Uroptychus trispinatus, 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 : 531-535

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Uroptychus trispinatus

n. sp.

Uroptychus trispinatus n. sp.

Figures 268 View FIGURE 268 , 269 View FIGURE 269 , 306G View FIGURE 306

TYPE MATERIAL — Holotype: New Caledonia. BIOCAL Stn DW37, 23°00’S, 167°16’E, 350 m, 30.VIII.1985, ov. ♀ 4.0 mm ( MNHN-IU-2014-16996 ) GoogleMaps . Paratypes: New Caledonia, Chesterfield Islands. MUSORSTOM 5 Stn DW337, 19°53.80’S, 158°38.00’E, 412-430 m, 15.X.1986, 1 ♂ 5.2 mm, 1 ov. ♀ 4.8 mm (MNHN-IU-2014-16997) . New Caledonia, Norfolk Ridge. CHALCAL 2 Stn NORFOLK 1 Stn DW1654, 23°26’S, 167°51’E, 366-560 m, 19.VI.2001, 1 ov. ♀ 3.8 mm (MNHN-IU-2014-17002) . NORFOLK 2 Stn CP2130, 23°15.90’S, 168°13.54’E, 375-427 m, 2.XI.2003, 1 ov. ♀ 3.5 mm (MNHN-IU-2014-17003) . BATHUS 3 Stn DW830, 23°20’S, 168°01’E, 361-365 m, 29.XI.1993, 1 ov. ♀ 3.7 mm (MNHN-IU-2014-17004) . New Caledonia. MUSORSTOM 4 Stn CP213, 22°51.3’S, 167°12.0’E, 405-430 m, 28.IX.1985, 1 ♀ 3.0 mm (MNHN-IU-2014-16998) . SMIB 2 Stn DW05, 22°56’S, 167°15’E, 398-410 m, 17.IX.1986, 1 ♂ 3.0 mm (MNHN- IU-2014-16999) . BIOCAL Stn DW37, collected with holotype, 2 ♂ 2.0, 3.0 mm (MNHN-IU-2014-17000) . Vanuatu. MUSORSTOM 8 Stn CP1026, 17°50.35’S, 168°39.33’E, 437-504 m, 28.IX.1994, 1 ♂ 4.5 mm (MNHN-IU-2014-17001) .

ETYMOLOGY„ From the Latin tri (three) and spinatus (spined), in reference to three strong spines on the anterior part

of the carapace lateral margin.

DISTRIBUTION„ Chesterfield Islands, New Caledonia, Vanuatu, and Norfolk Ridge, 350- 560 m.

SIZE„ Males, 2.0- 5.2 mm; females, 3.0- 4.8 mm; ovigerous females from 3.5 mm.

DESCRIPTION„ Small species. Carapace: Broader than long (0.7-0.8 × as long as broad); greatest breadth 1.6-1.8 × distance between anterolateral spines. Dorsal surface smooth, moderately convex from anterior to posterior, with shallow depression between gastric and cardiac regions; epigastric region with pair of well-developed spines. Lateral margins divided by constriction anterior to midlength (between anterior and posterior branchial regions) into anterior and posterior parts; anterior part divergent posteriorly, with 3 prominent spines, all directed anterolaterally, first anterolateral, overreaching base of antennal scale, second slightly smaller than first, third strongest, dorsal to level of preceding spines; posterior part strongly convex, with 4 or 5 (usually 5), rarely 3 sharp spines diminishing posteriorly, all directed anterolaterally. Rostrum narrow triangular, with interior angle of 25-28°, slightly upcurved; dorsal surface concave; length 0.3-0.4 × that of remaining carapace, breadth much less than half carapace breadth at posterior carapace margin. Lateral orbital spine small but distinct, slightly anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to strong spine, followed by a few spines often small, occasionally pronounced, along lower margin and/or in midline of anterior part; height of posterior portion 0.4 × that of anterior portion.

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

Abdomen: Somites short relative to breadth. Somite 1 convex from anterior to posterior. Somite 2 tergite 3.2 × broader than long, pleuron concave on lateral margin, posterolaterally strongly produced. Pleura of somites 3-4 laterally tapering more strongly in females than in males. Telson 0.4 × as long as broad; posterior plate 1.5-2.0 × longer than anterior plate, posterior margin feebly or moderately concave, or distinctly emarginate.

Eye: Elongate, 2.0-2.1 × longer than broad, slightly falling short of apex of rostrum, somewhat narrowed distally. Cornea not dilated, less than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 1.8-2.1 × longer than high. Antennal peduncle reaching or slightly overreaching apex of rostrum. Article 2 with strong lateral spine. Antennal scale 1.3-1.6 × broader than article 5, usually slightly falling short of, rarely reaching distal end of article 5. Article 4 distomesially broadened and produced to short spine. Article 5 unarmed, length 1.4-1.5 × that of article 4, breadth 0.5-0.6 × height of ultimate article of antennule. Flagellum of 11-13 (rarely 9) segments not reaching distal end of P 1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 distal denticle on mesial ridge. Ischium with flexor margin distally rounded, crista dentata with about 20 distally diminishing 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 blunt spines on distal third of length; lateral face with strong, blunt distal spine. Carpus unarmed.

P 1: 6.3-6.8 × longer than carapace, smooth and barely setose except for fingers. Ischium with strong dorsal spine; ventromesial subterminal spine distally blunt and well developed, overreaching distal end of ischium, followed distantly by several protuberances on proximal portion. Merus mesially with blunt spines roughly in 3 rows (mesial, ventromesial, dorsomesial); length 1.3 × (1.6 × in largest male) that of carapace. Carpus 1.4-1.5 × length of merus, with several small or obsolescent spines in 2 rows along mesial margin, one of these somewhat dorsal. Palm unarmed, depressed, with lateral and mesial margins subparallel or somewhat convex; length 3.3-3.8 × (males), 3.6-4.1 × (females) breadth, subequal to or at most 1.1 × that of carpus. Fingers relatively slender distally, sparingly setose, moderately gaping in distal half, not spooned along opposable margins, barely incurved distally and slightly crossing when closed; fixed finger inclined somewhat laterally; movable finger‰.4-0.5 × as long as palm, opposable margin with prominent blunt process (distal margin of process perpendicular to opposable margin) fitting into narrow longitudinal groove on opposite ventromesial face of fixed finger when closed.

P 2-4: Relatively slender, well compressed mesio-laterally, sparsely with simple setae, more setose on dactyli. Ischia with 2 short dorsal spines. Meri subequal in length on P 2 and P 3 or very slightly shorter on P 3 than on P 2, shortest on P 4 ( P 4 merus‰.6 × length of P 3 merus); subequally broad on P 2 and P 3, narrower on P 4 ( P 4 merus‰.8 × breadth of P 3 merus); dorsal margin unarmed; length-breadth ratio, 3.6-4.3 on P 2, 3.5-4.2 on P 3, 2.5-2.8 on P 4; P 2 merus 0.8-0.9 × length of carapace, 1.1-1.2 × length of P 2 propodus; P 3 merus 0.9-1.1 × length of P 3 propodus. P 4 merus 0.7 × length of P 4 propodus. Carpi subequal in length on P 2 and P 3 or slightly longer on P 2 than on P 3, shortest on P 4 ( P 4 carpus 0.7-0.8 × length of P 3 carpus), 0.4-0.5 × length of propodus on P 2, 0.4 × on P 3, slightly less than 0.4 × on P 4. Propodi longest on P 3, shortest on P 4; flexor margin slightly concave in lateral view, with pair of slender movable distal spines only. Dactyli subequal in length on P 2-4; dactylus-carpus length ratio, 1.1-1.3 on P 2, 1.2-1.3 on P 3, 1.6-1.8 on P 4; dactylus-propodus length ratio, 0.5 on P 2 and P 3, 0.6-0.7 on P 4; flexor margin slightly curving (slightly concave in lateral view), with 8-9 sharp spines loosely arranged, proximally diminishing and nearly perpendicular to margin, ultimate spine slightly more slender than penultimate.

Eggs. Number of eggs carried, 5-10; size, 0.97 × 1.06 mm - 1.30 × 1.00 mm.

Color. Based on male and ovigerous female from Musorstom 5 Stn DW337, Chesterfield Islands (MNHN-IU-2014-16997): ground color translucent seashell pink. Visceral parts under carapace pinkish. P 1 with pinkish bands on distal portion of merus, on both distal and median portions of carpus and palm and on fingers; P 2-4 totally translucent pinkish, faded proximally on meri and carpi, proximally and distally on propodi, and distally on dactyli.

REMARKS — The carapace shape including the presence of a pair of epigastric spines, the pterygostomian flap with spines on the anterior surface and the spination of P 2-4, especially the arrangement of spines on dactyli link the species to U. corbariae n. sp., U. paraplesius n. sp., U. mesodme n. sp., U. clarki n. sp. and U. defayeae n. sp. Three of these, i.e. Uroptychus trispinatus , U. paraplesius and U. mesodme , share the carapace lateral margin bearing 3 anterior spines remotely separated from another group of 3-5 posterior spines, the antennal scale overreaching the midlength of article 5, and article 4 bearing a distomesial spine. The other three species, U. corbariae , U. clarki and U. defayeae , differ from the above three in having irregular spination on the anterior third of the carapace lateral margin, in having the antennal scale barely reaching the midlength of article 5, and in having the articles 4 and 5 unarmed. Uroptychus trispinatus is differentiated from U. paraplesius by the carapace lateral spines that are directed more laterally instead of more anteriorly; the antennal article 5 is unarmed instead of bearing a distinct distomesial spine; the epigastric spines are stronger; and the pleura of the abdominal somites 2-4 in females are more sharply tapering. Uroptychus mesodme can be distinguished from U. trispinatus by the anterolateral spine directed forward, the branchial marginal spines much smaller than the anterior three spines, the epigastric region bearing an additional pair of small spines between the usual epigastric spines, and the smaller subterminal spine of the P 1 ischium.

This species is somewhat similar to U. macrolepis n. sp. (see above) in the spination of the carapace lateral margin and in having elongate eyes. Uroptychus trispinatus , however, is readily distinguished from that species by the P 2-4 propodi that bears the flexor margins nearly straight instead of convex in lateral view, distally ending in a pair of terminal spines only instead of bearing a row of 6 or 7 single spines proximal to the terminal pair; sternite 3 bears a distinct instead of obsolescent median notch on the anterior margin; the antennal scale usually slightly falls short of (at most slightly overreaching) instead of extending far beyond the antennal article 5; the P 2-4 ischia each bear 2 short spines instead of being unarmed on the dorsal margin; and the flexor marginal spines of P 2-4 dactyli are elongate and perpendicularly directed, instead of being short and obliquely directed.