Uroptychus vegrandis, 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 : 546-550

Uroptychus vegrandis n. sp.

Figures 276 , 277

TYPE MATERIAL — Holotype: Solomon Islands. SALOMON 1 Stn DW1827, 9°59.1’S, 161°05.8’E, 804-936 m, 4.X.2001, ♂ 7.2 mm ( MNHN-IU-2014-17015 ) . Paratypes: Collected with holotype, 1 ♂ 6.0 mm (MNHN-IU-2014-17016) . Fiji Islands. BORDAU 1 Stn DW1459, 17°18’S, 179°33’W, 820-863 m, 5.III.1999, 2 ♀ 4.1, 5.8 mm (MNHN-IU-2014-17017) . MUSORSTOM 10 Stn CP1344, 16°45.3’S, 177°40.5’E, 588-610 m, 10.VIII.1998, 1 ov. ♀ 6.6 mm (MNHN-IU-2014-17018) .

ETYMOLOGY — From the Latin vegrandis (not large), alluding to the anteriormost branchial marginal spine smaller than the anterolateral spine, a character to separate the species from the nearest congener U. karubar n. sp.

DISTRIBUTION„ Solomon Islands and Fiji Islands; 588- 936 m.

SIZE„ Males, 6.0- 7.2 mm; females, 4.1-6.6 mm, ovigerous female, 6.6 mm.

DESCRIPTION„ Medium-sized species. Carapace: About as long as broad; greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, with feeble, indistinct groove between cardiac and posterior branchial regions; granulose in large specimens, feebly or barely so in small specimens. Lateral margins slightly convexly divergent posteriorly, with 5 well-developed spines: first anterolateral, overreaching much smaller lateral orbital spine; second smaller than first, located at anterior end of anterior branchial region, preceded by 1 or 2 very small or obsolescent denticle-like spines; third to fifth on posterior branchial region, all acute, third larger than second, fifth situated at point one-fifth from posterior end, followed by ridge. Rostrum slightly deflected ventrally, narrow triangular, with interior angle of 24-25°, length 0.6 × that of remaining carapace, breadth slightly less than half carapace breadth at posterior carapace margin; dorsal surface feebly concave; lateral margin with 2-6 very small, denticle-like spines in distal two-thirds. Lateral orbital spine situated directly mesial to and distant somewhat from anterolateral spine. Pterygostomian flap granulose on surface, anteriorly angular, produced to distinct spine.

Sternum: Excavated sternum with convex anterior margin. Sternal plastron about as long as broad, lateral extremities gently divergent posteriorly. Sternite 3 well depressed, anterior margin moderately concave, with 2 small incurved submedian spines separated by semicircular or broad U-shaped sinus, anterolateral corner angular with tiny accompanying denticle on each side. Sternite 4 having anterolateral margins sharply produced anteriorly, weakly divergent posteriorly, with posteriorly diminishing spines; posterolateral margin slightly shorter than anterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly convex or bluntly rectangular, about as long as posterolateral margin of sternite 4.

Abdomen: Smooth and glabrous. Somite 1 with distinct transverse ridge. Somite 2 tergite 2.6-2.8 × broader than long; pleuron angular on anterolateral and posterolateral termini, lateral margins well concave, feebly or somewhat divergent posteriorly. Pleuron of somite 3 with blunt (small specimens) or angular lateral tip. Telson half as long as broad, posterior plate 1.6 × longer than anterior plate, laterally somewhat convex, and posteriorly emarginate. Eye: Relatively short (1.7 × longer than broad), ending at most in midlength of rostrum, lateral and mesial margins subparallel or feebly convex. Cornea not dilated, length much more than half that of remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.6-2.9 × longer than high. Antennal peduncle extending far beyond cornea, far falling short of apex of rostrum. Article 2 with well-developed lateral spine. Antennal scale tapering, twice as broad as article 5, reaching proximal first or second segment of flagellum. Distal 2 articles each with distomesial spine. Article 5 2 × longer than article 4, breadth slightly more than half height of antennular ultimate article. Flagellum of 9-11 segments far falling short of distal end of P1 merus.

Mxp: Mxp1 with bases more or less close to each other. Mxp3 basis with 3-4 denticles, distalmost distinct, remainder obsolescent. Ischium with 20-23 denticles on crista dentata, flexor margin distally rounded. Merus 2.4 × longer than ischium, well ridged along flexor margin bearing 3 or 4 small spines distal to midlength, distolateral spine distinct. Carpus with small or moderate-sized distolateral spine and a few smaller spines along extensor margin.

P1: 3.9-4.5 × longer than carapace, sparsely setose but fingers more setose. Ischium with strong dorsal spine accompanying small spine proximally, ventromesial margin with well-developed subterminal spine. Merus as long as carapace, somewhat granulose; distomesial and distoventral (mesial) spines well developed; strong spine at midlength of mesial margin, with or without accompanying smaller spine proximal to it; ventral spines (1 or 2) small or obsolescent. Carpus 1.2-1.4 × longer than merus, granulose on surface. Palm slightly longer to slightly shorter than carpus, 3.1-3.6 × longer than broad. Fingers slightly or largely gaping in males, not gaping in females, distally ending small incurved spines, not distinctly crossing when closed (only distal spines crossing); movable finger 0.5-0.6 × length of palm, opposable margin with proximal process well developed in males, less so in females, fitting to longitudinal groove on opposite face of fixed finger when closed.

P2-4: Relatively broad, compressed mesio-laterally, sparsely setose. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 2.7-3.5 on P2, 2.3-3.3 on P3, 2.6-2.9 on P4; dorsal margin with 8-12 small spines on P2, 7-8 spines on P3, 4-8 spines on P4; P2 merus 0.6-0.7 × length of carapace, subequal to or slightly shorter than P2 propodus; P3 merus 0.8 × length of P3 propodus; P4 merus 0.7-0.8 × length of P4 propodus. Carpi subequal on P2-4, 0.3-0.4 × as long as propodi on P2-4, shorter than dactyli (carpus-dactylus length ratio, 0.6-0.7 on P2 and P3, 0.6 on P4); dorsal margin with 5-6 spines on P2, less numerous or obsolescent spines on P3 and P4. Propodi subequal in length on P3 and P4, shorter on P2, or subequal on P2 and P3, longer on P4; flexor margin nearly straight, ending in pair of spines preceded by 1 or 2 spines on P2, 1 spine on P3, 1 or 0 spine on P4. Dactyli subequal in length on P2-4, proportionately broad, longer than carpi (dactylus-carpus length ratio, 1.5-1.7 on P2, 1.5-1.8 on P3, 1.6-1.7 on P4), 0.6 × as long as propodi on P2-4; flexor margin straight, bearing row of spines, ultimate slender, as broad as antepenultimate, penultimate about 2 × broader than ultimate, remaining proximal spines slender, strongly inclined and nearly contiguous to one another, but not oriented parallel to flexor margin.

Eggs. Number of eggs carried, 25 (normal number probably more); size, 0.88 mm × 1.04 mm - 0.93 mm × 0.97 mm.

REMARKS„ The ovigerous female from MUSORSTOM 10 Stn CP1344 is somewhat different from the others: the carapace bears a small spine dorsomesial to the second lateral spine; pereopods are more slender (length-breadth ratio, 5.0 on P1 palm, 4.1, 3.9, 3.4 on P2, P3, P4 merus respectively); the P1 merus is 1.2 times longer than the carapace and P1 carpus bears distinct spines along the mesial margin. Inasmuch as no other differences are found, this specimen is regarded as a variant of the species.

The carapace lateral marginal spination and the granulose dorsal surface in large specimens are very much like those of large specimens of U. nanophyes Alcock & McArdle, 1902 . Uroptychus vegrandis differs from U. nanophyes in having four instead of five spines on the branchial margin, the anteriormost of which is smaller instead of larger than the anterolateral spine; the P2 merus has a terminal spine only instead of bearing a row of spines on each of the ventrolateral and ventromesial margins; and the P1 ischium bears on the ventromesial margin a subterminal spine only instead of a row of spines.

The species is closely related to U. karubar n. sp. (see above) in having the branchial lateral margin with four strong spines, the abdominal somite 1 well ridged transversely, and the antennal scale distinctly overreaching the antennal peduncle.

However, the first of the four branchial lateral spines in U. karubar is larger than the anterolateral spine followed by a distinct spine on the hepatic margin, whereas in U. vegrandis this spine is smaller than the anterolateral spine followed by one or two tiny denticle-like spines (usually absent); the epigastric region bears a row of transverse spines in U. karubar , unarmed in U. vegrandis ; the Mxp3 ischium bears a small but distinct spine lateral to the distal end of flexor margin in U. karubar , which spine is absent in U. vegrandis ; and the pterygostomian flap is granulose in U. karubar , whereas covered with small spines in U. vegrandis .

As mentioned under U. quinarius n. sp. (see above), that species also resembles this new species. Uroptychus vegrandis can be distinguished from U. quinarius by the granulose carapace surface and pterygostomian flap and by the lack of three closely arranged spines on the proximal mesial surface of P1.

Figures

FIGURE 276 Uroptychus vegrandis n.sp.,holotype,male 7.2 mm (MNHN-IU-2014-17015).A,carapace and anterior partof 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, left antenna,ventral.F, left Mxp3,setae omitted, ventral.G, same, lateral. Scale bars: A, B, 5 mm; C-G, 1 mm.

FIGURE 277 Uroptychus vegrandis n. sp.,holotype,male 7.2 mm (MNHN-IU-2014-17015).A, right P1, proximal part, ventral. B, same,proximal part omitted,dorsal. C, right P2,lateral. D, same,distal part,setae omitted,lateral.E, right P3,setae omitted,lateral.F, right P4, setae omitted, lateral.Scale bars:A,B,5 mm; C-F,1 mm.