Uroptychus bispinatus Baba, 1988

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 : 107-109

Uroptychus bispinatus Baba, 1988

Figure 38

Uroptychus bispinatus Baba, 1988: 25 , fig. 9. — Baba et al. 2009: 40, figs 32-33. — Poore et al. 2011: 328, pl. 6, fig. E.

TYPE MATERIAL — Holotype: Indonesia, Molucca Sea between Halmahera and northern Sulawesi, ALBATROSS Stn 5614, 2013 m, female ( USNM 150311 ). [not examined].

MATERIAL EXAMINED — Fiji Islands. BORDAU 1 Stn CP1458, 17°22’S, 179°28’W, 1216-1226 m, 5.III.1999, 3 ♂ 5.3-5.6 mm, 2 ov. ♀ 5.4, 5.8 mm (MNHN-IU-2014-16332).

DISTRIBUTION„ Molucca Sea between Halmahera and northern Sulawesi and Taiwan, and now Fiji Islands; 1173- 2013 m.

DIAGNOSIS — Carapace as long as broad, greatest breadth 1.6-1.9 × distance between anterolateral spines; unarmed and smooth dorsally (epigastric spines vestigial); lateral margins ridged, with feeble crenulations (in dorsal view) along branchial region; anterolateral spine very small, distinctly posterior to level of small lateral orbital spine or acuminate lateral limit of orbit. Rostrum short triangular, with interior angle of 26-30°, dorsally flattish, length at most one-third that of remaining carapace, breadth less than half carapace breadth measured at posterior carapace margin. Pterygostomian flap anteriorly roundish with very small spine. Excavated sternum with convex anterior margin followed by longitudinal ridge in midline. Sternal plastron slightly broader than long; lateral extremities divergent posteriorly; sternite 3 depressed well, anterior margin deeply excavated in semicircular shape, with submedian spines flanking small median sinus; sternite 4 having anterolateral margins strongly divergent posteriorly, about as long as or slightly shorter than posterolateral margin. Anterolateral margin of sternite 5 convexly strongly divergent posteriorly, as long as anterolateral margin of sternite 4. Abdominal somite 1 without transverse ridge; somite 2 tergite 2.4-2.5 × broader than long; pleural lateral margins barely or slightly concave and posteriorly divergent, ending in bluntly angular tip; pleuron of somite 3 posterolaterally bluntly angular. Telson slightly more than half as long as broad; posterior plate 1.2-1.8 × longer than anterior plate, posterior margin slightly convex or slightly concave, not distinctly emarginate. Eyes relatively broad, 1.4 × longer than broad, distally broadened, proximally narrowed, barely or fully reaching, or slightly overreaching rostral tip. Distal article of antennular peduncle about twice as long as high. Antennal peduncle overreaching apex of rostrum; article 2 without distinct spine; antennal scale varying from slightly overreaching article 4 to terminating in midlength of article 5; distal 2 articles unarmed; breadth of article 5 one-third height of ultimate article of antennule; flagellum of 13-14 segments slightly falling short of distal end of P1 merus. Mxp1 with bases close to each other, not contiguous. Mxp3 basis with 1 distal denticle on mesial ridge; ischium with flexor margin not rounded distally, crista dentata with 3-7 loosely arranged denticles; merus not flattened, rather thick and unarmed, length 2.5-2.7 × that of ischium. P1 slender; ischium dorsally with antero-posteriorly compressed, basally broad, short spine; no spine elsewhere; merus 1.0-1.1 × longer than carapace; carpus 1.2-1.4 × longer than merus; palm 3.6-3.7 × (males), 4.4-5.6 × (females) longer than broad, 0.8 × length of carpus; fingers relatively broad distally, spooned on prehensile face, not crossing, length 0.5-0.6 × length of palm. P2-4 slender; meri with flattish lateral and mesial surfaces, unarmed on dorsal margin, successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), subequally broad on P2-4; P2 merus 0.8-0.9 × length of carapace, 1.3-1.4 × length of P2 propodus; P3 merus 1.1-1.2 × length of P3 propodus; P4 merus 0.9-1.1 × length of P4 propodus; carpi successively slightly shorter posteriorly; carpus-propodus length ratio, 0.7-0.8 on P2, 0.7 on P3, 0.6-0.7 on P4; propodi subequal or successively slightly longer posteriorly; flexor margin inflated at midlength, with 2 or 3 (usually 2) movable spines close to each other and located directly distal to midlength and remote from distal end of article; dactyli much shorter than carpi (dactylus-carpus length ratio, 0.6 on P2, 0.7 on P3 and P4), about half length of propodi (dactylus-propodus length ratio, 0.4 on P2, 0.4-0.5 on P3, 0.5 on P4); relatively slender, flexor margin strongly curving at proximal third, with 2 distal spines of moderate size (ultimate larger) preceded by 8 very small spines oriented parallel to flexor margin, all obscured by setae.

Eggs. Number of eggs carried, 8-10; size, 1.60 mm × 1.70 mm - 1.65 × 1.80 mm.

Color. A specimen from Taiwan was illustrated in Baba et al. (2009) and Poore et al. (2011).

Parasites. One of the males examined bears a rhizocephalan externa.

REMARKS — A slight difference between the type and the present material is noted: the excavated sternum bears a central spine on the surface in the type instead of a longitudinal ridge in the present material as well as in the material from Taiwan ( Baba et al. 2009).

The P2-4 dactyli bear thick setae along the flexor margin by which the small spines are obscured, as shown in Baba et al. (2009). The presence of these spines was also confirmed in the type material. The small anterolateral spine of the carapace and the P2-4 dactylar spines oriented parallel to the flexor margin link the species to U. australis ( Henderson, 1885) and U. setosipes Baba, 1981 from Japan. Uroptychus bispinatus differs from both in having the pterygostomian flap anteriorly rounded instead of produced, in having the sternite 4 anterolateral margin as long as or slightly shorter than instead of twice as long as the posterolateral margin, in having the P4 merus 0.9 × instead of 0.6 × as long as the P3 merus, and in having the P2-4 propodi with two or three flexor marginal spines remotely distant from the juncture with the dactylus instead of a pair of terminal spines preceded by a row of spines.

The species also resembles U. remotispinatus Baba & Tirmizi, 1979 in having a short antennal scale, in having the P2-4 dactyli with the ultimate spine distinctly larger than the penultimate, and in having the P2-4 propodi with the distalmost of flexor spines considerably remote from the juncture with the dactyli. Their relationships were discussed by Baba et al. (2009).

The coloration was illustrated by Baba et al. (2009) based upon the material from Taiwan.

Figures

FIGURE 38 Uroptychus bispinatus Baba, 1988, A, D, male 5.5 mm; B, C, ovigerous female 5.4 mm (MNHN-IU-2014-16332). A, carapace, dorsal. B, carapace and anterior part of abdomen,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, distal part of left P2,lateral.Scale bars:1 mm.