Uroptychus terminalis, 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 : 513-518

Uroptychus terminalis n. sp.

Figures 258-260

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. BIOCAL Stn CP 30, 23°09’S, 166°41’E, 1140 m, 29.VIII.1985, ♂ 8.4 mm ( MNHN-IU-2014-16975 ) . Paratypes: New Caledonia, Norfolk Ridge. Collected with holotype, 1 ♂ 7.5 mm, 2 ov. ♀ 7.0, 7.2 mm (MNHN-IU-2014-16976). BATHUS 3 Stn CP823, 23°23’S, 167°52’E, 980-1000 m, 29.XI.1993, 10 ♂ 2.9-8.6 mm, 9 ov. ♀ 5.8-6.8 mm, 3 ♀ 6.0- 6.8 mm (MNHN-IU-2014-16977) . – Stn CP831, 23°04’S, 166°56’E, 650-658 m, 30.XI.1993, 1 ♀ 6.7 mm (MNHN-IU-2014-16978) . NORFOLK 2 Stn CP2131, 23°13.19’S, 168°11.21’E, 1114-1190 m, 2.XI.2003, 4 ♂ 5.4- 7.9 mm, 3 ov. ♀ 5.8-6.0 mm, 1 ♀ 6.9 mm (MNHN-IU-2014-16979) . – Stn CP2138, 23°00.56’S, 168°22.80’E, 396-405 m, 3.XI.2003, 2 ♀ 6.4, 6.6 mm (MNHN-IU-2014-16980) . – Stn CP2139, 23°01’S, 168°23’E, 372-393 m, 03.XI.2003, 1 ♀ 6.5 mm (MNHN-IU-2014-16981). New Caledonia, Loyalty Basin. BIOGEOCAL Stn CP297, 20°37’S, 167°11’E, 1230-1240 m, 28.IV.1987, 1 ov. ♀ 5.7 mm, 3 ♀ 4.7-5.8 mm (MNHN-IU-2014-16982). Vanuatu. MUSORSTOM 8 Stn CP1111, 14°51.09’S, 167°14.00’E, 1210-1250 m, 8.X.1994, 1 ♂ 6.2 mm, 3 ov. ♀ 5.6-6.4 mm (MNHN-IU-2014-16983) . – Stn CP1125, 15°57.63’S, 166°38.43’E, 1160-1220 m, 10.X.1994, 3 ♂ 3.6-8.0 mm, 3 ov. ♀ 4.1-6.7 mm, 2 ♀ 5.7, 6.2 mm (MNHN-IU-2014-16984) . – Stn CP1126, 15°58.35’S, 166°39.98’E, 1210-1260 m, 10.X.1994, 1 ♂ 6.5 mm, 1 ov. ♀ 7.1 mm (MNHN-IU-2014-16985) . – Stn CP1129, 16°00.73’S, 166°39.94’E, 1014-1050 m, 10.X.1994, 1 ♂ 6.0 mm, 1 ov. ♀ 6.4 mm (MNHN-IU-2014-16986). Solomon Islands. SALOMON 2 Stn CP2189, 8°19.6’S, 160°01.9’E, 660-854 m, 23.X.2004, 1 ov. ♀ 5.1 mm (MNHN-IU-2014-16987) .

OTHER MATERIAL EXAMINED — Kermadec Islands . CHALLENGER Stn 170, 29°55’S, 178°14’W, 520 fms (946 m), 1 ov. ♀ 5.9 mm ( BMNH 1888 :33) [syntype of U. australis ( Henderson, 1885) ] . – Stn 171, 28°33’S, 177°50’W, 600 fms (1098 m), 1 ov. ♀ 7.4 mm ( BMNH 1888 :33) [syntype of U. australis ( Henderson, 1885) ] .

ETYMOLOGY„ From the Latin terminalis (terminal), alluding to the terminal flexor marginal spine of the P2 propodus, which is very close to the distal end of the article, one of characters to separate the new species from U. nigricapillis Alcock, 1901 .

DISTRIBUTION„ Solomon Islands, Vanuatu, Loyalty Basin, Norfolk Ridge, and Kermadec Islands; 372-1260 m.

SIZE„ Males, 2.9-8.6 mm; females, 4.1-7.4 mm; ovigerous females from 4.1 mm.

DESCRIPTION — Medium-sized species. Carapace: 1.1 × longer than broad; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface convex from anterior to posterior, with weak or feeble depression between gastric and cardiac regions; pair of epigastric spines distinct, often small. Lateral margins convexly divergent or with constriction about at midlength (between anterior and posterior branchial margin), ridged along posterior half of branchial margin; anterolateral spines small, not overreaching lateral orbital spine; tiny spine usually present at anterior end of branchial region, followed by at most 5 small, often obsolescent tubercle-like small spines on posterior branchial margin. Rostrum narrow triangular, with interior angle of 15-25°, straight horizontal, slightly upcurved distally or slightly deflected ventrally; dorsal surface flattish; length 0.4-0.5 × that of remaining carapace, breadth half or slightly less than half carapace breadth at posterior carapace margin. Pterygostomian flap anteriorly angular, produced to acute spine, smooth on surface.

Sternum: Excavated sternum anteriorly ending in sharp spine between bases of Mxp1, surface weakly ridged in midline, bearing small spine in center. Sternal plastron slightly broader than long; sternites successively broader posteriorly. Sternite 3 depressed well, anterior margin deeply excavated, with 2 submedian spines contiguous to each other or separated by narrow notch. Sternite 4 with transverse row of tubercles preceded by strong depression; anterolateral margin slightly convex, bearing posteriorly diminishing denticles, anteriorly produced to small spine; posterolateral margin more than half length of anterolateral margin. Anterolateral margin of sternite 5 strongly convex and denticulate, about as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somite 1 with antero-posteriorly convex transverse ridge. Somite 2 tergite 2.3-2.5 × broader than long; pleuron posterolaterally blunt, lateral margin concavely divergent posteriorly. Pleuron of somite 3 with blunt lateral end. Telson two-thirds as long as broad; posterior plate 1.7-1.8 × longer than anterior plate, posterior margin distinctly emarginate.

Eye: Broad relative to length (1.5-1.6 × longer than broad), broadened distally, overreaching midlength of rostrum. Cornea slightly dilated, more than half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle about twice as long as high. Antennal peduncle reaching distal margin of cornea. Article 2 with distinct distolateral spine. Antennal scale 1.3-1.7 × broader than article 5, reaching or overreaching midlength of, not reaching distal end of article 5. Distal 2 articles unarmed; article 5 2.1-2.4 × longer than article 4, breadth half height of ultimate article of antennule. Flagellum consisting of 14-16 segments, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases close but not contiguous to each other. Mxp3 barely setose on lateral surface. Basis with 5-6 denticles often obsolescent, distal one distinct. Ischium with 10-14 denticles on crista dentata; flexor margin distally not rounded. Merus and carpus unarmed; merus 2.5 × longer than ischium, not flattened, moderately thick, rounded along flexor margin.

P1: Somewhat massive in males, length 4.3-4.6 × that of carapace; smooth and barely setose except for fingers. Ischium with short, depressed dorsal spine, ventrally with a few denticle-like spinules, ventromesially with vestigial subterminal spine. Merus with a few longitudinally arranged ventromesial spines and row of small or obsolescent spines in ventral midline (both occasionally obsolescent in females); length 1.1-1.3 × that of carapace. Carpus 1.2-1.3 × length of merus. Palm 2.8-3.3 × (males), 3.4-4.4 × (females) longer than broad, 0.8 × (rarely 0.9 x) length of carpus. Fingers proportionately broad, somewhat curving ventrally, distally crossing in males, barely crossing in females; gaping or not gaping in males, not gaping in females; opposable margins fitting to each other in distal half in non-gaping fingers, fitting in distal third in gaping fingers, fitting along entire length in females; movable finger half as long as palm, opposable margin in females with proximo-distally broad process proximal to position of median low eminence on fixed finger.

P2-4: Relatively broad in lateral view, well compressed mesio-laterally, bearing long setae numerous on distal articles. P2 merus slightly shorter than or as long as, and as broad as P3 merus, P4 merus shortest and much narrower than P2-3 meri, 0.6-0.7 × length of P3 merus; length-breadth ratio, 3.7-4.8 on P2 and P3, 3.5-4.0 on P4; P2 merus 0.8-0.9 × length of carapace, 1.1-1.3 × length of P2 propodus; P3 merus subequal to length of P3 propodus; P4 merus 0.9 × length of P4 propodus; dorsal margin with or without a few very small spines or eminences proximally on P2; ventrolateral margin with very small terminal spine distinct on P2 and P3, often obsolete on P4. Carpi slightly longer on P3 than on P2 or subequal on P2-3, shortest on P4; carpus-propodus length ratio, 0.6 on P2, 0.5 on P3, 0.4-0.5 on P4. Propodi longest on P3, shortest on P4; broad relative to length, flexor margin nearly straight, with 7-11 spines on P2, 6-8 on P3, 5-7 on P4, terminal spine single, very close to juncture with dactylus on P2, somewhat remote on P3 and P4. Dactyli curving at proximal third, shorter than carpi (dactylus-carpus length ratio, 0.7 on P2, 0.7-0.8 and P3, 0.9-1.0 on P4); dactyluspropodus length ratio, 0.4 on P2 and P3, 0.5 on P4; flexor margin strongly curving, with 8 or 9 (mostly 9) subtriangular spines obscured by setae, inclined but not oriented parallel to flexor margin, ultimate and penultimate close to each other, antepenultimate remotely equidistant between penultimate and distal quarter; ultimate distinctly larger than penultimate, remaining spines successively diminishing toward base of article.

Eggs. Eggs carried 6-14 in number (normal number probably more); size, 1.20 mm × 1.30 mm - 1.93 mm × 1.97 mm.

PARASITES — Male from MUSORSTOM 8 Stn CP1129 (MNHN-IU-2014-16986) with bopyrid isopod on left branchial cavity.

REMARKS — As mentioned under Uroptychus australis (see above), the specimen (ovigerous female) from Challenger Stn 170 (see Figure 260 ) and another specimen (ovigerous female) from Challenger Stn 171, both syntypes of Diptychus australis Henderson, 1885 (currently U. australis ( Henderson, 1885)) , are referred to this new species (see above under U. australis ). Also one of the specimens, ovigerous female, from Challenger Stn 194 proved to be identical with U. empheres Ahyong & Poore, 2004 (see above under U. australis ). Uroptychus terminalis is distinguished from U. australis by having the P2-4 propodi with the terminal of the flexor marginal spines single, not paired, and the flexor marginal spines of the dactyli are obliquely directed, not oriented parallel to the margin. Uroptychus empheres has the P2-4 propodal terminal spine paired, not single as in this new species.

The general shape of the carapace and the flexor margin of the P2-4 propodi distally ending in a single spine link the species to U. dejouanneti n. sp., U. gracilimanus ( Henderson, 1885) , U. brevisquamatus Baba, 1988 , and U. nigricapillis Alcock, 1901 . Uroptychus terminalis is closer to U. nigricapillis than to the other species in having a pair of epigastric spines. However, U. nigricapillis (see above) has the terminal of the flexor marginal spines of P2-4 propodi rather remote from the juncture with the dactylus. This new species is distinguished from U. dejouanneti and U. gracilimanus by having the ultimate spine of the P2-4 dactyli distinctly larger than instead of smaller than ( U. gracilimanus ) or subequal to ( U. dejouanneti ) the penultimate; and the antennal article 2 bears a distinct instead of very small lateral spine. Uroptychus terminalis is distinguished from U. brevisquamatus by the anterolateral spine of the carapace that is small instead of stout, at most terminating in rather than distinctly overreaching the tip of the lateral orbital spine; the P4 merus is much shorter and narrower than the P3 merus; and the pterygostomian flap is anteriorly angular and produced to a sharp spine, instead of being roundish bearing a very small spine.

Figures

FIGURE 258 Uroptychus terminalis n. sp., holotype, male 8.4 mm (MNHN-IU-2014-16975). A, carapace and anterior part of abdomen, proximal part 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, right antennule and antenna, ventral. F, right Mxp3, setae omitted, ventral. G, same, lateral.H, left P1, proximal part, ventral.I, same,proximal part omitted,dorsal. Scale bars:A, B, H,I, 5 mm; C-G, 1 mm.

FIGURE 259 Uroptychus terminalis n. sp., holotype, male 8.4 mm (MNHN-IU-2014-16975). A, right P2, lateral. B, same, distal part, setae omitted, lateral.C, right P3, setae omitted, lateral. D, right P4, lateral.Scale bars:1 mm.

FIGURE 260 Uroptychus terminalis n.sp.,ovigerous female 5.9 mm from Challenger Stn 170.A, carapace and anterior part of abdomen,dorsal. B, anterior part of sternal plastron,with excavated sternum and basal parts of Mxp1.C, left antenna,ventral.D, right P1, proximal part,ventral.E, same, distal articles,dorsal.F, right P2, lateral.G, same,distal part,setae omitted,mesial.H, right P3, lateral.I, right P4,lateral.Scale bars:1 mm.