Uroptychus anacaena, Baba, Keiji & Lin, Chia-Wei, 2008

Baba, Keiji & Lin, Chia-Wei, 2008, Five new species of chirostylid crustaceans (Crustacea: Decapoda: Anomura: Chirostylidae) from Taiwan, Zootaxa 1919, pp. 1-24 : 6-9

Uroptychus anacaena sp. nov.

( Figs. 4 , 5 , 13A )

Type material. Holotype: NTOU A00851 , male (9.7 mm), E Taiwan, Stn DW46, 22°51.9’N, 121°25.2’E, 565–614 m, 2 Aug 2000.

Diagnosis. Carapace as long as broad, granulose on surface, with stout anterolateral spine, unarmed elsewhere. Pterygostomian flap anteriorly ending in small spine. Excavated sternum anteriorly sharp angular between close basal articles of Mxp1. Sternite 3 with submedian spines separated by V-shaped notch. Sternite 4 without spine on anterolateral angle. Abdomen glabrous. Eyes narrow elongate. Antennal article 2 with distinct spine; antennal scale much broader than peduncle, slightly overreaching midlength of article 5; articles 4–5 unarmed. Mxp3 merus and carpus unarmed. P1 relatively massive, ischium dorsally with broad, sharp spine, ventrally without distinct subterminal spine on mesial margin; merus as long as carapace. P2–4 meri subequal in breadth, successively shorter posteriorly; P2 merus shorter than carapace; carpi subequal, about half as long as propodi on P2–3, less than half on P4; propodi having flexor margin with pair of terminal spines preceded by 3 or 4 spines on distal two-fifths of length; dactyli slightly shorter than carpi, flexor margin moderately curved at proximal third, with 9–10 somewhat inclined, sharp spines.

Description. Carapace about as long as broad. Dorsal surface finely granulose, moderately convex from side to side, feebly so from anterior to posterior, with feeble depression between gastric and cardiac regions. Lateral margin weakly convexly divergent posteriorly, with fine granulations; anterolateral spine relatively stout, directed straight forward, overreaching article 2 of antenna; anterior end of branchial region somewhat elevated in dorsal view. Rostrum triangular, with interior angle of 28°, slightly deflexed anteriorly, ending in blunt tip; dorsal surface depressed, length 0.37 that of carapace. Lateral orbital angle with small spine obliquely leading to anterolateral spine of carapace. Pterygostomian flap granulose on surface, anteriorly ending in distinct spine.

Sternal plastron 0.9 times longer than broad; lateral extremities slightly divergent posteriorly. Excavated sternum anteriorly sharp angular, surface without spine and median ridge. Sternite 3 well depressed, anterior margin broadly excavated, with pair of submedian spines separated by narrow V-shaped notch; laterally with small spine. Sternite 4 with anterolateral margin smoothly convex, 1.7 times as long as posterolateral margin.

Abdomen smooth. Somite 1 without distinct transverse ridge, weakly convex from anterior to posterior. Pleura of somite 2 with lateral margins concave, weakly divergent posteriorly. Pleura of somite 3 with bluntly angular posterolateral margin. Somites 4 and 5 ending in rounded posterolateral margin. Telson half as long as broad; posterior lobe 1.3 times longer than anterior lobe, weakly concave on posterior margin.

Eyes relatively slender, overreaching point 3/4 of rostral length; lateral and mesial margins subparallel. Cornea slightly shorter than peduncle.

Ultimate article of antennule 2.5 times longer than broad. Antennal article 2 with distinct distolateral spine. Antennal scale slightly overreaching midlength of article 5, breadth about twice that of article 5. Articles 4 and 5 unarmed; article 5 2.1 times longer than article 4, breadth 0.4 that of ultimate antennular article. Flagellum consisting of 28 segments, slightly overreaching end of P1 merus.

Mxp1 with bases close to each other but not contiguous. Mxp3 barely setose on lateral surface. Basis with 3 proximally diminishing denticles on mesial ridge. Ischium with 23 denticles on crista dentata; flexor margin not rounded distally. Merus unarmed, well ridged along flexor margin. Carpus spineless.

P1 relatively massive, 4.7 times longer than carapace, lacking spines but granulose except for fingers and palm, barely setose but fingers with short setae. Ischium dorsally with basally broad, procurved spine, ventromesially without subterminal spine. Merus about as long as carapace. Carpus 1.2 times longer than merus, unarmed. Palm subequal to carpus in length, 2.3 times longer than broad. Fingers gently curving ventrally, not gaping, distally ending in incurved spine; opposable margin of fixed finger with 2 low processes proximal to midlength. Movable finger 0.55 length of palm, opposable margin with median process proximally followed by 3 smaller processes.

P2–4 moderately compressed, barely setose on meri and carpi, sparsely so on propodi and dactyli. Meri successively shorter posteriorly (P3 merus 0.9 P2 merus, P4 merus 0.8 P3 merus), breadth subequal; lengthbreadth ratio, 4.7 on P2, 4.1 on P3, 3.3 on P4; P2 merus 0.8 length of carapace, 1.25 times longer than P2 propodus; P3 merus 1.1 times longer than P3 propodus; P4 merus 0.8 length of P4 propodus. Carpi subequal, length 0.49 that of propodus on P2, 0.47 on P3, 0.43 on P4. Propodi successively longer posteriorly, lengthbreadth ratio, 5.0 on P2, 5.5 on P3, 4.2 on P4; flexor margin ending in pair of spines preceded by 4 (P2), 3 or 4 (P3), 3 (P4) spines on distal third of length. Dactyli subequal in length, gently curving, length 0.44 that of propodus on P2 and P3, 0.41 on P4; flexor margin with 9 posteriorly diminishing triangular spines, ultimate and penultimate subequal.

Color in life. Orange overall.

Etymology. The name is a noun in apposition from the Greek an (without) plus akaina (thorn), alluding to the absence of spine on the ventromesial margin of P1 ischium, a character separating the species from U. brucei Baba, 1986 .

Remarks. The new species is much closer to U. maori Borradaile, 1916 from the Three Kings Islands, New Zealand, than to U. brucei , from northwestern Australia, in nearly all aspects, but it can readily be distinguished by the P1 ischium lacking instead of bearing a distinct subterminal spine on the ventral mesial margin.

The species is also close to U. brucei Baba, 1986 from Western Australia in general shape of the carapace and slender ocular peduncles. It is differentiated from that species by the antennal article 4 unarmed instead of with a distomesial spine, the P1 ischium without instead of with a strong subterminal spine on the mesial ventral margin, the P2 propodus with fewer (3 or 4 instead of 10–19) spines on less than the distal half instead of at least on distal two-thirds (or nearly entire length) of flexor margin. The fringe of setae on the extensor margin of P2–5 dactyli is usually present in U. brucei , whereas in this species it is much weaker, present on the right side, obsolescent on the left side.

Distribution. Known only from the holotype from E Taiwan, in 565– 614 m.

Figures

FIGURE 4. Uroptychus anacaena sp. nov., holotype, male, NTOU A 00851. A, carapace and abdomen, proximal part of right P 1 included, dorsal. B, same, lateral. C, sternal plastron, with excavated sternum, proximal part of Mxp 1 included. D, telson. E, antenna, left, ventral. F, Mxp 3, left, ventral. G, same, lateral. Scales for A, B = 5 mm; scales for C – G = 1 mm.

FIGURE 5. Uroptychus anacaena sp. nov., holotype, male, NTOU A 00851. A, P 1, proximal part, right, ventral. B, same, distal part, dorsal. C, P 2, left, lateral. D, same, distal part, setae omitted, lateral. E, P 3, left, lateral. F, same, distal part, lateral. G, P 4, right, lateral. H, same, distal part, lateral. Scales for A, B = 5 mm. scales for C – H = 1 mm.

FIGURE 13. A, Uroptychus anacaena sp. nov., holotype, male (9.7 mm), NTOU A 00851. B, Uroptychus anatonus sp. nov., holotype, male (11.1 mm). C, Uroptychus orientalis sp. nov., holotype, ovigerous female (11.2 mm), NTOU A 00853. D, Uroptychus singularis sp. nov., paratype, female (8.0 mm), NTOU A 00868.