; pleural lateral margin weakly concave and weakly divergent posteriorly, posterolaterally rounded. Pleuron of somite 3 laterally blunt. Telson barely or fully half as long as broad; posterior plate 1.3-1.6 × longer than anterior plate, posterior margin feebly to distinctly concave.

Eye: Somewhat elongate (length 1.8 × breadth), slightly overreaching midlength of rostrum, somewhat broadened proximally. Cornea not dilated, more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate antennular article relatively slender, 3.2-3.6 × longer than high. Antennal peduncle overreaching cornea and falling short of rostral tip. Article 2 with sharp distolateral spine. Antennal scale distinctly overreaching article 5, at least reaching second segment of flagellum, breadth about twice that of article 5. Article 4 with small, often obsolescent distomesial spine. Article 5 unarmed, 1.2-1.5 × longer than article 4, breadth 0.5-0.6 × height of ultimate antennular article. Flagellum of 11-12 segments falling short of distal end of P1 merus.

Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 basis without denticles on mesial ridge. Ischium with distally rounded flexor margin; crista dentata with denticles very small, obsolescent or nearly absent. Merus and carpus each with distolateral spine; merus 2.2 × longer than ischium, mesial face flattish (slightly concave), lateral face convex, flexor margin sharply ridged, with a few spines around distal third of length.

P1: More than 5 × longer than carapace (5.4-6.1 × in males, 5.7-6.0 × in females). Ischium with strong, curved, compressed distodorsal spine, and ventromesially with strong subterminal spine proximally followed by a few diminishing spines. Merus 1.3-1.5 × longer than carapace, with 2 strong mesioventral spines and very often additional 1 or 2 small or obsolete spines proximal to these, and field of 3 small spines at mesial proximal portion. Carpus 1.4-1.7 × longer than merus; distoventral spines on each side. Palm 3.5-4.2 × (males), 4.3-6.6 × (females) longer than broad, as long as or slightly longer than carpus. Fingers gaping in large specimens, more strongly so in males than in females, fitting on distal third, distally slightly incurved, crossing when closed, not spooned; movable finger with median process on gaping opposable margin, length 0.3-0.4 × that of palm.

P2-4: Moderately depressed mesio-laterally, sparsely or moderately setose; meri successively shorter posteriorly (P3 merus 0.8-0.9 × length of P2 merus, P4 merus 0.8-0.9 × length of P3 merus), ventrolateral margin with small terminal spine, dorsal margin unarmed; length-breadth ratio, 4.0-5.3 on P2, 3.6-4.5 on P3, 3.0-3.3 on P4; P2 merus nearly as long as or slightly shorter than carapace, 1.2-1.5 × longer than P2 propodus, slightly more slender than P3-4 meri; P3 merus subequal to length of P3 propodus; P4 merus 0.8 × length of P4 propodus, as broad as P3 merus. Carpi subequal on P2-4, or slightly shorter on P2 than on P3-4; each distinctly less than half length of propodus (carpus-propodus length ratio, 0.34-0.36 on P2, 0.30-0.35 on P3, 0.29-0.33 on P4); extensor margin with small terminal spine distinct on P2, occasionally obsolete on P3, absent on P3. Propodi successively longer posteriorly, flexor margin nearly straight in lateral view, ending in pair of spines (placed at distal end) preceded by 6 spines on P2, 3-4 on P3, 2-3 on P4, at most on distal half of length. Dactyli successively longer posteriorly, more slender and more setose on P2 than on P3 and P4; much longer than carpi (dactylus-carpus length ratio, 1.5 on P2, 1.7 on P3, 1.8 on P4), and 0.5-0.6 × as long as propodi on P2-4; flexor margin straight, with 17-20 closely arranged, obliquely directed, short spines, penultimate about twice as broad as antepenultimate, ultimate more slender and longer than antepenultimate, all obscured by thick setae on P2.

Eggs. Number of eggs carried up to 16; size, 1.08 mm × 1.17 mm - 1.40 mm × 1.20 mm.

PARASITES — One of the females from NORFOLK 2, Stn DW2024 (MNHN-IU-2014-16430) bears a rhizocephalan externa.

REMARKS — This species is common around New Caledonia and the Norfolk Ridge.

The new species is grouped together with U. floccus n. sp., U. lumarius n. sp., and U. quinarius n. sp. (see below) by having a field of three closely arranged spines on the mesioproximal face of P1 merus. The spination of the carapace and P2-4 dactyli and the shape of the antenna displayed by U. dualis are very much like those of U. floccus n. sp. The relationships with these congeners are discussed under the remarks of the respective species (see below).

Figures

FIGURE 80 Uroptychus dualis n. sp., holotype, male 3.4 mm (MNHN-IU-2014-16396). A, carapace and anterior part of abdomen, proximal articles of left P1 included, dorsal. B, same, lateral.C, anterior part of sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, left antenna, ventral.F, right Mxp3, ventral. G, same, lateral.H, left P1, dorsal. I, same, proximal part, setae omitted, ventral. Scale bars:1 mm.

FIGURE 81 Uroptychus dualis n. sp.,holotype,male 3.4 mm (MNHN-IU-2014-16396).A, right P2,lateral.B, same,distal part, setae omitted,lateral.C, right P3, setae omitted,lateral.D, same,distal part,lateral. E, right P4, lateral. Scale bars: 1 mm.