Uroptychus defayeae, 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 : 155-159

Uroptychus defayeae n. sp.

Figures 63 , 64

TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP975, 19°23.60’S, 169°28.93’E, 566- 536 m, 22.IX.1994, 1 ♂ 5.0 mm ( MNHN-IU-2014-16375 ) . Paratypes: New Caledonia, Chesterfield Islands. MUSORSTOM 5 Stn CP387, 20°53.41’S, 160°52.12’E, 650-660 m, 22.X.1986, 1 ♂ 3.4 mm (MNHN-IU-2014-16376) . New Caledonia, Norfolk Ridge. CHALCAL 2 Stn DW73, 24°39.9’S, 168°38.1’E, 573 m, 29.X.1986, 1 ov. ♀ 4.5 mm (MNHN-IU-2014-16377) . NORFOLK 2 Stn DW2077, 25°20.63’S, 168°18.53’E, 666-1000 m, 27.X.2003, 1 ♂ 3.5 mm (MNHN-IU-2014-16378) .

ETYMOLOGY„ Name for Danielle Defaye of MNHN for her help during my stays at the Paris Museum.

DISTRIBUTION„ Chesterfield Islands, Vanuatu, and Norfolk Ridge; 536-1000 m.

DESCRIPTION„ Small to medium-sized species. Carapace: Broader than long (0.8 × as long as broad); greatest breadth 1.8-1.9 × distance between anterolateral spines. Dorsal surface smooth, somewhat convex from anterior to posterior, with very shallow depression between gastric and cardiac regions; somewhat ridged along posterior third of lateral margin; epigastric region with pair of small spines (left spine absent in paratype MNHN-IU-2014-16376); small spine mesial to second stout lateral marginal spine (absent in paratypes MNHN-IU-2014-16376 and MNHN-IU-2014-16378). Lateral margins gently constricted at anterior third; anterior part (anterior to constrictions) gently divergent posteriorly, with 2 well-developed spines: first anterolateral, directed forward, or inclined slightly mesially or slightly laterally, slightly overreaching antennal scale; second shorter than first, placed at anterior end of anterior branchial region; 2 tiny spines present or obsolescent between first and second; posterior part (posterior to constriction or posterior branchial margin) gently convex, with 4 or 5 short, posteriorly diminishing spines, anteriormost of these remotely separated from second spine on anterior part. Rostrum broad or narrow triangular, directed slightly dorsally, with interior angle of 22° (paratypes) or 30° (holotype); length 0.8 × (holotype) or subequal to (paratypes) breadth, and 0.4 × that of remaining carapace; dorsal surface concave; breadth less than half that of posterior carapace margin. Lateral orbital spine small, situated at same level as anterolateral spine. Pterygostomian flap anteriorly angular, produced to strong spine, surface with 2-5 spines on anterior part; height of posterior half 0.5 × that of anterior half.

Sternum: Excavated sternum with sharp ridge in midline leading onto anterior margin produced triangularly between bases of Mxp1. Sternal plastron 1.4 × broader than long, lateral extremities convexly divergent behind sternite 4, sternite 7 slightly narrower than sternite 6. Sternite 3 shallowly depressed; anterior margin moderately concave, with deep narrow or broad V-shaped median notch without flanking spine. Sternite 4 short relative to breadth; anterolateral margin anteriorly convex, length 1.5 × that of posterolateral margin. Sternite 5 with convex anterolateral margin subequal to or slightly longer than posterolateral margin of sternite 4.

Abdomen: Somites short relative to breadth. Somite 1 well convex from anterior to posterior. Somite 2 tergite 3.1-3.3 × broader than long; pleuron posterolaterally produced more strongly in female than in males. Pleura of somite 3-5 laterally rounded, with no great difference between sexes. Telson 0.4-0.5 × as long as broad; posterior plate 1.0-1.3 × longer than anterior plate, posterior margin slightly or moderately emarginate.

Eye: Elongate, 1.8-1.9 × longer than broad, reaching or slightly overreaching apex of rostrum, slightly broadened proximally, mesial margin slightly concave medially. Cornea very slightly dilated, 0.7-0.8 × length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.6-2.9 × longer than high. Antennal peduncle extending far beyond apex of rostrum. Article 2 with strong distolateral spine. Antennal scale proportionately broad, distally blunt, 1.3 × broader than article 5, slightly overreaching article 4, not reaching midlength of article 5. Article 4 unarmed or with very tiny tubercle-like process distomesially. Article 5 unarmed, length 1.3-1.4 × that of article 4, breadth 0.5 × height of ultimate article of antennule. Flagellum of 12-15 segments not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with obsolescent distal denticle on mesial ridge. Ischium having flexor margin distally rounded, crista dentata with 10-20 small or obsolescent denticles. Merus twice as long as ischium, mesial face flattish; flexor margin roundly ridged on proximal half, sharply ridged on distal half, bearing 1 or 2 very short blunt spine at distal third; distolateral spine obsolescent. Carpus unarmed.

P1: 6.9-7.2 × (males), 6.2 × (female) longer than carapace, smooth and barely setose except for fingers. Ischium with strong dorsal spine with or without small accompanying spine proximally, ventromesial margin with subterminal spine very short and blunt, not overreaching distal end of ischium, and a few obsolescent proximal protuberances. Merus with 2 rows each of a few short blunt spines (1 dorsomesial, 1 ventromesial), ventral distomesial spine blunt and short; length 1.4-1.5 × (males), 1.3 × (female) that of carapace. Carpus 1.5-1.6 × length of merus, distally with dorsomesial spine, no spine elsewhere. Palm unarmed, depressed, two-thirds as high as broad, slightly broader distally or with subparallel lateral and mesial margins, somewhat narrowed proximally; 3.5-4.5 × (males), 4.0 × (female) as long as broad. Fingers relatively slender distally, sparingly setose, moderately gaping in largest male and female, not gaping in smaller males, not clearly crossing when closed; fixed finger directed slightly laterally, opposable margin sinuous; movable finger 0.4 × as long as palm, opposable margin with prominent process (distal margin of process perpendicular to opposable margin); no longitudinal groove on ventromesial face of fixed finger.

P2-4: Relatively slender, well compressed mesio-laterally, with sparse simple setae, more setose on dactyli. Ischia with 2 short dorsal spines placed distally and proximally. Meri subequal in length on P2 and P3, shortest on P4 (P4 merus 0.5- 0.6 × length of P3 merus); subequally broad on P2 and P3 or slightly broader on P3 than on P2, slightly narrower on P4; dorsal margin unarmed; length-breadth ratio, 4.4-4.7 on P2, 4.0-4.4 on P3, 2.7-3.1 on P4; P2 merus 0.9-1.0 × length of carapace, subequal to or very slightly longer than P2 propodus; P3 merus subequal to length of P3 propodus. P4 merus 0.7 × length of P4 propodus. Carpi subequal in length on P2 and P3 or slightly longer on P2 than on P3, shortest on P4 (P4 carpus 0.7 × length of P3 carpus), carpus-propodus length ratio, 0.4 on P2 and P3, 0.3-0.4 on P4. Propodi longest on P3, shortest on P4; flexor margin slightly concave in lateral view, with pair of slender terminal spines only. Dactyli subequal in length on P2-4; dactylus-carpus length ratio, 1.1-1.3 on P2, 1.2-1.4 on P3, 1.7-1.8 on P4; dactylus-propodus length ratio, 0.5 on P2 and P3, 0.6 on P4; flexor margin slightly curving, with 7-9 sharp spines loosely arranged, proximally diminishing and nearly perpendicular to margin, ultimate spine slightly but consistently more slender than penultimate.

Eggs. Number of eggs carried, 25; size, 1.08 × 1.00 mm - 1.13 × 1.17 mm.

Color in preservative. Reddish bands on P1 as in U. trispinatus , but no bands on fingers.

REMARKS — Uroptychus defayeae resembles U. clarki n. sp. and U. corbariae n. sp. (see their similarities under U. clarki ). Morphological differences between U. clarki and U. defayeae are small. In U. defayeae the carapace dorsal surface has a pair of epigastric spines only, instead of bearing additional spines flanking the epigastric pair as in U. clarki ; the strong anterolateral spine of the carapace is followed by two obsolescent instead of small but distinct spines; the crista dentata bears denticles on the median part, not along the entire length as in U. clarki ; the distolateral spine of the antennal article 2 is much stronger. Uroptychus defayeae differs from U. corbariae in having the posterior branchial margin with 4 or 5 spines instead of 1 spine (followed by a few short oblique ridges), in having the antennal article 2 with a strong instead of very small distolateral spine, and in having more slender pleura of abdominal somites 3-4.

Figures

FIGURE 63 Uroptychusdefayeae n.sp.,A-D, F-I,holotype,male 5.0mm (MNHN-IU-2014-16375);E,ovigerous female paratype 4.5 mm (MNHN-IU-2014-16377). 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, right pleura of abdominal somites 2-5, dorsolateral. E, same. F, telson. G, left antenna, ventral. H, left Mxp3,setae omitted, ventral.I, same, lateral.Scale bars: 1 mm.

FIGURE 64 Uroptychus defayeae n.sp.,holotype,male 5.0 mm (MNHN-IU-2014-16375).A, right P1,proximal part,ventral.B, same,distal three articles,dorsal. C, left P2, lateral. D, same,distal part, setae omitted, lateral. E, left P3, setae omitted, lateral. F, same, distal part, setae omitted, lateral. G, left P4, setae omitted, lateral.H, same,distal part, setae omitted, lateral.Scale bars: 1 mm.