Uroptychus bertrandi, 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 : 100-103

Uroptychus bertrandi n. sp.

Figures 34 , 35

TYPE MATERIAL — Holotype: New Caledonia. VAUBAN 1978-1979 Stn DR 15, 22°49’S, 167°12’E, 390-395 m, 10.IV.1978, ov. ♀ 2.9 mm ( MNHN-IU-2013-8521 ) . Paratypes: Collected together with holotype, 1 ov. ♀ 3.2 mm, 1 ♀ (with exuviae) 3.2 mm (MNHN-IU-2014-1633). New Caledonia, Loyalty Ridge. MUSORSTOM 6 Stn CP 467, 21°05.13’S, 167°32.11’E, 575 m, 21.II.1989, 1 ♂ 2.3 mm (MNHN-IU-2013-8530). New Caledonia, Norfolk Ridge. NORFOLK 1 Stn DW 1651, 23°27.3’S, 167°50.4’E, 276-350 m, 19.VI.2001, 2 ov. ♀ 2.9, 3.1 mm (MNHN-IU-2013-8522) . – Stn DW1653, 23°28’S, 167°51’E, 328-340 m, 19.VI.2001, 1 ♂ 3.0 mm (MNHN-IU-2013-8523) . – Stn DW1654, 23°28’S, 167°52’E, 366-560 m, 19.VI.2001, 1 ov. ♀ 3.2 mm (MNHN-IU-2013-8524).

ETYMOLOGY„ Named for Bertrand Richer de Forges for his enormous efforts in the field work.

DISTRIBUTION„ New Caledonia and Norfolk Ridge; 276- 560 m.

SIZE„ Male, 2.3-3.0 mm; females, 2.9-3.2 mm; ovigerous females from 2.9 mm.

DESCRIPTION„ Small species. Carapace: Broader than long (0.8 × as long as broad); greatest breadth 1.7-1.8 × distance between anterolateral spines. Dorsal surface well convex from side to side and from anterior to posterior, without distinct groove or depression, covered with short fine setae, sparingly bearing denticles on hepatic, anterior branchial and lateral epigastric regions. Lateral margins moderately convex, somewhat divergent posteriorly, with row of denticles or small spines; anterolateral spine small, located slightly posterior to level of lateral orbital spine, distinctly separated from that spine in dorsal view. Rostrum triangular, with interior angle of 35°, nearly horizontal; length 0.9 × breadth, about 0.4 × that of remaining carapace, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface distinctly depressed along midline; lateral margin with obsolescent spine near tip. Lateral orbital spine larger than anterolateral spine. Pterygostomian flap covered with denticles or tubercle-like small spines on surface, anteriorly angular, ending in small spine.

Sternum: Excavated sternum with anterior margin convex between bases of Mxp1, surface with weak ridge in midline on anterior half. Sternal plastron 0.9 × as long as broad, lateral extremities slightly divergent between sternites 4 and 7. Sternite 3 shallowly depressed, with anterior margin gently emarginate with U-shaped median sinus flanked by small spine; anterolateral end rounded or angular. Sternite 4 with relatively short anterolateral margin anteriorly rounded with or without a few denticles; posterolateral margin slightly shorter than anterolateral margin. Anterolateral margin of sternite 5 anteriorly somewhat convex, about as long as posterolateral margin of sternite 4.

Abdomen: Setose like carapace. Somite 1 convex from anterior to posterior. Somite 2 tergite 2.3-2.7 × broader than long; pleuron posterolaterally rounded, lateral margin weakly concave and slightly divergent posteriorly. Pleura of somites 3 and 4 laterally rounded. Telson slightly less than half as long as broad; posterior plate 1.0-1.4 × longer than anterior plate, feebly concave on posterior margin.

Eye: Broad relative to length (1.4-1.6 × longer than broad), reaching at most distal fifth of rostrum, strongly inflated proximally, especially along mesial margin. Cornea not inflated, half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.8-3.3 × longer than high. Antennal peduncle relatively slender, reaching rostral tip. Article 2 with distinct distolateral spine. Antennal scale lanceolate, much broader (1.5-2.0 x) than article 5, reaching or slightly falling short of midlength of article 5. Article 4 with small distomesial spine. Article 5 unarmed, 1.1- 1.3 × longer than article 4, breadth about half height of antennular ultimate article. Flagellum of 12-14 segments slightly falling short of or nearly reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 moderately setose on lateral surface. Basis without denticles on convex mesial ridge. Ischium having flexor margin not rounded distally; crista dentata with 25 denticles distally diminishing. Merus 2.3 × longer than ischium, usually unarmed, occasionally with small or obsolescent spine at distal third of flexor margin, length 2.1-2.3 × that of ischium, flexor margin not sharply ridged. Carpus unarmed.

P1: Slender, subcylindrical, with fine setae thickly, unarmed except for ischium bearing short flattish, laciniate dorsal spine; length 7.4-7.6 × (males) or 6.7-7.5 × (females) that of carapace. Merus 1.4-1.6 × longer than carapace. Carpus 1.4-1.6 × longer than merus. Palm slightly depressed (0.8 × as high as broad), 0.9 × length of carpus, 4.9-5.0 × (males) or 6.0-7.4 × (females) longer than broad. Fingers slightly gaping, ending in slightly incurved spine, not spooned; movable finger 0.4 × (rarely 0.3 x) length of palm, opposable margin with 2 small subtriangular processes, proximal larger, situated proximal to position of opposing low prominence at midlength of fixed finger.

P2-4: Moderately compressed, with soft fine setae. Meri successively shorter posteriorly (P3 merus 0.9-1.0 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2 and P3, very slightly narrower on P4 than on P3; length-breadth ratio, 4.4 on P2, 4.1-4.3 on P3, 3.8-4.0 on 4; P2 merus 0.9-1.0 × length of carapace, 1.1 × length of P2 propodus; P3 merus subequal to length of P3 propodus; P4 merus 0.9 × length of P4 propodus; extensor margin with a few eminences or denticles often obsolete on P2, obsolete on P3 and P4. Carpi subequal, unarmed, length less than half that of propodi (carpus-propodus length ratio, 0.33-0.35 on P2, 0.31-0.33 on P3, 0.29-0.32 on P4). Propodi shorter on P2 than on subequal P3 and P4; flexor margin with pair of movable slender terminal spines only. Dactyli relatively broad distally in lateral view, longer than carpus (dactylus-carpus length ratio, 1.1-1.3 on P2 and P3, 1.2-1.4 on P4), less than half that of propodi (dactylus-propodus length ratio, 0.37-0.43 on P2, 0.35-0.42 on P3, 0.36-0.41 on P4); flexor margin nearly straight, with 6-9 (usually 7) spines often obscured by setae, ultimate short, slender, and very close to strongest penultimate spine preceded by 4-7 (usually 5) loosely arranged spines successively diminishing proximally and nearly perpendicular to flexor margin but proximal-most slightly inclined, antepenultimate spine three-quarters as broad as penultimate.

Eggs. Number of eggs carried, 7-15; size, 0.75 × 0.67 mm - 0.77 × 0.92 mm.

REMARKS — The combination of the following characters link the species to U. rutua Schnabel, 2009 , U. sarahae n. sp. and U. toka Schnabel, 2009 : the carapace with denticle-like small spines around the hepatic region, the anterolateral spine small, subequal to or smaller than the lateral orbital spine, the P2-4 dactyli with loosely arranged, perpendicularly directed flexor marginal spines, and the antenna with a short antennal scale ending at most in the midlength of article 5. Uroptychus bertrandi is readily distinguished from all of these species by the unique eyes that are noticeably inflated proximally. When viewed dorsally, the anterolateral spine of the carapace and lateral orbital spines are distinctly separated in U. bertrandi , U. rutua and U. sarahae , contiguous at the base in U. toka . The broad prominences on the gastric region as distinct in U. rutua are absent in U. bertrandi , U. sarahae and U. toka .

Figures

FIGURE 34 Uroptychus bertrandi n. sp., holotype, ovigerous female 2.9 mm (MNHN-IU-2013-8521). A, carapace and anterior part of abdomen, proximal part of right P1 included,dorsal.B, same, lateral. C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson.E, right antenna,ventral.F, right Mxp3, ventral. G, same,setae omitted,lateral. Scale bars:1 mm.

FIGURE 35 Uroptychus bertrandi n. sp., holotype, ovigerous female 2.9 mm (MNHN-IU-2013-8521). A, left P1, merus and proximal articles omitted, dorsal. B, same, proximal part, setae omitted, ventral. C, right P2, lateral. D, same, distal part, setae omitted, lateral. E, right P3, setae omitted, lateral. F, same, distal part, setae omitted, lateral. G, right P4, setae omitted, lateral. H, same, distal part,setae omitted, lateral. Scale bars: 1 mm.